Green manures and mineral nitrogen topdressing fertilization of wheat crop under no-tillage

The objective of this work was to evaluate the effect of different green manures associated with levels of mineral nitrogen topdressing in the agronomic performance of wheat crop under no-tillage. The experiment was performed in Dourados, MS, Brazil, in randomized blocks experimental design, with treatments arranged in a split-plot scheme with four repetitions. The plots were constituted by hairy vetch (Vicia villosa), sunn hemp (Crotalaria juncea), velvet bean (Mucuna deeringiana), hyacinth bean (Dolichus lablab) and a treatment-control, in fallow. In the split-plot were tested four levels of mineral nitrogen top dressing: 0 (zero), 45, 90, and 135 kg ha(-1), using urea as source. Evaluations of cover crops shoot dry biomass, nitrogen contents in green manures shoot and in wheat leaves, plant height, number of productive tillers per plant, length of spike, number of grains per spike, one thousand-grains weight, hectoliter weight and yield were done. It was concluded that higher yields in wheat are obtained when it is grown after hairy vetch and sunn hemp and that the wheat yield response to mineral nitrogen top dressing application varies according to the preceding crop.