MOVEMENT OF SUBSURFACE FERTILIZER AND LIMESTONE UNDER IRRIGATED AND NONIRRIGATED CONDITIONS

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Abstract
Subsurface application of amendments is advocated as a means for altering soil acidity and increasing yields of deep-rooted crops. Little information exists on the movement of lime and fertilizer placed in the plow sole. We conducted this investigation to study the movement of plow sole application of lime and fertilizer amendments 13 yr after application under irrigated and nonirrigated conditions. The experiment was conducted on a Davidson clay loam soil (Rhodic Paleudults, clayey, kaolinitic, thermic) where plow sole amendments (30 cm) were applied in 1969, 13 yr prior to soil sampling and analysis. The experimental design was a randomized split block design with irrigation as the split. The amendments consisted of dolomitic limestone in combination with various levels of P and K. In 1982 soil samples were collected at various depths and analyzed for pH, exchangeable Al, Ca, Mg, K, and extractable P. With the addition of plow sole lime. pH increased through the soil profile to a minimum depth of 25 to 35 cm. Irrigated soils were generally lower in pH than nonirrigated soils. There was also a trend toward increased Al concentration with depth, irrigated soils being, on the whole, higher than nonirrigated soils. Where the lime plow sole amendment was applied, there was a decrease in the exchangeable Al content, the effect being particularly noticeable where irrigation was applied. On the nonirrigated soil, Ca was still present in the plow sole, though on the irrigated plots Ca had penetrated some 10 cm downward in the soil horizon. With reference to Mg, no apparent differences were observed between lime-treated versus untreated plots in the absence of irrigation. With irrigation, Mg penetrated to a greater depth in the limed than in the unlimed soil. There was limited movement of soil K and P, and their levels were enhanced by fertilizer application. © Williams & Wilkins 1985. All Rights Reserved.