Humic Substances With Mineral Fertilization on Nutrient Availability in Irrigated Soil

This study aimed to evaluate the alternative use of humic substances (humic and fulvic acid) combined or not with mineral fertilization containing Nitrogen (N), Phosphorus (P) and Potassium (K) in the process of nutrient retention in the soil. For this, an experiment was conducted in a greenhouse with PVC columns of 40 cm high and 5 cm in diameter, where they were filled with Oxisol sample, being half of the treatments fertilized with NPK and half without at. Humic substances were added at doses equivalent to 0, 60, 120 and, 240 L ha-1. After this, 10 irrigations were made with 32 mm rain simulation. After 30 days, soil samples were collected in the upper (0-20 cm) and lower (20-40 cm) layers of the columns. Soil samples were evaluated for P, K, Ca, Mg content, pH, and soil conductivity. The experiment was in a completely randomized design, with a factorial statistical scheme of 2 × 2 × 4 with three replicates. The results showed that mineral fertilization complemented with the use of humic acid promoted a higher residual effect of Ca and K in the soil after 30 days. The fulvic acid, when used in a complementary way to mineral fertilization, promoted a higher amount of P in the soil. In the absence of mineral fertilization, the effect of humic substance use is low on the availability of nutrients in the soil.