How Bad Is It When Your Curing Hay Gets Rained On in the Field?

Rain occurring while cut hay is laying in the field causes both yield and quality losses that reduce the value of the crop as an animal feed and a marketable commodity. Weather-induced losses are caused by: 1. prolonged plant respiration reducing soluble carbohydrates and overall energy content 2. leaching of soluble carbohydrates, protein, and certain minerals from the hay 3. leaf shattering and loss, removing the highly digestible and high protein portion of the forage 4. microbial activity metabolizing soluble carbohydrates and reducing energy content 5. color bleaching How much does rainfall reduce dry matter yield? Several researchers have studied the effects of rainfall on cut alfalfa. Wisconsin researchers measured dry matter losses of 22% when alfalfa was exposed to 1 inch of rain after 1 day of drying (curing). Similar hay dried without rain damage lost only 6.3% of the initial yield. Losses appear to be greatest after partial drying of the forage has occurred. In this same study, alfalfa exposed to 1.6 inches of rain over several days suffered a 44% loss in dry matter. Michigan researchers conducted several different studies to examine the effects of rainfall on field cured alfalfa. The first study reported maximum dry matter losses of 34%. In a second study, rainfall intensity was kept con