Rendimento de feijão-caupi em função de doses e formas de aplicação de nitrogênio

The cowpea-bean, known as macassar-bean or rope-bean is one of the main crops in the Northeast region of Brazil. It is consumed either as fresh or dried beans. Cowpea is cultivated in almost all regions of the Paraiba State, representing 75% of the cultivated area with cowpea-beans. The low yield is attributed to the lack of a research program about mineral fertilization. The effect of levels and forms of nitrogen applications on yield of pods and green and dry grains of cowpea-bean, cv. IPA 206 was evaluates. The experiment was performed at the Universidade Federal da Paraiba, in Areia, Brazil, from April to August/2001, in a randomized blocks design. Treatments were distributed in a factorial scheme 5 x 2, where the first factor corresponded to nitrogen levels (0; 25; 50; 75 and 100 kg ha-1) and, the second factor, the application forms (soil and foliar application), in four repetitions. Each plot consisted of 20 plants, spaced 0.8 x 0.4 m apart. The estimated maximum pods yield (11 t ha-1), of green grains (9.3 t ha-1) and of dry grains (3.6 t ha-1) was obtained with 62, 61 and 56 kg ha-1 of nitrogen applied in the soil, respectively. With foliar applications the yield of pods (10 t ha-1), of green grains (8.4 t ha-1) and of dry grains (3.4 t ha-1) reached maximum values applying levels of 64, 63 and 59 kg ha-1 of nitrogen respectively.