Influence of early pasture growth on water movement and leaching of potassium and other cations from sandy soils in a Mediterrranean environment

Abstract

Water and cation losses from two soil types were studied in monolith lysimeters fertilized with 375 kg/ha potassium chloride (50 per cent K) and 375 kg/ha superphosphate (22 per cent Ca), in which subterranean clover was grown. An advance of five weeks in time of sowing and germination reduced the mean percolate loss from 26 to 16 cm ; the unsown control lost 31 cm. Potassium leaching decreased from 77 to 37 kg/ha and the unsown treatment lost 87 kg/ha. Magnesium decreased from 26 to 10 kg/ha and the unsown treatment lost 31 kg/ha. With calcium there was a marked decrease from 132 to 51 kg/ha ; the unsown control lost 164 kg/ha. Cation leaching was most severe during the first part of the growing season. Early plant growth reduced cation leaching by increasing the water use and cation uptake. The early sown treatment contained 136 kg/ha K in 9,500 kg/ha DM total tops, whereas the late sown treatment had 94 kg/ha K in 6,300 kg/ha DM total tops. The decreased uptake was similar in magnitude to the increase in leaching loss of potassium.