Corn response to long-term manure and fertilizer applications on a preceding perennial forage crop

Abstract

Removing solids from dairy slurry improves grass N response and reduces soil loading of P and organic N which makes this practice useful for sustainable farming. Therefore, it is important to understand the effects of long-term applications on grass of separated dairy slurry on the growth and N response of a subsequent corn crop. This two-year field study investigated the residual effects after 11 years with applications on a perennial grass (Festuca arundinacea Schreb.) of whole (WS), separated dairy slurry (LF) obtained from the second stage of a two stage lagoon system, mineral fertilizer (Fert), WS plus Fert (WS/Fert), and Control (no fertilizer), on two subsequent crops of silage corn (Zea mays L.). In addition to the legacy nutrients, the corn received commercial fertilizer at rates 0, 100, 200 kg N ha–1 or 200 kg N ha–1 plus starter P (40 kg ha–1) at time of planting. Whole-crop yield and N uptake were determined at harvest stage. Over two years, corn yielded more with greater N and P uptake after long-term applications of WS than LF, Fert and WS/Fert, regardless of current fertilizer applications. Additional mineral fertilizer N and P did not substitute for the historical effects. There was a significant linear relationship of corn N uptake with historical applications of organic-N but not with mineral-N or total-N across current fertilizer treatments. These results support farmer practice of supplementing first-year corn, after long-term manure application on grassland, with modest N and P as starter application only and then increasing N rates thereafter.