Manejo da adubação foliar do feijoeiro comum de inverno (Phaseolus vulgaris L.) proveniente de sementes com diferentes níveis de molibdênio

Abstract

Molybdenum (Mo) plays a fundamental role in increasing bean productivity by potentiating the biological fixation of nitrogen. Therefore, the use of seeds enriched with Mo generates benefits such as lower nutrient losses, present in the fertilizers, guaranteeing greater efficiency. In this sense, the objective of this work was to evaluate the nutritional quality of the cultivar "Madrepérola", produced in the winter period with variations of molybdenum contents in the seeds and under foliar application of this micronutrient. For the production of seeds with three levels of Mo, the "mother plant" was fertilized with sodium molybdate in the dosage of 300 and 600 g ha-1. This fertilization was parceled out, and for the dose of 300 g ha 1 was divided into stages V4 and R5 with 100 and 200 g ha 1, respectively; for the dose 600 g ha -1 was divided into stages V4, R5 and R7 with 100, 250 and 250 g ha -1, respectively. With the seeds of these plants, an experiment was carried out in a randomized block design, in a 3X2 factorial scheme with four replications. The treatments were constituted by three endogenous levels of molybdenum in the seeds, the bottom one being an undetected quantity; medium with 2.3 μg seed 1; and high with 5.2 μg seed 1 and two doses of molybdenum via leaf (0 and 500 g ha-1 of sodium molybdate). In this experiment there were foliar applications in the V4 stage; at the dose of 100 g ha-1 and at R7 at the dose 400 g ha-1. The contents of Co, Fe, K, Mo, N and Zn in leaves and bean grains were evaluated. The data were submitted to the analysis of assumptions, ANOVA and Tukey's test. It was concluded that the foliar application of molybdenum is a physiologically feasible technique to obtain increments of iron and molybdenum in the leaves and seeds as well as zinc only in the leaves. The use of Mo-enriched seeds should be considered as an alternative to conventional fertilization, since the contents of this nutrient in the seeds may be sufficient to improve plant nutrition (increase of 8.34 mg dm-3 of Zn in the leaves of plants from seeds with medium endogenous content of Mo), avoiding the foliar application.