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Precision Placement of Crop Production Inputs via Distributed Control
S. Shearer, T.S. Stombaugh, C.R. Dillon
Department of Biosystems and Agricultural Engineering
Off-target placement of crop production inputs is a costly and time consuming problem for agricultural producers. Typical seeding/application problems include: skipped areas, double treatment, unintentional treatment, or treatment of environmentally sensitive areas. Reducing or eliminating off-target treatments is increasingly important in a society that places high value on environmental quality and to global markets that are extremely competitive.
The goal of the proposed research is to develop a CAN-based distributed control systems for precision placement of crop production inputs such as seed, fertilizer, and pesticides. This control system will utilize dedicated microcontrollers for single element metering of inputs. Dynamic adjustment of machine operating parameters such as seed meter air pressure and shaft speed will be made in response to feedback from rate sensors, ground speed radar, and GPS position fixes.
Precision placement of inputs will improve Kentucky farm profitability through increased crop yield and minimized input costs through the elimination of skipped and doubled treated regions within a field, and by maintaining desired fixed and variable seeding/application rates across the toolbar or effective application width while turning and in point row regions of a field. The proposed control system represents a significant advance and is warranted in view of increasing input costs and the need for traceability.
2009 Project Description
Progress on two important fronts, section control for agricultural sprayers and high pressure single nozzle direct chemical injection were investigated.
Section Control: Reducing off-target chemical application errors can improve profitability and reduce pesticide and nutrient losses to the environment from agricultural operations. Off-target errors include: skipped-application, multiple-application, and unintentional-application to environmentally sensitive areas. Current spray application technologies limit the ability of producers to control pesticide application to a resolution of approximately 5-10m or greater with large self-propelled sprayers.
The objective of this case study was to present a summary of results from three fields that highlight the potential benefits of automatic boom section control technology. Map-based automatic section control was achieved through the addition of a ZYNX X15 control console with a 30 channel spray electronic control unit to a self-propelled sprayer with a 24.76m boom in Shelby County, Kentucky. For each field, the sprayed area calculated with map-based automatic boom section control was compared to the total area covered by the spray boom. A reduction of 15.2-17.5% in the area applied to each field was achieved with map-based automatic boom section control versus no boom section control.
As expected, savings were reduced with lower control resolution; however these arrangements still resulted in a reduction in applied areas where three sections (∼8% reduction) and five sections (∼11% reduction) were compared to no boom section control. Statistical analysis revealed significant reductions in control section "on" time from the center to exterior boom control section positions. These results indicate that map-based automatic boom section control can provide savings for producers adopting this technology.
Single Nozzle Direct Injection: Chemical application in production agriculture plays an important role in the control of pests such as weeds, insects and fungi. Crop damage, increased input cost and elimination of grassed waterways impact crop yield, profit, as well as the environment.
A significant objective of this research was to design and construct a high pressure chemical metering system for a single nozzle to control the amount of chemical applied while minimizing response time to rate changes. The metering of the chemical was achieved by actuating a direct acting solenoid valve. System pressure acting on the chemical was 8,270 kPa.
The operating envelope of the system was found to be between 5 and 8 Hz with a duty cycle of 0 to 100%. Operating the system at very low frequencies (< 5Hz) produced a very high coefficient of variation due to the time between chemical injection pulses. Rate of response was reduced by decreasing the mixing chamber size. The time constant for the system was found to be 0.30 s. The chemical concentration output of the system approached the predicted concentration output value as frequency increased; indicating that operating at lower frequencies reduces precision.
Results from the work on high pressure, single nozzle, direct chemical injection system demonstrates the ability to control chemical application at rates as low as 1 ml/s and with a very linear response. This capability translates to chemical concentrate application rate resolutions of 0.1 L/ha and spatial resolutions of 1 square meter with coefficients of variation of less than 5%.
If adopted this technology will reverse the current trend away from uniform application associated with increasing equipment widths. This technology will also facilitate true variable rate application within a 5% coefficient of variation when contrasting actual application with prescriptive rate maps.
Work completed on the evaluation of section control applied to agricultural sprayers illustrates the ability of producers in Kentucky to eliminate off-target application of agricultural chemicals and fertilizers and reduce the corresponding purchases and use of these inputs by up to 15%. An ancillary benefit of the application of this technology is the preservation of existing and planned vegetated conservation structures such as grassed waterways and field borders and buffers. Both technologies addressed here will be implemented using controller area networks (CAN) on agricultural field machinery.
Luck, J.D., S.K. Pitla, S.A. Shearer, T.G. Mueller, C.R. Dillon, J.P. Fulton, and S.F. Higgins. 2010. Potential for Pesticide and Nutrient Savings via Map-Based Automatic Boom Section Control of Spray Nozzles. Computers and Electronics in Agriculture 70(1): 19-26.