Soybean Response to Sulfur Fertilization

Materials and Methods Trial location was Field B, which has a Fruitfield coarse sand soil with 1 percent organic matter and soil pH of 7.4. A spring soil test reported 222 lb/acre phosphorus (very high), 180 lb/acre potassium (low), and 22 lb/acre of sulfur (low) in the topsoil. Potash (0-0-60) was broadcast at a rate of 200 lb/acre before chisel plowing and disking. Soybean seed, Pioneer 93Y05, was planted on May 20 at seed spacing of 6-7 per ft in rows 30 in. apart. Soybeans were irrigated as needed with subsurface drip irrigation lines placed 12 in. deep and 60 in. apart. Weed control was achieved with use of s-metolachlor and glyphosate herbicides. Plots were arranged in a randomized complete block design with four replications. A treatment plot consisted of six soybean rows 20 ft long with data taken from center two rows. Calcium sulfate (21% Ca, 17% S) was used as the sulfur source and banded between plot rows at rates to equal 0, 10, 20, and 40 lb/acre sulfur on June 22 when soybeans were at the V3 growth stage. Recently matured trifoliate leaves were collected on August 9 when soybeans were at R2 growth stage for percent sulfur in plant tissue determinations. Soybean plots were harvested on October 15 with a plot combine.