PR-464
Overview
Summaries and Reports of Applied and Field Research
The Department of Agronomy of the University of Kentucky has a tradition of excellence in both basic and applied research. Basic research by faculty in the department working in areas such as plant biochemistry, physiology, molecular biology, and genetics has the long-term objective of increasing crop plant productivity and value. Problem-solving applied research within the department is aimed at near-term benefits to Kentucky agriculture. In addition to research on crop productivity, another major focus of the department is research designed to preserve soil and water quality for agricultural and other uses.
The University of Kentucky recognized this unique combination of excellence in basic and applied research, and its contributions to Kentucky's economy when it designated the department as a "distinguished, nationally competitive" research program and one of 20 "targets of opportunity" for the university. As such, the department is looked upon as one of the programs to help lead the way in establishing the University of Kentucky as a top 20 research university by the year 2020.
While the department conducts both basic and applied research studies, this report emphasizes recent findings of applied and field experiments with importance to Kentucky agriculture. The report contains brief updates on continuing projects and initial reports on recently completed studies. Agronomy Research is published in even years to inform professional agronomists, crop producers, and crop consultants about recent developments in the University of Kentucky Department of Agronomy.
Examples of interesting and potentially useful accomplishments during the last year include:
New Crops: As more and more types of novel soybean varieties become available, Kentucky growers will need information on which, if any, management practices they may need to modify to successfully produce a given novel type. Food-grade tofu soybean may need to be planted at lower rates; planting rates that are too high may decrease soybean size and quality. Although seed protein concentration does not usually increase in soybean with nitrogen fertilization, the replacement of nitrogen from nitrogen fixation with mineral nitrogen has increased seed protein concentration. We found that additional mid- to late-season nitrogen is not needed to produce tofu or high-protein specialty soybean with acceptable protein concentrations. Also, standard planting rates should be maintained when growing these specialty soybean types.
No-Till Wheat: Studies at the University of Kentucky indicate that no-till wheat is beneficial and economically feasible for many growers in the state. Currently, 25 to 30 percent of the wheat acres in Kentucky is no-till planted. Research is continuing on the long-term effects and best management practices for no-till wheat. Long-term research has shown that both corn and soybean, when included in a cropping system with wheat, achieve higher yields (6 percent and 3 percent, respectively) when planted after no-till wheat as compared to tilled wheat.
Working with both primary wheat consulting groups in the state and with the support of the Kentucky Small Grain Growers Association and the Kentucky Soybean Board, we are conducting on-farm, side-by-side comparisons of tilled and no-tilled wheat and its effects on the double-cropped soybean and corn in the cropping system. Over the first year of this study, we have found the wheat yields and the following double-cropped soybean yields to be almost identical. Any long-term effects of the no-till wheat system on the soybean and corn yields would be expected to express themselves in the third or fourth year of the study.
Corn: A corn planting date study was initiated to substantiate optimum planting date periods for highest yield potential with recently developed corn technologies. A Bt corn hybrid and its non-Bt isoline are being compared in planting dates beginning in early/mid-April and ending in mid-June. From initial results after three years, it appears that the highest yield potential for corn is obtained if corn is planted prior to mid-May. There was no yield advantage for Bt corn at earlier planting dates. Use of Bt corn at later planting dates (mid-May or later) was also an economically viable management approach.
Soybean: Soils from a no-till rotation in Argentina were analyzed to examine microbial diversity by patterns of community substrate use. Higher soybean yields were correlated with higher microbial diversity. This may help explain rotation effects on soil microbial community structure.
Tobacco: The use of fatty alcohol compounds (e.g., Off-Shoot-T and Royaltac) at topping, followed by maleic hydrazide (MH) and/or combinations of MH and a dinitroanaline have proven to be effective strategies for controlling suckers in dark tobacco. Dark tobacco sucker control programs utilizing all three types of chemicals have been shown to provide excellent sucker control while minimizing bronzing and browning effects observed when MH was applied immediately after topping at rates sufficient to control suckers until harvest.
Forage Grasses: Sixty-five experimental endophyte-free tall fescue populations are being tested in forage yield trials at two locations in Kentucky. Several new varieties of tall fescue, orchardgrass, and timothy will be released during the summer of 2002. Our work with wide hybrids continues, with 3,500 new genotypes of hybrids between ryegrass and fescue planted in the field in 2001.
Red Clover: The value of certified Kenland red clover seed greatly exceeds the extra cost of the seed. The gross value of 3 tons of extra forage per acre can equal $240 per acre, which greatly exceeds the extra cost for the better seed (approximately $12 per acre at the time of seeding). Therefore, uncertified Kenland red clover is not a bargain at any price.
Freedom! red clover was bred for reduced pubescence to reduce dust and promote faster drying, and this variety was released in 2001. Certified seed may be available in the market in late 2002. Additional mildew and potato leafhopper resistance is being added to the variety by selection. Release date is tentatively set for 2003.
Five cycles of selection for low phenolic red clover (leaves cure green) have resulted in a partially green-leaved type. Further selection is under way to increase the intensity of the character. Plans are to investigate feeding value when development is complete. No release date has been established.
Grazing Corn: A SARE Producer Grant was awarded to study the agronomic, economic, and animal performance of beef cattle grazing standing mature corn. Results from Year 1 indicate that beef cattle utilize approximately 80 percent of the grain with an average daily gain of 1.8 pounds. Cost per pound of gain averaged $0.34. This study will continue in 2002.
Nitrogen Management: Using yield maps to vary the N rate within a field with highly variable yield areas is not agronomically sound. A single rate would be more economically and agronomically sound. N is mineralized at high rates in these soils and needs to be taken into account when making N recommendations. N recommendations that are proven with research based on tillage type, soil drainage class, and previous crop are still the most accurate.
Water Quality: Phosphorus (P) is an essential nutrient regulating plant growth and water quality, whose concentration and availability in soils is governed by many soil chemical properties and hydrologic factors. Soils with low P fertility and high amounts of oxalate extractable iron and aluminum retained the greatest amounts of P, suggesting that these may be useful measurements for identifying soils with the greatest P retention capacity and also for monitoring soils for agricultural production and environmental purposes.
Animal Waste Management: The broiler industry in Kentucky currently produces about 300,000 tons of litter per year. Research has shown that this provides enough nitrogen to fertilize up to 75,000 acres of corn. If litter application rates are limited to the phosphorus fertilizer needs of the crop, as they are likely to be in the long run, more than 300,000 acres of corn per year would be needed to utilize the litter that is currently produced.
The effectiveness of grass filters at trapping poultry litter runoff from no-till soils has not been previously examined. We determined that the concentration of fecal bacteria in runoff from litter-amended no-till soils exceeded that of incorporated litter. However, the total fecal bacteria loss was reduced because greater infiltration occurred. Excessive residue cover promoted fecal bacteria loss. Litter application to no-till soil was overall a better management practice to control fecal bacteria runoff than was incorporation by tillage.
Weed Management: Our research demonstrated the importance of following label restrictions regarding the planting of rotational crops. Certain sulfonylurea wheat herbicides were capable of persisting in the soil long enough to cause injury to double-cropped soybeans in Kentucky; however, this injury was less of a risk where STS soybeans were planted.
We showed that dense stands of Italian ryegrass are capable of limiting wheat yield by at least 70 percent. Applying the appropriate postemergence herbicide in a timely fashion can provide a net gain of $36 to $73 per acre.
Other Research: Differences in yield levels of crop varieties and their ranking with respect to crop yield are highly dependent on the environment in which they are tested. Work continues on development of new statistical methods for analyzing and identifying patterns in data from multi-site yield trials and using this information to increase the accuracy of estimates of variety performance.
General Research
J.H. Herbek, L.W. Murdock, J.R. Martin, J. James, and D. Call
No-till wheat production has been practiced in Kentucky for many years. Currently, between 25 and 30 percent of the wheat acres in Kentucky are no-till planted. Many farmers remain skeptical of the practice and believe significant yield is sacrificed with the practice.
Previous research in the 1980s by the University of Kentucky showed favorable results. With these conflicting reports and experiences, the Kentucky Small Grain Growers Association entered into a cooperative effort with the University of Kentucky to take an intensive look into no-till wheat.
A replicated trial was established on a Huntington silt loam soil at Princeton, Kentucky, in the fall of 1992. Two small adjacent fields were placed in a three-crop, two-year rotation of corn, wheat, and double-cropped soybean. Both no-till and conventionally tilled (chisel-disc) wheat were planted and compared with different nitrogen and herbicide treatments. The corn and double-cropped soybean crops were planted no-till. Stand counts, weed control ratings, disease and insect ratings, and yield results were obtained for wheat. The long-term effects of the two different wheat tillage practices on the succeeding soybean and corn crops and on soil changes were also measured and are included in another report.
Nine years of results (1993-01) are presented in this report.
Yields. The nine-year average yields have been high (Table 1). The conventional till planted wheat averaged about 4.5 bu/ac more than the no-till wheat. The yields of no-till wheat have been significantly lower than wheat planted with tillage four of the nine years, due to compaction one year (1993) and freeze damage in 1996, 1998, and 2001. The yields of no-till wheat have been similar or exceeded that of conventionally tilled wheat the other five years.
Stands. The number of emerged plants was lower with no-till. Planting at the rate of 32 viable seeds/ft2, the final stands averaged 26.6 and 28.9 plants/ft2 for no-till and conventional till, respectively. Both stands were high enough for maximum yields. Seeding rates may need to be increased by 10 percent as one moves from conventional till to no-till seeding.
Nitrogen Rates. No-till wheat may require more nitrogen than conventionally tilled wheat. Nitrogen in this trial was managed for intensive production with one-third applied at Feekes stage 3 (February) and the remainder at Feekes stage 5 (mid-March). The no-till wheat sometimes appeared to be slightly nitrogen deficient before the second application, but in most years this had little effect on yield. Increasing the nitrogen rate from 90 to 120 lb/ac had only a small effect on yield for the nine years (Table 1). Although more nitrogen is recommended for no-till plantings, it may not always be justified. The years that the high rate of nitrogen resulted in higher yields were when late winter/early spring freezes resulted in wheat damage or when excessive amounts of rain fell after the first application of spring nitrogen.
Weed Control. Good weed control was obtained in no-till wheat by three treatments: 1) Harmony Extra applied in the fall, 2) a contact herbicide at planting plus Harmony Extra in the spring, and 3) Harmony Extra in the spring. Yields were similar for all three herbicide treatments (Table 1). Wild garlic, which is sometimes associated with no-till wheat, was not a significant problem when Harmony was used. Without fall or spring herbicide treatments, weed competition was a problem (especially with henbit and common chickweed) and resulted in lower yields (no-till check).
Nitrogen Application Time. For five years (1996-2000), the trial included treatments with different rates of nitrogen applied at different times. The first two years, the highest yield was obtained with a 120 lb/ac nitrogen rate with half of the nitrogen applied in February and the remaining half applied in late March just prior to jointing. For the last three years, there was no effect related to time of nitrogen application.
Fungicides. Preventative disease control applications of fungicides were managed for intensive production. A control treatment receiving no fungicide treatment was included the first five years of the study in both tillage systems. Diseases were of no significance during the five years of this study. Therefore, fungicide applications had little effect on either tillage system (data not shown).
Insects. Insects were monitored by use of scouting and traps. No significant insect infestations occurred. The wheat seed was treated with Gaucho before planting for Barley Yellow Dwarf protection from 1994 through 1996, and all treatments have received a fall foliar insecticide after 1996.
