Sinergismo de biocarvão e bioestimulante no metabolismo, fisiologia e crescimento de plantas de melão submetidas ao estresse salino

Abstract

The use of saline water is a major bottleneck in irrigation, limiting agricultural production as it reduces crop productivity to economically impractical levels, especially in semiarid regions with soils more prone to salinization. The Northeast of Brazil is responsible for most of the country's melon production, a crop highly sensitive to salt stress, which directly affects its growth and development. Therefore, this study aimed to evaluate the combination of biochar produced from green coconut husk and the bio-stimulant FH Attivus®, formulated with seaweed extract (Ascophyllum nodosum L.) and fulvic acids, as potential mitigators of the deleterious effects of salinity on hybrid yellow melon Goldex F1. The experiment was conducted in a greenhouse at the Department of Crop Science of the Federal University of Ceará (UFC). A completely randomized design (CRD) was used in a 4×2 factorial scheme with five replications. The first factor corresponded to four management conditions (Control: Without Biochar and Biostimulant; Biochar only; Biostimulant only; and Biochar + Biostimulant). The second factor consisted of two levels of irrigation water electrical conductivity (EC): 0.35 dS m⁻¹ (non-saline water) and 4.5 dS m⁻¹ (saline water), totaling eight treatments. Growth parameters (plant height, leaf number, stem diameter, and leaf area), physiological parameters (gas exchange), and metabolic profile were analyzed. All data were collected during the fruit-filling stage, specifically from 55 to 59 days after sowing (DAS). Salinity negatively affected melon plant growth and physiological performance. Additionally, the synergy between biochar and the biostimulant, regardless of the salinity factor, promoted an increase in instantaneous carboxylation efficiency (EiC), net photosynthesis (A), and stomatal conductance (gs). Regarding primary metabolism, biochar fertilization, biostimulant application, or their synergy (Biochar + Biostimulant) increased metabolite accumulation in the absence of salinity. However, biochar and the biostimulant did not show true efficiency in mitigating salinity effects on Goldex F1 yellow melon plants, thus rejecting the initial hypothesis.