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Roundup-Ready Alfalfa in the Northeast

Over 80% of alfalfa sown in New York State is sown with a grass companion crop. This differs greatly from the Midwest, where approximately 20% of alfalfa is sown with grass, and from the Western USA, where very little alfalfa is sown with grass. Roundup-Ready (RR)-alfalfa has the potential to significantly reduce the current acreage of mixed seedings of alfalfa and perennial grass in the Midwest and the West. The impact of RR-alfalfa in the Northeast is less clear. RR-alfalfa sown on a marginal site for alfalfa may only result in a clean, thin stand of alfalfa with unsatisfactory yield.

Establishing RR-alfalfa and then interseeding perennial grass into the established alfalfa would allow for good weed control during alfalfa establishment, but does not appear to offset the risk of achieving successful grass introduction into an existing alfalfa stand. Alfalfa cannot spread from existing plants or reseed itself to fill in wet spots, nor can it fill in stands thinned by winter damage. RR-alfalfa is less likely to take over the market in the Northeast, as happened with RR-soybeans. It is more likely that the majority of alfalfa stands in the Northeast will remain as mixed seedings.

Pure alfalfa, particularly very high quality (low NDF) pure alfalfa, can be challenging to use as a sole fiber source in lactating dairy rations. One solution used by some dairy farmers is to include poor quality grass hay or straw in the diet. A better solution is to grow alfalfa mixed with cool-season grasses. Including grass in the diet has consistently resulted in a reduction in animal health problems while maintaining milk production. If a producer is marketing pure alfalfa, and has good land to grow it, RR-alfalfa should be considered. If a producer is feeding forage to lactating dairy cows, an alfalfa-grass mixture may be more appropriate in the Northeast.