Previous research has shown trifoliate leaf potassium concentration at the R1-R2 growth stage to be highly correlated with yield and soil test K for determinate soybean varieties, but not for indeterminate varieties. Tissue K concentrations of MG 4 varieties at the R2 stage is often lower than the threshold for deficiency. The problem with the current critical leaf K concentration could be that indeterminate varieties can be in the R2 growth stage for a long period, and that K is allocated differently than in determinate varieties. This research seeks to improve diagnostics for interpreting leaf K of indeterminate soybeans. It aims to determine a specific growth stage, critical leaf K concentration, and sampling protocol for indeterminate varieties that is highly correlated with soybean yield potential and evaluate cultivars to improve ability to accurately interpret leaf tissue analysis of indeterminate soybean varieties.

Key Benefactors:
farmers, agronomists, extension agents