Diseases. There was no significant disease on any treatments during the nine years except for Barley Yellow Dwarf during the first year. This is consistent with no yield increases obtained from the use of fungicides during the first five years.
No-till wheat can produce as well as conventionally tilled wheat when properly managed. Stand establishment and weed control appear to be where the greatest changes in management are necessary.
| Table 1. Summary of nine-year wheat results (1993-01). | ||
| Treatment Comparison | Yield (bu/ac) | Wheat Stands (plants/sq. ft.) |
| Tillage Effect | ||
| Conventional | 95.1 | 28.9 |
| No-Till | 90.6 | 26.6 |
| Nitrogen Rate (lb/ac) | ||
| No-Till (90) | 88.8 | |
| No-Till (120) | 92.4 | |
| Conventional (90) | 93.9 | |
| Conventional (120) | 96.2 | |
| Weed Control | ||
| No-Till Fall Gramoxone + Spring Harmony Extra | 92.5 | |
| No-Till Fall Harmony Extra | 92.1 | |
| No-Till Spring Harmony Extra | 90.8 | |
| No-Till Check | 78.8 | |
M. Collins, C.T. Dougherty, and J.C. Henning
Grassland agriculture is the most suitable land use for 8 million acres of the 13 million acres of agricultural land of Kentucky due to climate, topography and soils. Livestock convert forages that cannot be used directly by people into high-quality animal products. Forages make up more than 90 percent of the diet of beef cows, the major forage consumer in the state, and about 50 percent of the diet of high-producing dairy cows.
Grassland-based livestock enterprises (horses, beef and dairy cattle, and sheep and goats) generated $2.3 billion of the $3.6 billion farm income in 2000. Kentucky's grasslands supported the largest beef cow-calf herd east of the Mississippi and the eighth largest beef cow herd (1,075,000) in the United States. Equine sales topped $1 billion, and Kentucky ranked first in the United States. In addition, Kentucky producers harvest more than 5 million tons of hay each year for feeding, and cash sales of hay add $50 million each year.
Kentucky grasslands are a vast, renewable natural resource. Expansion of beef cattle and hay enterprises offers an opportunity for Kentucky's farmers facing declining incomes from tobacco.
Forage livestock research programs at the University of Kentucky have the overall goals of addressing constraints that currently limit profitability and productivity of grassland-based livestock systems. Forage research in the Department of Agronomy emphasizes grazing systems, breeding and evaluation of improved forage varieties, and harvested hay and silage, in addition to expanding areas of nutrient management and GIS technologies. Research and Extension agronomists work closely with their counterparts in the departments of Animal Sciences, Veterinary Science, Biosystems and Agricultural Engineering, Entomology, and Plant Pathology as well as with county Extension personnel plus faculty at the regional universities.
In 2000, the USDA CREES initiated a program titled "Forage for Enhanced Livestock Production" to help address constraints limiting productivity of forage/livestock systems. Forage research capabilities in Kentucky will be further enhanced by establishment of a forage livestock research unit of the USDA Agricultural Research Service within the College of Agriculture. Geneticists, biochemists, and nutritionists in this unit will conduct basic biology research to support applied research in grassland agriculture.
Forages support livestock enterprises by providing the least expensive source of nutrients. Agronomic research aims to increase productivity, extend the grazing season, and stabilize supplies of quality forage. There are essentially two thrusts: one directed at improving the amount and quality of herbage available to grazing animals and the other directed toward the economical provision of quality hay and silage for feeding during winter and other periods of limited pasture growth.
Grass Breeding. Cool-season grasses form the base of Kentucky pastures. The Department of Agronomy's grass breeding efforts are aimed at providing better grass cultivars for the pasture base. New, well-adapted cultivars of tall fescue, orchardgrass, timothy, and eastern gama grass are being readied for market. Endophyte-free tall fescue lines have been selected for seedling vigor, persistence, compatibility with pasture legumes, and yield in Kentucky grassland situations. Hybrids between fescue and ryegrass species have useful traits for adapted grasses.
Agronomists continue research in many aspects of tall fescue toxicosis. Essentially toxicant-free and "livestock-friendly" endophytes have been introduced into adapted tall fescue cultivars and are being tested. Ecological research is under way to determine the impact of endophyte absence and novel endophytes on tall fescue vigor and competitiveness of tall fescue.
Clovers. Among adapted species, legumes provide the highest quality forage. The Department of Agronomy maintains the Clover Germplasm Center with 1,900 accessions of 205 species of wild and cultivated clovers. It also includes genetic and breeding stocks of red, white, crimson, kura, and zigzag clovers. Breeding of red clover, kura clover, other Trifolium species, and hybrids aims at improving yield, quality, hay characteristics, persistence, and compatibility with pasture grasses. Freedom! red clover that dries more rapidly and makes less dusty hay will become available by the end of 2002, and a mildew- and potato leafhopper-resistant version is anticipated in 2003. North America's first tetraploid red clover cultivar that is high yielding and persistent is in seed multiplication. A red clover genotype that resists browning during hay curing is also being tested.
Processed and Stored Forage. Stored forages are essential to Kentucky livestock enterprises to meet animal needs during winter and other periods of low pasture productivity. Losses during outside hay storage commonly exceed one-third of the initial dry matter, and quality is also greatly reduced. Preservation systems are being refined to improve quality and minimize losses of stored forage. Baled silage shows promise as a harvesting system to minimize dry matter losses and to maintain forage quality during storage. Studies are under way, in cooperation with the Department of Animal Sciences, to compare forage intake and weight gains of cattle on hay and baled silage. This information is aiding producers in making informed decisions regarding forage preservation systems.
Integrated Systems. Grassland agronomists are also concerned with integration of new technologies and management practices into existing farming enterprises. Technologies include GPS, remote sensing technology, and GIS for assessment of alfalfa and tall fescue management practices. Integrated systems are being evaluated on beef cow-calf grazing systems on grasslands established on reclaimed mined land in eastern Kentucky and on summer stocker grazing systems using bermudagrass pastures.
Variety Testing. The Department of Agronomy operates a statewide testing program for evaluating forage species, cultivars, and plant breeding materials. Newly released and experimental grass and legume lines are subjected to overgrazing by cattle and horses to determine persistence under grazing. Agronomists, along with conservationists, wildlife biologists, and biofuel engineers, are also engaged in the introduction, agronomic, and grazing management of native and introduced warm-season grasses including switchgrass, eastern gamagrass, little and big bluestems, and bermudagrass.
Environmental Issues. Perennial forage species conserve and improve soil quality and fertility and form the basis for sustainable cropping systems on sloping land. Forage crops effectively utilize nutrients in animal waste to produce and offer the potential for effective use of these materials. Research programs within the Department of Agronomy are evaluating poultry litter effects on forage productivity, forage quality, and water quality.
Current Issue: Mare Reproductive Loss Syndrome (MRLS). Grassland agronomists are involved in investigating the cause of MRLS. In 2002, soils, pastures and fringes, and mares of "sentinel" farms are being sampled to establish background levels of potential toxicants and conditions that may contribute to MRLS. Agronomy laboratories are analyzing plant samples for plant alkaloid mycotoxins and soils and biological materials for toxicants and mineral imbalances that may disturb reproduction.
The Department of Agronomy has a long history in research, teaching, and extension in grassland agriculture. Future programs will emphasize improving forage quality and nutrient utilization by animals as well as matching seasonal distribution of pasture production with livestock needs.
Environmental Research
E. D'Angelo
Phosphorus (P) is an essential nutrient regulating plant growth and water quality, whose concentration and availability in soils is governed by many soil chemical properties and hydrologic factors. This study was conducted to (i) determine the major forms of P in representative soils of Kentucky (e.g., amount of P bound with iron, aluminum, and calcium minerals and organic matter), (ii) determine the maximum P retention capacity of the soils, (iii) find out which soil component is primarily responsible for retaining P, and (iv) discover whether P retention was related to easily measurable soil properties. It is expected that results will be useful for identifying soil chemical properties that govern P retention and for quantifying the amount of P (e.g., from manure sources) that can be added to soils to optimize soil fertility and minimize P impacts on water quality.
Total P in the soils ranged between 139 to 3861 mg/kg and was highest in soils from the Bluegrass region (Table 1). Using a chemical fractionation procedure, it was found that most of the soil P was bound with iron and aluminum minerals, organic matter, and other highly resistant inorganic and organic P forms. Soils from the Bluegrass also contained considerable amounts of P associated with calcium minerals.
In batch sorption isotherm experiments with the soils, it was discovered that
inorganic P added at 300 mg P/kg was rapidly removed from solution by iron and
aluminum minerals in the soil (47 to 100 percent in 48 hours). Phosphorus was
not
removed by calcium minerals, which was likely explained by acidic pH values
of the soils used in the study (pH 4 to 7). Dissolution of calcium phosphate
minerals and decomposition of organic matter were the main sources of readily
available P in the Kentucky soils.
The maximum P retention capacity of the soils, as determined from the isotherm studies, ranged between 193 and 1300 mg P/kg. When 23 to 63 percent (median 41 percent) of the soil's maximum P retention capacity was reached, the soil solution contained elevated levels of P (>1 mg P/liter), which exceeded plant requirements (~0.2 mg P/liter) and may threaten water quality. Therefore, it is critical to maintain P levels below this level for economic and environmental reasons.
Two factors were primarily responsible for determining the soil's P retention capacity: P fertility and the amount of iron and aluminum extractable with oxalate solution (e.g., amorphous iron and aluminum oxyhydroxides). Soils with low P fertility and high amounts of oxalate extractable iron and aluminum retained the greatest amounts of P, suggesting that these may be useful measurements for identifying soils with the greatest P retention capacity and also for monitoring soils for agricultural production and environmental purposes. Studies are planned to investigate whether these relationships are valid for predicting P retention and losses from agricultural fields with different P fertility and other chemical characteristics.
This research was partially supported by Senate Bill 271 Water Quality Grant to the author. The author wishes to thank Drs. Bill Thom, Frank Sikora, and Martin Vandiviere for their contributions to the study.
| Table 1. Phosphorus distribution in native soils from four physiographic regions of Kentucky. | |||||||
| Soil | Inorganic P | Organic P | Residual P | Total P | |||
| Water+Weakly Exchangeable (Labile-Pi) | Fe+Al (NaOH-Pi) | Ca+Mg (HCl-Pi) | Fulvic+Humic (NaOH-Po) | ||||
| Bluegrass | mg P kg soil-1 | ||||||
| Eden | 1 | 127 | 78 | 381 | 295 | 882 | |
| Lowell 1 | 9 | 272 | 61 | 440 | 431 | 1213 | |
| Lowell 2 | 3 | 570 | 146 | 298 | 401 | 1418 | |
| Maury 1 | 9 | 1230 | 1107 | 769 | 746 | 3861 | |
| Cumberland Plateau | |||||||
| Shelocta 1 | 1 | 109 | 0 | 223 | 226 | 559 | |
| Trappist | 1 | 151 | 11 | 191 | 274 | 528 | |
| Highland Rim | |||||||
| Mountview | 1 | 132 | 0 | 158 | 126 | 417 | |
| Nolin | 1 | 176 | 0 | 193 | 180 | 550 | |
| Pembroke | 2 | 197 | 18 | 104 | 159 | 480 | |
| Vertrees | 1 | 51 | 0 | 75 | 148 | 275 | |
| Shawnee Hills | |||||||
| Frondorf | 1 | 33 | 3 | 62 | 40 | 139 | |
| Grenada 1 | 1 | 65 | 11 | 146 | 138 | 361 | |
| Newark | 1 | 73 | 1 | 155 | 118 | 348 | |
| Sadler | 1 | 20 | 0 | 111 | 134 | 266 | |
| Tilsit | 1 | 99 | 0 | 169 | 97 | 366 | |
Figure 1. Relationship between oxalate extractable iron and aluminum and P sorption behavior of 20 soils in Kentucky. Smax is the soil's maximum P retention capacity, and k is the soil's P sorption affinity. Soils with higher log Smax/k values have increased P retention capacity.
