Forage sorghum grown in a conventional wheat-grain sorghum-fallow rotation increased cropping system productivity and profitability

Authors: HOLMAN, JONATHAN - Kansas State University; OBOUR, AUGUSTINE - Kansas State University; ASSEFA, YARED - Kansas State University

Submitted to: Canadian Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2022
Publication Date: 1/13/2023
Citation: Holman, J.D., Obour, A.K., Assefa, Y. 2023. Forage sorghum grown in a conventional wheat-grain sorghum-fallow rotation increased cropping system productivity and profitability. Canadian Journal of Plant Science. 103(1):61-72. https://doi.org/10.1139/cjps-2022-0171.
DOI: https://doi.org/10.1139/cjps-2022-0171

Interpretive Summary: Cropping systems intensification in the semi-arid Great Plains can be successfully accomplished using annual forages with reduced water use. The traditional dryland (rainfed) cropping system in the Southern High Plains is winter wheat-grain sorghum-fallow rotation, which while typically reliable could be intensified for greater profitability by inclusion of forages in the rotation. Annual forages use less water than either sorghum or corn grain crops. Kansas State University researchers, working in an ARS Ogallala Aquifer Program project, found that double cropping forage sorghum after winter wheat in the traditional rotation improved water utilization and profitability overall. A more intensified double-cropped rotation [winter wheat followed by double-cropped forage sorghum rotating to forage sorghum in the second year followed by fallow (W/FS-FS-FL)] increased overall forage productivity by 46%. Importantly, averaged-across-years, growing forages in place of fallow tended to improve cropping system profitability even when increased cropping intensity reduced grain yields. Replacing fallow with forage oats increased overall forage yield by 56%. This finding means that farmers may opt to grow forages rather than grain crops with reasonable expectation of improved profitability and reduced water use, extending the life of the Ogallala aquifer.

Technical Abstract: Intensifying winter wheat (Triticum aestivum)–grain sorghum [Sorghum bicolor (L.) Moench]–fallow (W–GS–FL) crop rotation with annual forages can increase productivity and resource use efficiency. The objective of this research was to quantify the impact of increasing crop intensity by growing forages in a traditional W–GS–FL rotation on cropping system productivity, water use, precipitation use efficiency, and net income. The study was conducted at the Southwest Research-Extension Center near Garden City, Kansas, from 2013 through 2020. Winter wheat (W), grain sorghum (GS), forage sorghum (FS), and forage oats (FO, Avena sativa L.) were used to generate six crop rotation treatments. These rotation treatments interspersed with fallow periods (FL) were W–GS–FL, W–FS–FL, W/FS–GS–FO,W/FS–FS–FO, W/FS–GS–FL, and W/FS–FS–FL. A W/FS indicates winter wheat double crop FS planted in the same year. The yield of FS was 45%–56% more with W/FS–FS–FO and W/FS–FS–FL compared with W–FS–FL. Available soil water at GS planting was 23%–30% less, and GS yield was 52%–60% smaller with W/FS–GS–FL compared to W–GS–FL. Water productivity and pre-season soil water storage were greatest with W/FS–FS–FL and W/FS–FS–FO. Inclusion of W/FS increased cost of production compared with W–GS(FS)–FL rotations. Gross return was greatest with W/FS–FS–FO and W/FS–FS–FL. The W/FS–FS–FO increased cropping intensity, productivity, resource use, and gross margin relative to other rotations in the semi-arid Great Plains. Producers should consider double-cropping of FS after wheat harvest, followed by a second year of FS in dryland cropping systems if there is sufficient forage demand.