Many data are available on the relative efficiencies of various fertility treatments for corn (Zea mays L.) when grown by the conventional methods of clean tillage. Few data are available, however, on the relative efficiencies of sources and rates of N, P, and K on the growth, chemical composition, and yield of corn grown with the notillage system.
An experiment was conducted at Blacksburg, Virginia, on Groseclose silt loam (Typic, Hapludults; clayey, mixed, mesic) to determine the effects of 168 and 280 kg N/ha, 0 and 100 kg P/ha from partially and fully acidulated rock phosphate, 25 kg P/ha from fully acidulated rock phosphate, and 140 kg K/ha from KCI and K~SO4 on the growth, chemical composition of leaves and yield of notillage corn on a chemically killed orchardgrass sod.
Growth was significantly slower with the higher rate of N, but significantly increased with increased rates of applied P. Plant growth rate was unaffected by sources of K. Leaf concentrations of N and K were unaffected by rates of N and sources of K, respectively, but the P and K concentrations were significantly increased with the higher P rates. Leaf Mn concentration was higher with the higher rate of N than with the lower rate. The Ca, Mg and Mo concentrations in the leaf increased with P fertilization, but the Zn concentration decreased with P fertilization.
Corn yields were significantly higher with concentrated superphosphate than with partially acidulated rock phosphate applied at the same rate of P. The higher rate of N resulted in a significant reduction in grain yield of 552 kg/ha. There was no response to S in the K2SO4.