Forage Production Research
R. Spitaleri, J.C. Henning, N.L. Taylor, G.D. Lacefield, D.C. Ditsch, and G.L. Olson
Red clover is one of the primary renovation legumes for pasture in Kentucky. Kenland red clover is a release of the University of Kentucky Agricultural Experiment Station and is still marketed in Kentucky. However, most of the Kenland sold is uncertified. Because of confusion about the value of certification, farmers think that uncertified Kenland is an "improved" variety of red clover. Uncertified Kenland red clover is always cheaper than certified, and so most purchases are of the uncertified type.
Experiments were established in spring of 1998 and 2001 at the Robinson Forest Substation at Quicksand in eastern Kentucky to compare the yield of several varieties of red clover, including certified and uncertified Kenland red clover. Several common red clovers (designated by letters X, Y, Z, and A) were also included.
Certified Kenland outperformed uncertified Kenland in both the 1998 and 2001 seeding (Tables 1 and 2). Over three harvest seasons from the 1998 seeding, certified Kenland produced over 3 tons more dry matter yield per acre than uncertified (Table 1). In the year of seeding (the 2001 seeding), certified Kenland produced 1.5 tons more yield than uncertified (Table 2). Uncertified Kenland clover performed much more like common entries than the improved counterparts like Kenland, Kenstar, and others.
The value of certified Kenland red clover greatly exceeds the extra cost of the seed. The gross value of 3 tons of extra forage per acre can equal $240 per acre, which greatly exceeds the extra cost for the better seed (approximately $12 per acre at the time of seeding). Therefore, uncertified Kenland red clover is not a bargain, at any price.
| Table 1. Dry matter yields (tons/acre) of red clover varieties sown 13 April 1998 at Quicksand, Kentucky. | |||||||
| Variety | 1998 Total | 1999 Total | 2000 Harvests | 2000
Total |
3-yr. Total | ||
| May 5 | Jun 30 | ||||||
| Commercial Varieties--Available for Farm Use | |||||||
| Kenland, certified | 1.34 * | 6.55 * | 1.50 * | 1.19 * | 2.69 * | 10.59 * | |
| Kenstar | 1.24 * | 6.17 * | 1.60 * | 1.12 * | 2.71 * | 10.12 * | |
| Cinnamon | 1.10 | 6.09 | 1.22 | 1.04 | 2.26 | 9.45 | |
| Greenstar | 1.15 * | 6.02 | 1.18 | 1.05 * | 2.22 | 9.39 | |
| Solid | 1.06 | 5.96 | 0.89 | 0.91 | 1.80 | 8.82 | |
| Common Y | 0.87 | 5.48 | 0.49 | 0.70 | 1.19 | 7.53 | |
| Kenland, uncertified | 1.01 | 4.78 | 0.73 | 0.78 | 1.51 | 7.30 | |
| California Ladino | 0.95 | 3.99 | 1.36 * | 0.94 | 2.29 | 7.24 | |
| Regal Ladino | 0.99 | 3.91 | 1.30 | 0.98 | 2.28 | 7.18 | |
| Common X | 0.92 | 4.86 | 0.37 | 0.77 | 1.14 | 6.92 | |
| Common Z | 0.75 | 4.93 | 0.43 | 0.73 | 1.15 | 6.83 | |
| Mean of trial (not all varieties shown) | 1.05 | 5.51 | 1.04 | 0.94 | 1.99 | 8.55 | |
| CV, % | 13.14 | 6.46 | 25.83 | 11.54 | 17.15 | 6.84 | |
| LSD, 0.05 | 0.2 | 0.51 | 0.38 | 0.16 | 0.49 | 0.83 | |
| * | Not significantly different from the highest value in the column, based on the 0.05 LSD. | ||||||
| Table 2. Dry matter yields (tons/acre) of red clover varieties sown 29 March 2001 at Quicksand, Kentucky. | |||||
| Variety | 2001 Harvests | Total 2001 | |||
| Jul 3 | Aug 6 | Oct 10 | |||
| Commercial Varieties--Available for Farm Use | |||||
| Kenland certified | 1.86 | 2.13 | 2.18 | 6.17 * | |
| Sienna | 1.80 | 1.88 | 2.04 | 5.73 * | |
| Duration | 1.89 | 1.89 | 1.87 | 5.64 * | |
| Emarwan | 1.73 | 1.85 | 1.96 | 5.54 * | |
| Vesna (tetraploid) | 1.60 | 1.77 | 2.04 | 5.41 * | |
| Rojo Diablo | 1.73 | 1.75 | 1.74 | 5.22 | |
| Red Gold Plus | 1.60 | 1.82 | 1.74 | 5.16 | |
| RedlanGraze II | 1.63 | 1.69 | 1.67 | 4.99 | |
| Kenland uncertified | 1.51 | 1.52 | 1.60 | 4.63 | |
| Common A | 1.41 | 1.31 | 1.40 | 4.12 | |
| Mean of trial (not all varieties shown) | 1.67 | 1.81 | 1.81 | 5.29 | |
| CV,% | 10.75 | 12.21 | 17.58 | 11.27 | |
| LSD, 0.05 | 0.25 | 0.31 | 0.45 | 0.84 | |
| * | Not significantly different from the highest numerical value in the column, based on the 0.05 LSD. | ||||
R. Spitaleri, J.C. Henning, G.D. Lacefield, and T.D. Phillips
Kentucky's pasture and hay acres are largely cool-season species. Therefore, there is a natural decline in production in midsummer. This decline limits livestock production in many cases. A high-yielding, summer perennial grass would be beneficial to Kentucky livestock enterprises. Little is known about the performance of different varieties of the primary native warm-season grass species in Kentucky, which are switchgrass (SG), big bluestem (BB), indiangrass (IG), and eastern gamagrass (EG).
Small (5 by 15 feet) plots of switchgrass, big bluestem, indiangrass, and eastern gamagrass were established in the spring of 2000 by transplanting small plants raised in greenhouse float trays from seed or from sprigs. Plots were allowed to become established during the remainder of 2000. In 2001, plots were harvested for yield on July 6 and August 7 for all species but indiangrass, which was harvested only once on the second date. The date for approximate 50 percent heading as well as plant height at this stage was observed.
Ranking the species by overall dry matter yield, IG>EG>SG>BB (Table 1). However, IG was so late in maturity that it allowed only one harvest (August 7). The species earliest to mature were SG and EG, followed by BB and IG.
Varieties of native grasses are limited, and the overall supply of seed varies annually. The commercial varieties shown here appear to be adapted to Kentucky but will vary in yield potential (Table 1). These studies indicate that native grasses can contribute significantly to pasture and hay systems in Kentucky.
Several concerns remain about these species, the most notable being establishment. At the time of initiation of this project, no herbicides were labeled for the establishment of these grasses except for those applied to suppress the existing vegetation such as paraquat or glyphosate. This situation is changing, but it is likely that Kentucky farmers will never have many options for residual weed control for these grasses.
In addition, these materials are slow to germinate and emerge and are susceptible to weed competition during the seeding year. Therefore, producers should plan for cultural weed control options such as mowing or light grazing. Finally, these species must be rotationally grazed and allowed to rest in the fall to build up energy reserves to overwinter.
However, the yields of these species are high and come in midsummer to late summer when cool-season grasses are not productive. They can play a role in Kentucky hay and pasture systems provided that producers are prepared to manage these through the establishment phase and also will supply proper management for persistence.
| Table 1. Dry matter yield (tons/acre) and maturity measurements of native warm-season perennial grasses planted 18 July 2000 at Lexington, Kentucky. | |||||||
| Species | Variety | Maturity | |||||
| Harvests | Total | Date of 50% | Height (in.) | ||||
| Jul 6 | Aug 7 | 2001 | Heading | at Heading | |||
| Big bluestem | Pawnee | 3.43 | 1.4 | 4.83 | July 13 | 46 | |
| Kaw | 3.41 | 1.37 | 4.78 | July 10 | 53 | ||
| Rountree | 3.27 | 1.40 | 4.67 | July 13 | 48 | ||
| KYAG 9601* | 3.05 | 1.32 | 4.37 | July 20 | 42 | ||
| Mean | 4.66 | ||||||
| Eastern gamagrass | Meade Co.* | 3.45 | 4.46 | 7.91 | June 28 | 45 | |
| PMK 24 (Pete) | 2.56 | 3.82 | 6.38 | June 28 | 41 | ||
| Rider Mills Farm | 1.52 | 3.47 | 4.98 | July 1 | 33 | ||
| Mean | 6.42 | ||||||
| Indiangrass | NE54 | 7.12 | 7.12 | Aug 8 | 59 | ||
| Cheyenne | 6.44 | 6.44 | Aug 15 | 65 | |||
| Rumsey | 6.25 | 6.25 | Aug 18 | 64 | |||
| Osage | 6.24 | 6.24 | Aug 11 | 59 | |||
| Mean | 6.51 | ||||||
| Switchgrass | Alamo | 5.6 | 3.08 | 8.68 | July 5 | 51 | |
| Cave-In-Rock | 4.89 | 2.37 | 7.26 | June 28 | 46 | ||
| KYPV 9504* | 3.98 | 1.55 | 5.53 | July 2 | 44 | ||
| KYPV 9505* | 3.83 | 1.68 | 5.52 | July 2 | 35 | ||
| KYPV 9506* | 3.49 | 1.58 | 5.08 | July 1 | 35 | ||
| Trailblazer | 3.84 | 0.56 | 4.41 | July 1 | 41 | ||
| Mean | 6.08 | ||||||
| * | Indicates that the variety is an experimental or a collection and is not commercially available. | ||||||
R. Spitaleri, J.C. Henning, G.D. Lacefield, and T.D. Phillips
Recent mild winters in Kentucky have enabled trial seedings of annual ryegrass to provide significant amounts of fall and "winter" forage across the state. Much more forage is produced when this species is clear seeded following a summer annual or tobacco crop rather than when interseeded into overgrazed sod. However, some have had success with these sod interseedings as well. However, the yield on these fields comes later than in clear seedings.
