Nitrogen (N) is required in large quantities by corn and its supply causes technical concerns related to crop performance and profitability, and environmental concerns in view of the high risk of nitrate leaching. Results of 61 field experiments conducted through 13 years, in a cooperative effort of the Fundação Agrária de Pesquisa Agropecuária (FAPA) and the Universidade Federal do Rio Grande do Sul (UFRGS), were analyzed and interpreted aiming at establishing a N fertilizer indication for high corn yields, adjusted to the use of winter cover crops in no-till soils in the South-Central region of Parana, Brazil. The urea-N rates were calculated based on the N required for different corn yield levels (6-8, 8.1-10, 10.1-12 and 12.1-14 t ha-1) and taking into account the N availability in soils with different soil organic matter contents in the layer 0-10 cm (< 40, 40-60 and > 60 g kg-1), the effect of winter cover crops (grass, leguminous, grass-legume consortium, and wild radish) on N availability, and the efficiency of N fertilizer. The indicated rates of urea-N were closely related to the N rates for maximum economic efficiency (MEE) for different soil OM contents, cover crop and corn yield (N indication = 39+0.80MEE, R² =0.74, n=20, p=0.03) corroborating the adequacy of this N indication for corn. The N rates were closely correlated with the rates recommended in the states of Rio Grande do Sul (RS) and Santa Catarina (SC) (Indication PR = -14+1.06 RS/SC, R² = 0.88, n=12, p=0.02). This confirms the use of the indication of Central South Parana for subregions of RS and SC with high corn yield potential. Likewise, the recommendation for RS and SC can also be used in subregions in PR that are climatically less suitable for corn.
N fertilization; urea; cover-crops; organic matter
