Intercropping forage sorghum with sunnhemp at different seeding rates to improve forage production

Authors: MOSQUEDA, HALEY - North Dakota State University; BLASER, BROCK - West Texas A & M University; Oshaughnessy, Susan; RHOADES, MARTY - West Texas A & M University

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2023
Publication Date: 12/13/2023
Citation: Mosqueda, H.M., Blaser, B.C., O'Shaughnessy, S.A., Rhoades, M.B. 2023. Intercropping forage sorghum with sunnhemp at different seeding rates to improve forage production. Agronomy. 13(12). Article 3048. https://doi.org/10.3390/agronomy13123048.
DOI: https://doi.org/10.3390/agronomy13123048

Interpretive Summary: In the semi-arid Texas Panhandle region, water for crop production is limited as the main water source is the highly depleted Ogallala Aquifer. Improving crop water productivity along with producing a high-quality forage are paramount to support the beef and cattle industry. While forage sorghum can be grown with less water, it is deficient in crude protein and other nutrients. Cropping forage sorghum with a legume, such as sunn hemp, could increase crude protein and its relative feed value. However, studies on sunn hemp have not been conducted in a semiarid region, and the optimum seeding ratio of sunn hemp to forage sorghum to ensure production of a nutritive forage with high dry matter content is unknown. Researchers from USDA-ARS, Bushland, Texas, and West Texas A&M University initiated a study to intercrop forage sorghum and sunn hemp. The results of this study indicated that sunn hemp can be grown in a semiarid region and produce a high value of crude protein. However, the planting geometry and seed ratios for the intercropping of sunn hemp and sorghum requires further investigation to produce an optimal forage.

Technical Abstract: Forage sorghum [Sorghum bicolor (L.) Moench] is well-established in the Texas High Plains as a drought tolerant forage that often requires additional feed to provide adequate protein for livestock. Intercropping sunn hemp (Crotalaria juncea L.), a legume, with forage sorghum, may increase crude protein (CP). However, the optimal intercrop seeding ratio of sunn hemp to sorghum to improve crude protein content and maintain sufficient biomass is unknown. This study was conducted to (1) evaluate growth potential for sunn hemp in a semiarid environment, (2) find a seeding ratio that can maintain forage sorghum dry matter (DM) production and improve forage quality, and (3) determine if a midseason harvest can be supported and further improve quality of the forage produced. A two-year field experiment was conducted using sunn hemp intercropped at three seeding rates (16.8, 33.6, and 50.4 kg ha-1) with forage sorghum at four seeding rates (0, 2.8, 5.6, and 11.2 kg ha-1) under drip irrigation. Midseason, full season, and regrowth biomass and forage quality were evaluated in a split-plot nested field design. Results showed that sunn hemp grown as a monocrop produced a significantly more nutritive forage based on RFV (Relative Feed Value) at a mid-season harvest. At mid-season and full-season harvest, the monocrop produced a higher precent CP than when intercropped with forage sorghum. However, DM production in this monocrop was significantly less than when intercropped with forage sorghum. Future studies should focus on determining the appropriate row spacing and seeding ratio for intercropping to optimize the contribution of % CP from sunn hemp and DM from forage sorghum.