Measuring Alfalfa Yield and Persistence on Wisconsin Farms.

Our knowledge of alfalfa (Medicago sativa) production performance on farms is limited, especially when most of the crop is harvested as haylage. Unlike annual grain crops, perennial forage crops require measurements be made over several cuttings. Historically, forage producers have been unwilling to invest the time during multiple harvests, and have lacked the equipment to obtain accurate measurements of yield. Some larger Wisconsin dairies have now installed on-farm, drive-over scales. These make it possible to accurately weigh forage production from entire fields over the life of the stand. In 2007 the University of Wisconsin-Extension Team Forage initiated the Wisconsin Alfalfa Yield and Persistence (WAYP) project. Alfalfa fields are voluntarily entered beginning the year after seeding and remain in the project until the owner decides to terminate the stand. All production is weighed from project fields at each cutting and two composite forage samples are taken to determine forage dry matter (DM) and quality. The county extension agent coordinates local data collection and shares results with the grower after each cutting. At the end of each year, statewide results are accumulated and summarized. Data has been collected from a total of 36 fields with 5000-6000 DM ton of forage weighed and sampled annually. Annual state average total season DM yield across project fields has ranged from 4.0 to 5.1 ton/acre. The large majority of fields are being cut four times from late-May through early September. Production persistence, measured as a percent of 1st production year yield, is being maintained through the 3rd production year, but drops significantly in the 4th production year. First-cutting has accounted for 36% of the total-season harvest in 4-cut systems. Forage quality has been excellent over the 5 years of the project, and in some cases debatably too good at the expense of yield.