Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/1997
Publication Date: N/A
Interpretive Summary: Low precipitation limits dryland crop production in the semiarid southern Great Plains. To improve crop yields under those conditions, water storage in soil between crops must be increased and plant roots must be able to grow deeply into the soil to extract the water. In this study, effects of furrow diking (FD), conventional tillage (CT), no-tillage with wheat residue (NT+), and no-tillage without wheat residue (NT-) treatments on grain sorghum root growth, soil water depletion, and grain yield were determined. The soil's resistance to penetration by a pointed probe (penetrometer), known as cone index (CI) was also determined. All determinations were made for the grain sorghum crop of a winter wheat- sorghum-fallow rotation. The CI was lower and rooting depth, soil water use, and grain yield were greater with the FD treatment than with the CT and NT- treatments. Most result with the NT+ treatment were similar to those with the FD treatment. An exception was grain yield in one year whe it was lower because of a nitrogen deficiency on the NT+ treatment plots. The generally more favorable results with the FD and NT+ treatments are attributed mainly to little or not runoff, which resulted in greater water storage, lower CI, greater root penetration, and, hence, greater water use and grain yields by the sorghum. Furrow diking and no-tillage suitable systems for the wheat-sorghum-fallow rotation in the southern Great Plains.
Technical Abstract: Crop production in the Southern Great Plains of Texas is limited by insufficient precipitation. Consideration must be given to the possible influence of tillage and residue management on root growth and water extraction and consequently plant growth and yield. Field studies were conducted in unfertilized rotation systems to determine the effects of cultural practices on grain sorghum [Sorghum bicolor (L.) Moench] rooting depth and to relate this with changes in soil water content and cone index (CI). Four cultural treatments conducted 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 residue removed from the plots (NT-). The FD system decreased penetrometer resistance and increased depth of rooting, profile water use and grain yield. Conventional tillage (CT) and NT+ adversely affected all these variables. Tillage operations loosened the soil, and hence CI of the tilled layer was low. The effect was greater in 1992 than in the 1991 growing season. In the NT+ treatment, a decrease in CI values was related to increased root development and penetration of roots to deeper soil layers which in turn improved the profile water utilization and sorghum yield. No-tillage in the absence of crop residues affected root length density and water utilization adversely and decreased sorghum grain yield compared to FD and NT+ management systems. The higher rooting densities, at all 3 growth stages (30, 60, and 90 days after emergence of sorghum) under FD and NT+ treatments compared to CT and NT- treatments, was associated with higher soil water contents throughout the profile.