Poliennal results on soil N management and maize N nutrition by green manuring

Summary

Several field trials were carried out in 5 years in Central Italy to study the effect of green manuring on soil N management and N availability for grain maize as a succeeding crop. Hairy vetch, field bean, rapeseed and barley were grown in autumn-winter as pure crops or mixed in leg-non leg couples. Maize was sown in early spring just after green manure incorporation. The amount of N supplied by green manures, as well as the maize N uptake and the estimated N effect (i.e. the N taken up by maize that actually derives from green manure N) depended on species used, but with a high between-year variability. The N effect at harvest over 3 years was found to depend on the amount of incorporated biomass (DW) and its N content (N%) according to a multiple linear regression (Neff = -3.9*DW + 47.8*N%, R2 = 73%).