Real-time use of soil moisture data for refined GreenSeeker sensor based N recommendations in winter wheat (Triticum aestivum L.) and effect of foliar p fertilization on corn (Zea mays L.) grain yield and phosphorus use efficiency

Abstract

Scope and Method of Study: I. The hypothesis was that soil moisture measurements would allow for more precise prediction of yield potential and more efficient N fertilizer use efficiency. The objectives were: to determine the effect of mid-season soil profile moisture on prediction of yield potential in winter wheat, and to establish the functional relationship for adjusting fertilizer N recommendations based on profile moisture and to refine the on-line Sensor Based Nitrogen Rate Calculator. Correlation of 64 parameters that incorporated soil moisture (WC and FWI) at 4 depths (5, 25, 60, and 75 cm) were evaluated to assess if soil moisture can assist to estimate winter wheat grain yield. II. The objectives were: 1. to determine whether foliar applications of P can result in increased corn grain yields and P uptake, and improve use efficiency; 2. to determine the optimum time for foliar P application in corn. Combinations of 2 P rates, 2 fertilizer application times, and 4 P sources were evaluated.

Findings and Conclusions: I. The results of this study showed that NDVI and INSEY were good predictors of grain yield in winter wheat for all site-years. All of the 64 indices incorporating volumetric water content and fractal water index were equally as good in predicting winter wheat grain yield for all site-years. II. In 2006 there were no statistically significant differences between any of the treatments. Many factors significantly affected corn grain yields in 2008. Phosphorus use efficiencies were very low for both growing seasons. This was due to lack of response to P fertilizer applied.