1Richard Coffey (Co-Chairman), Department of Animal Sciences; Ron Bowman (Co-Chairman), Nelson County Extension Agent for Agriculture and Natural Resources; Les Anderson, Department of Animal Sciences; Jenny Cocanougher, Agricultural Programs; Bill Crist, Department of Animal Sciences; Ron Fleming, Department of Agricultural Economics; Kim Henken, Agricultural Programs; Janet Johnson, Allen County Extension Agent for Family and Consumer Sciences; Reva Mitchell, Henderson County Extension Agent for 4-H/Youth Development; Doug Overhults, Department of Biosystems and Agricultural Engineering; Tony Pescatore, Department of Animal Sciences; Monroe Rasnake, Department of Agronomy; Scott Samson, Department of Sociology; and Bill Thom, Department of Agronomy.
Livestock and poultry manure has been used for many years to provide basic fertilizer nutrients to improve crop and forage production. In addition, it has long been known that the chemical and physical properties of soils can be improved by applications of animal manure. Because of these benefits, much of the manure produced by livestock and poultry has been and continues to be applied to cropland and pastureland. Not only does this practice benefit crop production, it also has the environmental benefit of recycling nutrients to the soil from which they originated.
Over the past few decades, significant structural changes in animal production have occurred. Farms have become more specialized, with livestock and poultry operations becoming fewer in number but larger in size. In some cases, livestock or poultry operations are more concentrated in certain geographical regions. As these changes have occurred, concerns have been raised regarding the potential environmental effects of continued manure application to the land. One particular question is whether the current land base in crop and pasture production is adequate to utilize all nutrients (especially nitrogen and phosphorus) from manure produced by Kentucky’s livestock and poultry operations. Stated another way, there is concern about the potential application of manure nutrients at rates that will exceed current crop and pasture production requirements.
The primary purpose of this publication is to provide a conservative assessment of the degree to which nutrients removed annually from the land by harvested crops and grazed forages potentially could be supplied from nutrients present in livestock and poultry manure in each Kentucky county. The intent of the assessment is to provide a snapshot comparison of estimated manure nutrient production relative to potential nutrient removal capacity on a fairly large scale and does not include many farm level variables that will determine environmental impact. Due to the broad nature of the assessment, the information presented here should only be used as a starting point for discussions pertaining to animal production and manure nutrient use.
The basic approach in the assessment was to estimate, for each county in Kentucky, the amount of recoverable (potentially land-applied) nitrogen, phosphorus, and potassium from all livestock and poultry manure and the quantity of these nutrients that would normally be removed from the land through harvested crops and grazed forages. Once the manure nutrient supply and the crop and forage nutrient removal estimates were made, the following ratio was computed on a county-by-county basis:
Total recoverable manure nutrients from livestock and poultry/Total nutrients removed by harvested crops and grazed forages
Crop acreage, crop yields, and livestock inventories were obtained primarily from the 1997-1998 Kentucky Agricultural Statistics report. Some missing information was obtained from the 1997 U. S. Census of Agriculture and from industry surveys. Manure nutrient production was estimated for beef cattle, dairy cattle, swine, layers, and broilers. Crops and forages included in the assessment were corn harvested for grain, corn harvested for silage or green chop, soybean harvested for beans, winter wheat harvested for grain, sorghum harvested for grain, barley harvested for grain, alfalfa hay, all other types of hay (excluding alfalfa), burley tobacco, dark fire-cured tobacco, dark air-cured tobacco, and forages from pastureland.
The methods used to estimate manure and nutrient production from livestock and poultry operations and nutrient removal potential of crops and forages grown in Kentucky were based on the procedure developed by Lander et al. (1998). Where appropriate, modifications were made to more accurately reflect conditions unique to Kentucky. However, the major difference between this assessment and that of Lander et al., which used 1992 U.S. Census of Agriculture data, is the use of more recent animal inventory data (which includes significant recent expansion in Kentucky’s poultry industry) and crop production data. The following discussion outlines the methods and assumptions used.
