Yield and Forage Nutritive Value of Reduced Lignin and Reference Alfalfa Varieties Subject to Diverse Cutting Treatments.

Reduced lignin alfalfa varieties have potential to improve the digestibility and utilization of alfalfa by livestock and to provide increased management flexibility for producers. The objectives were to compare the yield and forage nutritive value of reduced lignin and reference alfalfa varieties when subject to diverse cutting treatments in the seeding and first production year. In 2015, alfalfa was seeded in a randomized complete block with a split-plot arrangement of treatments at four locations in Minnesota. Whole plots were four cutting treatments with variable intervals between harvests. Sub-plots were four alfalfa varieties, which included ‘54R02’, ‘DKA43-22RR’, ‘WL355.RR’, and the reduced lignin variety ‘54HVX41’. At harvest, alfalfa plots were hand-sampled for maturity and forage nutritive value determination and then mechanically harvested to determine yield. Data was analyzed using the MIXED procedure of SAS, with statistical significance set at P ≤ 0.05. Cutting treatment by variety interactions were not significant; therefore, the main effects of cutting treatment and variety are reported. Seasonal forage yield did not consistently differ among alfalfa varieties. The addition of a fall harvest increased seeding year yields, while first production year yields were generally highest under a 40-day cutting schedule. Compared to reference alfalfa varieties, ‘54HVX41’ was similar in crude protein and neutral detergent fiber but had reduced acid detergent lignin and increased neutral detergent fiber digestibility concentrations. Cutting treatments with shorter harvest intervals generally resulted in higher forage nutritive value. Compared to reference varieties harvested under a 30-day cutting schedule, ‘54HVX41’ harvested under a 35-day cutting schedule produced 21% greater yield with a 3% reduction in relative forage quality. These results demonstrate that the reduced lignin variety ‘54HVX41’ allows alfalfa growers the flexibility to either harvest for increased forage quality or to delay harvest and achieve higher yields while maintaining forage quality.