The quality of vegetal residues from crops and green manure can influence the mineralization/immobilization rate of nitrogen and the subsequent utilization of this nutrient by the following crops. The aim of this study was to evaluate the effect of nitrogen rates applied to the cover of summer corn, succeeding winter cover crops under direct drilling system. The experimental design consisted of randomized blocks with four replications in a scheme with subdivided plots. The main plot was composed of two crops previous to corn: Common oat (Avena strigosa Schieb), forage turnip (Raphanus sativus) and a fallow area (weed). The subplot consisted of four rates of nitrogen (0, 30, 60 and 120 kg ha-1). The production components analyzed were: Ear diameter, rows of grains/ear, mass of 100 grains and yield. Cover crops did not affect the components of corn production. The corn cultivated in succession to forage turnip showed responses to nitrogen fertilization.

This work aimed to assess the yield of five forage species subjected to nitrogen (N) levels at three different cutting ages. The experiment was carried out in the city of Santa Tereza do Oeste, at IAPAR's (Agronomic Institute of Paraná) experimental field, by applying a randomized complete block design in a factorial scheme 5×4×3, with five species: common black oat (Avena strigosa Schreb cv. Common), IPR 61 oat (Avena strigosa Schreb cv. IPR 61), Triticale Tpolo 981(Xtriticosecale wittmack), IPR 126 White oat (Avena sativa cv. IPR 126) and ryegrass (Lolium multiflorum Lam.); N levels were (0, 30, 60 and 120 kg ha-1); cutting ages were 66, 95 and 116 days after emergence (DAE), with three replications. Dry matter (DM) productivity was assessed in kg ha-1 by cut and total. The common black oat proved to be different from the other forage plants in DM yield, accumulating less quantities of it due to its cycle. The application of nitrogen fertilization to the coverage linearly influenced the ryegrass at 66 DAE and all other species at 116 DAE in a positive manner. Nitrogen did not influence the total accumulation of dry matter of both common black oat and Triticale Tpolo 981.