Long-Term No-Till in a Wheat-Sorghum-Fallow Rotation

Grain yields of wheat and grain sorghum increased with decreased tillage intensity in a wheat-sorghum-fallow (WSF) rotation. In 2014, available soil water at wheat planting was 2 inches greater for no-till (NT) than for reduced-tillage (RT) or conventional tillage (CT). For grain sorghum in 2014, available soil water at planting was greatest with RT and least with CT. Averaged across the 14-year study, available soil water at wheat and sorghum planting was similar for RT and NT and about 1 inch greater than CT. Averaged across the past 14 years, NT wheat yields were 5 bu/a greater than RT and 7 bu/a greater than CT. Grain sorghum yields in 2014 were 22 bu/a greater with longterm NT than short-term NT. Averaged across the past 14 years, sorghum yields with long-term NT have been nearly twice as great as short-term NT (61 vs. 33 bu/a).


Summary
Grain yields of wheat and grain sorghum increased with decreased tillage intensity in a wheat-sorghum-fallow (WSF) rotation.In 2014, available soil water at wheat planting was 2 inches greater for no-till (NT) than for reduced-tillage (RT) or conventional tillage (CT).For grain sorghum in 2014, available soil water at planting was greatest with RT and least with CT.Averaged across the 14-year study, available soil water at wheat and sorghum planting was similar for RT and NT and about 1 inch greater than CT.Averaged across the past 14 years, NT wheat yields were 5 bu/a greater than RT and 7 bu/a greater than CT.Grain sorghum yields in 2014 were 22 bu/a greater with longterm NT than short-term NT.Averaged across the past 14 years, sorghum yields with long-term NT have been nearly twice as great as short-term NT (61 vs. 33 bu/a).

Procedures
Research on different tillage intensities in a WSF rotation was initiated in 1991 at the Southwest Research-Extension Center near Tribune, Kansas.The three tillage intensities in this study are conventional (CT), reduced-tillage (RT), and no-till (NT).The CT system was tilled as needed to control weed growth during the fallow period.On average, this resulted in four to five tillage operations per year, usually with a blade plow or field cultivator.The RT system originally used a combination of herbicides (one to two spray operations) and tillage (two to three tillage operations) to control weed growth during the fallow period; however, in 2001, the RT system was changed to NT from wheat harvest through sorghum planting (short-term NT) and CT from sorghum harvest through wheat planting.The NT system exclusively used herbicides to control weed growth during the fallow period.All tillage systems used herbicides for in-crop weed control.

Soil water
The amount of available water in the soil profile (0 to 8 ft) at wheat planting varied greatly from year to year (Figure 1).In 2014, available soil water was 2 inches greater for NT than for RT or CT.Averaged across the 14-year study, available soil water at wheat planting was similar for RT and NT (about 7 inches) and 1 inch greater than CT.
Similar to the situation for wheat, the amount of available water in the soil profile at sorghum planting varied greatly from year to year (Figure 2).In 2014, available soil water at sorghum planting was greatest with RT and least with CT.On average, available soil water at sorghum planting was similar for RT and NT and about 1 inch more than CT.

Grain yields
Wheat yields have been severely depressed in 9 of 14 years since 2001, primarily because of lack of precipitation.Reduced-tillage and NT increased wheat yields (Table 1).On average, wheat yields were 7 bu/a higher for NT (21 bu/a) than CT (14 bu/a).Wheat yields for RT were 2 bu/a greater than CT, even though both systems had tillage prior to wheat.NT yields were significantly less than CT or RT in only 1 of the 13 years.
Available soil water in 8-ft profile at wheat planting in a WSF rotation as affected by tillage intensity, Tribune, Kansas, 2001-2014.The last set of bars (Mean) is the average across years.Figure 2. Available soil water in 8-ft profile at grain sorghum planting in a WSF rotation as affected by tillage intensity, Tribune, Kansas, 2001-2014.The last set of bars (Mean) is the average across years.