Effect of harvest residue management on soil properties of Eucalyptus hybrid and Acacia mangium plantations planted on steep slopes in northern Vietnam

Burning harvest residues during site preparation can compromise the soil-nutrient stock in short-rotation plantations, but this practice remains common in northern Vietnam. This study compared the effect of two contrasting harvest-residue treatments (burning vs retention) on soil total carbon (TC), total nitrogen (TN), extractable P (ext-P), exchangeable K (exch-K) and bulk density (BD) of two adjacent randomised complete-block trials, one of Eucalyptus hybrid (Eucalyptus urophylla × E. pellita) and the other of Acacia mangium planted on steep slopes. Harvest-residue management had no effect on soil properties of either E. hybrid or A. mangium two years after planting. Soil pH in E. hybrid increased and exch-K in A. mangium decreased during the first year; ext-P decreased over time in both species though this was only significant in the residue-retention treatment in A. mangium. Slope significantly influenced pH and TC of E. hybrid and TC and TN of A. mangium. It appeared that slope position and correlative factors such as surface runoff and erosion had led to the observed distribution of some soil properties along the steep slope.