Nutrient Cycling in Young Teak Plantation II - Biomass Production and Nutrient Cycling

Biomass production and nutrient cycling studies were carried out in a young teak (Tectona grandis L. f.) plantation of five year old (density 2,500 trees ha^-1). The trees attained an average girth and height of 23.1cm and 7.6m, respectively and the above ground biomass (agb) amounted to 76.9 t/ha, of which stem wood contributed 60%. The percentage of ischolar_main to agb was 20.5%. Investigations on nutrient content in the standing crop have shown that the per cent concentration of nitrogen (N), phosphorous (P), potassium (K), calcium (Ca) and magnesium (Mg) were highest in leaf. But on unit area basis, wood accumulated the major portion (39 to 60%) of all nutrients. Among the nutrients, maximum accumulation was accounted for Ca (1,619 kg ha^-1) and the minimum for P (178 kg ha^-1). With reference to nutrient return via litter, it was observed that the total litter produced was 4,574 kg ha^-1 and the nutrients returned amounted to 46 kg ha^-1 N; 3 kg ha^-1 P; 39 kg ha^-1 K; 86 kg ha^-1 Ca and 21 kg ha^-1 Mg. Studies on interception of rainfall and nutrient return through rain-wash have shown that among the nutrients return was highest for Ca (1.87 kg ha^-1) followed by Mg (1.09 kg ha^-1), K (0.98 kg ha^-1), N (0.36 kg ha^-1) and the least for P (0.11 kg ha^-1). Nutrient cycling on an annual basis was worked out for the plantation and it was found that of the total uptake of various nutrients (178kg N ha1 yr1, 248 kg K ha^-1 yr^-1, 387 kg Ca ha^-1 yr^-1 and 109 kg Mg ha^-1 yr^-1, 74 to 91% was retained in the non-photosynthetic biomass and the rest returned to soil. These results were compared with nutrient cycling in 20-year-old teak plantation and found that at younger age teak retains more nutrients in its biomass. As the plantation gets older, it retains less and returns more quantity of nutrients. These results suggest that as the age of plantation increases, teak becomes an eco-friendly species by not adversely affecting the ecology of the site.