Best tillage practices for early-growth of clonal eucalyptus in soils with distinct granulometry, drainage and profile depth

Abstract

Soil tillage influences early-growth, uniformity, and productivity of commercial forests. Best tillage practices for soils with constraints of compaction, drainage or shallow soils, all reducing the effective rooting-depth, are widely unknown for subtropical forest plantations in South America. The study aimed to quantify the effects of different tillage methods on breaking up and/or turning over the soil and on physical properties in three different soils, and relationships with early growth (up to 24 months of age) of clonal Eucalyptus saligna in southern Brazil. The tillage methods consisted of subsoiling to 50 cm plus rototilling, subsoiling to 50 cm plus ridging, and subsoiling to 70 cm plus rototilling. The soils were low-drainage Planosol, shallow sandy Regosol, and compacted clayey well-drained Nitisol. The dendrometric evaluations for initial growth show the best tillage method depended on soil type and dendrometric variable. Tree height is maximized by deep subsoiling (70 cm) in Nitisol, and by shallow subsoiling (50 cm) plus ridging in Regosol and Planosol. Tree diameter at breast height and basal area were maximized by shallow subsoiling with or without ridging in Planosol, deep subsoiling in Nitisol, and shallow subsoiling with ridging or with deep subsoiling in Regosol. When considering all the studied dendometric variables (tree height, diameter at breast height, and basal area), subsoiling plus ridging is recommend for low-drainage or shallow soils, whereas deep-subsoiling is necessary in clay soils.