Experiences with Variable Rate Fertilizer and Lime Applications in Kentucky. (A08-hancock924642-oral)
Authors:
D.W. Hancock* - Univ. of Kentucky S.A. Shearer - Univ. of Kentucky L.W. Murdock - Univ. of Kentucky R.I. Barnhisel - Univ. of Kentucky G.J. Schwab - Univ. of Kentucky
Abstract:
In a recent survey, 61.7% of precision farmers in Kentucky have used variable rate application (VRA) of fertilizer and lime. A multi-disciplinary research effort at the University of Kentucky has studied varying fertilizer and lime rates based on short-scale soil fertility variability, technologies used to
implement this practice, and the profitability of the system in Kentucky. Very little correlation (R2=0.05, 0.22, and 0.10, respectively) was found between the variability of corn yield and soil test P, K, and pH variability in diverse fields and climate conditions. Accuracy of VRA was also questioned, since P, K, and lime are usually applied by error-prone spinner-spreaders in Kentucky. A poor relationship (R2=0.21) was observed between K prescribed and K applied using common VRA methods. In a theoretical analysis that assumed perfect application, researchers used response curves for high yield potential soils and found that VRA of P and K would only be profitable if 50% or more of the field was above the economic threshold for application and 50% or less of the field was low in P and K. In Kentucky, such a divergence in P or K level usually only occurs where animal manure applications have been concentrated or historical management differences are present. Such limits the profit potential of VRA of P, K, and lime using spinner-spreaders in Kentucky.
Speaker Information: Dennis Hancock, Univ. of Kentucky, 119 C.E. Barnhart Bldg.University of Kentucky, Lexington, KY 40546; Phone: 859-257-3000 x331; E-mail: [email protected]
Session Information: Tuesday, November 4, 2003, 12:55 PM-5:55 PM Presentation Start: 3:45 PM
Keywords: Variable Rate Application; Fertilizer; Precision Agriculture; Lime