A major question with annual ryegrasses is winterhardiness. Marshall is an older variety and has the reputation of being the most winterhardy. New varieties are being released faster than they can be tested for Kentucky performance. The University of Kentucky established its first annual ryegrass trial in several years in the fall of 1999. This trial (located in Lexington) provided four harvests in the mild winter and summer of 1999-2000. Two more annual ryegrass trials were seeded in 2000 (at Princeton and at the Western Kentucky University Farm near Bowling Green). Yields in the 2000-2001 growing season were between 3 and 4 tons of dry matter per acre with most coming in the first two spring harvests (Tables 1 and 2). These yields were half that observed from similar tests the previous year. No harvestable yield was achieved in the fall or winter of 2000-2001 with annual ryegrass. A clear prerequisite for success with annual ryegrasses is rainfall. This requirement is doubly important when ryegrass is seeded into sod.
| Table 1. Dry matter yields (tons/acre) for annual ryegrass varieties sown 22 September 2000 at Bowling Green, Kentucky. | |||||
| Variety | Harvests | Total Yield | |||
| April 6 | April 27 | June 11 | July 24 | ||
| Zorro | 1.18 | 1.46 | 0.82 | 0.41 | 3.88 |
| Marshall | 1.32 | 1.46 | 0.56 | 0.05 | 3.39 |
| Big Daddy | 1.19 | 1.29 | 0.58 | 0.04 | 3.09 |
| Floralina | 1.27 | 1.35 | 0.43 | 0.04 | 3.08 |
| Rio | 1.21 | 1.33 | 0.45 | 0.06 | 3.05 |
| Cis Florida | 1.07 | 1.26 | 0.57 | 0.07 | 2.97 |
| Fantastic | 1.35 | 1.07 | 0.42 | 0.03 | 2.87 |
| Common | 1.15 | 1.20 | 0.44 | 0.02 | 2.81 |
| Gulf | 1.10 | 1.01 | 0.43 | 0.03 | 2.56 |
| Spark | 1.01 | 0.90 | 0.52 | 0.10 | 2.53 |
| Mean | 1.18 | 1.23 | 0.52 | 0.08 | 3.02 |
| LSD, 0.05 | 0.23 | 0.13 | 0.17 | 0.08 | 0.39 |
| Percent of yield | 39% | 41% | 17% | 3% | 100% |
| Table 2. Dry matter yields (tons/acre) for annual ryegrass varieties sown 21 September 2000 at Princeton, Kentucky. | |||||
| Variety | Harvests | Total Yield | |||
| April 5 | April 26 | June 12 | July 17 | ||
| Zorro | 1.34 | 1.81 | 1.03 | 0.49 | 4.66 |
| Hercules | 1.05 | 1.51 | 0.81 | 0.42 | 3.80 |
| Avance | 1.03 | 1.50 | 0.83 | 0.40 | 3.76 |
| Marshall | 1.15 | 1.84 | 0.48 | 0.04 | 3.52 |
| Rio | 1.29 | 1.63 | 0.51 | 0.02 | 3.45 |
| Andy | 0.88 | 1.37 | 0.84 | 0.33 | 3.42 |
| Big Daddy | 0.93 | 1.54 | 0.60 | 0.03 | 3.10 |
| Fantastic | 1.31 | 1.36 | 0.38 | 0.05 | 3.09 |
| Common | 1.07 | 1.41 | 0.42 | 0.03 | 2.93 |
| Cis Florida | 0.66 | 1.53 | 0.58 | 0.05 | 2.82 |
| Gulf | 0.91 | 1.44 | 0.42 | 0.01 | 2.79 |
| Mean | 1.05 | 1.54 | 0.63 | 0.17 | 3.39 |
| LSD, 0.05 | 0.16 | 0.16 | 0.12 | 0.09 | 0.33 |
| Percent of yield | 31% | 45% | 19% | 5% | 100% |
| Average percent across both studies | 35% | 43% | 18% | 4% | 100% |
R. Spitaleri, J.C. Henning, G.D. Lacefield, and T.D. Phillips
Since the discovery of the endophyte in tall fescue, scientists have hoped for a tall fescue plant with the fungus that would give all the good agronomic characteristics of tall fescue but not cause the animal performance problems.
A unique strain of the endophyte, termed a "novel" endophyte, was identified that did not cause the fescue plant to produce the animal toxins of the "traditional" E+ tall fescue. This first novel strain was identified by Ag Research scientists in New Zealand. The objective was to allow the friendly endophyte to give the tall fescue plant the toughness and persistence of toxic tall fescue and the animal performance of nontoxic tall fescue.
To obtain this unusual combination, Dr. Joe Bouton at the University of Georgia and Dr. Gary Latch of Ag Research in New Zealand reinfected a reportedly nontoxic fungal endophyte into the endophyte-free Jesup and Georgia 5 varieties.
The first commercial combination was named Max Q, which was tested at the University of Kentucky as Jesup 542. This novel endophyte material has been in yield and grazing trials since 1999. Yields of Max Q (Jesup 542) have been comparable to Jesup without the endophyte (Table 1) and to other commercial endophyte-free tall fescues (Table 2). Grazing tolerance data at Lexington have shown that Max Q is slightly more tolerant than Jesup without the endophyte after three years of abusive grazing (data not shown).
Therefore, Max Q appears to be adapted to and productive in Kentucky, at least under the conditions of these trials. Its persistence in the grazing tolerance trials is encouraging and is consistent with data in other states that find Max Q to be more persistent under grazing stress than other endophyte-free varieties. Since there are endophyte-free tall fescues that persist as well as Jesup 542 (Max Q) in the Lexington trials (data not shown), more work is needed to see if the novel endophyte is required for producers to have a persistent tall fescue that also supports good livestock gains.
In the near term, Max Q appears to be a sound option for those producers who have fields that are free of endophyte-infected tall fescue at present and can manage them to prevent contamination from seed of tall fescue plants infected with the "wild" or toxic endophyte.
| Table 1. Dry matter yields (tons/acre) of tall fescue varieties and a perennial ryegrass (PRG) sown 12 October 1998 at Princeton, Kentucky. | ||||||||
| Variety | Maturity1 May 15, 2000 | 1999 Total | 2000 Harvests | 2000 Total | 2-yr. Total | |||
| May 15 | Jun 22 | Jul 21 | ||||||
| Commercial Varieties--Available for Farm Use | ||||||||
| KY 31+ 2 | 61.50 | 4.89 * | 3.61 * | 0.95 * | 0.97 * | 5.53 * | 10.43 * | |
| Jesup - 2 | 66.75 * | 4.23 | 3.16 | 0.78 | 0.85 | 4.78 | 9.01 | |
| Select | 64.00 | 3.88 | 3.33 * | 0.90 * | 0.84 | 5.06 * | 8.95 | |
| Vulcan | 58.25 | 3.36 | 3.01 | 0.93 * | 0.98 * | 4.92 | 8.28 | |
| TF 33 | 61.00 | 2.59 | 1.58 | 0.93 * | 0.88 * | 3.38 | 5.97 | |
| Experimental Varieties--Not Available for Farm Use | ||||||||
| KY31- 2 | 65.00 * | 4.78 * | 3.34 * | 0.86 | 0.93 * | 5.12 * | 9.90 * | |
| Jesup EI | 66.25 * | 4.63 * | 3.15 | 0.97 * | 1.09 * | 5.21 * | 9.84 * | |
| Jesup 542 (Max Q) | 64.50 * | 4.19 | 2.94 | 0.81 | 0.88 * | 4.63 | 8.82 | |
| Mean of trial
(not all varieties shown) |
63.07 | 4.12 | 3.21 | 0.89 | 0.90 | 5.02 | 9.14 | |
| CV, % | 2.94 | 11.12 | 9.64 | 17.17 | 22.97 | 7.42 | 8.13 | |
| LSD, 0.05 | 2.65 | 0.66 | 0.44 | 0.22 | 0.30 | 0.53 | 1.06 | |
| * | Not significantly different from the highest value for tall fescue entries in the column, based on the 0.05 LSD. | |||||||
| 1 | Maturity rating scale: 37 = flag leaf emergence, 45 = boot
swollen, 50 = beginning of inflorescence,
58 = complete emergence of inflorescence, 62 = beginning of pollen shedding. |
|||||||
| 2 | "+" indicates variety is endophyte infected; "-" indicates variety is endophyte free. | |||||||
| Table 2. Dry matter yields (tons/acre) of tall fescue and festulolium (FL) varieties sown 23 August 1999 at Lexington, Kentucky. | ||||||||
| Variety | 2000 Harvests | 2000 Total | ||||||
| May 9 | Jun 14 | Jul 27 | Aug 28 | Oct 18 | Nov 24 | |||
| Commercial Varieties--Available for Farm Use | ||||||||
| Duo (FL) | 5.49 * | 1.87 * | 1.29 | 0.93 | 0.94 | 0.52 | 11.04 * | |
| Atlas | 2.96 | 1.49 * | 1.92 * | 1.53 * | 1.63 * | 0.77 * | 10.30 * | |
| Select | 3.62 | 1.54 * | 1.85 * | 1.25 | 1.26 | 0.52 | 10.03 * | |
| Ky31+ 1 | 3.20 | 1.45 | 1.81 * | 1.31 * | 1.33 | 0.50 | 9.60 * | |
| Fuego | 3.29 | 1.41 | 1.41 | 1.25 | 1.34 | 0.63 * | 9.33 * | |
| Bar 9 TMPO | 2.97 | 1.34 | 1.58 | 1.18 | 1.45 * | 0.63 * | 9.15 * | |
| Seine | 2.57 | 1.23 | 1.71 | 1.27 | 1.52 * | 0.63 * | 8.93 * | |
| Johnstone | 3.09 | 1.38 | 1.66 | 1.19 | 1.13 | 0.44 | 8.89 | |
| Maximize | 2.64 | 1.28 | 1.70 | 1.28 | 1.39 | 0.59 | 8.88 | |
| DLF-B | 3.00 | 1.26 | 1.47 | 1.23 | 1.32 | 0.58 | 8.86 | |
| Experimental Varieties--Not Available for Farm Use | ||||||||
| Jesup 542 (Max Q) | 3.01 | 1.25 | 1.80 * | 1.36 * | 1.29 | 0.57 | 9.29 * | |
| Ky31- 1 | 1.17 | 1.45 | 1.91 * | 1.50 * | 1.50 * | 0.56 | 8.09 | |
| Mean of trial (not all varieties shown) | 3.29 | 1.47 | 1.62 | 1.27 | 1.31 | 0.55 | 9.50 | |
| CV, % | 33.99 | 19.01 | 16.22 | 12.42 | 15.75 | 18.23 | 15.85 | |
| LSD, 0.05 | 1.58 | 0.39 | 0.37 | 0.22 | 0.29 | 0.14 | 2.12 | |
| * | Not significantly different from the highest value in the column, based on the 0.05 LSD. | |||||||
| 1 | "+" indicates variety is endophyte infected; "-" indicates variety is endophyte free. | |||||||
D.C. Ditsch, J. Henning, and J.W. Turner
Bermudagrass (Cynodon dactylon) is a warm-season perennial that produces ample forage during the summer when cool-season grass production is low. Following the drought of 1999, considerable interest in the use of bermudagrass in Kentucky emerged along with several new varieties that claimed to be high yielding and high quality. Therefore, a field study to evaluate several new sprigged and seeded bermudagrass varieties was initiated in Morgan County, Kentucky.
This study was conducted on a well-drained, deep silt loam soil formed from alluvium. The plot area was conventionally prepared for sprigging of Quickstand and World Feeder at the rate of 20 bu/ac and seeding of Wrangler and CD90160 at the rate of 10 lb/ac. Fertilization during the establishment year followed World Feeder recommendations. Sprigging and seeding date was April 14, 2000. Dry matter yield was measured by mechanically harvesting the center section of each plot and correcting for moisture content. Nutritive quality was determined by near infrared reflectance (NIR) (data not presented). During the spring of 2001, green-up and winter injury ratings were taken.
