Sinergismo do biochar e bioestimulante na mitigação do estresse salino em meloeiro

Abstract

Melon (Cucumis melo L.) production in Brazil is well-established in the Northeast region due to its high adaptability to local climatic conditions. However, due to the irregularity of rainfall in the region, supplementary irrigation is necessary. The water used in the system originates from underground sources, has high electrical conductivity, and is rich in salts, which can cause salt stress in plants. This condition compromises the development and productivity of melon crops. To mitigate the negative effects of salinity and improve crop performance, the use of biochar and biostimulants has proven effective. These products have positive physiological, biochemical, and growth-promoting effects, helping plants cope with salt stress conditions. Therefore, this study aims to evaluate the synergistic potential of using biochar, derived from green coconut husks, in potassium fertilization at melon planting, combined with the foliar application of a biostimulant obtained from seaweed extract and fulvic substances. The study focuses on assessing the effects on growth, physiology, nutrition, and melon production, aiming to mitigate the impact of salt stress on the crop. The experiment was conducted in a greenhouse using pots with a capacity of 8 L. The experimental design adopted was a completely randomized design (CRD) in a 2 × 4 factorial scheme, corresponding to two salinity levels of irrigation water (0.3 and 4.0 dS m⁻¹) and four fertilization management strategies: (1) Control (conventional potassium fertilization at planting without the use of a biostimulant); (2) Biochar (application as a potassium source at planting); (3) Biostimulant (foliar application of the biostimulant combined with conventional potassium fertilization); and (4) Biochar + Biostimulant (biochar as a potassium source at planting combined with foliar application of the biostimulant). This setup resulted in a total of eight treatments, each with five replications, totaling 40 experimental units. Throughout the experimental period, non-destructive assessments of plant growth and gas exchange were performed at 25, 40, and 55 days after sowing (DAS). At the end of the cycle, plant nutritional status, fruit quality, and soil chemical properties were analyzed. The data were subjected to analysis of variance (ANOVA) using the F test, and when significant, means were compared at 1% and 5% probability levels using the Tukey test and dendrogram analysis. According to the results obtained, the deleterious effect of irrigation water salinity (4 dS m⁻¹) on Goldex F1 melon was confirmed. Furthermore, the synergistic effect between biochar and the biostimulant was limited, showing no significant impact on the nutritional status or fruit quality of the melons. Biochar derived from green coconut husks can serve as a sustainable source of potassium (K⁺) for fertilization at planting. However, the biostimulant did not exhibit a significant effect on the physiology or overall performance of melon plants.