Can co-application of silicate rock powder and humic-like acids increase nutrient uptake and plant growth in weathered tropical soil?

Silicate rock powder (SRP) restores the fertility of weathered soils. However, its slow nutrientrelease is a disadvantage for short-duration crops. Humic-like acids (HLAs) are plantbiostimulants that enhance root development and nutrient uptake. This work evaluates theeffects of the co-application of HLA extracted from a vermicompost and SRP on the nutrientuptake and growth of maize cultivated in weathered soil in Brazil. The chemical composition ofHLA was assessed using Fourier-transform infrared spectroscopy and13Carbon-nuclear magneticresonance, revealing an overall characteristic of hydrophobicity. A preliminary trial with differentHLA concentrations (0, 20, 40, 80, and 160 mg L−1) revealed that 40 mg L−1HLA resulted in thehighest increase in the root area, dry root weight, H+efflux, and the number of lateral roots,compared with other concentrations. The main experiment using soil treated with SRP atdifferent rates (0, 600, 1200, 1800, and 2400 kg ha−1) showed that the co-application of SRP andHLA caused a significant difference in the root and total plant weights, compared with the soleSRP application. Furthermore, it increased the nutrient content of the plants. These effects aremainly because of increased proton pump activity and the hydrophobicity of HL