Inventories for beef, dairy, swine, and poultry within each Kentucky county were included in the assessment. It is recognized that significant inventories of horses and mules are found in some counties (particularly many counties located in Central Kentucky), but reliable inventory estimates for these animals are not available. Therefore, horses and mules were not included in the assessment.
The county inventory estimates for beef, dairy, and swine were taken from Kentucky Agricultural Statistics. For counties with only a limited inventory of beef, dairy, or swine, no inventory estimate was available. For example, counties with an inventory estimate of less than 500 head of cattle and calves were included in an “Other Counties” category within a district in the Kentucky Agricultural Statistics report. This was also true for counties that had inventories of less than 500 head of hogs and pigs and less than 300 head of milk cows. A two-step approach was used to determine an inventory estimate for each county that was included in the “Other Counties” category. The first step in the process involved determining which counties included in the “Other Counties” category had an actual inventory of zero (0). Because this information was not available in the Kentucky Agricultural Statistics report, the 1997 U.S. Census of Agriculture was consulted. The U.S. Census of Agriculture makes a distinction between counties with an inventory of zero (0) and those with an inventory that is not reported for reasons of confidentiality. Counties with a reported inventory of zero (0) in the 1997 U.S. Census of Agriculture were assigned an inventory of zero (0) in this assessment. The second step of the process involved equally dispersing the inventory estimate given for “Other Counties” among those counties within the district whose inventory was greater than zero (0) but whose actual inventory estimate was not given in the Kentucky Agricultural Statistics report.
To more accurately estimate manure and nutrient production from swine, it was necessary to partition the reported inventory for hogs and pigs into two groups: (1) breeding stock and (2) nursery and finishing pigs. This grouping allowed for separate evaluations of swine that are limit fed versus those that are fed ad libitum (full fed). It was assumed that 12% of the reported hogs and pigs inventory was breeding stock and the remaining 88% was nursery and finishing pigs (Coffey 1999). The breeding stock inventory was further segregated into lactating sows with litters (18% of breeding stock inventory) and gestating sows, boars, and replacement gilts (82% of breeding stock inventory). Gestating sows, boars, and replacement gilts were assumed to be limit fed, and lactating sows with litters and nursery and finishing pigs were assumed to be fed ad libitum.
The inventory estimates for milk cows in the Kentucky Agricultural Statistics report does not include dairy heifers. On most dairy operations, the inventory of heifers is approximately 80% of the inventoried mature cows; therefore, dairy heifer inventory was estimated as 80% of the reported inventory for milk cows (Crist 1999).
The inventory estimates for all cattle and calves in the Kentucky Agricultural Statistics report includes both dairy and beef cattle. To estimate the inventory for all beef cattle and calves, the inventory estimates for dairy cows and dairy heifers were subtracted from the reported inventory for all cattle and calves.
Due to limited availability of data, county inventory estimates for layers, breeder layers, pullets, breeder pullets, and broilers were determined by a survey of private companies that operate in Kentucky (Pescatore 1999). These inventory estimates are not reported in Kentucky Agricultural Statistics for reasons of confidentiality. Poultry inventories for many counties are also not given in the U.S. Census of Agriculture, which does not report a poultry inventory estimate for a county if doing so would disclose information about an individual farm or owner.
For purposes of this assessment, the production year was set at 365 days for all animal classes. No adjustments were made to livestock and poultry inventories to account for periods of time when facilities would be empty between production cycles. For some operations, particularly swine and poultry operations that have multiple growth cycles per year, this lack of adjustment could result in either overestimation or underestimation of manure and nutrient production on an annual basis. The inventory estimates in the Kentucky Agricultural Statistics report represent inventories as of December 1, 1997, rather than total animal capacity at an operation. The number of operations that were between production cycles and had facilities empty at the time the inventories were taken would influence the annual manure and nutrient production. However, the direction of this influence on the assessment is not known.