Only two harvests were taken during the establishment year. The highest yield variety was CD90160 although it was not statistically different from Quickstand (Table 1). Spring ratings, following a moderately hard winter, resulted in total winter kill of CD90160. Quickstand and Wrangler had the highest winter survival. During the 2001 growing season, there was not a significant difference in dry matter yield between the remaining three varieties, which averaged 8.1 ton/ac.
In conclusion, bermudgrass can be a valuable forage crop for livestock producers in Kentucky. However, the results from this study indicate that variety selection should be based on research conducted under Kentucky's growing environment.
| Table 1. 2000/2001 Morgan County bermudagrass variety trial. | |||||
| Variety | 8/21/00 Harvest* | 10/13/00 Harvest | Total DM | ||
| lb/ac | |||||
| 2000 | Quickstand | 2825 b*** | 1359 b | 5198 ab | |
| World Feeder | 2652 b | 1413b | 4065 b | ||
| Wrangler** | 2825 b | 675 c | 3500 b | ||
| CD90160** | 4550 a | 2142 a | 6693 a | ||
| Variety | 6/20/01 Harvest | 7/31/01
Harvest |
10/9/01 Harvest | Total DM | |
| lb/ac | |||||
| 2001 | Quickstand | 4141 a | 5295 a | 7509 a | 17580 a |
| World Feeder | 3054 a | 5720 a | 5718 b | 14490 a | |
| Wrangler | 4735 a | 6043 a | 5896 b | 16640 a | |
| CD90160 | winter killed - no measurable bermudagrass harvest | ||||
| Green-Up and Winter Injury Rating | |||||
| Variety | % Winter Survival | (0 - 9 scale)**** | |||
| Vigor | Color | ||||
| Quickstand | 81 a | 5 b | 4 b | ||
| World Feeder | 53 b | 4 b | 5 b | ||
| Wrangler | 78 a | 7 a | 8 a | ||
| CD90160 | 0 c | 0 c | 0 c | ||
| * | 100 lb N per acre applied after each harvest in the form of ammonium nitrate. | ||||
| ** | Seeded varieties. Seeding rate: 10 lb/ac. Sprigging rate: 20 bu/ac. Seeding and sprigging date: 4/14/00. | ||||
| *** | Values within a column followed by the same letter are not significantly different at the 95% level of probability. | ||||
| **** | (0 = worst, 9 = best). | ||||
M. Rasnake
Nine bermudagrass cultivars that were selected for potential adaptability to Kentucky climatic conditions were established at Princeton in May 1998. Sprigs were placed in two rows that were spaced 4 ft. apart in 10-ft.-by-20-ft. plots. Two replications were established in a randomized complete block design. Growing conditions were good during the summer of 1998, and all cultivars developed excellent stands. The plots were harvested twice in 1998 and four times each year thereafter. Fertilizer was applied according to soil test results. Nitrogen was applied at the rate of 300 pounds per acre split into three separate application times.
Yields were measured in tons per acre at the hay equivalent moisture of 12.5 percent. The growth of Quickstand shown in the following table was best in the first two years, although not significantly different from Tifton 44. Tifton 44 has remained at the top throughout the study. However, the experimental cultivars 74 x 12-6 and 74 x 21-6 were equal to Tifton 44 in 2000 and 2001, which were excellent growing seasons. Stands were visually evaluated in the fall of 2001 since some of the cultivars had shown injury from the previous winter. Stand ratings shown in the table indicate that Tifton 44, Quickstand, 74 x 12-6, and 74 x 21-6 were better able to survive Kentucky winters than the other five cultivars. Both Russell and Midland were severely damaged.
The experimental strain 74 x 21-6 was released as "Midland 99" in 1999. Limited supplies of sprigs should be available this year. The 74 x 12-6 has recently been released as "Ozarka" through the University of Missouri. A limited supply of Ozarka foundation sprigs should be distributed this year.
These new cultivars will add significantly to the selection of cold hardy bermudagrasses available to growers in Kentucky and other states in the northern range of bermudagrass adaptability.
| Bermudagrass cultivar yields, Princeton, Kentucky. | ||||||
| Cultivars | 1998 | 1999 | 2000 | 2001 | Stands (10/01) | |
| Tons/Ac at 12.5% Moisture | ||||||
| Tifton 44 | 2.1 ab* | 7.7 ab | 8.4 a | 8.4 ab | Excellent | |
| Quickstand | 2.7 a | 8.5 a | 7.0 abc | 7.8 abc | Excellent | |
| 74 x 12-6 | 1.7 abc | 7.1 bc | 7.7 ab | 9.2 a | Very Good | |
| 74 x 21-6 | 2.4 a | 6.6 bc | 6.9 abc | 8.8 a | Very Good | |
| Hardie | 2.1 abc | 6.3 c | 6.6 bc | 8.0 ab | Fair | |
| Russell | 2.2 a | 6.1 c | 5.9 c | 5.8 c | Poor | |
| 16 x 66 | 1.1 bc | 6.1 c | 6.6 bc | 7.9 abc | Good | |
| 19 x 16 | 1.0 c | 6.1 c | 6.4 bc | 7.8 abc | Good | |
| Midland | 1.1 bc | 6.3 c | 5.9 c | 6.4 bc | Poor | |
| * | Means within a column followed by the same letter are not significantly different. a = 0.05. | |||||
| Numbered cultivars (e.g., 16 x 66) are experimentals from Oklahoma and Kansas. | ||||||
T.D. Phillips, P. Wu, and P.S. Shine
The tall fescue/forage grass breeding project has been active for the past decade, concentrating on endophyte-free tall fescue. We have continued work with wide hybrids among ryegrasses and other relatives of tall fescue, but most of our efforts have focused on variety development. To date, we have produced more than 100 experimental populations of tall fescue, ryegrass, orchardgrass, timothy, Kentucky bluegrass, and smooth bromegrass. More than 80 percent of these populations are endophyte-free tall fescue. We entered six experimental tall fescue populations and several orchardgrass and timothy lines in the official University of Kentucky Forage Variety Testing Program over the past several years. We will be releasing two new tall fescue varieties, as well as an orchardgrass and timothy during the coming year. Our new orchardgrass has been named `Prairie' and will be marketed by Turner Seed. The other new cultivars will take a few seasons to become available for Kentucky's forage producers.
We anticipate introducing strains of nontoxic endophyte into our most promising tall fescue populations, in partnership with Ag Research and Pennington. These endophytes allow the grass to persist and survive stress better than endophyte-free tall fescue but do not cause the serious animal health problems associated with the normal (toxic) endophyte strain in Kentucky 31 and other infected cultivars.
During May 2001, more than 3,500 wide hybrid genotypes were established in the field for evaluation of agronomic performance and subsequent vernalization. These plants represent a range of wide hybrids between ryegrass and tall fescue, meadow fescue x tall fescue, and other crosses among relatives of tall fescue. Methods for restoring fertility to these sterile F1 hybrids are being studied. Preliminary results from the greenhouse in April 2002 have revealed that colchicine treatment succeeded in doubling chromosome number much more frequently than treatment with oryzalin. Hybrids and their derivatives will be used to introgress favorable genes into forage-type tall fescue.
In September 2001, four yield trials were established to measure yield potential and agronomic performance of 65 experimental synthetics of tall fescue, ryegrass, and festulolium, along with eight commercial check cultivars. Plots will be harvested and evaluated for two growing seasons at Lexington and Princeton, Kentucky. Additional yield trials will be established for orchardgrass, timothy, and miscellaneous cool-season forage grass species in the fall of 2002. Based on these early yield trials, we will enter six or more of our best experimentals in the University of Kentucky Forage Variety Testing Program to obtain sufficient information to decide if these should be released as new cultivars. We need a minimum of four production location-years to be able to release new, improved varieties of forage grasses.
Weed Management Research
C.L. Brommer and W.W. Witt
Over the last few decades, conservation tillage practices have increased in row crops in Kentucky where no-tillage now accounts for more than 50 percent of the total row crop acreage. These conservation tillage practices have many benefits; however, there are problems associated with no-till fields in Kentucky. These problems can include a higher population of perennial weeds. Perennial weeds can increase primarily because of the lack of pre-plant tillage to disrupt the root systems of broadleaf perennial weeds.
Extension personnel and producers have noticed that perennial weed communities establish in similar areas in many different fields. These areas may include low or bottom portions of fields and places where water would be more available. Producers also face the problem of having to manage larger farms, which decreases the amount of time a producer has to scout fields and make herbicide applications. A system that would decrease scouting time or that would predict weed occurrence in a portion of a field would be beneficial. With these observations in mind, a study was established to correlate the terrain attributes of no-till fields with occurrence of perennial weed colonies.
A cooperator field was located in Calloway County for the study. The field selected had been in no-till production for several years and was currently planted to corn. Populations of hemp dogbane, trumpetcreeper, and hedge bindweed were located and their positions documented using a Starlink® GPS backpack unit. These weed colonies were located six weeks after corn planting. Colonies were identified by walking through the entire field in 10- to 20-meter passes in a north to south orientation. Colonies of these weed species were used if the colony contained at least four plants within a 5-meter radius. Identified colonies were then marked by walking around the diameter of the colony with the GPS unit, and the approximate center of the colony was also marked.
Digital Elevation Map Creation. A Digital Elevation Map (DEM) was used to calculate the terrain attributes. The DEM was produced by digitizing a previously created landform elevation map, at a 10-meter resolution, using ARCINFO®. The landform survey map was created using survey equipment, with measurements taken on a north-south oriented transect of the entire field. A universal kriging program was used to interpolate the approximately 1,500 irregular points to a regular grid of 1,978 points (43 by 46).
Terrain Analysis and Stepwise Regression. The terrain analysis was conducted by using the DEM and ARCINFO to calculate terrain attributes. Primary terrain attributes were extracted from the farm-scale grids using the sample function in ARCINFO. For calculation of secondary terrain attributes, data were collected from the previous calculation and analyzed using Microsoft Excel®. Statistical analysis was conducted using a split-sample method to generate and validate using multivariate linear models to describe the variability of the perennial plant locations, by species, as a function of the terrain attributes.
The occurrence of hemp dogbane in this field was not correlated with any terrain attribute. There was a correlation between the location of trumpetcreeper colonies and the catchment area and the slope index. Hedge bindweed locations correlated with the catchment area and the slope index. The catchment area and slope index values are indicators of water runoff in the field and the topography of the field.
Catchment area is defined by area per unit width orthogonal to the flow direction. When calculated from DEM data, it is the drainage area divided by the grid-cell size. Definition of the slope index, also known as the slope gradient, is described in terms of percent slope. Both of these hydrological characteristics are good indications of the potential amount of water that may be flowing through a plant colony. The presence of trumpetcreeper and field bindweed in these areas suggests that these species may have a need for this environmental condition or that they simply outlast the other species, thus creating a niche for their development. There is also the potential that waterborne nutrients or reproductive structures were carried to these portions of the field. The map at Figure 1 indicates how the occurrence of trumpetcreeper varies with elevation and that most of the colonies occur in lower portions of the field (catchment area).
This experiment revealed that trumpetcreeper and hedge bindweed occurred in areas where water flowed or collected in the field. If these results are confirmed in other fields, then the difficult task of locating weed colonies in growing corn and soybean can be simplified. Growers can utilize digital elevation maps of their fields to identify specific areas of the field to scout for perennial weeds. This process speeds up scouting of fields for weeds since the entire field does not need to be scouted and herbicides can be targeted to specific areas of the field to reduce the cost of controlling these perennial weeds.
