Synergy of Phosphate-Controlled Release and Sulfur Oxidation in Novel Polysulfide Composites for Sustainable Fertilization
Stella F. Valle, Amanda S. Giroto, Heitor Pontes Gestal Reis, Gelton Geraldo Fernandes Guimarães, Cauê Ribeiro
Abstract
The development of smart and eco-friendly fertilizers is pivotal to guarantee food security sustainably. Phosphate rock and struvite are promising alternatives for P fertilization; nevertheless, the solubility of these sources is a challenge for consistent use efficiency. Here, we propose using a polysulfide obtained via inverse vulcanization as a novel controlled-release fertilizer matrix in a system containing either Bayóvar rock (Bay) or struvite (Str). The polysulfide provides S for plants after being biologically oxidized to sulfate in soil, generating local acidity for P solubilization. After 15 days of soil incubation, the composites with 75 wt % Str and 75 wt % Bay achieved, respectively, 3 and 2 times the S oxidation from the elemental sulfur reference. Results indicated that P content stimulates the soil microorganismsʼ activity for S oxidation. The matrix had a physical role in improving Bay dissolution and regulating the rapid release from Str. Moreover, the available P in soil was 25–30 mg/dm3 for Bay composites, while for pure Bay, it was 9 mg/dm3.