Abstract
As field beans (Phaseolus vulgaris) are low N fixers, N fertilizers are generally recommended. A study was conducted on a Coto soil, Tropeptic Haplorthox, to ascertain N demands of a high yielding selection of native white beans. Six levels of N were studied: 0, 20, 40, 80, 160, and 320 kg/ha on Bonita, a variety consumers prefer. The Capó fertilizer-yield equation, useful in predicting dry bean yields in terms of the fertilizer N used, was applied to the mean yield data. Not more than 180 kg/ha of N fertilizer are required to complement native soil N to obtain maximum dry bean yield, indicated by the finding that with 80 kg/ha of N, 96.7% of the maximum yield was obtained. Significant differences were evident in some of the yield components: weight of 10 plants, and number of pods and weight of pods/10 plants were significantly higher in the 160 kg/ha N levels than in the no- and 40 kg/ha levels. Number of seeds/pod was significantly lower in the no-N as compared to the 80-N level. No significant differences were found in plant canopy diameter, but plants from the 160 kg/ha treatment were taller than those from the no- and 20-kg/ha N levels.