Figure 1. Trumpetcreeper locations overlaid on an elevation contour map (elevation is in feet). Filled circles represent trumpetcreeper colonies.
J.R. Martin, W.W. Witt, and D.L.Call
Studies were conducted between 1999 and 2001 as a part of an ongoing investigation to evaluate the potential for certain wheat herbicides to persist long enough in soil to cause injury to double-cropped soybeans. Herbicides in these experiments included Ally (metsulfuron), Everest (flucarbazone), Maverick (sulfosulfuron), and Peak (prosulfuron). Soybeans, with or without the STS trait, were planted after wheat harvest to determine if this herbicide-resistant technology would help limit injury from wheat herbicides that persist in soil.
Ally and Peak, applied in the spring of 2000, appeared to stunt soybeans without the STS trait; however, the effects of these herbicides on the yield of double-cropped soybeans were inconclusive.
Maverick or Peak applied to wheat in the spring of 2001 caused 35 percent injury to non-STS double-cropped soybeans. This injury was expressed as stunted soybeans. However, very little injury (i.e., < 3 percent) occurred with the STS variety. Soybean plants stunted by Peak eventually recovered; however, stunting of the non-STS soybeans from Maverick was still evident when soybeans were harvested. The injury that was observed with these herbicides did not limit the yield of either soybean variety; however, there was a slight but nonsignificant reduction in yield of the non-STS variety where Maverick or Peak was applied to wheat in 2001.
This research demonstrated the importance of following label restrictions regarding the planting of rotational crops. Certain sulfonylurea wheat herbicides were capable of persisting in the soil long enough to cause injury to double-cropped soybeans in Kentucky; however, this injury was less of a risk where STS soybeans were planted.
C.L. Brommer, C.H. Slack, and W.W. Witt
Accent and Beacon have been labeled for use in corn since 1989. These herbicides have provided excellent control of johnsongrass and foxtail species. Corn injury from these herbicides has been noted in certain corn varieties, and this injury was the result of late application, antagonism from interactions with in-furrow insecticides, and environmental influences. Injury symptoms include pinched ears, leaf chlorosis, plant stunting, and rolled leaves. Previous research focused on visual injury and plot yields. The yield of corn from a plot does not necessarily show if there is a physiological impact to corn from herbicide treatment. Often, yield components can indicate crop injury where plot yield alone does not. Many hybrids are released each year including transgenic hybrids for glyphosate tolerance. Producers may use herbicides other than glyphosate in glyphosate-tolerant corn. Data are needed to determine the impact of Accent, Beacon, and other sulfonylurea herbicides on yield and yield components in glyphosate-tolerant corn. Currently, there are no published studies with glyphosate-tolerant corn and sulfonylurea herbicides.
A study was conducted on the Spindletop Research Farm in 2001. The glyphosate-tolerant field corn DeKalb 626RR was planted May 23 and emerged on May 30. A conventional tillage regime was used with 30-inch row spacing with a seeding density of 25,000 seeds/ac. The following treatments were made: Roundup Ultra at 1.0 qt/ac, Accent SP at 0.67 oz/ac, Beacon 75DF at 0.76 oz/ac, Exceed 57 DF at 1 oz/ac, and a mixture of Accent SP at 0.33 oz/ac plus Beacon at 0.38 oz/ac. Each treatment was applied to either the V3, V6, or V9 growth stage of corn. All herbicide treatments contained the recommended adjuvant and were applied at 25 gallons per acre. Data on visual injury of corn and solar penetration through the canopy were collected two and four weeks after treatment. Harvest data included plot plant population, plot yield, seed weight, seed number per plot, and seed number per ear. The environmental conditions at Lexington were above average for the season. Timely rainfalls and average temperatures occurred from the V3 stage through harvest.
Treatments of Accent, Beacon, Exceed, or Roundup Ultra made at the V3, V6, or V9 growth stage did not reduce corn yield. The mixture of Accent plus Beacon reduced corn yield when applied at the V3 stage compared to treatment at the V6 or V9 stage and was lower than the nontreated control.
Seed number can be considered the best indicator of yield in a plot as well as for stress situations that directly correspond to the corn life cycle when seed numbers were determined. The expectation is that, as seed number was reduced, seed weight will increase to offset the reduced number of seed. Yield will not fall unless the number of seeds drops below a point where the seed weight can no longer offset the loss. No difference in seeds per square yard was found within the Roundup Ultra, Accent, Beacon, or Exceed treatments made to any growth stage of corn. The V3 treatment of Exceed was significantly lower than either the V6 or the V9 Exceed treatment, and this was similar to the yield data discussed above.
Again, no seed weight differences within herbicide and treatment stage were found except for Exceed treatment at V6 and the Accent plus Beacon mixture at V9. These treatments had seed weights significantly lower than Beacon applied at V9 and Exceed applied at V9.
The number of seeds per ear was not different for any herbicide or growth stage except for the Exceed treatment at V3.
A.T. Lee and W.W. Witt
Simazine (Princep) applied to soybean stubble in the fall before no-till corn production is a relatively new weed management practice in Kentucky. Fall-applied herbicides benefit applicators because they shift some of the workload from the spring to the fall. The producer's primary expectation from fall-applied simazine is to control cool-season weeds such as henbit, deadnettle, chickweed, and marestail. Controlling cool-season weed species may provide warmer spring soil temperatures and rapid surface dry-down by enabling more direct solar radiation (sunlight) and airflow (wind) to reach the soil surface. In addition, controlling cool-season weeds may reduce early season water stress by conserving soil moisture in the germination zone.
Information available concerning fall-applied simazine, or other triazine herbicides, in Kentucky is limited, and many of the previous studies on early preplant treatments have conflicting results. Areas with consistently cold, dry winters generally see better performance because of slower herbicide degradation. Growers in Kentucky need to be aware of fall-applied herbicide persistence and performance relevant to their location.
Simazine (Princep) and atrazine (AAtrex and other product names) were evaluated in this research. Both herbicides are similar in chemical structure and use and have been on the market for more than 30 years. The primary difference between the two is that Princep is generally more soil persistent but has less foliar activity than AAtrex. Princep provides greater control of annual grasses, but AAtrex provides more overall control of broadleaves. Growers and herbicide applicators are familiar and comfortable using both products.
There were three main objectives of this research. The first was to determine the length of fall-applied Princep and fall-applied AAtrex persistence in Kentucky soils. The second objective was to examine control of cool-season weeds from Princep and AAtrex applied in the fall. Finally, the third objective was to identify the performance level and potential advantages a Kentucky corn producer should expect from Princep or AAtrex applied in the fall.
Field studies were conducted from November 2000 through October 2001 to determine herbicide persistence and efficacy of fall-applied AAtrex and Princep. A nine-treatment study, comprised of three fall-applied herbicide options followed by three spring-applied herbicide options, was replicated at three climatically and topographically diverse regions in Kentucky (Lexington, Princeton, and Bowling Green). AAtrex 4L at 1.5 qt/ac, Princep 4L at 1.5 qt/ac, and no herbicide were the three fall-applied herbicide treatments. Spring-applied herbicide treatments were Bicep II Magnum at 2 qt/ac, Bicep II Magnum at 2 qt/ac plus Touchdown IQ at 1 qt/ac, and no herbicide applied. Herbicide concentration in the soil, visual efficacy ratings, surface soil temperature, and corn seed yield were used to compare differences among treatments. Soil samples were collected at 30-day intervals (January through May) and analyzed for AAtrex, Princep, and total triazine concentration. February, March, April, and May visual ratings were collected on a percent control basis for cool-season weeds. Surface soil temperatures at a depth of 2 inches were taken at three-hour intervals during March and April. Plots were harvested at the Princeton and Lexington locations in October with a two-row plot combine.
Persistence (Table 1). The half-life of Princep in the soil ranged from 33 to 43 days and from 34 to 40 days for AAtrex. Previous research at the University of Kentucky has shown the half-life of spring-applied Princep and AAtrex in the soil to be approximately 15 days. The longer persistence of these herbicides applied in the fall was attributed to the cooler soil temperatures that existed in December, January, and February that slowed herbicide degradation processes.
Weed Control (Table 2). Henbit control at the Princeton location in February with fall-applied AAtrex was 95 percent and statistically greater than Princep at 83 percent. Both herbicides gave up to 95 percent control of henbit in March and April, but neither herbicide controlled nor suppressed summer annual weed populations (data not presented). Wild garlic control with AAtrex was statistically greater than with Princep in February (95 days after treatment [DAT]) and December 2001 (1 year after treatment [YAT]). Wild garlic control ranged from 51 percent to 82 percent in March and April but was not different among treatments within each month.
Soil Temperature at a Depth of 2 Inches (Figure 1). Soil temperatures ranged from 32° to 84°F. The Princep treatment provided excellent control of the cool-season weeds that resulted in more daily soil temperature fluctuation (compared to the untreated check). Daily high soil temperatures were a result of more solar radiation reaching the soil surface in the Princep treated plots; however, the daily low soil temperatures were cooler as a result of this treatment. Although fluctuations in soil temperature were greater in the Princep treatment, the soil temperature was sufficiently warmer to allow for slightly earlier planting of corn.
Seed Yield. Fall-applied Princep or AAtrex did not statistically increase corn seed yield when spring-applied Bicep II Magnum was used (data not presented).
In conclusion, fall-applied Princep and AAtrex half-life in the soil ranged from 33 to 43 days. Fall-applied Princep and AAtrex were both effective options for henbit control, but AAtrex offered greater control of wild garlic 95 DAT and 1 YAT than did Princep. Henbit control resulted in warmer daily soil temperatures but more variability during the diurnal cycle. When fall-applied Princep and AAtrex were integrated with a traditional spring-applied herbicide program, no statistical yield difference was observed. However, fall-applied Princep and AAtrex offered soil temperature and cosmetic advantages that may be beneficial to Kentucky corn producers.
Princep is currently registered for fall treatments in Kentucky, but AAtrex is not registered. Corn producers should practice good land stewardship when using Princep in the fall. Elimination of cool-season vegetation can increase soil erosion and therefore is not recommended for highly erodible areas. Applicators should follow label instructions while being cautious of ground and surface water restrictions. To ensure fall-applied Princep performance, growers should maintain soil pH levels. Growers should remain conscious of cool-season and early warm-season weed populations by routinely scouting fields to determine if a burndown herbicide is needed before corn planting. It should also be noted that Princep applied in the fall limits spring planting options. Therefore, corn planting should be prioritized so fields treated with Princep are the first ones to be planted.
This project was partially funded by the Kentucky Corn Growers Association and supported by the University of Kentucky Regulatory Services. Sincere appreciation is expressed to both contributors.
