A large-scale rainfed cropping systems research and demonstration project has been underway since 2008 at the Southwest Research-Extension Center station in Tribune to evaluate several alternative systems that are more intensive than two- or three-year rotations. We are testing two summer crops (corn and grain sorghum) along with winter wheat in crop rotations varying in length from 1 to 4 years.
The crop rotations in the test are:
- Continuous grain sorghum
- Wheat-fallow, wheat-corn-fallow
The objective of the study is to identify cropping systems that enhance and stabilize production in rainfed cropping systems to optimize economic crop production. Averaged across the past six years, wheat yields tended to be less in four-year rotations than in two- and three-year rotations. Corn and grain sorghum yields (six-year average) were about twice as great when following wheat than when following corn or grain sorghum.
The objectives of the study are to (1) enhance and stabilize production of rainfed cropping systems through the use of multiple crops and rotations using best management practices to optimize capture and utilization of precipitation for economic crop production, and (2) enhance adoption of alternative rainfed cropping systems that provide optimal profitability.
The crop rotations are two-year (wheat-fallow), two three-year (wheat-grain sorghum-fallow and wheat-corn-fallow), and two four-year rotations (wheat-corn-sorghum-fallow and wheat-sorghum-corn-fallow), and continuous sorghum. All rotations are grown using no-till practices except for wheat fallow, which is grown using reduced-tillage. All phases of each rotation are present each year. Plot size is a minimum of 100 × 450 ft. In most instances, grain yields were determined by harvesting the center 60 feet (by entire length) of each plot with a commercial combine.
Results and Discussion
Wheat yields averaged across the past six years (2008–2013) tended to be slightly greater in two- and three-year rotations than in four-year rotations. Corn yields following wheat averaged about twice as much as when following sorghum. Similarly sorghum yields following wheat were about twice as much as when following corn or sorghum.