Tillage and residue effects on root growth and yields of grain sorghum following wheat

Crop production in the Southern Great Plains of TX (USA) is limited by insufficient precipitation. Furrow diking and residue management systems in water deficit regions can influence water infiltration, root growth and water extraction and, consequently, plant growth and yield. Field studies were conducted on a clay loam soil in unfertilized rotation systems to determine the influence of tillage and residue management practices on grain sorghum [Sorghum bicolor (L.) Moench] rooting depth and changes in soil water content and cone index (CI). Treatments imposed on a wheat-sorghum-fallow (WSF) rotation system included furrow diking (FD), conventional tillage (CT), no-tillage with wheat (Triticum aestivum) residue maintained on the field (NT +), and no-tillage with wheat residue removed from the field (NT -). Furrow diking and NT + management systems increased sorghum grain yields 19 and 15%, respectively, compared to CT. Grain yields from the NT - system were not significantly different from the CT system. The FD system decreased CI and increased depth of rooting, profile water use and grain yield. Conventional tillage and NT - adversely affected these variables. Tillage operations loosened the soil and reduced the CI of the tilled layer. A decrease in CI values in the NT + treatment was related to increased root development and penetration of roots to deeper soil layers. Root length in the 40 to 60 cm depth of FD and NT + treatments was 30 to 85% greater compared to the CT and NT - treatments. Greater rooting densities, at all three growth stages (30, 60 and 90 days after emergence of sorghum), under FD and NT + were associated with higher soil profile water contents. Data from this study show that profile water content, root development and sorghum grain yield can he significantly increased in semiarid regions with limited rainfall by incorporating furrow diking or surface residues into the management system. (C) 1997 Elsevier Science B.V.