Back to Contents6.2.2 Field Demonstration of Variable-Rate P, K and Lime Application
Investigators: Scott Shearer, Tom Mueller, Richard Barnhisel, Sam McNeill, Lloyd Murdock, Steve Issacs, Carl Dillion and Steve Higgins.
Variable-rate application of fertilizer and other soil amendments has generated a significant amount of interest among producers and service providers. As the markets for fertilizer sales have matured they are also becoming more competitive. In part, service providers may be selling variable-rate application services in an effort to protect their markets. While variable-rate application is a logical process, there are many ancillary issues that may influence the profitability associated with this technology. The goal of this portion of the investigation will be to establish a methodology for investigating crop response to variable-rate application throughout Kentucky and the attendant economics. This method will then be used to assess the economics of variable-rate application with cooperating producers.
On-farm investigations are preferable to plot studies for investigation of precision agriculture technologies. Testing approaches at field scale eliminate the concern of using equipment and cultural practices that may deviate from typical production situations. Larger investigation sites also insure a range in large-scale variation that may not exist within smaller plots. Two cooperators will be selected annually. Constraints on the selection will include availability of yield history for potential investigation sites and excellent record keeping and business management practices. Preferences will be given to producers who want to move into variable-rate management of nutrients. Variable-rate management will continue for the duration of the project. Integral to this activity will be the generation of profit maps to coincide with the fields under investigation.
Target fields will be sampled using traditional approaches to grid sampling. All soil samples will be analyzed by the University of Kentucky's Regulatory Services. Management practices will consist of a randomized block experiment where one-half of the grid cells are managed using variable-rate application and the remaining cells with field average techniques. The University of Kentucky's Cooperative Extension Service's AGR-1 publication will be used for fertility recommendations for both approaches. Soil test parameters will be averaged to obtain nutrient and pH values for fertility recommendations for cells managed with the field-average approach. All management zones considered in the investigation must be large enough to insure that 100 yield data points are available for establishing the average yield of each management cell. In addition there should be a sufficient number of cells for either management approach to insure a characterization of variability, and so that sufficient data exist to enable a statistical comparison of both management approaches. An annual re-sampling interval will be used to track changes in soil fertility.
Variable-rate application for this portion of the investigation will be limited to P and K fertilizer, and agricultural lime. Biosystems and Agricultural Engineering currently maintains and operates a two-bin variable-rate applicator capable of spreading agricultural lime and granular fertilizers. This truck will be used at the investigation sites to accomplish variable-rate application, and to insure similar treatments between investigation sites. The Department of Biosystems and Agricultural Engineering has existing DGPS receivers, soil sampling equipment and software capabilities to accomplish the tasks as defined above.
The results of these field investigations will be published in refereed journals as appropriate, and in circulars and extension bulletins for dissemination to producers. This work will also be used in support of the handbook development as noted in Section 8.0 of this proposal. Economic results will be utilized to aid in the development of economic decision support tools identified under sub-objective 6.4.1.