Applied Fertility Management for Irrigated Soybean Production

Past research from Kansas State University's (KSU) North Central Kansas Experimental Field near Scandia has demonstrated that more intensive fertility management, including direct application of P and K, has the potential to significantly improve irrigated soybean yield. Despite these findings, soybean producers have been slow to adopt more intensive fertility management programs. This project, initiated in 2012, sought to expand upon previous soybean fertility work by performing both a small plot study and a farmer field strip trial to increase awareness of irrigated soybean yield potential with proper fertility management.

The small plot work in 2012 was conducted at the KSU Irrigation Experimental Field, and the field-scale study on a producer’s field in the same region. Small plot treatments included a zero fertilizer control, and all combinations of 30 and 80 lb P₂O₅/A, and 80 and 120 lb K₂O/A. The effects of N and S were evaluated at higher P and K rates. Soil test P concentration in the small plot study was low (7 ppm Bray-1) while soil test K was high (542 ppm). The zero fertilizer control yield in the first year was 53 bu/A and yield with fertilizer input ranged from 59 to 63 bu/A. The effect of fertilizer treatments over the control was significant, but there was no significant difference among the fertilizer treatments. Field scale plot design was simpler, with a zero fertilizer control, one P (30 lb P₂O₅) and one K (80 lb K₂O) rate and a combination of the two. During the second year (2013) of this study the principal investigator suddenly and unexpectedly left his position with the university. Consequently no data or reports were available for the 2013 season, despite numerous requests. This project will not be continued in 2014.