Contrasting tillage effects on stored soil water, infiltration and evapotranspiration fluxes in a dryland rotation at two locations

Authors: Schwartz, Robert; SCHLEGEL, ALAN - Kansas State University; BELL, JORDAN - Texas A&M University; Baumhardt, Roland - Louis; Evett, Steven - Steve

Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2019
Publication Date: 3/18/2019
Citation: Schwartz, R.C., Schlegel, A., Bell, J.M., Baumhardt, R.L., Evett, S.R. 2019. Contrasting tillage effects on stored soil water, infiltration and evapotranspiration fluxes in a dryland rotation at two locations. Soil and Tillage Research. 190:157-174. https://doi.org/10.1016/j.still.2019.02.013.
DOI: https://doi.org/10.1016/j.still.2019.02.013

Interpretive Summary: As water availability for irrigation from Ogallala Aquifer decreases, producers are growing crops on more dryland acres. The yield and profitability of dryland farming is heavily dependent on the fraction of rainfall that is used by the crop. Tillage can influence rainfall capture by the soil, however no-till has shown mixed results across the US Great Plains in improving sorghum grain yield compared with reduced or conventional tillage. Scientists from ARS (Bushland, Texas) and Kansas State University in the ARS-led Ogallala Aquifer Program evaluated the amount of rainfall that infiltrated into the soil as well as that lost to evaporation and drainage during phases of a winter wheat-sorghum-fallow rotation under no-till and reduced tillage. The study was carried out at Bushland, Texas and at Tribune, Kansas with differing soil properties. Deep drainage comprised only a small proportion of available water lost to the cropping system. Evaporation during summer fallow periods was not reduced under no-till at both locations. At the Bushland location, tillage did not significantly influence infiltration, soil water available to crops, and long-term sorghum yield. At the Tribune location, cumulative rainfall infiltration was 60% greater under no-till compared with reduced tillage and increased water available to sorghum during the growing season, thus explaining the long-term 35% sorghum yield advantage compared with reduced tillage. The study demonstrates that no-till does not perform similarly across all environments in increasing effective rainfall that is available to crops.

Technical Abstract: There are significant uncertainties in partitioning growing season precipitation into the water balance components that determine water available for dryland crop yield across a range of environments and tillage practices. We evaluated profile soil water contents at a high temporal resolution during phases of a dryland wheat (Triticum aestivum L.) –sorghum (Sorghum bicolor L.) -fallow rotation under no tillage (NT) and stubble-mulch tillage (ST) management at Bushland, Texas and Tribune, Kansas to assess event-based soil water balance components. Cumulative infiltration and evaporation were estimated based on hourly changes in stored soil water using a water balance approach and a drainage model. Estimated deep drainage comprised a small proportion of the soil water budget averaging five percent of annual precipitation in Bushland. Tillage did not significantly influence cumulative infiltration during summer fallow and growing season periods at Bushland. In contrast, NT at the Tribune location exhibited significantly greater (P=0.023) cumulative infiltration compared to ST during the wheat fallow period just prior to sorghum planting. At both locations during summer fallow periods, NT was no more efficient in increasing stored soil water over that obtained with ST. Evaporation during summer fallow periods was more a function of the soil water content near the surface than the tillage practice. Effective infiltration expressed as a fraction of precipitation averaged 0.55 and 0.57 under NT and ST, respectively, at Bushland compared with 0.83 and 0.52 under NT and ST, respectively, at Tribune. Observations of effective infiltration elucidate historical results of the incremental sorghum grain yield response of NT over ST that averaged 12 percent at Bushland and 35 percent at Tribune. Partitioning of growing season precipitation to transpiration was insufficient in Bushland to generate yield increases under NT of similar magnitude to that observed in Tribune demonstrating that NT does not perform similarly across all environments.