Strategic tillage effects on crop yields, soil properties, and weeds in dryland no-tillage systems

Authors: OBOUR, AUGUSTINE - Kansas State University Agricultural Research Center-Hays; HOLMAN, JOHNATHON - Kansas State University Extension Center; SIMON, LOGAN - Kansas State University Agricultural Research Center-Hays; SCHLEGEL, ALAN - Kansas State University Extension Center

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2021
Publication Date: 3/31/2021
Citation: Obour, A.K., Holman, J.D., Simon, L.M., Schlegel, A.J. 2021. Strategic tillage effects on crop yields, soil properties, and weeds in dryland no-tillage systems. Agronomy. 11. Article 662. https://doi.org/10.3390/agronomy11040662.
DOI: https://doi.org/10.3390/agronomy11040662

Interpretive Summary: Long-term no-till (NT) systems in the semiarid Southern Ogallala Aquifer region tend to increase wheat and grain sorghum yields by increasing soil moisture at planting. However, the advantages of NT systems are being threatened by the occurrence of herbicide resistant (HR) weeds, including kochia and tumble windmill grass. Working in a project funded by the USDA ARS Ogallala Aquifer Program, scientists from Kansas State University examined strategic tillage (ST) to control HR weeds and improve crop yields in three long-term dryland NT cropping systems: 1) continuous winter wheat; 2) wheat-fallow; and (3) wheat-grain sorghum-fallow. The ST treatment consisted of two sweep tillage events three days apart during the summer fallow period. Soil water content at wheat planting was significantly less with reduced tillage (RT) compared to NT or ST. Strategic tillage did not affect wheat or grain sorghum yields, but RT decreased sorghum yields by 15% compared to NT. Increasing cropping intensity reduced wheat yields. Strategic tillage as compared to NT had no effect on soil organic carbon or nitrogen concentrations. These results suggest ST could provide a mitigation option for herbicide resistant weeds in NT systems with little impact on crop yields and soil properties.

Technical Abstract: Long-term no-till (NT) systems in the semiarid central Great Plains of the United States require flexible management strategies to minimize the impacts of herbicide resistant (HR) kochia (Kochia scoparia L.) and tumble windmill grass (Chloris verticillata Nutt.) as well as nutrient stratification on soil and crop productivity. This study examined strategic tillage (ST) to control HR weeds and improve crop yields in an otherwise long-term NT cropping system. Treatments were three crop rotations: (1) continuous winter wheat (Triticum aestivum L.) (WW); (2) wheat-fallow (WF); and (3) wheat-grain sorghum (Sorghum bicolor L.)-fallow (WSF); as main plots. Subplots were reduced tillage (RT), continuous NT, and ST of NT. Results showed ST and RT treatments provided significant control of HR weeds. Soil water content at wheat planting was significantly less with RT compared to NT or ST. Strategic tillage did not affect wheat or grain sorghum yields, but RT decreased sorghum yields by 15% compared to NT. Increasing cropping intensity reduced wheat yields. Strategic tillage reduced bulk density and had no effect on aggregate size distribution or mean weight diameter (MWD) compared to NT though RT reduced the proportion of large macroaggregates and MWD. Similarly, ST compared to NT had no effect on soil organic carbon (SOC) or nitrogen (N) concentrations. Soil phosphorus (P) was not different among the tillage treatments though RT increased potassium (K) concentration near the soil surface. The SOC, MWD, and micronutrient availability were greatest with WW though it had significantly lower pH and K concentration. Our results suggest ST could provide a mitigation option for HR weeds in NT systems with little impact on crop yields and soil properties.