From k-state extension Agronomy e-Updates
by Barney Gordon, Agronomist
“Soybeans are heavy users of K, and K deficiency has occurred with greater frequency in recent years under conservation tillage systems. We conducted a series of tests in 2004 and 2005 at the Irrigation Experiment Field near Scandia to find out if K applied as a starter, either alone or in combination with foliar applications, would increase yields of irrigated, ridge-till soybeans.”
“Treatments consisted of liquid K (Trisert-K+) applied alone as a starter, 2 inches to the side and 2 inches below the seed; liquid K applied as a starter in combination with various foliar applications; and liquid K applied only as a foliar application, at various growth stages.”
“All the K fertilizer treatments increased soybean yields. The treatments also increased whole-plant K concentrations (data not shown). Yields were maximized with either the combination of starter plus an application at the R3 (early pod) stage; or two foliar applications at the 5 gpa rate, one at V5 and one at R3.”
“The preplant broadcast application was not as effective as starter plus foliar-applied K. The maximum demand for K by soybeans occurs at full bloom, so it is not surprising that foliar applications at the V5 and R3 stages would benefit yields more than a preplant broadcast or starter application alone.”
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