AGING AND FERTILIZATION AFFECT NUTRIENT CONTENT IN LEAVES OF Acacia mangium TREE

Understanding the nutrient contents (Nitrogen/N, Phosphorous/P, and Potassium/K) in leaves of Acacia mangium trees is important for maximizing timber production and carbon sequestration of a plantation. This study aimed at investigating the nutrient contents in different leaf types (young, medium and old) collected from fertilization and non-fertilization treatments in two different ages of A. mangium trees grown in Northeast Vietnam. The leaf samples were collected in March 2018 (1-year old trees) and March 2019 (2-year old trees). The results indicated that leaf water content decreased with leaf ages but not with tree ages. While N, P, and K content were significantly different among three leaf types as highest in young leaves, reducing to medium and old leaves. N content ranged 1.72-1.77% in young leaves, 1.21-1.24% in medium leaves, and 0.89-0.91% in old leaves. P content ranged 0.81-0.97% in young leaves, 0.41-0.54% in medium leaves, and 0.16-0.23% in old leaves. While K content was 1.31-1.53% in young leaves, 0.76-1.00% in medium leaves, and 0.15-0.31% in old leaves. In each leaf type, the differences of N contents between fertilization and non-fertilization, and between tree ages were not significant. While the differences of P and K contents between fertilization and non-fertilization were significant, indicating higher values in fertilization treatment, but the difference was not significant between tree ages. The low P content may indicate a nutrient deficiency in this study site, therefore P fertilization is necessary to improve the production of A. mangium plantation.