DRY-MATTER AND NITROGEN ACCUMULATION AND RESIDUES OF OIL AND PROTEIN CROPS

Oil and protein crops are of growing importance in cropping systems. T his study was carried out to compare oil crops of linseed, rapeseed, s unflower and protein crops of faba bean and white lupin for grain prod uction, residual plant dry matter and nitrogen. Two field experiments with either oil or protein crops were conducted in 1993 and 1994, resp ectively. Total dry matter production, grain yield, residues, N concen trations and mineral N in the soil were measured. Dry matter productio n and distribution as well as N uptake and residues varied greatly amo ng species and between years. In 1993, oil crops gave up to 3 t ha(-1) grain and 16 t ha(-1) residues with sunflower, while in 1994 up to 5 and 11 t ha(-1), respectively, were recorded with winter rape. Protein crops showed an opposite reaction in years. Nitrogen uptake and resid ual N amounts were correlated with dry matter production. Plant residu es of oil crops contained 20-140 kg N ha(-1); those of protein crops u p to 80 kg N ha(-1). Despite the variation of residual plant N the var iability of mineral N in the soil at harvest was hardly influenced by crops and amounted to only 20-50 kg NO3--N ha(-1).