A variable-rate decision support tool

Abstract

Profitable precision or variable application of inputs depends on many factors; however, the inherent variability in a soil and or crop property and the relative responsiveness of yield to fertilizer inputs at different soil concentration levels are the most important factors in influencing economic gain. Generally, the greater is the spatial variation in the property influencing the input rate, the greater is the potential economic return from precision application compared to uniform application of an input. Based on a quantitative assessment of the spatial variation in soil properties that influence rates of input, a variable-rate decision support tool (VRDST) was developed to: (1) assess the potential profitability of variable-rate compared to uniform application and (2) identify the economic optimal uniform application rate if this is selected. The VRDST was evaluated using spatially distributed soil data from selected fields in North Carolina. Net return from variable-rate application and the economically optimal uniform rates are illustrated. Varying fertilizer cost, crop price and sampling costs greatly influenced net return from variable-rate application.