Animal inventory estimates by county that were used in the assessment are shown in Table 1. For reasons of confidentiality, poultry inventory estimates are not included.
|Table 1. Livestock inventories and crop production estimates.|
|County||All beef cattle and calves1 (head)||Dairy cows1 (head)||Dairy heifers2 (head)||Lactating sows with litters3 (head)||Gestating sows, boars, and gilts (head)||Nursery and finishing pigs4 (head)||Corn for grain1 (bu)||Corn for silage or green chop5 (tons)||Soybean for beans1 (bu)||Winter wheat for grain1 (bu)||Sorghum for grain1 (bu)||Barley for grain1 (bu)||Alfalfa hay1 (tons)||All other hay1 (tons)||Burley tobacco1 (lbs)||Dark fire-cured tobacco1 (lbs)||Dark air-cured tobacco1 (lbs)||Pastureland forage5(tons)|
|1Estimates adapted from Kentucky Agricultural Statistics, 1997-1998.|
2Dairy heifer inventory estimated as 80% of dairy cow inventory reported in Kentucky Agricultural Statistics.
312% of hogs and pigs inventory reported in Kentucky Agricultural Statistics partitioned into breeding stock. Breeding stock inventory partitioned into lactating sows with litters (18%) and gestating sows, boars, and replacement gilts (82%).
4Nursery and finishing pig inventory estimated as 88% of hogs and pigs inventory reported in Kentucky Agricultural Statistics.
5Estimates adapted from U.S. Census of Agriculture, 1997.
The manure parameters estimated in the assessment were dry matter manure production, nitrogen (expressed as total nitrogen), phosphorus (expressed as P2O5), and potassium (expressed as K2O). Manure production and nutrient composition values published by the 1993 American Society of Agricultural Engineers (ASAE) Standards were the primary source for calculating these parameters. The ASAE Standards do not report manure production and manure nutrient content data for pullets and breeder pullets; therefore, these values were taken from the Natural Resources Conservation Service (NRCS) Agricultural Waste Management Field Handbook (1992). For certain classes of livestock, the reported values were adjusted to more accurately estimate manure and nutrient production. For example, the values given in the ASAE Standards for swine overestimate the manure production and manure nutrient content of swine that are limit fed (gestating sows, boars, and replacement gilts). For these classes of swine, the values reported in the 1993 ASAE Standards were lowered by 50% to more accurately reflect the reduced manure output and nutrient content resulting from limit feeding. Table 2 shows the manure production and nutrient content values and the average animal liveweights used in the assessment.
|Table 2. Average liveweights, manure production, and manure nutrient content from livestock and poultry.|
|Animal type||Average live-weight (lbs)||Lbs per day per 1,000 lbs liveweight|
|Dry matter manure||Total nitrogen||P2O5||K2O|
|Beef (all cattle and calves)1||800||8.5||0.34||0.21||0.25|
|Lactating sows with litters1||350||11.0||0.52||0.41||0.35|
|Gestating sows, boars, and replacement gilts1||325||5.5||0.26||0.20||0.17|
|Nursery and finishing pigs1||135||11.0||0.52||0.41||0.35|
|1Adapted from 1993 ASAE Standards.|
2Adapted from 1992 NRCS Agricultural Waste Management Field Handbook.
It was necessary to estimate the amount of excreted manure (and, consequently, manure nutrients) that is recoverable and available for land application. In the process of collecting and storing manure from livestock and poultry production facilities, a portion of the manure and nutrients is lost. The degree to which these losses occur is dependent on the type of manure collection and storage system used by the livestock enterprise (the reader is referred to the NRCS Agricultural Waste Management Field Handbook, Chapter 11, Table 11-15, for estimates of losses from various types of manure systems). Unfortunately, there are no available estimates of the number of each type of manure system used in Kentucky. Therefore, values used in the assessment to estimate recoverable manure, nitrogen, phosphorus, and potassium were adapted from Lander et al. and are shown in Table 3. The recovery factors reported by Lander et al. were derived from consultation with numerous individuals from the U.S. Department of Agriculture (USDA), universities, and industry groups, and were based on the following general assumptions:
|Table 3. Annual recovery of dry matter, nitrogen, phosphorus, and potassium from animal manures1.|
|Component of manure||Annual recovery2 (% of total)|
|Total dry matter||10||70||80||95|
|Phosphorus (expressed as P2O5)||85||85||85||85|
|Potassium (expressed as K2O)||90||90||90||90|
|1Adapted from Lander et al. (1998).|
2These recovery factors only account for losses that occur during collection and storage of manure.
