Nutrient release and decomposition time of Eucalyptus urograndis harvest residues practices under Brazil tropical conditions

The forest areas, besides their importance in the economic sector, have an important role in soil conservation when sustainable silvicultural practices are adopted. The objective of this study was to assess the amount of nutrients released and their stock in two types of eucalyptus harvest residues (with bark and without bark) in eastern Mato Grosso do Sul. Litter bags were used to evaluate the decomposition of harvest residues and nutrient (N, P, K, Ca, Mg, S, and C) content of the remaining residues under two different harvesting systems during a 36-month period. The “cut-to-length” (CTL) system is an eucalyptus harvesting method in Brazil, returning the most tree residues to the soil as trees are delimbed in situ. The “tree-length” (TL) harvest system returns a moderate level of eucalyptus residues to the soil, as they cut the trees and semi-process on-site to remove the pointer and bark, leaving on the field leaves, branches, and litter. Both CTL and TL differ from the traditional harvesting system, in which all trees are removed from the site to be delimbed at processing facilities outside the growing area, leaving no residues on the soil surface, this system was not evaluate during this research. Harvesting in the CTL system provided greater phytomass and N, P, K, Ca, and C contents. The decomposition of harvest residues in the CTL system was greater during the six initial months. Removing the bark, from the residues, reduced the amount of N and increased the decomposition time, as observed in the TL system. The amount and composition of forest harvest residues affect their decomposition and nutrient release.