Foliar Deposition and Nutrient Cycling in Eucalyptus under Different Residue Management Practices and Fertilizer Omissions

The Brazilian forestry sector is growing in importance, with most of the planted forests located on low-fertility soils. Intensive forestry reduces mineral and organic matter reserves, making conservation practices such as maintaining forest residues on the soil essential. This study evaluated the effect of forest cover, residue management, and omission of N, P, K, Ca, and Mg on litter deposition and nutrient accumulation in the third rotation of Eucalyptus grandis in a long-term experiment in Itatinga, SP. Litterfall was evaluated by installing 0.25 m² collectors (via Voronoi diagram) and 6 m² collectors for branches during dry and rainy periods. Nutrient concentration was determined using the method proposed by Malavolta et al. (1989). The accumulation of nutrients was determined by the product of biomass and nutrient concentration in each compartment. Seasonality and management significantly affected litterfall, with higher deposition in the treatment without aboveground residues and without potassium fertilization (577.3 kg ha⁻¹ month⁻¹), 45% higher than with aboveground removal and complete fertilization in the rainy season. Nutrient deposition is higher in the rainy season, with higher deposition values for treatments with removal of the aerial part and without liming and total removal of residues and with fertilization, increasing N (31%), Mg (24%), Zn (32%), and B (16%). The results confirm that rainy periods influence nutrient cycling in eucalyptus, which is optimized when residues are maintained on the soil.