3Potential manure recovery from beef cattle is very low because a vast majority of the beef cattle in Kentucky are pastured.
Calculated estimates of the amounts of recoverable manure (on a dry-matter basis), nitrogen, phosphorus, and potassium produced annually in manure from livestock and poultry by county are shown in Table 4. In addition to the recovery factors shown in Table 3, these calculated estimates are also based on nutrient availability factors that were established for each manure nutrient considered in the assessment. For phosphorus and potassium, an availability factor of 100% was used. This factor was based on the assumption that over time, all of the phosphorus and potassium in manure applied to land would be available for plant removal. For manure nitrogen, an availability factor of 70% was used. Under ideal conditions in Kentucky, approximately 30% of the nitrogen in land-applied manure will not be available for plant removal due to nitrogen losses associated with denitrification, volatilization, etc. To account for these losses, 1.43 pounds of manure nitrogen would be needed for each pound of nitrogen that would be removed by plants.
|Table 4. Recoverable manure, nitrogen, phosphorus, and potassium produced annually by livestock and poultry and nutrients removed annually by crops and forages.|
|County||Recoverable manure and manure nutrients from livestock and poultry1 (lbs per year)||Nutrients removed by crops and forages2 (lbs per year)|
|Dry matter manure||Total nitrogen||P2O5||K2O||Total nitrogen||P2O5||K2O|
|1Includes manure and manure nutrients from beef, dairy, swine, and poultry. The calculated estimates of the amounts of recoverable manure, total nitrogen, P2O5 and K2O are based on the recovery factors shown in Table 3 and on nutrient availability factors of 70% for total nitrogen and 100% for P2O5, and K2O.|
2Includes nutrient removal from corn harvested for grain, corn harvested for silage or green chop, soybean harvested for beans, winter wheat harvested for grain, sorghum harvested for grain, barley harvested for grain, alfalfa hay, all other hay (excluding alfalfa hay), burley tobacco, dark fire-cured tobacco, dark air-cured tobacco, and forage from pastureland.
The manure and nutrient recovery factors and the nutrient availability factors used in the assessment do not account for nutrient losses that might occur as a result of the method used to apply manure to land. It should be recognized that additional nitrogen losses would occur when manure is not injected or incorporated into the soil immediately after surface application. However, reliable estimates of the proportion of manure that is applied using the different land application methods are not available.
Harvested crops included in the assessment were corn harvested for grain, corn harvested as silage or green chop, soybean harvested for beans, winter wheat harvested for grain, sorghum harvested for grain, barley harvested for grain, alfalfa hay, all other types of hay (excluding alfalfa), burley tobacco, dark fire-cured tobacco, and dark air-cured tobacco. With the exception of corn harvested as silage or green chop, county estimates for the production of these harvested crops were taken from Kentucky Agricultural Statistics. Production estimates were not available for some counties within a district that had limited production of certain crops, in particular for many counties located in the eastern half of Kentucky. For example, counties with less than 500 acres of harvested corn for grain were included in an “Other Counties” category within a district. Crop production estimates for these counties were determined using the process described under “Livestock and Poultry Inventory Estimates.” For crops that are grown almost exclusively in certain geographical regions (sorghum, barley, dark fire-cured tobacco, and dark air-cured tobacco), only counties with a reported production estimate in Kentucky Agricultural Statistics were included in the assessment.
Production estimates for corn harvested as silage or green chop are not reported in Kentucky Agricultural Statistics, and were taken from the 1997 U.S. Census of Agriculture. Production estimates for corn harvested as silage or green chop were not given for 10 counties in the census to avoid disclosing data for individual farms. For these counties, production estimates were assigned by (1) determining the difference between the total production of corn harvested as silage or green chop reported for the state and the total production that was reported for the other counties and (2) equally dividing this difference among the 10 counties whose production estimate was not reported.
