Seed yield and its components of Brachiaria decumbens cv. Basilisk, Digitaria milanjiana cv. Jarra and Andropogon gayanus cv. Kent in north-east Thailand under different rates of nitrogen application

In a study of seed yields of pasture grasses in Thailand, pure seed yields of Brachiaria decumbens cv. Basilisk. Andropogon gayanus cv. Kent and Digit aria milanjiana cv. Jarra in one season were 81-123 kg/ha. 326-569 kg/ha an d 48-97 kg/ha. respectively. Corresponding thousand-seed weights were 4.68, 3.35 and 0.42 g. Germination rates were 3h. 73 and 17% at 4-6 months post harvest. In Thailand, low plant density and seeds per inflorescence. not mo isture availability. are likely to be the most important factors causing lo w seed yields of B. decumbens. Seed production and quality of A. gayanus we re exceptionally high, while seed yields of D. milanjiana were: similar to reported values. The nylon gauze seed collection bags facilitated full seed retrieval. Nitrogen application increased seed yield and inflorescence den sity but produced significant lodging in all species at 200 kg/ha N on this sandy loam. However. it did not affect seed weight. purity. germination or viability of any of these species. Seed yields of B. decumbens,ls in Thail and are characteristically low and present results indicate that low plant density and few seeds per inflorescence are contributing factors. The reaso ns for this are unknown. Gamba grass (Andropogon gayanus), with its drought -resistant characteristics, high dry matter production, high seed productio n and quality and low nitrogen requirement for seed production is a useful addition to pasture options for north-east Thailand.