Alfalfa Termination Strategies Determine Subsequent Wheat and Haygrazer Forage Yield and Nutritive Value

Core Ideas The effect of two alfalfa termination methods on subsequent crop forage yield and nutritive value were evaluated. Under better mineralization conditions, tillage termination method showed an advantage in increasing subsequent wheat forage yield at both jointing and boot stages. Spraying glyphosate for the termination of alfalfa achieved 9–18% greater forage yield in subsequent wheat compared with the untreated control. The forage yield of subsequent haygrazer was increased with either imposing tillage or spraying herbicide termination technique in alfalfa compared with non‐termination treatments at the boot growth stage. Applying both termination techniques had no advantage in increasing the subsequent forage yield. The effect of termination techniques on subsequent wheat and haygrazer forage nutritive value varied greatly with growth stage and test year. Crop rotation involving alfalfa ( Medicago sativa L.) requires effective alfalfa termination to secure maximum benefits for subsequent crops, and ineffective methods may cause counterproductive consequences to subsequent crops. Two identical studies in successive years at New Mexico State University's Agricultural Science Center at Tucumcari, NM USA compared the effects of alfalfa termination techniques on forage yield and nutritive value of subsequent wheat ( Triticum aestivum L.) followed by haygrazer [ Sorghum bicolor L. × ( Sorghum × drummondii )]. Treatments applied once to terminate the alfalfa included 1.25 lb a.i./acre glyphosate, tillage, glyphosate followed by tillage, and an unsprayed/untilled control in four randomized complete blocks. In the second study, glyphosate achieved near zero termination of alfalfa stands; whereas, tillage provided up to 90% alfalfa termination as a more consistent method. When glyphosate was effective for termination, the benefits to the subsequent crops were equal to tillage. In haygrazer, when glyphosate was ineffective, forage yield was increased with tillage compared with the control at the boot growth stage (2.12, 2.45, 2.99, and 3.34 tons/acre for the control, glyphosate only, tilled only, and both techniques, respectively; P < 0.05, SEM = 0.25). Wheat and haygrazer forage nutritive value varied with growth stage and test year and were less influenced by termination technique. Non‐ or inadequate termination of alfalfa can result in considerable regrowth of alfalfa in the following season that ultimately results in reduction of subsequent crop forage yield. Consequently, conventional tillage was the most reliable practice that led to alfalfa termination.