Potencial do biocarvão da casca do coco verde nos atributos do solo e no desenvolvimento do meloeiro

Abstract

This investigation addresses the valorization of agro-industrial residues as a strategy to mitigate the physicochemical limitations of soils under fruit cultivation in arid regions. Within this context, this doctoral thesis investigated the feasibility of using green coconut husk-derived biochar as both a soil conditioner and a potassium (K2O) source for muskmelon crops under semi-arid conditions. The research was predicated on the premise that water scarcity, low water-holding capacity in sandy soils, and a heavy reliance on imported potassium fertilizers represent critical challenges for the sustainability and resilience of melon production in the Brazilian Northeast.The experiment followed a completely randomized design (CRD) with six treatments and four replicates, comparing increasing doses of biochar (ranging from 50% to 150% of the recommended K2O for the crop) against conventional fertilization via potassium chloride (KCl). Regarding physical characterization, undisturbed soil samples were collected to determine the water retention curve, fitted using the Van Genuchten model, alongside an analysis of macropore and micropore distribution. At 70 days after sowing (DAS), soil chemical attributes, nutritional status, and plant dry matter accumulation were evaluated.The results demonstrate that the application of green coconut husk biochar promoted significant improvements in soil hydro-physical attributes. Notably, biochar treatments increased water retention capacity; specifically, the dose supplying 100% of the potassium requirement resulted in a 33.3% increase in available soil water compared to the unfertilized control. Chemically and nutritionally, the biochar served as a source of readily available potassium with release regulated by physicochemical properties, consequently increasing soil pH, available K, and organic matter content. Multivariate analysis confirmed that biochar use mitigated soil salinization risks typically associated with KCl. Furthermore, a synergistic effect on nutritional efficiency was observed: the 100% biochar treatment promoted increments of 44.3% in total K accumulation and 25.6% in P accumulation, while the 125% dose increased N accumulation by 30.6%.These improvements translated positively into vegetative development, with significant gains in stem diameter and plant vigor, although the 150% dose indicated physiological saturation. In conclusion, this research highlights green coconut husk biochar as a promising and sustainable alternative for soilmanagement. Its dual function—as a hydro-physical soil improver and a potassium source—contributes to the regional circular economy by repurposing an abundant waste product while simultaneously enhancing the resilience of muskmelon production systems, particularly in environments prone to water stress.