Micronutrients

Field experiments were carried out in three States of Brazil in order to test the response of several crops (beans, cabbage, citrus, coffee, corn, Guinea grass, rapeseed, upland rice, soybean, sugar cane, sweet sorghum, wheat) to sources (ammonium sulfate, potassium magnesium sulfate and phosphogypsum) and rates of sulfur. Yield increases ranged from 8 to 69% over the control. Sulfur additions, on the other hand had beneficial effect on product characteristics (grain/cob ratio in corn, crude protein in forage, oil content of soybeans and sucrose content of sweet sorghum). Ammonium acetate extractable SO4‐S in the range of 10–15 ppm seems adequate. Both leaf and soil analysis showed positive correlations with yield increases. Sulphur containing fertilizers at the rates of 20 kg/ha, and 30 kg/ha are recommended, for annual and perennial crops, respectively.