Residual effect and leaching of N and K in cropping systems with clover and ryegrass catch crops on a coarse sand

In low input farming systems without inorganic N-fertilizer input, cereal cropping is a challenge because of the need for an adequate N supply. The objective of this investigation was to explore the feasibility of using clover (red/white) catch crops instead of ryegrass in crop production on coarse sand. Two field experiments tested the effects of clover and ryegrass catch crops on N and K leaching and on grain yield of a succeeding spring barley. Treatments included animal manure regimes, main crops (spring barley = low soil N status or lupin = high soil N status) and levels of K fertilizer (no K or 80 kg K ha−1). The residual effect of the clover catch crop on grain yield of the succeeding spring barley was significantly higher than that of the ryegrass, especially under the low N conditions. When animal manure (70 kg total-N ha−1) was added to the spring barley succeeding a ryegrass catch crop, the difference in residual effect between clover and ryegrass catch crops disappeared. Thus, clover appeared to have the potential to substitute animal manure. Leaching of NO3-N and K was estimated by means of porous ceramic suction cups installed at 1 m depth. Both the clover and ryegrass catch crops reduced the annual flow-weighted mean NO3-N concentrations from 13–16 to 5–8 mg L−1, which is below the WHO maximum for drinking water. The annual NO3-N leaching from a spring barley treatment without catch crops was approximately 100 kg ha−1. Clover and ryegrass catch crops reduced the losses significantly by approximately 40–80% depending on year and treatment, with ryegrass being more effective than clover. Catch crops reduced K leaching significantly but the relative effect was lower than for N. The clover catch crops appeared suitable for low-N cropping systems on coarse sand with respect to both production and environment.