Heavy Applications of Liquid‐Digested Sludge on Three Ultisols: II. Effects on Mineral Uptake and Crop Yield

Abstract

AbstractA study was made of the nutrient uptake of corn (Zea mays L.), grain sorghum (Sorghum bicolor (L.) Moench), and soybeans (Glycine max L.) grown on land to which liquid‐digested sludge (sludge) containing 2.6% solids had been applied as a source of plant nutrients. The sludge was applied over a 6‐year period to give a total of 0, 87, 174, 241, 288, and 335 metric tons/ha dry matter. Corn did not contain Pb in the leaves or grain but the leaves contained up to 2.0 ppm Cd and 0.23 ppm Hg when high levels of sludge were applied. Cadmium and Hg were not detected in the corn grain. No measurable amount of Cd and Pb were found in the leaves or grain of grain sorghum, however Hg accumulated in the leaves up to 0.06 ppm. Soybeans took up Cd and Hg in the leaves but none accumulated in the seed. Some soybean seedlings became chlorotic and died at the 288 and 335 metric tons of dry matter/ha treatments. These seedlings contained 963 and 1,188 ppm Zn and 484 and 725 ppm Mn, respectively, probably causing the soybean plant injury. Soybean leaves taken from the 335 metric tons/ha treatment at the R5 stage contained 619 ppm Zn and 220 ppm Mn, and corn leaves taken at the hard‐dough stage contained 707 ppm Zn and 458 ppm Mn, but neither showed any detrimental foliar symptoms.The yield and plant data analyses indicated that annual applications of sludge from Pensacola, Fla., equivalent to 28 metric tons dry matter/ha would be an acceptable rate of disposal by land‐spreading for corn, grain sorghum, and soybeans grown on three Paleudults: Orangeburg, Troup, and Lucy soils.