Improving Pasture Performance for Milk Production: Lessons Learned from Organic Dairies.

Concern exists that organic dairies are not maximizing pasture performance which is resulting in reduced milk production. Previous research has shown that pasture productivity, forage quality, soil fertility and pasture management are all critical to maximizing milk production, but these factors have been observed to vary widely across farms. To determine what factors are associated with high levels of milk production on organic dairy pastures we evaluated key variables across twenty organic dairies in the Upper Midwest during 2013 and 2014.  At each farm, two paddocks were chosen and visited just prior to a grazing event in June and September. During each visit, pasture species composition, productivity and nutritive value were evaluated. Soil fertility measurements and management practices in each paddock were collected in October. Forage productivity and nutritive value were used to estimate milk production within each paddock. A classification and regression tree (CART) was used to prioritize factors affecting milk production. Improved legume cover (>40%) and lower levels of unimproved grass cover (<70%) were associated with higher milk production in both June and September. Improved legume cover exceeding 40% in June increased milk production by 97%. Unimproved grass cover less than 70% in June and September increased milk production by more than 75%. Grazing management practices such as, maintaining a residue height greater than 9 cm throughout the year was also associated with more milk production. None of the soil fertility variables evaluated were associated with milk production at either time period. Results suggest that legume and grass composition and residual height management are key contributors to greater milk production from pasture. This information is currently being disseminated to organic dairies to help them prioritize pasture renovation or changes in grazing management to improve milk production.