* All herbicides mentioned are trademarks of their manufacturers.
| Table 1. Princep (simazine) and AAtrex (atrazine) dissipation at Princeton, Lexington, and Bowling Green, Kentucky. a | |||||
| Location | Herbicide | Half-Life (days) | Dissipation Rate (k) | Coefficient of Determination (r2) | |
| Princeton | AAtrex | 34 | -0.020 | 0.96 | |
| Princep | 36 | -0.019 | 0.98 | ||
| Lexington | AAtrex | 40 | -0.017 | 0.95 | |
| Princep | 43 | -0.016 | 1.00 | ||
| Bowling Green | AAtrex | 40 | -0.017 | 0.62 | |
| Princep | 33 | -0.021 | 0.78 | ||
| a | Based on January through March, 2001 concentrations of atrazine and simazine that was applied November and December, 2000. | ||||
need an alpha for this table
| Table 2. Cool-season weed control provided by Princep and AAtrex applied 11/17/00 (Princeton), 11/20/00 (Lexington), and 12/18/00 (Bowling Green). | ||||||||||
| Location | Treatment | Control of Weed Species a | ||||||||
| Henbit Control | Wild Garlic Control | |||||||||
| February | March | April | February | March | April | December | ||||
| % | ||||||||||
| Princeton
|
Princep | 83 b | 95 a | 95a | 21 b | 51 a | 68 a | 10 b | ||
| AAtrex | 95 a | 95 a | 95a | 57 a | 70 a | 82 a | 65 a | |||
| Lexington
|
Princep | 96 a | 96 a | |||||||
| AAtrex | 96 a | 96 a | ||||||||
| Bowling Green | Princep | 51 a | 91 a | 93 a | ||||||
| AAtrex | 51 a | 93 a | 93 a | |||||||
| a | Means within a column and location followed by the same letter are not significantly different according to Fisher's protected LSD test (a = 0.05). | |||||||||
Figure 1. Soil temperature at a depth of 2 inches as affected by fall-applied Princep (March 22 to April 24, 2001) at Princeton, Kentucky.
M.W. Marshall, J.D. Green, D. Ditsch, and W. Turner
The grazing quality of a grass pasture can be substantially lowered by the presence of perennial broadleaves, such as tall ironweed (Vernonia altissima Nutt.). Selective grazing due to differential palatability of troublesome broadleaf weeds tends to increase the populations of these weeds over time. In addition, lack of good and timely management practices such as proper soil fertility, using good grazing practices, mowing at the prescribed weed growth stage, and allowing weed seedlings to become established, can also increase the prominence of these weeds over time. Periodic pasture renovation is an important step in maintaining a proper forage stand. In addition, removal of perennial broadleaves, such as tall ironweed, can greatly improve the quality of a grazed pasture.
The objectives of this study were to evaluate tall ironweed control in a grass pasture with herbicide treatments applied in the fall and to evaluate the quantity of the forage produced under various treatments.
Field experiments were conducted at the University of Kentucky Robinson Research Station near Quicksand, Kentucky, in 2000 and 2001 to evaluate and compare tall ironweed control using broadleaf herbicides labeled for grass pastures. The experimental design was a split-plot with the main plot being legume-seeded in the early spring and no-legume seeded. Subplots consisted of the herbicide treatments with individual plot sizes 10 by 30 feet. Herbicide treatments were applied September 5, 2000, when regrowth of tall ironweed reached approximately 24 inches in height after mowing the entire experimental site on July 27, 2000. Herbicide products evaluated are shown in Table 1. Approximately six months after herbicide treatment, red clover was seeded on March 1, 2001. Tall ironweed visual control and density counts were taken on the following dates: May 17, July 12, and September 21, 2001. In addition, total forage biomass was collected on the following dates: May 17, July 25, and September 21, 2001. The four subsamples were separated into grass, tall ironweed, and other plant species.
Crossbow at 2 qt/ac and Redeem R&P at 1.5 pt/ac plus 2,4-D at 2 pt/ac provided greater than 90 percent visual control the following year after treatment (Table 2). Redeem R&P at 1.5 pt/ac and Redeem R&P at 2 pt/ac also provided acceptable visual control (> 80 percent) the year following treatment. Initially, Banvel provided good control in the spring (May 17); however, visual control decreased to 70 percent in midsummer and dropped to 50 percent one year after treatment.
The untreated check indicated that tall ironweed population nearly doubled the following year (Table 2). Treatments with Crossbow at 2 qt/ac, Redeem R&P at 1.5 pt/ac, Redeem R&P at 2 pt/ac, and Redeem R&P at 1.5 pt/ac plus 2,4-D at 2 pt/ac showed a few tall ironweed plants present in the areas treated by midsummer (July 12), but overall the level of control achieved was good to excellent. The Banvel treatment initially suppressed tall ironweed populations (May 17); however, populations increased rapidly throughout the summer (July 12).
The highest forage yield at each harvest date was obtained in the untreated check plots, which consisted of the total forage yield of desirable forage grasses plus tall ironweed (Table 3). Differences among herbicide treatments were not significant with respect to forage yield, except on May 17, 2001 (Table 3). Compared to the untreated check, biomass yield of tall ironweed was lower for all herbicide treatments. Among the herbicide treatments, tall ironweed biomass was the highest with the Banvel treatment, which supports the control and population data.
Tall ironweed populations were reduced with the use of a fall-applied herbicide; however, the use of triclopyr-containing treatments (Redeem R&P and Crossbow) showed the greatest suppression the following year. Herbicide treatments resulted in a slight decrease in total forage yield since fewer tall ironweed plants were found in treatment plots. The use of herbicide is only part of an integrated program, which includes mowing, proper fertility levels, and a good grazing program. Reseeding is an important step in conjunction with herbicide applications because new weeds will emerge in bare areas left by controlled weeds.
| Table 1. Herbicide treatments applied 5 September, 2000. | |||
| Treatment1 | Rate/Ac | Active Ingredient(s) | |
| Crossbow | 2 qt | triclopyr + 2,4-D | |
| Redeem R&P2 | 1.5 pt | triclopyr + clopyralid | |
| Redeem R&P2 | 2 pt | triclopyr + clopyralid | |
| Redeem R&P2 + 2,4-D | 1.5 pt + 2 pt | triclopyr + clopyralid + 2,4-D | |
| Banvel | 2 pt | dicamba | |
| 1 | Carrier volume of 20 GPA and pressure of 38 PSI. | ||
| 2 | Redeem R&P treatments applied with X-77 nonionic surfactant at 0.25% v/v. | ||
| Table 2. Tall ironweed control and plant populations as affected by fall herbicide treatments. | ||||||||
| Treatment | Rate/Ac | Tall Ironweed1 | ||||||
| May 17 | July 12 | Sept 25 | May 17 | July 12 | ||||
| (% control) | (stems 100 ft2) | |||||||
| Untreated Check | - | 0 | 0 | 0 | 80 | 84 | ||
| Crossbow | 2.0 qt | 93 | 96 | 94 | 4 | 3 | ||
| Redeem R&P | 1.5 pt | 98 | 95 | 84 | 0 | 5 | ||
| Redeem R&P | 2.0 pt | 99 | 97 | 88 | 0 | 4 | ||
| Redeem R&P + 2,4-D | 1.5 pt + 2.0 pt | 99 | 98 | 98 | 0 | 1 | ||
| Banvel | 2.0 pt | 87 | 71 | 53 | 4 | 33 | ||
| LSD (0.05) | 7 | 7 | 11 | 30 | 17 | |||
| 1 | The initial population was 52 tall ironweed stems per 100 ft2 at the time of fall herbicide treatment on September 5, 2000. | |||||||
| Table 3. Forage and tall ironweed yield taken on three harvest dates in 2001 as affected by previous fall-applied herbicide treatments. | ||||||||
| Treatment | Rate/Ac | Biomass Yield | ||||||
| Forage | Tall Ironweed | |||||||
| May 17 | July 25 | Sept 21 | May 17 | July 25 | Sept 21 | |||
| (lb/ac) | ||||||||
| Untreated Check | - | 6524 | 7105 | 8440 | 447 | 945 | 439 | |
| Crossbow | 2 qt | 6427 | 5881 | 7401 | 31 | 147 | 0 | |
| Redeem R&P | 1.5 pt | 5693 | 6317 | 7830 | 0 | 92 | 15 | |
| Redeem R&P | 2 pt | 5387 | 5291 | 7480 | 0 | 0 | 0 | |
| Redeem R&P + 2,4-D | 1.5 pt + 2 pt | 5339 | 5181 | 7449 | 0 | 62 | 44 | |
| Banvel | 2 pt | 4302 | 5667 | 7430 | 31 | 440 | 112 | |
| LSD (0.05) | 1814 | 1624 | 1265 | 322 | 503 | 176 | ||
J R. Martin
Honeyvine milkweed (Ampelamus albidus) causes lodging of corn as a result of the vines climbing and becoming entangled with the crop. The stems and leaves of this weed often remain green after the crop has matured, thus adding more burden during the harvesting process.
Honeyvine milkweed plants grow as a warm-season perennial that reproduces from seed and long creeping roots. Plants that develop a well-established root system are difficult to control with traditional synthetic auxin-type herbicides such as 2,4-D and Banvel (dicamba).
Compare effectiveness of relatively new auxin type herbicide products as well certain Acetolactate-Synthase (ALS)-inhibiting herbicides on managing honeyvine milkweed in corn.
Studies were conducted in Meade and Simpson counties during 2000. Both sites were treated with atrazine plus a chloroacetamide herbicide for preemergence control of annual weeds. An Imidazolinone Tolerant (IT) corn hybrid was planted in mid-April.
Postemergence herbicide treatments are listed in Table 1. These were applied as a broadcast spray when corn plants had five to six collars and honeyvine milkweed plants were 4 to 18 inches in length.
Honeyvine milkweed infestations were fairly uniform and heavy at both sites. By late season the percent of infested corn plants in the nontreated check plots was 18 percent at Meade County and 30 percent at Simpson County (Table 1). Although none of the postemergence herbicides provided complete kill of honeyvine milkweed, they did limit its growth. All treated plots had a smaller percentage of infested corn compared with the nontreated check plots. The level of suppression of vine growth was the same regardless of herbicide treatment.
This research shows there are several postemergence herbicides that suppress the top growth of honeyvine milkweed plants. Additional research is needed to determine if any of these options offer long-term benefits by reducing populations of this problem weed the following growing season.
The author expresses appreciation to the growers and county Extension agents who assisted with this research.
| Table 1. The effect of postemergence herbicides on percent of corn plants wrapped with honeyvine milkweed. | |||
| Herbicidea | Percent Infested Cornb | ||
| Meade County | Simpson County | ||
| Accent Gold 2.9 oz/ac | 7 | 3 | |
| Clarity 8 oz/ac | 8 | 6 | |
| Distinct 4 oz/ac | 5 | 5 | |
| Exceed 1 oz/ac | 7 | 8 | |
| Lightning 1.28 oz/ac | 2 | 1 | |
| Permit 1.33 oz/ac | 3 | 6 | |
| Nontreated Check | 18 | 30 | |
| LSD (0.05) | 8 | 14 | |
| a | Adjuvants were included with herbicides according to label directions. | ||
| b | The percent infested corn plants is based on the number of plants wrapped with honeyvine milkweed (approximately 12 inches or more above the soil surface) relative to the total number of corn plants in the plot. Evaluations were made in early August. | ||
J.R. Martin
Four studies were initiated in Simpson and Warren counties to evaluate and compare herbicides for postemergence control of cornflower in wheat. The dry soil conditions in the fall of 1999 delayed emergence of cornflower; therefore, results of some of the research was inconclusive and not reported.
