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Sulfur – The 4th Major Plant Nutrient for Crop Production
Where does the time go? 2020 has arrived, and moving forward into the New Year, we begin to prepare for the 2020 growing season. Equipment is brought into the shop for evaluation and maintenance. Annual updates, replacement of worn parts, fluid, tires, and bearing changes take place ensuring that when things begin to green up everything is ready to go.
Growing crops ins 2019 came with it’s challenges that extended planting season. We saw many acres of corn planted in late June & July, crop rotation plan adjustments were continuous, seed postponed or abandoned, corn and soybean acres not planted, and first cutting delayed.
Just like we all spend the winter months working on equipment so we are ready to go in the springtime, it’s important to plan and look at past crop histories. This week, we’re going to focus on one major plant nutrient for crop production – Sulfur.
Sulfur has become the fourth major plant nutrient for crop production. Sulfur in the plant increases nitrogen efficiency, increases protein in forage and grain, boosts yield, helps develop enzymes and vitamins, promotes nitrogen fixation in legumes, aids in seed production, controls nitrate build up in plants, and is necessary in the formation process of chlorophyll. There is a strong relationship between nitrogen and sulfur in the plant ratios – varying between N/S 15/1 – 7/1. When fertilizing with nitrogen, the addition of sulfur will increase Nitrogen Use Efficiency. The addition of sulfur to nitrogen fertility has an environmental effect of reducing the nitrate leaching potential.
The soil organic matter contains the largest amount of the soils sulfur. For this sulfur to be converted to the plant available sulfate (SO4), bacterial oxidation must occur. The sulfate form is soluble, moves through the soil with the soil water, and is readily leached under high rainfall events. Soil texture will affect sulfur opportunity. Sandy soils present the biggest challenge maintaining high organic matter levels and their high leaching potential.
The intensification of agriculture with improved crop varieties pushing higher yield potentials, improved air quality, low sulfur fuels, and sulfur free plant protection materials have increased the need for the addition of sulfur in crop production. Increasing organic materials in the soil by using animal wastes and cover crops will help stabilize soil sulfur. Along with the addition of sulfur through the growing season, paying close attention to high protein crops and crops using large amount of nitrogen is important in sulfur management.
Measuring sulfur in crop production systems is challenging. Testing for organic matter levels through soil testing, knowledge of cropping systems, and tissue analysis will provide some of the best indicators. Forage samples may also give some insight into sulfur use by the crop by observing the percent protein and sulfur containing amino acids. The soil test for sulfur without additional information may be misleading depending on the time of year the sample is taken and the soil temperature.
Again, it is best to look at other soil and crop needs before choosing a source, but sulfur can be added to fertility programs with several products. Crop type, soil information,and yield goals should be used to determine crop needs and sources.
K-Mag or SPM will provide sulfur, potassium, and magnesium
Ammonium Thiosulfate (ATS) with UAN liquids
Gypsum, which is calcium sulfate, will provide calcium, if needed
MgSo4, or Epsom Salt, can provide Magnesium and be used as a foliar
Sulfate of Potash can provide a low salt source of potassium along with sulfur