The ability of soil tests to identify nutrient‐deficient soils and recommend fertilizer rates that optimize agronomic yield is essential for profitable soybean [ Glycine max (L.) Merr.] production. Our objectives were to correlate relative soybean yield to Mehlich‐3 and 1 mol L −1 HNO 3 –extractable soil K and trifoliolate‐leaf K concentration at the R1 to R2 development stage and calibrate the K rates for Mehlich‐3‐extractable soil K. Experiments were established on silt loams at 34 site‐years planted with a Maturity Group IV or V cultivar and fertilized at five K rates (0–148 kg K ha −1 ). Mehlich‐3‐extractable soil K ranged from 46 to 167 mg K kg −1 and produced relative soybean yields of 59 to 100% when no K was applied. Eleven sites had Mehlich‐3‐extractable K < 91 mg K kg −1 and all responded positively to K fertilization. Soybean grown in soil having 91 to 130 mg K kg −1 responded positively at nine of 15 sites. Mehlich‐3 soil K explained 76 to 79% of the variability in relative yields and had critical concentrations of 108 to 114 mg K kg −1 , depending on the model. The linear‐plateau model predicted the critical HNO 3 –extractable soil K to be 480 mg K kg −1 Trifoliolate‐leaf K concentration increased significantly, positively, and linearly as Mehlich‐3‐ and HNO 3 –extractable soil K increased, but Mehlich‐3 soil K explained only 49 to 53% of the variation in trifoliolate‐leaf K. Mehlich‐3‐extractable K is an excellent predictor of soil K availability for soybean grown on silt loams in eastern Arkansas.
No takes yet. Share an insight, caveat, or question.
Slaton et al. (2010) studied this question.