Nitrogen and phosphate fertilizer on green corn grown in succession to the melon crop

Melon producers, in Chapada do Apodi, Rio Grande do Norte State, Brazil, located between the states of Ceara and Rio Grande do Norte, have cultivated corn in succession to the melon crop. However, this crop rotation is not yet evaluated on the extent to which the residual effect of nitrogen and phosphate fertilization carried out in melon can supply partially or completely the corn demands of nitrogen and phosphorus. This work aimed to evaluate the effect of nitrogen (N) and phosphorus (P) in the production of corn in succession to the cultivation of melon (Cucumis melo) irrigated in an Alkaline Inceptisol of Chapada do Apodi. Ten treatments from the combinations between five N rates (0; 45; 90; 160 and 220 kg/ha) and four levels of P2O5 (0; 40; 80; and 120 kg/ha) were compared. The experimental design was a randomized block with four replications. The corn cultivar was the hybrid AG 1051 and the characteristics evaluated were number and total weight of ears, number and weight of marketable unhusked ears and concentrations of N and P in plant and P in the soil. This study also estimated critical levels of N and P in the plant and P in the soil. Producing green corn in succession to melon is viable, in this experiment conditions, without application of nitrogen and phosphorus to the soil. However, for maximum corn productivity, application of 90 kg/ha N combined with 40 kg/ha P2O5 is recommended. The average critical level of N and P in the plant for corn production was 32.29 and 4.31 g/kg, respectively. This value for P in the soil was 20.7 mg/dm(3).