Importance of Fertilization on Growth and Biomass of Acacia Plantations in Vietnam

To increase productivity of forest plantation, fertilization has been widely applied, especially in poor soil condition, of which Nitrogen (N), Phosphorous (P), Potassium (K) and compost are usually used. The amount is decided basing mainly on species and soil condition. The objective of this study is to examine the effects of fertilization on growth of acacia plantations. Four fertilization treatments (100 g NPK+200 g compost, 150 g NPK+150 g compost, 200 g NPK+100 g compost, and control) were applied at planting for Acacia hybrid and Acacia auriculiformis plantations with planting density of 1,330 trees ha-1 (spacing 2.5 × 3 m) in Northeast Vietnam at 21o38’N and 107o32’E. Data included survival rate, diameter at breast height (DBH), stem height, and crown diameter (Dc) were collected, and then dry biomass was calculated basing on available allometries. The results indicated that fertilizations had significant effects on DBH, Dc, and dry biomass of 4-year-old plantations of both species. Meanwhile, fertilization did not affect on survival rate. A 4-year-old A. hybrid plantation had largest DBH (12.4 cm) and highest dry biomass (66.1 Mg ha-1) in the treatment of 200 g NPK+100 g compost, and smallest DBH (11.3 cm) and lowest dry biomass (53.3 Mg ha-1) in control. A 4-year-old A. auriculiformis had largest DBH (8.6 cm) and highest dry biomass (36.6 Mg ha-1) in treatment of 100 g NPK+200 g compost, and smallest DBH (5.1 cm) and lowest dry biomass (12.3 Mg ha-1) in treatment of 200 g NPK+100 g compost. In all fertilization treatments, dry biomass of a 4-year-old A. hybrid plantation was significant higher than that of a 4-year-old A. auriculiformis plantation; ranging from the highest of 537% in treatment of 200 g NPK+100 g compost to the lowest of 178% in treatment of 100 g NPK+200 g compost. To grow A. hybrid, 200 g NPK+100 g compost should be applied, while 100 g NPK+200 g compost should be applied for A. auriculiformis.