Effects of Timing of Nitrogen Application on the Yield of Super Early Genotypes of Common Bean.

The common bean (Phaseolus vulgaris L.) is economically significant in several countries and is considered to be an important source of protein for human consumption. In the growing season 2012/2013, 23 million metric ton of common bean grain were produced worldwide, with the main producers Myanmar, India, Brazil, China, USA and Mexico. The use of super early cycle cultivars of common bean with irrigation is designed to allow high grain yields to be achieved a  shorter time compared with the season length for traditional genotypes. Provision of irrigation thus results in savings of water and power and reduces the overall the costs of production. Embrapa has developed common bean genotypes that are designed for use with early cycle management practices. These genotypes have life cycles of 65-75 days, compared with life cycles of 90-100 days for traditional cultivars. This reduction in length of the life cycle of 40% could mean that there is insufficient time for uptake of nitrogen (N) if this is applied at the same times as those for the traditional cultivars. Therefore, further research is needed to validate the effects of super early genotypes on management practices to ensure efficient use of N. The aim of this study was to determine the effect of timing of nitrogen application on the development of super early genotypes for the common bean. A field experiment was conducted in the 2014/15 growing seasons in central Brazil with a randomized block experimental design with split plots and four replicates. The plots comprised the common bean genotypes (IPR Colibri - control, CNFC 15873, CNFC 15874 and CNFC 15875) with subplots with applications of N at different timings: 90 kg of N at sowing, 90 kg N at top-dressing; 45 kg of N at sowing and 45 kg at top-dressing, with urea as the source of N. We also included a control treatment with no application of N. There were no differences in the number of pods per plant, number of seeds per pods, mass of 100 seeds and yield of common bean with timing of N application for the super early cycle genotype. This could be attributable to the high soil organic matter content at the site (3.99 g kg^-1) that may have provided the necessary N to the plants. Our findings suggest that application of N fertilizer is not required for super early genotypes of common bean growing on soils with high level of soil organic matter. The yields from the super early genotypes CNFC 15873 (2379 kg ha^-1) and CNFC 15875 (2340 kg ha^-1) were higher than that for the control IPR Colibri genotype (1910 kg ha^-1).

ACKNOWLEDGEMENTS

To the National Council for Scientific and Technological Development (CNPq) (Process 471812/2013-7) due to funding this research. To Dr. David Whitehead for having revised this abstract.