Effect of Swath Width on Drying Rate of Alfalfa.

A study was conducted to determine the effect of initial swath width after mowing and conditioning on drying rate and forage quality of alfalfa (Medicago sativa L.).  During 2005, 2006 and 2007, alfalfa was mowed, conditioned with rollers, and placed either into a wide swath (covering 65 to 72% of cut area) or a windrow (covering 25 to 30% of cut area).  Trials were conducted at University of Wisconsin Arlington Research Station with a John Deere 920 MoCo disc mower with 3.6 m cutter head and Marshfield Research Station with a Case International 8830 self-propelled sickle bar mower-conditioner with 3 m cutter head.  In each trial the same mower and settings were used for both wide swath and windrows with only back baffles adjusted to affect swath width.  In 14 trials, drying time to 650 g kg^-1moisture averaged 11 hours less (P<.01) for wide swath, often allowing harvest for haylage the day of cutting.  Greater differences were noted in drying time when taken to 200 g kg^-1 moisture. Forage quality at harvest averaged higher for the wide swath (1 g kg^-1 less neutral detergent fiber and 0.5 g kg^-1 more nonfiberous carbohydrate (P<.01)) than the windrow but response was not observed in every trial.  Forage sampled approximately two months after ensiling in 3 m diameter tubes showed similar responses as well as 0.8 g kg^-1 higher lactic acid.