LEACHING OF PHOSPHORUS, CALCIUM, MAGNESIUM AND POTASSIUM IN BARLEY, GRASS AND FALLOW LYSIMETERS

Leaching of total and dissolved phosphorus, calcium, magnesium and pot assium from fallow, unfertilized and fertilized barley and grass ley w as studied in a four-year experiment carried out in lysimeters filled with clay, silt, coarse sand and Carer peat. Half of the lysimeters we re irrigated with 290-480 mm of water annually. Irrigation increased t he nutrient leaching. Phosphorus losses were anyway small (tot. P 0.02 -0.26 kg ha(-1) a(-1) from the fallowed soils) owing to omission of su rface runoff. Leaching of cations was more comparable with field obser vations. The annual average varied in the bare soils from 50 to 120 an d from 30 to 70 kg ha(-1) a(-1) for Ca and Mg, respectively. The avera ge leaching of K was small (4-24 kg ha(-1) a(-1)) in other than sand s oil (56-94 kg ha(-1) a(-1)). Cropping of soil generally decreased the leaching of dissolved and total phosphorus and cations compared with t he fallow treatment. Fertilization did not have any consistent effect.