No-tillage (NT) systems provide several benefits to dryland crop production in the semiarid central Great Plains (CGP). These include improvements to soil health, reduced wind and water erosion, fewer energy inputs, increased retention of soil moisture, and improved crop yields. Despite these benefits, maintaining continuous NT and the associated soil conservation benefits are at risk due to a lack of effective control of herbicide-resistant (HR) weeds, as well as issues of compaction and stratification (abrupt changes by soil depth) of soil pH and nutrients. Stratification of soil nutrients and soil acidity could reduce nutrient availability and uptake by crops and increase the chances of nitrogen and phosphorus losses in surface runoff.

What is strategic tillage? Strategic tillage (ST) with a sweep plow, timed when soil erosion risk is low in an otherwise NT cropping system, could help manage HR weed populations and reduce stratification of soil properties. After the one-time tillage operation, the field goes back to NT production. 

This ST approach could increase productivity and profitability of dryland cropping systems in the region. However, the soil health impacts of ST are unclear, particularly in water-limited environments of the CGP where susceptibility to wind erosion can be high. Few studies have investigated the effects of ST on soils that have been in continuous NT in dryland conditions in the CGP. 

The objectives of this study were to determine the effects of strategic tillage in long-term NT systems: Determine soil quality following tillage of an otherwise long-term NT soil, soil water content at winter wheat planting, winter wheat and grain sorghum yields, effectiveness of ST to redistribute soil nutrients, reduce soil acidity, and control perennial grass and herbicide-resistant weeds.

This strategic tillage study was conducted using long-term tillage and crop rotation experiment plots established in 1976 at the K-State Agricultural Research Center - Hays.

Summary of strategic tillage study - in general, broadleaf and grassy weeds were significantly less with RT and ST compared to the NT treatments.

Soil water content - irrespective of crop rotation, soil water content at wheat planting was significantly less with RT treatments compared to NT or ST. Soil water content with NT was not different from that of ST under cropping systems with fallow. Tillage (ST or RT) reduced soil water content at wheat planting in a continuous wheat system.

Winter wheat grain yields decreased with increasing cropping intensity. Averaged across years and crop rotations, wheat yield with ST was greater than the NT or RT systems, mostly due to better weed control and increased nutrient availability.

Sorghum grain yield over the 2 years with ST was not different from that of NT, but were both greater than RT. Increasing cropping intensity reduced sorghum grain yield, average grain yield with summer fallow (SF) was similar to wheat sorghum fallow (WSF), but greater than sorghum, sorghum (SS). 

Soil properties - tillage had no effect on soil bulk density. However, increasing cropping intensity lowered the bulk density measured in the upper 0 to 2 in. of the soil.

Take-home message - these results suggest strategic tillage could provide a mitigation option for herbicide-resistant weeds in no-till crop production with little impact on crop yields and soil chemical properties. Currently, research studies at Garden City, Hays, and Tribune are evaluating occasional tillage (one or two tillage operations every three years in a wheat-sorghum-fallow rotation compared to NT) to determine the effect of low-frequency tillage in the cropping system.

Information provided by Augustine Obour, John Holman and Alan Schlegel Soil and Cropping Systems Scientists with K-State Agricultural Research Centers in Hays, Garden City and Tribune. 

Stacy Campbell is an Agriculture and Natural Resources agent for Cottonwood Extension District. Email him at scampbel@ksu.edu or call the Hays office, 785-628-9430.