Document Type

Article

Publication Date

1-1-2018

Abstract

Quantifying soil-K availabilities at deeper depths may be necessary to determine optimum fertilizer-K rate for soybean [Glycine max (L.) Merr.] grown on low cation exchange capacity (CEC) soils that are prone to K leaching. We characterized full-season soybean response to fertilizer-K across 19 coarse-textured low- CEC sites during 2013 and 2014. Mehlich-1 soil-K concentrations at 0- to 15- and 0- to 30-cm depths better correlated with relative yield and explained 90% of relative yield variation compared to 77% for 0- to 60-cm depth. Critical soil-K concentrations were similar for relative yield, V5 plant-K concentration, and R2 leaf-K concentration, ranging from 48 to 73 mg K kg–1 for 0- to 15-cm and 41 to 63 mg K kg–1 for 0- to 30-cm depths. Soil-K concentrations less than this critical range accurately predicted positive yield responses to fertilizer-K 89% of the time for 0- to 15-cm and 80% for 0- to 30-cm depths. Plant- and leaf- K concentrations were equally good in predicting relative yield with critical concentrations of 19 to 22 g plant K kg–1 and 18 to 21 g leaf K kg–1. Plant-K concentration was better than leaf- K concentration in diagnosing K-deficient sites. Calibration model confirmed that soybean requires no fertilizer-K to maximize yield for soil-K concentrations above the critical ranges at both depths. However, for K-deficient soils, soil-K concentrations at 0- to 30-cm depth resulted in 7 to 32% less fertilizer-K requirements than 0- to 15-cm depth, indicating the value of deeper sample in recommending fertilizer-K for soybean grown on coarse-textured low-CEC soils.

Publication Source (Journal or Book title)

Agronomy Journal

First Page

369

Last Page

379

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