Soil quality bioindicators in initial eucalyptus growth under organomineral fertilization based on sugarcane filter cake

Pelletized organomineral fertilizers (OMFs) are a promising, sustainable alternative for eucalyptus fertilization, the most widely cultivated hardwood tree globally. However, little is known about the effects of OMFs on initial plant development and soil quality. We evaluated the effects of different doses of a pelletized OMF derived from sugarcane filter cake (0%, 50%, 100%, 150%, and 200% relative to the recommended phosphorus dose for cultivation) and a mineral treatment (mineral fertilizer at the recommended dose for eucalyptus), as well as the effects of time (30, 60, 90, and 120 days after transplanting), on the morphophysiological responses of eucalyptus plants (diameter at neck height, plant height, and chlorophyll a and b content) and soil pH, microbial biomass (MBC), and microbial activity (soil basal respiration [SBR]). Increases in fertilizer dose led to increased chlorophyll a values, but values decreased under the highest doses (150% and 200%). OMF addition led to an initial increase in soil pH, followed by a reduction. The highest values of plant height, stem diameter, and fresh and dry masses of leaves, stems, and roots were observed when the OMF dose of 50% was administered. MBC values were inversely proportional to the OMF dose, and the SBR and metabolic quotient (qCO2) values observed under the 50% and 100% treatments were equal to or better than those observed under the mineral fertilizer treatment. Pelletized OMFs derived from filter cake could potentially replace mineral fertilization in the early development of Eucalyptus urophylla × Eucalyptus grandis without damaging soil quality