Root, soil water and nitrogen dynamics in a catch crop - soil system in the Wageningen Rhizolab

Catch crops (winter rye and fodder radish) were grown on lysimeters with rh izotron facilities from August or September till March in two consecutive y ears, to study root growth and water and nitrogen dynamics under different regimes of irrigation and N supply. Catch crops took up 20 to 30 g N m(-2), of which a considerable part (37-48%) was present in dead leaves in March. Rooting depth increased by 2.6 cm day(-1) for both species at the start of the growing season. Catch cropping reduced the NO3--N concentration in the soil considerably du ring the whole duration of the experiments, first in the top layers, than f urther down the soil profile. The reduction in total leached N was similar to the total crop N uptake. Nitrate-N concentrations in leached water were reduced by 49-85 mg l(-1) (by 62 to 99%), dependent on N availability and i rrigation. Due to catch cropping the NO3--N concentration in the percolate decreased with increasing irrigation (or precipitation), whereas the amount of N leached increased with irrigation. Evapotranspiration from a catch cr opped soil is close to the potential evapotranspiration under optimal growt h conditions.