Dry matter and nitrogen accumulation and residues of oil and protein crops

Oil and protein crops are of growing importance in cropping systems. This study was carried out to compare oil crops of linseed, rapeseed, sunflower and protein crops of faba bean and white lupin for grain production, residual plant dry matter and nitrogen. Two field experiments with either oil or protein crops were conducted in 1993 and 1994, respectively. Total dry matter production, grain yield, residues, N concentrations and mineral N in the soil were measured. Dry matter production and distribution as well as N uptake and residues varied greatly among 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 residual N amounts were correlated with dry matter production. Plant residues of oil crops contained 20–140 kg N ha⁻¹; those of protein crops up to 80 kg N ha⁻¹. Despite the variation of residual plant N the variability of mineral N in the soil at harvest was hardly influenced by crops and amounted to only 20–50 kg NO⁻₃-N ha⁻¹.