Forage production from land that is used strictly for pastureland was also included in the assessment. Pastureland acreage for each county was taken from two categories of pastureland reported in the 1997 U.S. Census of Agriculture: (1) “Cropland Used Only for Pasture or Grazing” and (2) “Pastureland and Rangeland Other than Cropland and Woodland Pastured.” The acreage of “Cropland Used Only for Pasture or Grazing” in two counties and the acreage of “Pastureland and Rangeland Other than Cropland and Woodland Pastured” in three counties were not reported in the 1997 U.S. Census of Agriculture to avoid disclosing data for individual farms. Acreage estimates for these categories of pastureland within those counties whose estimate was not reported were determined by finding the difference between the total acreage reported for each category in the entire state and the acreage total that was reported for each category in the other counties. This difference was then equally divided among those counties whose pastureland acreage was not reported. The amount of forage produced on each acre of “Cropland Used Only for Pasture or Grazing” within each county was assumed to be the same as the harvested per acre yield of hay (the “all other hay” category, which excludes alfalfa hay) as reported in Kentucky Agricultural Statistics. Land that is included in the category of “Pastureland and Rangeland Other Than Cropland and Woodland Pastured” tends to be of lower quality than land from the category of cropland used only for pasture or grazing. Therefore, it was assumed that forage production from this category of pastureland would only be 60% of the reported hay production value for the “all other hay” category (excluding alfalfa hay) in Kentucky Agricultural Statistics (Thom 1999).
Crop and forage production estimates (annual yields) by county used in the assessment are shown in Table 1.
The removal of nitrogen (expressed as total nitrogen), phosphorus (expressed as P2O5), and potassium (expressed as K2O) was estimated for each of the crop and forage categories. For purposes of the assessment, nutrient removal refers to the amount of a nutrient that will be removed from the land when the crop is harvested or the forage is grazed by livestock. Nutrient removal should not be confused with the nutrient requirements of the crops and forages or the total nutrient uptake by crops and forages. The nutrient removal capacity of crops and forages will be lower than the total amount of a nutrient that is taken up and utilized by the plant for growth.
For harvested crops, nutrient removal was estimated based on the total yield and the nutrient content of the harvested biomass. A basic assumption was made that plant residues from harvested crops were not removed from the field unless they routinely were considered a part of the harvested material. For example, the crop residue from corn harvested as grain was assumed to remain in the field. For corn harvested as silage or green chop, both the ears and stalks were considered to be removed from the field. Similar logic was used for all other harvested crops included in the assessment.
For grazed forages, it was recognized that a large percentage of the nutrients consumed by livestock grazing pastureland would be recycled back onto the land through excreted manure. To account for these recycled manure nutrients, nutrient removal from forages on pastureland was estimated as 30% of the nutrient removal values used for the “all other hay” category (Thom 1999).
The values used to estimate nutrient removal by harvested crops and grazed forages were based on data from Wells and Thom (1994) and Lander et al. and are shown in Table 5. Based on these nutrient removal values and the annual production yields for each crop and forage category, annual nutrient removal was calculated. The annual removal of nitrogen, phosphorus, and potassium by crops and forages for each county is shown in Table 4.
|Table 5. Nutrient removal by crops grown in Kentucky1.|
|Crop||Yield unit||Lbs per yield unit||Nutrients removed (lbs per yield unit)|
|All other hay (except alfalfa)||ton||2,000||35||12||53|
|Barley for grain||bushel||48||0.900||0.410||0.300|
|Corn for grain||bushel||56||0.700||0.400||0.350|
|Corn for silage or green chop||ton||2,000||7.5||3.6||8.0|
|Forage from pastureland2||ton||2,000||10.5||3.6||15.9|
|Sorghum for grain||bushel||56||0.950||0.410||0.300|
|Soybean for beans||bushel||60||3.000||0.700||1.100|
|Tobacco, dark air-cured||pound||1||0.070||0.006||0.060|
|Tobacco, dark fire-cured||pound||1||0.070||0.006||0.060|
|Winter wheat for grain||bushel||60||1.200||0.500||0.300|
|1Adapted from Wells and Thom (1994) and Lander et al. (1998).|
2Nutrient removal for forage from pastureland estimated as 30% of the values given for all other hay (except alfalfa).
