Severely drought stressed soybeans can be left in the field, harvested as silage, harvested as hay, or harvested as beans. If the plant has lost leaves and has little seed development, leaving the crop is probably best option (i.e., nutrient value of the harvested crop will not pay for the harvesting costs).
Making into silage
If beans are at R6 stage (green seed that fills the pod cavity) or less mature, they should ensile without a problem. If beans have matured beyond the R7 stage (R7 = one normal pod on main stem has reached mature pod color) the plant probably contains too much oil to make good silage. The R7 stage is the grey area. The majority of time the plants should ensile without a problem but there is reasonable risk of a poor fermentation. If you really need forage, it probably is worth the risk but if you are not desperate for forage, waiting and harvesting for beans may be a better option.
Making into hay
Oil content is less an issue for hay than silage, but the soybean varieties commonly planted for beans do not make good hay. Leaf shatter will be severe and since the leaves contain a substantial proportion of the protein and energy in the soybean plant, haymaking results in a large loss of nutrients and nutrient value. Soybean hay, made from today's hybrids will probably not be of adequate quality for lactating dairy cows. If you are feeding beef cows (much lower nutrient requirements than a dairy cow), soybean hay may be an acceptable feed.
To make silage, you need to have silage equipment and a silo or have access to custom operators that can chop the crop and then put it into a silo bag. Storage and harvest costs are almost always higher for silage than hay but for soybeans, leaf shatter can be so severe that cost of soybean silage/ton of nutrients is less than cost of soybean hay/ton of nutrients. Even though soybean hay (on a cost per unit nutrient basis) will likely be more expensive than silage it can still be a reasonable option for beef producers that lack silage making equipment and silage feeding equipment. The cost per unit of nutrients for home-grown soybean hay may be less than the cost per unit of nutrients for purchased 'beef-quality' hay
1. If beans are immature (R6 stage or less), silage is probably the best option.
2. If beans are at R7 or more mature, waiting and harvesting as beans may be the most profitable.
3. Making beans into hay will probably result in the lowest return, but may still be more profitable than having to purchase other types of hay (for beef cows).
SOURCE: The Ohio State University