Eucalypt root growth and yield are affected directly by soil compaction during forestry operations, particularly harvesting. These effects are intensified under high soil moisture conditions. An experiment was carried out under controlled conditions in order to evaluate the effects of compaction under increased soil moisture levels, on seedling growth and nutrition. An oxidic-gibbsitic Red Yellow Latosol (LVA) and a kaolinitic Yellow Latosol (LA) were used. The treatments consisted of five compaction pressure levels (0, 60, 120, 180, and 240 kPa) and three soil volumetric water content (0.05, 0.10 and 0.20 kg kg-1, the last one corresponding to field capacity), arranged in four randomized blocks. A quantity of soil was calculated to occupy 1.66 dm³ in a PVC pipe section at a bulk density of 1.05 and 1.10 kg dm-3, respectively, for the LVA and LA. Subsequently, the soil samples were fertilized, moistened, placed in PVC ring pots and compacted with a CBR press. After soil compaction, the resulting bulk density was calculated, according to the new volume occupied by the soil. Sixty days after eucalypt seedling emergence, the plants were harvested for root and shoot dry weight determination, root density estimation, and plant nutrient analyses. The increase of bulk density by soil compaction was intensified by soil moisture. Increasing soil compaction reduced root and shoot growth, root density and plant nutrient content at the highest volumetric water content (0.20 kg kg-1) in oxidic-gibbsitic soil (LVA), but did not affect eucalypt dry matter yield at the lower volumetric water levels. The most affected nutrients under the compacted condition were: Fe > Zn > Cu > P = Mg in the oxidic-gibbsitic soil, and K in the kaolinitic soil. This soil was more sensitive to compaction than oxidic-gibbsitic soil, causing stronger restrictions on the root dry matter yield and Fe, Cu, N, S, and Zn uptake. This study results support soil moisture at pressure application as the main factor for the negative effects of soil compaction on eucalypt seedling growth and nutrition.
Soil bulk density; root density; plant nutrition; soil mineralogy
