Evaluation of leguminous tree species using as soil improver at Nhong Koo Gene Conservation Center in Surin province

Tree growth characteristics with its survival and the change of soil conditions were properly evaluated at the 10th year (or 9 year-old tree). It appeared that there were only 5 out of 8 species showed over 75 percent survival rate and statisfaction for the growth characteristics of the studied site. The best growth performance was A. mangium, followed by A. auriculaeformis, P. pterocarpum, C. siamea and X. xylocarpa, respectively. The general condition of soil chemical characteristics was best in soil under C. siamea, followed by P. pterocarpum, A. auriculaeformis, A. mangium and X. xylocarpa, respectively. It appeared that the chemical characteristics of top soil (0-10 cm depth) under each species and bare land (control treatment) were shown as followed. The soil under C. siamea had pH 4.01, O.M. 0.87 percent, N 64.97 mg/100 g, P 3.13 ppm, K 0.031 me/100 g, Ca 0.240 me/100 g, Mg 0.097 me/100 g, C.E.C 2.65 me/100 g and B.S. 14.31 percent, the soil under P. pterocarpum had pH 3.86, O.M. 0.95 percent N 45.30 mg/100 g, P 1.49 ppm, K 0.025 me/100 g, Ca 0.152 me/100 g, Mg 0.132 me/100 g, C.E.C. 2.86 me/100 and B.S. 10.78 percent, the soil under A auriculaeformis had pH 3.75, O.M. 1.25 percent N 40.67 mg/100 g, P 2.90 ppm, K 0.025 me/100 g, Ca 0.120 me/100 g, Mg 0.074 me/100 g, C.E.C. 2.79 me/100 g and B.S. 8.53 percentthe soil under A. mangium had pH 3.86, O.M. 1.00 percent, N 39.32 mg/100 g, P 2.16 ppm, K 0.026 me/100 g, Ca 0.138 me/100 g, Mg 0.070 me/100 g, C.E.C 2.76 me/100 g and B.S. 9.97 percent, the soil under X. xylocarpa had pH 3.71, O.M. 0.67 percent, N 81.30 mg/100 g, P 1.94 ppm, K 0.019 me/100 g, Ca 0.095 me/100 g, Mg 0.073 me/100 g, C.E.C. 3.11 me/100 g and B.S. 7.28 percent and the bare land soil had pH 3.71, O.M. 0.42 percent, N 27.11 mg/100 g, P 1.06 ppm, K 0.013 me/100 g, Ca 0.106 me/100 g, Mg 0.035 me/100 g, C.E.C. 2.46 me/100 g and B.S. 8.21 percent. The species seemed to be suitable for using as soil improver were C. siamea, P. pterocarpum, A. auriculaeformis, A. mangium and X. xylocarpa, respectively. If wood utilization and soil improving are concerned, however, A. mangium, A. auriculaeformis, P. pterocarpum, C. siamea and X. xylocarpa are recommended.