EFFECT OF DIFFERENT FACTORS ON MOVEMENT OF SULFATE IN SOILS OF SEMIARID REGIONS OF INDIA

Effects of soil texture, application rates of sulfate, initial water c ontent, water application rates, and water management regimes on movem ent of sulfate were studied in a series of laboratory experiments in t hree soils. Soils in the plexiglass columns were compacted to 1.45 g c m-3 bulk density in each column, and K2SO4 was applied as a source of sulfate. In a sulfate application rate experiment, 100, 200, and 400 m ug, and in other experiments, 100 mug SO4(2-)-S g-1 soil was applied i n the top 3-cm soil layer. To 120-cm-long columns, 2.5, 5, and 10 cm o f water was applied in a water application rate experiment, 10 cm of w ater in a water management regime experiment, and in the rest of the e xperiments, 5 cm of water was applied. Different rates of sulfate appl ication did not change the leaching behavior, and sulfate moved to 27- cm depth at all applied sulfate concentrations when 5 cm of water was used. The maximum depth of sulfate with 5 cm of water in initially dry soil was down to 15-, 21-, and 24-cm and in initially wet soil, down to 27-, 30-, and 64-cm depth in Kaul clay loam, Dabra sandy loam, and Shahpur sandy soil, respectively. Increasing water application rates i ncreased leaching, whereas application of water in small fractions dec reased sulfate leaching losses. Leaching of sulfate was observed to 10 5-, 99-, 93-, and 87-cm depths when 10 cm of water was applied once, 5 cm twice, 2.5 cm four times, and 1 cm ten times, respectively. These results indicate that leaching of sulfate in sandy soils can be contro lled by applying irrigation up to 5 cm.