A soil test plus a tissue sample analysis is the best way to find out if alfalfa needs added sulfur, say University of Wisconsin soil scientists.
The two tests can be used to determine the sulfur availability index, which accounts for sulfur from precipitation, manure and other sources besides the soil.
In recent years, sulfur shortages have been reported in areas where they weren't expected. If the nutrient is lacking, 25 lbs of sulfur per acre, applied preplant, is enough to last the life of an alfalfa stand, say the scientists.