EFFECTS OF FERTILIZER APPLICATION, MANUAL WEEDING, AND SPACINGS ON SEED PRODUCTION OF LEUCAENA LEUCOCEPHALA

Abstract

Field investigation was carried out at the ASEAN-CANADA Forest Tree Seed Centre Field Station, Pak Chong District, Nakhon Ratchasima Province aiming to find out the effects of fertilization, weeding, and stand density on seed production of Leucaena leucocephala. The experiments were in 2x2x4 factorial having two levels of fertilizer application (F₁: control, F₂: NPK (15-15-15) at the rate of 500 g/tree), two weeding frequencies (W₁: manual weeding once a year prior to rainy season, W₂: manual weeding twice a year both before and after rainy season), and 4 spacings (S₁: 2x2 m, S₂: 2x4 m, S₃: 3x3 m, and S₄: 4x4 m) with 4 replications of 9 trees making the total numbers of 576 sample tress. Seeds were harvested on July 31, three months after being treated. The results showed the highly significant difference of fertilizer-spacing interactions on seed production, while weeding had no effect. The amounts of seeds gained were found to be increased with increasing spacings, ranking from 2,781 to 3,043, 4,580 and 5,325 seeds per tree of non-fertilization plots of 2x2 m, 2x4 m, 3x3 m, and 4x4 m spacings, respectively. Seeds collected from fertilization plot was 1.3 times over those from the control at 2x2 m spacing. Such multiplying figures were of 1.8, 1.6, and 2.8 for 2x4 m 3x3 m, and 4x4 m spacing, respectively.