Nutrição boratada em cultivares de soja

Abstract

The effects of boron (B) on soybean yield are known. However, new studies on B doses must be carried out in order to investigate the response of new cultivars, since the existing recommendations are outdated and for old cultivars. Thus, it is pertinent to test the hypothesis that boron fertilization, depending on the cultivar, may present different responses on the components of production and productivity, as it promotes improvement in reproductive processes, ensuring greater soybean production potential. The objective of this study was to evaluate the effects of B doses applied to the soil on nutrition, yield components and yield of soybean cultivars. The design used was in randomized blocks, with three replications, in a 5x3 factorial scheme (0; 1; 2; 4; 6 kg ha-¹ of B) and three soybean cultivars (DM73I75, DM75I76 and Aporé). The following evaluations were carried out: soil boron content (0-0.20 and 0.20-0.40 m), leaf boron content (BF), production components (number of flat pods (VC), number of pods with one grain (NV1), number of pods with 2 grains (NV2) and number of pods with 3 grains (NV3), number of normal pods (VN), mass of a thousand seeds (MMS)) and yield (PROD). The results indicated that, for BS20 and BS40 increased with the supply of B doses, for BF the cultivars showed an increasing linear effect as a function of B doses. The number of CV was reduced at the dose of 3.31 kg ha-¹ of B in the Aporé cultivar. The dose of 2.56 kg ha-¹ of B in cultivar DM75I76 promoted the lowest production of NV1, for NV2 in the cultivar DM73I75 it presented maximum production of pods with 2 grains at the dose of 3.18 kg ha- V of B, for VN in the cultivar DM73I75 at a dose of 3.16 kg ha-¹ of B provided greater production of normal pods. MMS was not affected by boron doses. However, yield showed a quadratic adjustment, and the dose of 2.31 kg ha-¹ of B in the soil promoted maximum yield represented by 4,684.22 kg ha-1 of grains. Thus, it can be concluded that the B content in the soil (0-0.20 and 0.20-0.40 m) and in the leaf increased as a function of the increase in the doses of B, production components by reducing the number of flat pods, pods with one grain and by increasing the number of pods with 2 grains, reflecting in higher soybean grain yield at a dose of 2.31 kg ha-¹ of B, regardless of the cultivar tested.