Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/19/2000
Publication Date: N/A
Technical Abstract: Soil sampling for fertilizer recommendations is most often from the surface 15 to 20 cm. Variability in nutrient quantity and availability to crops may be significant when considering the changes in topsoil thickness (i.e., depth to the claypan) across a Mexico silty clay loam (Mollic Endoaqualf) soil landscape. This research was conducted to assess the potential interaction between topsoil thickness and soil-test phosphorus (P) and potassium (K) on corn and soybean crop response. Plots were established in 1996 on a corn-soybean field near Centralia, Missouri with varying topsoil thickness (5 to 119 cm). Topsoil thickness was estimated using bulk soil electrical conductivity (ECa)(R**2>0.95). A range of soil-test P and K values was achieved with fertilization in the springs of 1996 and 1999. Both soil-test P and K decreased dramatically over the 1997 and 1998 cropping period indicating minimal buffering capacity of the surface soil for fertilizer additions. Topsoil depth significantly explained the majority of corn yield variation in 1997 and 1999. In three instances (one soybean crop and two corn crops), yield response to increasing soil-test values was best in areas of enhanced topsoil thickness. Generally, sub- soil P and K were negatively correlated with topsoil thickness, an explanation of why we observed a reoccurring crop response to surface soil-test P and K in areas with greater topsoil thickness. A topsoil thickness map obtained by ECa sensing has the potential of being a valuable tool in claypan soil fertility management.