Combining Cropland Data Layers to Identify Alfalfa-Annual Crop Rotation Patterns and Opportunities.

Alfalfa (Medicago sativa L.) can provide many economic and environmental benefits to crop rotations. Our objectives were to quantify alfalfa stand lengths, identify the two crops following alfalfa, and determine the soil and temporal factors affecting them. The USDA-NASS cropland data layers for 2006 to 2012 and USDA-NRCS soil survey layers for North Dakota, South Dakota, Nebraska, Minnesota, Iowa, and Wisconsin were combined and used to meet these objectives. Location and soil textural class were related to stand length, with alfalfa being kept in production longer outside the major Corn Belt area of this region and on coarse- and medium-textured soils. Corn (Zea mays L.) was the most common crop planted during the first and second year following alfalfa (79 and 61%, respectively), except in North Dakota (35% both years). Soybean [Glycine max (L.) Merr.] was grown in 11 and 28% of cases, respectively. Small grains were planted as the first-year crop in 29% of cases in the Dakotas and 6% of cases in the other four states. As a second-year crop, small grains occurred in 26% of cases in North Dakota and 5% of cases in the other five states. Stand length, soil textural class, state, and year significantly influenced grower choice of both following crops. These results indicate opportunities to increase net return to alfalfa by increasing rotation frequency and to improve utilization of alfalfa N by decreasing the frequency of soybean and alfalfa as the two crops following alfalfa termination. They also will guide research and extension education designed to increase use of perennials for economic and environmental benefits. Similar methods can be applied to other crop rotations or U.S. regions.