Effects of cultural practices on nitrate in soil and nitrogen in grain sorghum

Abstract

Crop residue management influences the soil physical, chemical, and biological environment. Our objective was to examine, in unfertilized rotation systems and a semi‐arid environment, the effects of cultural practices on soil nitrate, nitrogen (N) in plant tissue, and yield of rainfed grain sorghum [Sorghum bicolor (L.) Moench]. Field experiments conducted on a wheat‐sorghum‐fallow (WSF) rotation system included conventional tillage plus furrow diking (FD), conventional tillage (CT), no‐tillage with wheat (Triticum aestivum) residue maintained on the plots (NT+), and no‐tillage with residue removed (NT‐). Wheat residues in FD and CT plots were incorporated during tillage operations. Treatments were imposed 2 weeks before seeding of sorghum. Soil water was measured at three growth stages of sorghum: emergence, flowering, and harvest. The FD and NT+ treatments resulted in increased storage of growing season precipitation, which subsequently produced higher sorghum grain yield. Diking resulted in about 44 mm more stored soil water at emergence and about 770 kg ha^‐1 more sorghum grain yield than the CT treatment. The NT+ treatment also resulted in significant increases in water storage (42 mm) and sorghum grain yield (870 kg ha^‐1) compared to NT‐ treatment. Furrow diking resulted in greater (P≤0.05) soil NO₃‐N at the 30‐ to 60‐cm depth at flowering. Concentrations of N in leaf, stover, and grain were greater in plants with FD than with other treatments. Available soil water, soil NO₃‐N, sorghum leaf‐N concentration, and grain and stover yields were noticeably responsive to cultural practices.