Productivity and economic implications of alfalfa–grass mixtures under variable irrigation

A field study was established at the University of Wyoming James C. Hageman Sustainable Agriculture Research and Extension Center in 2020 with the following objectives: (1) Assess the performance of alfalfa–grass mixtures under reduced irrigation. (2) Identify the best grass species and optimum seeding ratio of alfalfa–grass mixtures for improved productivity and nutritive value under full and deficit irrigations; (3) Compare the net economic return from different seeding ratios of alfalfa–grass mixtures under full and deficit irrigations. Treatments included monocrop alfalfa, 75–25 ratio, 50–50 mixed row planting, and 50–50 alternate row planting of alfalfa with each of three perennial cool-season grasses (orchardgrass, tall fescue, and meadow bromegrass) under full and deficit irrigation. Under full irrigation, 75–25 mixture with tall fescue produced the highest 2-year total forage dry matter, while alternate row planting of alfalfa and orchardgrass produced the highest under deficit irrigation. Deficit irrigation affected forage dry matter yield negatively. Economic analysis revealed that a 75–25 mixture of alfalfa and tall fescue under full irrigation produced the highest net present value (NPV). Although deficit irrigation reduced costs, that did not result in higher NPV than full irrigation. However, alternate row planting with orchardgrass under deficit irrigation produced an NPVsimilar to the treatments under full irrigation.