Performance of the marine algae biostimulant Macrocystis sp. on soybean growth and production components

Abstract

The soybean crop is an activity of significant socioeconomical importance for Brazil; however, the intensification of agricultural practices to increase productivity can lead to the excessive use of concentrated fertilizers and synthetic agrochemicals, which cause negative environmental impacts. The use of alternative inputs, such as biostimulants extracted from seaweeds, has contributed to the integration of sustainable practices, particularly regarding nutritional factors and the regulation of biotic and abiotic stresses. The objective was to analyze the effect of the Macrocystis sp. seaweed biostimulant on growth and production components in three soybean cultivars. The study was conducted on three commercial soybean fields located in the Maranhão state, Brazil. The experimental design was a randomized block design with 2 treatments and 9 replications. The treatments were applied via foliar spray at the V₅ growth stage. The first treatment consisted in a no-treated (without seaweed application), while the second involved the application of biostimulant. The following parameters were analyzed: plant height; number of trifoliates, branches, nodes, and pods; chlorophyll a, b, and total indices; vegetative index (NDVI); and soybean yield. The seaweed biostimulant application of the Macrocystis sp., at the V₅ stage and 750 mL ha⁻¹ dosage, increased the number of branches (33–40%), nodes (9–36%), pods (9–23%), and soybean yield (10%) in the DM 82i78 IPRO and FTR 3191 IPRO cultivars. The treatment was ineffective for BMX Domínio IPRO cultivar, causing a plant size reduction, but it not improved branching, number of pods, and yield. The results demonstrate that the use of seaweed biostimulant in soybean has complex responses. The genotype is a determinant factor in bioestimulant efficiency and soybean yield.