Effect of soil conditioners based on geomimetic materials on plant growth in degraded soils: Poly(acrylic acid)/bentonite

Abstract

Geomimetic materials (GEOMI) are composite materials based on polymer and clays, able to imitate structural and functional properties of soils, including their structure, cationic exchange capability (CEC), water uptake capability (WUC), pH buffering ability, immobilizing of substances, among other. Because they can be used to develop of fertilizer slow-release systems, they have been identified as a novel approach to advance toward a most sustainable agriculture. The aim of this work was to study the effect of GEOMI on the plant growth in degraded soils. For this, GEOMI-1.0 was synthesized using poly(acrylic acid) as model of humic substances and bentonite modified with trichlorovinylsilane as mineral fraction model. Materials were characterized by different techniques. GEOMI-1.0 showed a hybrid, homogeneous, and amorphous structure. In addition, it was thermally stable at below ⁓200 °C with a Tg about 49.3 °C, showed a high WUC (⁓1384 g of water per 100 g of material). Likewise, it was verified that GEOMI-1.0 can decreases the pH values and increases the CEC of degraded soils depending on the added amount of geomaterial; but also, the electric conductivity values showed no dependence on the added amount of GEOMI-1.0. By correlation analysis, an exponential dependence of CEC was observed respect to pH changes, the relative amount added of GEOMI-1.0 and the initial CEC. Finally, using Brachiaria Brizantha cv. Marandú as plant model, the increase in the biomass content of roots and leaves, and the number of germinated seeds, were observed when GEOMI-1.0 was used for restoration of in-lab degraded soils.