Conversion of pastureland into cropland has occurred at a rapid rate on the Great Plains. A reduction in total acreage of pastureland from this conversion has resulted in a decline of total numbers of beef cows in the same region. One method to mitigate the decline in cow numbers is to increase the carrying capacity of the remaining pastureland acres. To achieve this goal, a study was conducted to introduce warm-season annual grass species into perennial cool-season grass pastures to increase dry matter production during the mid-summer time period that perennial cool-season grasses would be most dormant. An increase in production during this time period could result in a significant overall increase in total land area production.
Three warm-season annual grasses (sorghum-sudangrass, crabgrass, and teff) were no-till drilled at three seeding rates (0.5X, 1.0X, and 1.5X) into perennial cool-season western wheatgrass pasture. Following wheatgrass harvest, warm-season annual grasses were seeded with a no-till drill in 12-inch spaced rows, and the plots were then fertilized with 60 lb N/acre.
The lack of rainfall in June 2021 reduced forage yield potential of western wheatgrass compared to 2020. Following wheatgrass harvest in June, soil was dry in both years, and precipitation was not adequate for germination of annual warm-season grasses. Sorghum-sudangrass was the only warm-season annual grass that established and maintained acceptable stands in either year. At 90 days after seeding, sorghum-sudangrass plots averaged 6600 lb/acre additional forage in 2020, but just over 800 lb/acre additional forage was produced in 2021.
Establishing sorghum-sudangrass in cool-season western wheatgrass pasture improved total forage production over two years with a net increase of nearly 3 tons of forage/acre compared to the cool-season grass alone. Vast improvements in production on limited pastureland resources are possible during years of greater precipitation. Greater forage production in turn increases the total number of beef cows the land area could support through grazing or haying.
The above information was summarized from the Agricultural Research Center-Hays Roundup 2022 Report. The full research report is available online. Harmoney, Keith and Guretzky, John (2022) “Interseeding Sorghum-Sudangrass into Perennial Cool-Season Western Wheatgrass Pasture,” Kansas Agricultural Experiment Station Research Reports: Vol. 8: Iss. 2. https://doi.org/10.4148/2378-5977.8276