Evaluating adoption of intensified forage systems effects on water, soil, and nutrient retention under variable precipitation cycles of the Southern Plains

Authors: DUNCAN, KIKOYO - Texas A&M University; Fortuna, Ann-Marie; SMITH, PATRICIA - Texas A&M University; Hunt, Sherry; Zhang, Xunchang; Busteed, Phillip; Flanagan, Paul; JEONG, JAEHAK - Texas A&M University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/24/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Agriculture in the Southern Plains (SP) is driven in part by the timing and quantity of precipitation. Variable precipitation often reduces the potential for diversifying forage crops and limits prevailing grazing systems. Incorporating mixed cool-and warm-season cover crops can potentially reduce forage shortages, enhance ground cover as well as reduce sediment and nutrient losses. This study assessed forage intensification’s effects on water, soil, and nutrient retention under the variable weather conditions existing in the SP. Using the Agricultural Policy/Environmental eXtender (APEX) model, summer and winter forage crop rotation systems in grazed and hayed watersheds were simulated and compared to tilled winter wheat (Triticum aestivum L.) on 1.6 ha watersheds in El Reno, OK. Categories of wet, dry, and average precipitation years were simulated using ~100-yr of measured data (https://www.mesonet.org). Droughts of 30–90 days were also simulated and are common throughout the year. The mixed forage cover crops in APEX were represented using the dominant crop in the forage mixtures measured for 6-years. Biomass of cool season forages was >50% winter wheat and ~50-25% triticale (Triticum x Secale). The dominant crop in summer forage mixtures was 70-90% sorghum sudangrass (Sorghum bicolor L.). Winter wheat followed sorghum sudangrass frequently during the 30-years simulated (1997-2006). Results demonstrated that intensified alternative warm- and cool-season forages, grazed or hayed, enhanced water, soil, and nutrient retention compared to prevailing tilled winter wheat. No-till winter wheat-sorghum rotations with multiple harvests increased retention of water by 16.4%, soil by 10.8%, nitrogen by 11.4%, and phosphorus by 9.6%, compared to tilled winter wheat with a single harvest. Conversely, multiple grazing operations improved water retention (15.9%) but resulted in increased soil and phosphorous losses (5.9% and 14.9% respectively) whereas changes in nitrogen losses were marginal. The benefits of intensified systems were more pronounced in dryer years (annual rainfall totals below the 25th annual precipitation percentile) compared to wet years (above the 75th percentile), emphasizing their potential for improving drought resilience and environmental stewardship. These findings offer valuable insights for policymakers, farmers, and stakeholders to promote sustainable agricultural practices, enhance productivity, and mitigate soil and nutrient-related environmental impacts in the SP. USDA is an equal opportunity provider and employer. USDA is an eual opportunity provider and employer.