Bioestimulante a base de algas marinhas e ácidos fúlvicos como atenuador do estresse salino em soja

Abstract

Soil salinization is a limiting factor in world productivity, and crops of great economic importance such as soybeans show relevant reductions in their growth caused by the deleterious effects of salinity. As a way to minimize production losses, new agricultural practices have been developed aiming at better crop performance. In this sense, the use of biostimulants in agriculture can be an alternative to mitigate the effects of salt stress on plants. Among the compositions of some biostimulants, there is the extract of seaweed (Ascophyllum nodosum (L)) and fulvic acids that show promise for better agronomic performance of crops. The objective of this work was to evaluate the action of a biostimulant composed of Ascophyllum nodosum (L) and fulvic acids applied at different phenological stages (V3, V3/R1 and V3/R1/R4) on the growth and physiology of soybean plants subjected to irrigation with saline water (no stress and saline water irrigation with EC 5.0 dS.m-1). The experiment was carried out in a greenhouse in pots containing 6 kg of soil under a completely randomized design in a factorial scheme (3 x 2) + 2 (three applications, two levels of salinity, negative control (without biostimulant and with stress), positive control (no biostimulant and no stress) and five repetitions. Biometric parameters (height, number of leaves, diameter, leaf area and dry matter), physiological (water potential, gas exchange, chlorophyll a fluorescence, photosynthetic pigments), biochemical (electrolyte, ion leakage) and productive components were evaluated. Biometric and productive components were affected by salinity. In plants under stress, accumulations of aerial biomass, chlorophyll b, total chlorophyll and carotenoids were observed. The Na + / K + ratios in the V3 and V3/R1 application were lower than in plants without stress, showing better metabolic efficiency. The best instantaneous efficiency of water use in plants with and without stress was higher in the application in V3 and V3 / R1, and the intrinsic efficiency of water use also in the application V3 and V3 / R1 in plants with stress, shows better absorption of CO2 with less water loss. Photosynthesis and transpiration in plants under stress were higher in applications at stages V3 and V3 / R1 / R4. Photosynthesis in plants without stress was superior to the positive control in all applications. The biostimulant showed positive results in the mitigation of salt stress and improved performance in plants without stress.