Michigan agriculture is very diverse and most farmers will have several crops per year they need to manage
Alfalfa is a heavy user of S, and a crop of alfalfa hay yielding 4 tons per acre can remove up to 20 pounds S per acre. As a result of the Clean Air Act and the reduction in sulfur dioxide emissions from power plants, S levels in Michigan soils have been decreasing for many years.
Knowing how much S is available for plant uptake from a soil sample is difficult because the reliability of soil testing for S is poor. The most reliable way to determine if alfalfa plants are deficient in S is to have a plant tissue test performed. Plants with S deficiency will show symptoms that include stunting of plants, yellowing of youngest leaves and veins, and reductions in yield. Generally, the coarser the texture of the soil, the less S it will hold and the greater the potential will be for S deficiency.
To take samples for an alfalfa tissue test, Michigan State University Extension recommends collecting the top 6 inches from 35 alfalfa shoots at the bud to first flower stage and submitting them to the MSU Soil and Plant Nutrient Laboratory for analysis. The sufficiency level of tissue S for alfalfa is above 0.25 percent to
Alfalfa growers applying S fertilizers without knowing whether the plant needs additional nutrients can be incurring an unnecessary expense. Consider taking a tissue sample just prior to first cutting to assess the level of S uptake before applying
Source: Phil Kaatz, Michigan State University Extension
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