Occasional Tillage in a Wheat-Sorghum-Fallow Rotation Occasional Tillage in a Wheat-Sorghum-Fallow Rotation

Summary Beginning in 2012, research was conducted in Garden City and Tribune, KS, to determine the effect of a single tillage operation every 3 years on grain yields in a wheat-sor-ghum-fallow (WSF) rotation. Grain yields of wheat and grain sorghum were generally not affected by a single tillage operation every 3 years in a WSF rotation. Grain yield varied greatly by year from 2014–2018. Wheat yields ranged across years from mid-20s to 80 bu/a at Tribune and less than 10 to near 60 bu/a at Garden City. Grain sorghum yields ranged from less than 50 to greater than 140 bu/a, depending upon year and location. In no year or location, were grain yields significantly affected by a single tillage operation. However, at Tribune, when averaged across the 5-year period, a single tillage after wheat harvest reduced grain sorghum yields compared to a complete no-till system. This indicates that if a single tillage operation is needed to control troublesome weeds, that grain yields will generally not be significantly affected. Furthermore, if weed populations were high enough to cause yield reductions, then tillage might improve yields.


Introduction
Previous research has shown lower dryland wheat and grain sorghum yields with reduced tillage compared with no-tillage in a wheat-sorghum-fallow (WSF) rotation.The reduced tillage systems generally used four or more tillage operations in the 3-yr rotation.With increased incidence of herbicide-resistant weeds, the use of a complete no-tillage system may not be economical and tillage may be needed for effective control.The objective of the research project is to determine the effect of a single tillage operation every 3 years on grain yields in a WSF rotation.

Procedures
Research on occasional tillage intensities in a predominantly no-tillage WSF rotation at the Kansas State University Southwest Research-Extension Center research stations at Garden City and Tribune were initiated in 2012.The three tillage treatment intensities in this study are a single tillage in May or June during fallow, a single tillage after wheat harvest, and a complete no-tillage system.A sweep plow (Minimizer by Premier Tillage) was used for all tillage operations.When needed, herbicides were used to control weeds during fallow for all treatments.All treatments used herbicides for in-crop weed control.All other cultural practices (variety/hybrid, seeding rate, fertilization, etc.) were the same for all treatments.

Results and Discussion
Weeds were effectively controlled in all treatments and there were no visual differences in weed population across treatments.
At Tribune, wheat yields were 57-58 bu/a in 2018 compared with 41-43 bu/a for the 5-year average (Table 1).There were no significant yield differences among tillage treatments in any year or across years.Grain sorghum yields were very good in 2018 ranging from 115-130 bu/a (Table 2).Similar to wheat, there were no significant yield differences among tillage treatments in any year.However, averaged across years, NT produced greater yields than tillage post-wheat harvest.
At Garden City, wheat yields in 2018 were very low at 2-7 bu/a (Table 3).Between November 1, 2017, and April 1, 2018, 0.4 inches of precipitation was received, compared to the long-term period average of 3.46 inches.Wheat yields in 2014 were severely reduced by hail.There were no significant yield differences among tillage treatments in any year or averaged across years.Grain sorghum yields in 2018 were good with all yields near 90 bu/a or greater (Table 4).Similar to wheat, there were no significant yield differences among tillage treatments in any year or averaged across years.

Table 1 .
Grain yield response of dryland wheat to a single tillage operation (sweep plow) in a 3-year wheat-sorghum-fallow rotation grown from 2014-2018 near Tribune, KS

Table 2 .
Grain yield response of dryland grain sorghum to a single tillage operation (sweep plow) in a 3-year wheat-sorghum-fallow rotation grown from 2014-2018 near

Table 3 .
Grain yield response of dryland wheat to a single tillage operation (sweep plow) in a 3-year wheat-sorghum-fallow rotation grown from 2014-2018 near Garden City, KS

Table 4 .
Grain yield response of dryland grain sorghum to a single tillage operation (sweep plow) in a 3-year wheat-sorghum-fallow rotation grown from 2014-2018 near Garden City, KS