Nitrate in waters from sewage-sludge amended lysimeters

Nitrate nitrogen was measured in runoff and tile-drainage during two years of operation of instrumented, large-scale lysimeters planted to corn ( Zea mays L.) and amended with sewage sludge which was applied at rates supplying total N amounting to 2292 kg ha − in 1972 and 3286 kg ha −1 in 1973. Other lysimeters were amended with inorganic fertiliser at the rate of 336 kg N ha −1 year −1. Annual losses in runoff and tile-drainage from sludge treatments were 0·9 and 5·1 and 371 and 663 kg NO 3 −-N ha −1. Losses from lysimeters treated with inorganic fertiliser were 1·1 and 3·3 kg NO 3 −-N ha −1 year −1 in runoff and 31 and 79 kg NO 3 −-N ha −1 year −1 in tile-drainage. Given the nitrogen inputs accounted for in the study design, unaccounted for losses of 1800 to 2400 kg ha −1 year −1 were calculated for sludge and 277 kg ha −1 year −1 for inorganic fertiliser treatments. For one year there was a 300 kg ha −1 increase in N in the lysimeters receiving inorganic fertiliser. Median NO 3 −-N concentrations ranged from 8·9 to 14·0 mg litre −1 in runoff from sludge-treated lysimeters and 3·6 to 5·9 mg litre −1 in runoff from lysimeters receiving inorganic fertiliser. In tile-drainage the median NO 3 −-N concentrations were 148 to 223 mg litre −1 and 24 to 44 mg litre −1 for sludge and inorganic fertiliser treatments, respectively. Highest runoff levels occurred in early summer storms, whereas highest tile-drainage concentrations occurred in late winter and early spring.