Organomineral fertilization with sewage sludge on the production and nutrient accumulation in Urochloa brizantha cv. Paiaguás

Abstract This study evaluated the effects of sewage-sludge-based organomineral fertilizers, produced using different technologies, as a sustainable alternative to mineral fertilization for biomass production and nutrient accumulation in Urochloa brizantha cv. BRS Paiaguás. The experiment was conducted for 120 days in a greenhouse under a randomized block design with four replicates. Treatments included mineral fertilizer (NPK), granulated biochar (GB), powdered biochar (PB), granulated composted sludge (GS), powdered composted sludge (PS), and a control (Test) without fertilization. After 120 days, granulated biochar and mineral fertilizer promoted the highest dry matter production and Mg and Ca accumulation in the uniformity cut. The unfertilized treatment did not reach 40 cm in height and therefore did not allow biomass harvesting. The granulated biochar increased P accumulation in shoots by 49% (1.48 mg plant −1 ) compared with mineral fertilizer. Root dry weight ranged from 8.28 to 13.42 g plant −1 across the fertilized treatments; no significant differences were observed between organomineral and mineral fertilizers. The GB treatment showed a total P accumulation of 5.92 mg plant −1 , close to NPK (6.20 mg plant −1 ) and 37.8% higher than the average of the other organomineral fertilizers. Furthermore, the GB and NPK treatments exhibited the highest total accumulations of N (62.90 and 70.56 mg plant −1 ), Mg (21.22 and 21.01 mg plant −1 ), and S (29.38 and 38.75 mg plant −1 ). GB fertilization increased CEC compared to mineral fertilization (NPK) and the control treatment, although the highest values were observed in the sludge-based organomineral treatments (GS and PS). These changes, linked to increased organic matter, helped reduce potential acidity and aluminum toxicity, thereby improving nutrient availability and plant uptake. Overall, the granulated sewage-sludge biochar outperformed the other organomineral formulations and represents a promising and sustainable strategy to enhance U. brizantha productivity and improve the fertility of tropical soils.