The composition of the leachate through cropped and uncropped soils in lysimeters compared with that of the rain

Summary The composition of the leachate from undisturbed monolith lysimeters cropped with white clover or meadow fescue or maintained bare was compared with that of the rain falling on them. No nitrogen fertilizer was applied only an initial dressing of phosphorus and potassium. The grass received much more nitrogen from the rain than it lost by leaching whereas the clover lost more than it received. Most of the leached nitrogen was NO₃-N - 92 per cent on the bare soil and 90 per cent on the clover. About 27lb nitrogen per acre (30 kg/ha) per year was drained from the actively growing clover sward rising to about 117lb N/acre/year (131 kg/ha) when the clover died or was removed. Only 2.3lb/ac (2.5 kg/ha) was drained from the actively growing grass sward. It was estimated that the clover fixed at least 270lb N/ac/year (303 kg/ha/year. The rates of leaching of potassium from a grass sward was about 1.7lb/ac/year (1.9 kg/ha) and 0.8 lb (0.9 kg) phosphorus. The quantities were similar for clover. The grass received from the rain more phosphorus and potassium than was leached but only 60 per cent of the calcium and 13 per cent of the magnesium, similar results being obtained with white clover. During the year of establishment of the grass sward there was evidence of loss of gaseous nitrogen (elemental and/or compound) from the soil: subsequently the nitrogen content of the soil slowly increased. Calcium loss from the bare soil with an average rainfall of 26″ (650 mm) was about 100 lb Ca/ac/year (112 kg/ha).