The results for the estimated balance between nitrogen in livestock and poultry manure and nitrogen removed by crops and forages are shown in Figure 1. The potential for nitrogen removal by harvested crops and grazed forages substantially exceeds the amount of recoverable manure nitrogen produced annually by livestock and poultry in all 120 counties. On a statewide basis, crops and forages have the capacity to remove almost 600 million pounds of nitrogen annually. At the present level of animal production, nitrogen from livestock and poultry manure could potentially supply only approximately 6% of the nitrogen that is removed by crops and forages grown in Kentucky.
Less than 10% of the nitrogen removed annually by crops and forages could be supplied by manure nitrogen in 112 counties. At the highest level for any county, manure from livestock and poultry operations in Muhlenberg County could potentially provide approximately 29% of the nitrogen its crops and forages have the capacity to remove (i.e., approximately 1.1 million pounds of the approximately 3.8 million pounds of nitrogen removed annually by crops and forages could be supplied by livestock and poultry manure).
After accounting for nitrogen that could be supplied from livestock and poultry manure, the crops and forages in each of 97 counties have the ability to remove greater than 1 million additional pounds of nitrogen. Five of these counties (Christian, Logan, Daviess, Union, and Henderson) each have the capacity to remove more than 16 million additional pounds of nitrogen. A majority of the 23 counties that could each remove less than 1 million additional pounds of nitrogen are located in the eastern half of the state and have limited animal and crop production.
The results for the estimated balance between phosphorus in livestock and poultry manure and phosphorus removed by crops and forages are given in Figure 2. Crops and forages grown in Kentucky have the potential to remove about 204 million pounds of phosphorus on an annual basis. Manure phosphorus from livestock and poultry presently produced within the state could potentially supply only about 26% of the phosphorus that is removed annually by crops and forages.
Based on these estimates, seven counties have manure phosphorus production levels that could supply between 50% and 94% of the phosphorus removed annually by the crops and forages grown in those counties (Letcher, 51%; Graves, 57%; Allen, 65%; Ohio, 67%; Webster, 84%; McLean, 86%; and Hopkins, 94%). Results for Muhlenberg County indicate that its livestock and poultry generate more manure phosphorus than its crops and forages have the capability to remove (134%). However, when drawing conclusions from these results, it must be recognized that all factors influencing the true balance of phosphorus for a county were not included in the assessment due to limitations in available data. A detailed discussion of factors that likely contributed to these high values, which should be considered when interpreting these results, follows later in the “Limitations of the Assessment” section of this publication.
Crops and forages in each of 57 counties have the capacity to remove more than 1 million additional pounds of phosphorus annually above the phosphorus that is currently recovered from livestock and poultry manure in those counties. Fifteen of these counties could each remove between 2 and 3 million additional pounds of phosphorus, and five counties (Christian, Union, Logan, Henderson, and Daviess) each have the potential to remove more than 5 million additional pounds of phosphorus on a yearly basis. A majority of the 63 counties whose crops and forages could each remove less than 1 million additional pounds of phosphorus (in excess of the phosphorus from livestock and poultry manure) are located in the eastern half of the state, although a few are located in the western half.
The results for the estimated balance between potassium in livestock and poultry manure and potassium removed by crops and forages are shown in Figure 3. The potassium removal capacity of crops and forages substantially exceeds the amount of potassium recovered from livestock and poultry manure in all 120 Kentucky counties. Of the almost 584 million pounds of potassium removed annually by crops and forages in Kentucky, only approximately 10% could be supplied by the potassium in animal manure.
