Effect of Gypsum, Soil Disturbance and Tile Spacing on the Amelioration of Huey Silt Loam, a Natric Soil in Illinois

Gypsum is by far the most commonly used amendment for ameliorating natric or solonetzic soils. Previous laboratory leaching studies with these soils in Illinois indicated that gypsum was more effective on disturbed than on undisturbed soil columns of natric horizons. The present investigation, therefore, was undertaken to formulate an effective field procedure for ameliorating the natric soils in Illinois. Effects of the treatment combinations of 0, 24, and 62 tons/ha of gypsum mixed to 15 or 90 cm or chiseled to 60 cm in soil on plots not tiled or having tile spacings of 3, 9, or 18 m, were studied on Huey silt loam, a natric soil at Newton in south-central Illinois in terms of corn yields (Zea mays L.), removal of extractable sodium from the soil, corn root growth and development, and water table fluctuations. Corn yields from 1964 to 1971 inclusive and removal of extractable Na from 1964 to 1972 inclusive were studied on all plots. Corn root growth and development studies in 1972 included four 9 m tiled plots with various gypsum and soil disturbance combinations. Water table fluctuations were studied from 1969 to 1972 inclusive on three plots with different treatment combinations. Of all the combinations studied, 62 tons/ha of gypsum mixed to 90 cm and tiled 3, 9, or 18 m, were the only effective combinations in improving corn yields, removing Na from the soil, and increasing water transmission in the soil. On plots with gypsum mixed to 15 cm only, tiling was not effective, but on plots with gypsum mixed to 90 cm, 3 m tile spacing was significantly better than 18 m spacing in increasing corn yields and improving soil conditions. Mixing the soil to 90 cm without gypsum resulted in reduced corn yields and no improvement in Na removal in comparison to the conventionally treated plots without gysum.