Effects of sewage sludge application on the yield of different crops and the uptake of some heavy metals

Authors

• Asbjørn Sorteberg Department of Soil Fertility and Management, Agricultural University of Norway, 1432 Ås-NLH, Norway

DOI: https://doi.org/10.23986/afsci.72051

Abstract

An account is given of two pot experiments with sewage sludge. H/73. Sewage sludge was added in amounts of 0, 50 and 200 g of dry matter per pot of 5 litres =0, 20 and 80 tons per hectare respectively, given at the start of the experiment. Two soils, a loamy sand and a clay soil, were included in the experiment which has been running for 6 years (1973—78), with oats and barley every second year. The sewage sludge was anaerobically digested and had a relatively high content of heavy metals. Relative yields (grain + straw) for the experimental period were, as a mean of the two soil types, 100, 126 and 166 respectively for 0,50 and 200 g sewage sludge per pot. The uptake of N was 43.9 percent of added N in 50 g sludge and 32.6 percent of added N in 200 g sludge. For P the uptake was 23.9 and 18.5 percent respectively. The effect of sludge on the content of heavy metals in the yields was: Cd. Heavy effect. Heavier effect on the grain of oats than on the grain of barley. Cu. Distinct effect. Higher content in barley than in oats, and higher content in grain than in straw for both crops. Ni. Heavy effect, particularly in grain of oats. Higher content in grain of oats than in straw. For barley the content was slightly higher in straw than in grain. Zn. Distinct effect, particularly in the first two years. Highest increase in the straw. Pb and Hg. No effect. 14/71 included rates of up to 400 g dry matter per pot of anaerobically digested sewage sludge, two rates of lime, with crops of oats, barley, red clover and timothy. The experiment ran for two years (1971—72). Soil: Loam. The sludge had a positive effect on the total yield of all crops, but the highest rate had a negative effect on the grain of barley in the first year, and in the second year the hight rates caused retarded germination of all crops. The concentration of Cd, Cu, Ni and Zn was substantially higher in red clover than in timothy. With the addition of roughly the same amounts of heavy metals to unlimed loamy sand (H/73)and loam (14/71), oats obtained a higher concentration of Cd, Ni and Zn from the sludge with the highest content of these metals (H/73).