Prolificacy in Corn: Its Effects on Nitrate and Ammonium Uptake and Utilization

Corn ( Zea mays L.) genotypes differing in prolificacy were evaluated for N uptake and utilization from NO ‐ 3 and NH + 4 sources. Five single‐cross hybrids which differed in capacity to produce more than one ear per plant were field grown to maturity on a Dothan loamy sand (plinthic Paleudults), with two different N sources, calcium nitrate, or urea plus nitrapyrin. The two N sources were applied at two rates, each in multiple applications throughout the growing season. This minimized (i) the magnitude of nitrification within the urea treatments, and thereby enhanced the supply of N in the NH + 4 form to the plants grown under the urea treatment, and (ii) differences in N availability due to differential leaching rates of NH + 4 and NO ‐ 3 . At the low N supply there was little difference in N uptake or grain yield between the two N sources. At the high N supply, genotypes that produced > 1.5 ears per plant absorbed more N from the urea treatment and produced more dry matter during ear development. These increases were associated with an enhanced grain yield over the comparable NO ‐ 3 treatment. Fully prolific plants demonstrated greater remobilization of N from vegetative tissue to grain. However, they also showed a lesser capability to absorb N during ear development, particularly from the NO ‐ 3 source. The latter trait may have limited yields as indicated by the enhanced grain production in these genotypes when grown with a NH + 4 source.