Avaliação da aplicação de molibdênio e nitrogênio no crescimento do feijão-caupi irrigado com água salina em ambiente semiárido

Abstract

Cowpea (Vigna unguiculata (L.) Walp.) has its center of origin located in the African continent, being introduced in Brazil around the 16th century and is still recognized today as one of the most consumed legumes in the North and Northeast regions. Its cultivation is expressive by irrigating farmers, however, the water used is of poor quality and extremely saline. This salinity can affect the absorption of nitrogen, an important macronutrient for the growth and development of the legume and associating with this condition the deficiency of molybdenum, an important micronutrient in nitrogen metabolism, which together can be an important nutritional management strategy to provide the expression of maximum productive potential of cowpea. The objective of this work was to evaluate the behavior of cowpea cv. IPA 207, when subjected to increasing doses of molybdenum associated with nitrogen doses, aiming to establish the treatment that would enable the best increment of the studied variables. The experimental design used was in randomized blocks, generating a factorial scheme, 5x2x4, totaling 40 experimental units, with the following treatments: 5 doses of molybdenum (0, 40, 80, 120 and 160 g/ha) and two doses of nitrogen ( 0, 80 kg/ha) and 4 repetitions. The molybdenum source used was sodium molybdate, and urea was nitrogen. Treatments were applied 23 days after seedling emergence. The variables studied were: plant height (cm), stem diameter (mm), number of pods per plant, number of grains per pod, mass of one hundred grains (g), fresh and dry mass of shoot (g), fresh and dry root mass (g) and the activity of the nitrate reductase enzyme. The data obtained were submitted to analysis of variance and then to polynomial regression analysis. The increasing doses of molybdenum applied via the leaves in association with nitrogen fertilization positively influenced the activity of the nitrate reductase enzyme, as well as the accumulation of fresh and dry matter of cowpea, in addition to the significant increase in the variables number of grains per pod and number of pods per plant.