One study compared Buctril (bromoxynil) at 1.5 or 2 pt/ac; Clarity (dicamba) at 2 or 4 oz/ac; and Sencor (metribuzin) at 4 or 8 oz/ac applied to three-leaf cornflower on 9 February 2000 or six-leaf cornflower on 15 March 2000. Buctril at 2 pt/ac was the most effective in controlling cornflower plants up to six-leaf stage. The trend in reduction of cornflower control when applications of Buctril at 1.5 pt/ac was delayed helps support the fact that Buctril is most effective in controlling plants that are relatively small. Sencor was effective in controlling cornflower plants, provided the high rate of 8 oz/ac was applied to small plants. It should be noted that the favorable weather conditions observed during the spring treatments may have played a role in the success with Buctril and Sencor. Clarity was not effective when applied at 2 or 4 oz/ac.
Another study compared Buctril at 2pt/ac alone or Buctril at 1.5 pt/ac applied alone or in tankmix combination with Clarity at 4 oz/ac or with Harmony Extra (thifensulfuron + tribenuron) at 0.5 oz/ac plus nonionic surfactant at 0.25 percent v/v. Treatments were applied on 3 December 2000, 2 March 2001, and 13 March 2001. Buctril at the rate of 2 pt/ac was consistent in controlling cornflower at all application timings; however, the 1.5 pt/ac rate tended to be less effective when applications were delayed until spring. Including Clarity or Harmony Extra with Buctril at 1.5 pt/ac helped improve cornflower control with the spring applications. These tank mixtures caused wheat injury, yet injury was less evident near the end of the season.
The author expresses appreciation to the growers, county Extension agents, and farm-supply business consultants who assisted with this research.
J.R. Martin, W.W. Witt, D. Call, and J. James
Current herbicide options are somewhat costly and inflexible in regard to application timing. Also, repeated use of some options such as Hoelon (diclofop-methyl) or Achieve (tralkoxydim) may increase the risk of developing populations that are resistant to Accase-inhibiting herbicides. Although herbicide-resistant Italian ryegrass has not been confirmed in Kentucky, there are a number of states in the Southeast that have documented its presence.
Studies were conducted during 2000 and 2001 to compare and evaluate certain products recently registered for ryegrass control as well as experimental herbicides being developed for controlling weedy grasses in wheat.
Achieve (tralkoxydim), Axiom (flufenacet + metribuzin), Discover (clodinafop-propargyl), Everest (flucarbazone), Hoelon (diclofop-methyl), and Maverick (sulfosulfuron) were evaluated for controlling Italian ryegrass during 2000 and 2001 in Pioneer 2552 wheat. Beyond (imazamox) was evaluated in 2001 in an experimental Clearfield wheat variety that is tolerant to imidazolinone herbicides. Hoelon, Achieve, and Everest are currently registered and available for controlling Italian ryegrass, whereas Axiom, Discover, Maverick, and Beyond (for Clearfield wheat only) are not registered for use in Kentucky.
Achieve, Axiom, and Everest were more consistent in controlling Italian ryegrass when applied in the fall compared with applications made in the spring (Table 1). Hoelon and Discover provided at least 87 percent control of Italian ryegrass for applications made in the fall or early spring and were superior to the other herbicides when applications were delayed until mid-March. Beyond at 5 or 6 oz/ac provided at least 90 percent control of Italian ryegrass up to mid-February (Table 2). However, control declined substantially when Beyond applications were delayed until mid-March. Italian ryegrass control with Maverick did not exceed 60 percent in either year.
All herbicides generally provided better control when applied in the fall compared with spring applications. Hoelon and Discover were usually more effective than the other herbicides in managing Italian ryegrass plants that had overwintered and were beginning to tiller. Achieve, Axiom, and Everest were capable of providing early-season control, but regrowth did occur in some instances. The level of Italian ryegrass control with Beyond applications in Clearfield wheat was similar to that of Hoelon when applied to small plants in the fall, but regrowth may be a problem when Beyond applications are applied in the spring to weeds that are fully tillered. Maverick did not offer effective postemergence control of Italian ryegrass and persisted long enough in soil to injure double-cropped soybeans in other research (data not presented).
| Table 1. Italian ryegrass control with fall or spring herbicide applications in Pioneer 2553 wheat (UK Research and Education Center, 2000 and 2001). | |||||||
| Herbicide
Treatments1 |
% Ryegrass Control for Different Application Timings2, 3 | ||||||
| 2000 | 2001 | ||||||
| Fall | Spr 1 | Fall | Spr 1 | Spr 2 | |||
| Achieve 7 oz/ac | 67 | 70 | 90 | 63 | ---- | ||
| 9.5 oz/ac | 67 | 67 | 90 | 77 | 60 | ||
| Axiom 10 oz/ac | 63 | ---- | 100 | 80 | 60 | ||
| Discover 4 oz/ac | ---- | ---- | 100 | 100 | 93 | ||
| Everest 0.62 oz/ac | 77 | ---- | 80 | 77 | 43 | ||
| Hoelon 1.33 pt/ac | 87 | 83 | 100 | 87 | ---- | ||
| 2 pt/ac | ---- | ---- | 100 | 96 | ---- | ||
| 2.67 pt/ac | 95 | 90 | 100 | 100 | 80 | ||
| Maverick 0.5 oz/ac | 60 | 7 | ---- | ---- | ---- | ||
| 0.67 oz/ac | ---- | ---- | ---- | 33 | ---- | ||
| LSD (0.05) | 13 | 26 | |||||
| 1 | Adjuvants were included with Achieve, Discover, Everest, and Maverick according to label directions. | ||||||
| 2 | Fall = approximately 2-leaf ryegrass in mid-November; Spr 1 = 2 to 3 tillered ryegrass in mid-February; and Spr 2 = fully tillered ryegrass in mid-March. | ||||||
| 3 | Control ratings were made in the spring and were based on a scale of 0 to 100 with 0 = no control and 100 = complete control. | ||||||
| Table 2. Italian ryegrass control with fall or spring herbicide applications in an experimental Clearfield wheat variety (UK Research and Education Center, 2001). | ||||
| Herbicide Treatments1 | % Ryegrass Control for Different Application Timings2, 3 | |||
| Fall | Spr 1 | Spr 2 | ||
| Beyond 4 oz/ac | 80 | 80 | 53 | |
| Beyond 5 oz/ac | 90 | 93 | 43 | |
| Beyond 6 oz/ac | 93 | 100 | 60 | |
| Hoelon 1.67 pt/ac | 100 | ---- | ---- | |
| LSD (0.05) |
17 |
|||
| 1 | Crop oil concentrate at 1% v/v was included with Beyond. | |||
| 2 | Fall = mid-November approximate 2-leaf ryegrass. Spr 1 = mid-February and 2 to 3 tillered ryegrass. Spr 2 = mid-March and fully tillered ryegrass. | |||
| 3 | Control ratings were made in the spring and were based on a scale of 0 to 100 with 0 = no control and 100 = complete control. | |||
Row Crop Research
J. Calvert and G. Palmer
Removal of the inflorescence (topping) of tobacco plants is a standard practice in the production of burley and dark tobacco. Prior to the introduction of effective sucker control chemicals in the mid-1950s, suckers were removed manually. Hand suckering was a difficult and time-consuming process, requiring up to 50 hours of labor per acre. In the late 1950s tobacco growers began using maleic hydrazide (MH) to control suckers. MH had outstanding ability to control suckers, and its use was quickly adopted by growers. However, tobacco leaf processors and manufacturers opposed its use, claiming it lowered leaf quality by leaving residues and altering physical characteristics. As the industry gained experience with MH-treated leaf, its effects on physical characteristics were overcome by manufacturing processes, and a residue tolerance of 80 parts per million (ppm) was accepted.
In the early 1960s, the U.S. Department of Agriculture and scientists at agricultural experiment stations in tobacco-producing states initiated research to study MH effects on all U.S. tobacco types and to evaluate new chemicals being proposed for the control of suckers. Their research has been reported through the Regional Tobacco Growth Regulator Committee. The Committee's research (and that of others) has shown that MH leaf residues are highly correlated with (1) the amount of MH applied, (2) the application technique, (3) the time of topping and MH application, and (4) the amount of rainfall between MH application and harvest. In burley tobacco, it has been demonstrated repeatedly that acceptable residue levels are attained when recommended rates of MH are applied immediately after topping.
Since its beginning, the Regional Committee has tested scores of potential sucker control chemicals, and it continues to evaluate new chemicals and application technologies. Their research has shown that dinitroanaline compounds (e.g., Prime+ and Butralin) when used with reduced rates of MH have provided excellent sucker control while producing leaf with low MH residues. They found that sucker growth was suppressed for longer periods of time where both MH and a dinitroanaline compound were used. Dinitroanaline compounds have both contact and systemic activity and are most effective when the spray solutions contact or thoroughly wet the sucker buds. Spray equipment should be adjusted to deliver coarse droplets, under low pressure, at solution rates of 40 to 45 gallons per acre.
Sucker control in dark tobacco types is more difficult and exacting than in burley. Dark tobacco requires a longer maturity interval between topping and harvest than burley, requiring dark-tobacco growers to exercise greater care in their choice of chemicals and their times of application. The use of fatty alcohol compounds (e.g., Off-Shoot-T and Royaltac) at topping, followed by MH and/or combinations of MH and a dinitroanaline have proven to be effective strategies for controlling suckers in dark tobacco. Dark tobacco sucker control programs utilizing all three types of chemicals have been shown to provide excellent sucker control while minimizing bronzing and browning effects observed when MH was applied immediately after topping at rates sufficient to control suckers until harvest.
L. Murdock, J. Herbek, J. Martin, J. James, and D. Call
The objective of this experiment was to verify the effects of no-till wheat and tilled wheat on the subsequent yield of soybeans and corn planted after wheat in a wheat, double-cropped soybean and corn rotation and measure differences in fertility and physical effects on the soil on a long-term basis.
The experiment is at Princeton, Kentucky, on a Huntington silt loam soil that is moderately well drained. Wheat was planted no-till and with tillage, and the tillage plots were chisel plowed and disced twice. The plots were 10 feet by 30 feet. The experiment was soil sampled each year, and lime and fertilizer were applied according to University of Kentucky recommendations before planting. N was sidedressed on corn at 150 lb/ac. Soybeans are planted no-till immediately after wheat harvest, and no-till corn is planted the following year, and wheat (tilled and no-tilled) is again planted after corn harvest.
Yields of Succeeding Crops. The data indicate that both no-till corn and no-till soybeans tend to yield more (3.5 percent for soybeans and 5.5 percent for corn) where the wheat is planted no-till (Table 1). However, the differences are not always statistically significant, but the trend has been fairly consistent.
These yield differences indicate that changes between the two systems have taken place with time, and the changes favor the system that has only no-tillage wheat plantings in it. The reason for the difference is not completely known at this time, but research that is taking place indicates the differences may be due to residue cover, soil moisture, soil physical changes, and more specifically a change in pore size distribution.
Soil Changes. There is no difference in the soil density between the systems. This indicates that there was no compaction of significance in either system. The soil strength, as indicated by penetrometer measurements, was higher in the exclusively no-tillage system. Soil measurements indicate that the soil structure has changed and has larger aggregates and more medium-sized pores than the system that is tilled every second year for wheat planting.
Moisture measurements taken during the 1999 growing season on the no-till corn and in 2000 on the no-till soybeans found more moisture available for plant growth in the treatments where tillage was not used for wheat. This resulted in 18 percent and 6.2 percent higher grain yields, respectively, for these treatments during these years. There was little difference in measured soil moisture in