The estimates indicate that the potassium recovered from livestock and poultry manure would supply less than 25% of the potassium removed annually by crops and forages in each of 114 counties. After accounting for potassium that is supplied by animal manure, the crops and forages in 101 counties have the capacity to remove more than 1 million additional pounds of potassium each. The 19 counties whose crops and forages could each remove less than 1 million additional pounds of potassium are located solely in the eastern one-third of Kentucky, where forests and terrain limit crop and forage production. A total of 88 counties could each remove in excess of 2 million additional pounds of potassium, and 59 counties could each remove more than 4 million additional pounds of potassium.
At the highest levels for any counties, manure potassium from livestock and poultry operations in McLean County and Webster County could supply 46% and 41%, respectively, of the potassium removed annually by crops and forages. However, after accounting for the potassium from animal manure, the crops and forages in these counties have the capacity to remove substantial amounts of additional potassium (McLean, 2.7 million additional pounds; Webster, 3.2 million additional pounds).
As stated previously, the purpose of this assessment is to provide an estimate (for each Kentucky county) of the degree to which nutrients removed annually by harvested crops and grazed forages could potentially be supplied by nutrients from livestock and poultry manure. The results of the assessment are only a snapshot of potential manure production and nutrient removal on a relatively large scale (a county or statewide basis) and do not allow for evaluations at the individual farm level, so prudence must be used when drawing conclusions from the results.
The assessment may be most beneficial when used as a benchmark of potential manure utilization for a county or region of the state, based on current animal inventories and crop and forage production levels. When used in this manner, these estimates may help identify large areas within the state where additional manure (either from the expansion of existing operations or the construction of new operations) could be utilized. This information may also help in identifying areas where alternative uses for manure should be explored. For example, if a county’s crop and forage production is limited, manure utilization options other than for plant growth may need to be considered. The assessment may also be used to provide some insight into the concentration of livestock and poultry within Kentucky relative to crop and forage production.
The assessment is not intended to define the potential for any county’s future livestock or poultry production, nor should it be used to place any restrictions on future production. While this information may be used as a starting point for discussion, when evaluating the potential for expansion of existing animal enterprises or the opportunity for new animal operations, farms must be evaluated individually, based on their own merits. It also would be erroneous to conclude from this assessment that livestock or poultry production either does or does not cause environmental problems in any county or region. No assessment of environmental impact can be made from the nutrient production and removal estimates that are presented here. The environmental impact of livestock and poultry operations within a county or area is dependent on manure management practices at the individual farm level.
It is important when using this information to understand that it does not provide a complete balance of nutrients for a county, since it does not account for the distribution of crops within a county or for farm-level variables. Data for these factors, as well as others known to influence nutrient balance, are simply not available at the present time.
For purposes of this assessment, it was necessary to make several general assumptions concerning livestock and poultry inventories, crop and forage production levels, manure management strategies, and crop nutrient removal potential. It should be recognized that actual animal inventories, crop and forage acreage, soil fertility, production efficiencies, and management practices at the farm level affect the balance of nutrients within a county.
A specific county may have a high or excessive level of manure nutrients compared to crop nutrient removal capacities because of either a relatively large animal inventory or a relatively small acreage of cropland and pastureland. Since either of the two is a possibility, a county which may appear to have or to be approaching an excess of manure nutrients must be studied more closely. A number of factors not included in the assessment (due to unavailable or insufficient data) could significantly alter the estimated nutrient balance within a county. Following is a discussion of some of those factors and how they may affect the use or interpretation of this assessment. These factors represent areas where additional research and (or) data collection are needed to gain a better understanding of the true nutrient balance within Kentucky counties:
What can be assumed if crop nutrient removal capacity is greater than manure nutrient production? The results of the assessment indicate that nearly all Kentucky counties currently have crop nutrient removal capacities that exceed the amount of manure nutrients produced annually by livestock and poultry. For these counties, nutrients supplied solely from manure would be insufficient to meet the nutrient removal capacity of the total acreage of crop and pastureland.
