Soil Solution Properties of Tropical Soils and Brachiaria Growth as Affected by Humic Acid Concentration

• Published in: Soil systems Vol. 8; no. 3; p. 86
• Main Authors: Valenciano, Murilo Nunes, de Morais, Everton Geraldo, Rosa, Sara Dantas, Silva, Carlos Alberto
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-09-2024
• Subjects: Acidic soils; Acids; Agricultural production; Beef industry; Biomass; Brachiaria; Carbon; Carbon content; Crops; Dry matter; Electrical conductivity; Electrical resistivity; Fertilizers; Fourier transforms; highly weathered soils; Humic acid; Humic acids; International economic relations; Micronutrients; Nutrient availability; Nutrient content; Nutrients; Nutritional status; Phosphorus; Plant growth; Plant layout; Sandy soils; Soil fertility; Soil investigations; Soil properties; Soil solution; Soil types; Soils; Solid phases; Spectrum analysis; Statistics; Tropical environments; tropical grass fertilization; Tropical soils; water-soluble carbon; Brazil
• ISSN: 2571-8789; 2571-8789
• DOI: 10.3390/soilsystems8030086

The soil solution is the compartment where plants uptake nutrients and this phase is in equilibrium with the soil solid phase. Changes in nutrient content and availability in the soil solution can vary among soil types in response to humic acid concentrations, thereby affecting Brachiaria growth. However, there are no studies demonstrating these effects of humic acid application on different soil types and how they affect Brachiaria growth. Thus, the aim of this study was to evaluate the effects of humic acid concentrations (0, 5, 10, 25, and 60 mg kg−1 carbon-humic acid) on Brachiaria brizantha growth and soil solution properties of contrasting tropical soils. Plants were grown for 35 days in greenhouse conditions in pots containing Sandy Entisol, Clayey (Red Oxisol), and Medium Texture (Red-Yellow Oxisol). Soil solution was assessed for pH, electrical conductivity (EC), carbon, and nutrient content. Shoot and root dry matter, as well as macro and micronutrients accumulation in the shoot, were determined. In a soil type-dependent effect, pH, EC, and concentrations of nutrients in solutions changed in response to carbon-humic acid concentration. In the less-buffered soils, Sandy Entisol and Red-Yellow Oxisol, the addition of 30–40 mg kg−1 carbon-humic acid increased root proliferation by 76–89%, while Brachiaria biomass produced in all soils increased by approximately 30%. Levels of carbon in solution were high (>580 mg L−1) and varied depending on the investigated soil type. Though solution carbon contents did not appear to be a driving factor controlling the positive effects of humic acid concentrations on Brachiaria dry matter, there was a direct relationship between other properties and nutrient content in the soil solution, and Brachiaria dry matter production.