MANEJO DA ADUBAÇÃO NITROGENADA NO FEIJOEIRO IRRIGADO SOB PLANTIO DIRETO

Abstract

Ground mulching can affect the availability of nitrogen to a common bean crop depending on the C/N relationship. The objective of this paper was to study the response of the crop grown after corn to nitrogen application rates and time, under no-tillage. The study was conducted at the ‘Embrapa-Arroz e Feijao’ experimental station, located in the municipality of Santo Antonio de Goias, GO, Brazil, in 1999 and 2000. The soil of the experimental site was Oxisol and experiments were conducted during the dry season using center pivot sprinkler irrigation. The experiment was conducted in a randomized complete block design, with four replications. The common bean cultivar used was Apore. All treatments received 120 kg/ha of N during the crop cycle, with split applications or not, in different doses twenty days before sowing, at sowing, and at topdressing. The treatments were: T1 (0-0-120 kg/ha), T2 (0-17,5-102,5 kg/ha), T3 (0-40-80 kg/ha), T4 (0-60-60 kg/ha), T5 (0-80-40 kg/ha), T6 (0-120-0 kg/ha), T7 (40-40-40 kg/ha), T8 (0-17,5-102,5 kg/ha), and T9 (0-60-60 kg/ha). In the last two treatments, the corn mulch was chopped. Common bean under no-tillage needed a higher nitrogen dose at sowing in relation to conventional tillage. In the no-tillage system, the appropriate rate of N at sowing was 60kg/ha. When the N rate was higher than 60kg/ha, grain yield decreased. The same N split application rate produced higher yield when the corn mulch was chopped. KEY-WORDS: Phaseolus vulgaris ; N split application; mulch.