Has a county reached or exceeded the level of animal production it can support if manure nutrient production is equal to or greater than crop and forage nutrient removal capacity? This assessment should provide some overall perspective and serve as a starting point for discussion about expanding livestock or poultry production in a county or an area of the state. An apparent surplus of manure nutrients does not automatically mean that those nutrients cannot, or are not, being used appropriately. Where the quantity of manure nutrients is relatively high in comparison to crop and forage nutrient removal, close attention should be given to several other factors, such as:
As an example of how other factors can be important, consider the estimates for Muhlenberg County, which indicate that the production of manure phosphorus exceeds crop and forage phosphorus removal by 443,282 pounds. It is well known that much of the manure in that county is handled as a solid and is routinely transported to various off-site destinations, including some sites out of the county. Much manure has been used locally in strip mine reclamation projects, a large land area that is not included in the crop and forage land base of this assessment. Also, the assessment shows that in nearby counties, crop and forage phosphorus removal exceeds manure phosphorus production by over 20 million pounds. Thus, there is substantial potential to effectively use the apparent surplus of manure phosphorus, and it cannot be stated unequivocally that the limits of animal production have been reached in Muhlenberg County.
Proper manure management is ultimately site specific and is more correctly evaluated on a farm-by-farm basis rather than county by county. The operative question becomes one of distribution and appropriate land application rather than a simple computation of quantities. Thus, this assessment alone is inadequate to define future livestock and poultry production potential.
Does a high percentage of manure nutrients meeting crop nutrient removal capacity indicate an environmental problem exists or is likely to occur within the county? Although the assessment may indicate a county requires a high percentage of its crops and forages to remove the manure nutrients produced by livestock and poultry, it does not imply that environmental problems presently exist, nor does it imply they are likely to occur. The potential for the occurrence of nutrient imbalances and environmental problems is dependent on the manure management practices at the farm level. Therefore, when addressing environmental concerns, each animal operation should be evaluated on an individual basis.
It is important to understand that animal operations are presently subject to several regulations to help ensure that manure is utilized in an environmentally sound manner. Animal operations that collect and store manure as a liquid are required to obtain an operating permit (the No Discharge Operational Permit) from the Kentucky Division of Water. A part of the permitting process requires operators to provide assurances that they have an adequate land base to utilize the manure that will be produced. Additionally, all farm animal enterprises within Kentucky are required to evaluate their system of manure management and develop an Agricultural Water Quality Plan to ensure that manure nutrients are being utilized in a manner that protects the environment.
This assessment provides a comparison of total recoverable manure nutrients from livestock and poultry and total nutrients removed by harvested crops and grazed forages for each county in Kentucky. The estimates derived from the assessment provide a snapshot (or point-in-time) picture, which is based primarily on animal and crop production data collected by established agricultural statistics services.
The following conclusions are drawn from the results of the assessment:
Through discussions and reviews of the assessment, several areas were noted where data were either incomplete or not available. Listed below are some suggestions for future research and (or) data collection to improve the existing information base:
American Society of Agricultural Engineers (ASAE), “D384.1—Manure Production and Characteristics,” ASAE Standards, D384.1, revised December 1993.
Coffey, R.D., personal communication, University of Kentucky, Department of Animal Sciences, 1999.
Crist, W.L., personal communication, University of Kentucky, Department of Animal Sciences, 1999.
Kentucky Department of Agriculture—Kentucky Agricultural Statistics Service, 1997-1998 Kentucky Agricultural Statistics.
Lander, C.H., D. Moffitt, and K. Alt, “Nutrients Available from Livestock Manure Relative to Crop Growth Requirements,” Resource Assessment and Strategic Planning Working Paper 98-1, USDA—Natural Resources Conservation Service, February 1998.
Pescatore, A.J., personal communication, University of Kentucky, Department of Animal Sciences, 1999.
Thom, W.O., personal communication, University of Kentucky, Department of Agronomy, 1999.
USDA—National Agricultural Statistics Service, 1992 Census of Agriculture.
USDA—National Agricultural Statistics Service, 1997 Census of Agriculture.
USDA—NRCS Agricultural Waste Management Field Handbook, 1992.
Wells, K.L. and W.O. Thom, “Estimated Nutrient Content and Uptake by Kentucky’s Crops.” Soil Science News & Views (Volume 15, No. 4), University of Kentucky, Department of Agronomy, 1994.