INFLUENCE OF DENSITY AND FERTILIZER ON PRODUCTIVITY OF 9.5 YEAR-OLD ACACIA HYBRID PLANTATION AT QUANGTRI

Abstract

Intensive forest plantation to improve productivity and quality of forests has been concerned . The Acacia hybrid clones BV10, BV16 and BV32 that were approved by MARD as technical germplasms were used to study on influences of density and fertilizer on the growth and productivity of 9.5 year-old plantation in Dong Ha - Quang Tri. The result showed that initial planting density, basal and top dressing fertilizing applications at the 2nd year period did not strongly affect survival percentage of 9.5 year-old Acacia hybrid plantation as the plantation was too mature for small timber business which was
normally 7 years old. Competition for nutrient resources amongst individuals in the polulation resulted in strongly natural thinning and the survival rate reduced, ranging from 44 to60%, compared with the
initial planting density and affected the growth and quality of plantation. The growth in D1.3 for the lowest density treatments (722 - 738 trees/ha) was the best with 17.22 - 17.49 cm in which proportion
of trees having D1,3 over 18cm were 42.55 - 43.75%; however, timber productivity of standing tree was not high. In contrast, the highest density treatments (968 - 999 trees/ha) obtained the highest productivity of standing tree althoughthe D 1.3 was the lowest and the proportion of trees with D1.3 ≥18cm was quite low with 15-26%.. Therefore, the plantation needs to be thinned and the final density
should be from 400-500 trees /ha for sawlog production.