O boro foliar auxilia a resiliência de cultivares de soja ao estresse ambiental?

Abstract

Among micronutrients, boron has received attention due to its importance in the reproductive phase of plants, as it acts on metabolic processes considered essential. However, management of boron fertilization must be careful, as the range between deficiency and toxicity is narrow when compared to other nutrients. Despite the numerous studies carried out with micronutrients, doubts still arise regarding the effect of the sources, as well as the most appropriate time of application. Therefore, the objective was to quantify the efficiency of boron use in soybeans, associated with application at different phenological stages aiming to mitigate water stress as well as increase grain yield, using different production environments. On the field experiment was conducted over two crop season, in the municipality of Ijaci-MG. Furthermore, an experiment was carried out in a greenhouse, conducted in Lavras-MG. In the field, a randomized complete block design was adopted in a triple factorial scheme, with three cultivars with different relative maturity groups adopted, with sowing in strips. As management, the sources were Boron-MEA (0.5L/ha), Boric acid (700 g/ha) in two application times, in the vegetative stage (V6/Vn) and another in the reproductive stage (R1/R2), and control (water); and the third factor was the two agricultural years. The agronomic traits of plant height, insertion of the first pod, days to maturation, lodging index, grain productivity, as well as production components were evaluated. In addition to agronomic characters, physiological analyzes were carried out to quantify proteins, proline, hydrogen peroxidation and malondialdehyde, mineral composition in the leaves and relative chlorophyll content. In a greenhouse, a randomized block design was adopted, in a triple factorial, with the factors being (i) investment in soil fertility (high and low), (ii) treatments (boron sources and their application times and (iii) ) cultivars. Control of water availability was carried out to induce water deficit from stage V3 to R4. Statistical analyzes were carried out in the R computing environment, with joint analysis of data, correlation analysis and PCA. Leaf boron at the V6/Vn and R1/R2 stages is a promising alternative to alter the phenotypic plasticity of production components and, consequently, provide gains in grain productivity in soybean, in addition to contributing to resilience to water deficit conditions.