Do soil test levels and fertilization with phosphorus and potassium impact field crop tissue concentrations?

Abstract

Soil testing and plant tissue nutrient concentrations form the basis for fertilizer recommendations in Ohio. The response of crop phosphorus (P) and potassium (K) nutrient concentrations to soil test levels and fertilizer applications influences fertilizer recommendations but have not been rigorously evaluated in this region. The objective of our study was to determine the effects of (a) soil test P and K levels and (b) P and K fertilization on mid-season leaf and grain P and K concentrations of corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.). From 2014–2018, we conducted 186 on-farm trials (99 P, 87 K trials) over a diversity of soil types, crop genetics, and management histories in 39 counties throughout Ohio. Soil test P and K levels, mid-season leaf P and K concentrations, and grain P and K concentrations were measured on randomized and replicated plots. Both leaf and grain nutrient concentrations generally increased with the soil test levels, but the relationships were weak in all three crops. Fertilization of P and K marginally but consistently increased leaf tissue concentrations in all crops but had a lesser effect on grain P and K concentrations. Our data suggest that current sufficiency ranges for corn, soybean, and wheat are too high and need revision. Collectively, our results show that crop P and K tissue concentrations are positively, but weakly related to soil test levels and fertilization, and this information has important implications for future development of nutrient management frameworks in Ohio.