Precipitation, runoff, and yields from terraced drylands with stubble-mulch or no tillage

Authors: Baumhardt, Roland - Louis; Johnson, Grant; DOCKAL, JUSTIN - Former ARS Employee; Brauer, David; Schwartz, Robert; JONES, O - Retired ARS Employee

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2020
Publication Date: 10/19/2020
Citation: Baumhardt, R.L., Johnson, G.L., Dockal, J.R., Brauer, D.K., Schwartz, R.C., Jones, O.R. 2020. Precipitation, runoff, and yields from terraced drylands with stubble-mulch or no tillage. Agronomy Journal. 112(5):3295-3305. https://doi.org/10.1002/agj2.20331.
DOI: https://doi.org/10.1002/agj2.20331

Interpretive Summary: Precipitation is the only water source for increasingly important dryland crops in the western Great Plains and runoff decreases both water conserved and crop yields. ARS scientists from Bushland, TX quantified storm water runoff and precipitation storage under variable precipitation and field conditions using conservation practices like no-tillage (NT) or contour farming. The goal of increasing yields of wheat and sorghum grown in a three-year wheat-sorghum-fallow (WSF) rotation from 1984 to 2010 were better achieved with NT than stubble-mulch (SM) tillage. Less soil loss with NT than SM showed NT residue cover prevented entrainment despite greater fallow runoff. By reducing evaporation during fallow, NT had greater soil water and grain sorghum yield than SM. These results will help farmers and crop consultants improve semiarid dryland cropping practices by decreasing evaporation and soil erosion with NT residues.

Technical Abstract: Dryland crops rely on precipitation as their exclusive water source, but storm water runoff decreases the amount available for biomass and grain production. Management practices that minimize runoff often increase the opportunity time for infiltration and improve precipitation storage as soil water. Our objective was to quantify storm water runoff from contour farmed terraces in relation to precipitation and field characteristics and then relate runoff to soil water at planting and yields of wheat (Triticum aestivum L ) and sorghum [Sorghum bicolor (L.) Moench] grown in a three year wheat-sorghum-fallow (WSF) rotation. Comparisons of long-term, 1984 to 2010, runoff observations indicated mean annual runoff for both uncropped periods of the WSF rotation were significantly greater with no-tillage (NT) than stubble-mulch (SM) tillage. By contrast, soil loss was greater for SM than NT because residue cover of undisturbed NT soil was less subject to entrainment and loss. Increasing field slope from 1.2% to 1.8% produced greater fallow runoff, which is water lost from dryland production. Nevertheless, soil water was significantly greater with NT, which reduced evaporative losses during fallow compared with SM. Long-term wheat yields exhibited no difference due to tillage, but NT grain sorghum yields increased significantly over SM tillage. The data show that while runoff with NT was typically greater than SM, profile soil water at planting was also greater for NT and increased grain sorghum yields significantly. We conclude that decreasing evaporative water losses with NT residues is the primary factor affecting soil water conservation.