Sulfur application effects on soil properties in a calcareous soil and on sugarcane growth and yield

High pH soils limit availability of pH sensitive nutrients including phosphorus (P), even though abundant levels are present. Application of such nutrients to the soil is ineffective because they quickly get tied up in unavailable forms. Elemental sulfur (S) application in a narrow band to lower root zone pH and increase nutrient availability to the crop is a possible economically feasible solution. A four year field study was conducted in which S was applied to sugarcane (Saccharum spp.) at rates up to 1120 kg S ha−1 each of the 1st three years in a band using different application methods. Sulfur application effects on soil pH were gradual, causing only a slight reduction in the application zone after one year; but was long lasting, resulting in continuing substantial declines in soil pH in an adjacent zone four years after the first S application. Soil available P, sulfate (SO4)-S, and salinity levels increased with increasing S applied. Sugarcane plant growth, as indicated by leaf area index during the grand growth period responded to moderate S application levels. Sugarcane yields increased linearly in the plant crop, but showed quadratic responses to S applications in the 1st through 3rd ratoon crops. Initial soil available P levels prior to the first treatment application were at the critical level considered adequate for crop requirements, yet growth and yield increases in response to S application suggest that the critical available soil P levels for sugarcane may be higher than previously established. Sulfur application at rates beyond those necessary to produce maximum yields resulted in salinity problems which probably reduced yields. The ‘stool splitter’ application method, which slices the plant stool using a coulter and places the fertilizer directly in the middle of the furrow caused crop damage and stand loss which persisted for the remainder of the sugarcane crops. Based on the results of this study, a single application of elemental S at up to 1120 kg S ha−1 directly below the seed cane at planting is recommend for sugarcane on a calcareous soil, with no additional applications in later crops.