After the moisture content of hay declines below 35 to 40 percent, most harvest losses are due to weathering and handling. Losses due to leaching increase with the number of rain showers, amount of rain, and the dryness of the hay. Leaching can cause yield losses as high as 20 percent, mostly as digestible soluble nutrients. Carbohydrates, B vitamins, and some soluble minerals, such as potassium, are readily leached from dry hay. Rain not only leaches nutrients, it can also increase leaf loss due to the extra handling needed to dry the hay.
Leaves are the most valuable part of the hay since they have the highest quality.
Therefore, losing leaves can be very expensive. Losses in alfalfa as influenced by moisture content when raked. Leaf shatter, especially from legumes, can be serious at harvest time. For example, leaf loss is often 5 to 10 percent greater when hay is cut, conditioned, and raked separately than when all three operations are done at one time. Alfalfa hay raked and packaged very dry can yield 35 percent less dry matter and be of poorer quality than properly handled hay.