Nitrogen Fertilization of No‐Till Cotton on Loess‐Derived Soils

Abstract

Information on nitrogen (N) fertilization of no‐till (NT) cotton (Gossypium hirsutum L.) is needed to optimize lint yields and earliness. We evaluated five N rates and three application methods for NT cotton production on Loring silt loam (fine‐silty, mixed, active, thermic Oxyaquic Fragiudalfs) with natural winter annuals as a cover; and on Memphis silt loam (fine‐silty, mixed, active, thermic Typic Hapludalfs) having corn (Zea mays L.) stover as a cover and on Lexington silt loam (fine‐silty, mixed, active, thermic Utlic Hapludalfs) having winter wheat (Triticum aestivum L.) as a cover. Nitrogen rates of 0, 34, 67, 101, and 134 kg ha−1 were either broadcasted as ammonium nitrate (AN) or injected as urea–ammonium nitrate (UAN) at planting. Additional treatments included broadcasting 67 kg N ha−1 as AN at planting with either 34 or 67 kg N ha−1 banded 6 wk later. Relative to no N, broadcasting 67 kg N ha−1 as AN increased 4‐yr average NT lint yields on Loring silt loam from 739 to 1281 kg lint ha−1 and 2‐yr average yields on Lexington silt loam from 1086 to 1535 kg ha−1. A higher N rate (101 kg N ha−1) was needed to increase 2‐yr average yields on Memphis silt loam from 821 to 1169 kg ha−1. Broadcasting AN was a satisfactory placement method producing yields equal to or higher than injecting UAN or splitting AN for NT cotton produced on these loessial soils despite different covers and residues.