Effect of date of closing cut on seed yield and its components of Andropogon gayanus cv. Kent

The effect of date of closing cut on seed production of Andropogon gayanus cv. Kent was studied in NE Thailand. Cutting in August, September or Octobe r produced progressively lower pure seed and pure live seed yields than the uncut control (433.9 vs 285.2, 159.3 and 62.1 kg/ha; and 302.6 vs 206.7, 9 9.2 and 38.6 kg/ha, respectively). Delayed peak flowering in association wi th increasing moisture stress, and a reduced leaf area at flowering may hav e led to decreased yields. Thousand-seed weight was unaffected by cutting d ate. Tiller density increased with later cuts, but as inflorescence density remained similar, tiller fertility decreased. Seed purity was unaffected b y cutting date. Closing cuts had a large, negative effect on inflorescence size, indicated by dramatic reductions in pure seed yield per inflorescence with successive cuts. Seed germination percentage decreased following cutt ing in September or October, resulting in lower pure live seed yield. Closi ng cut dates between May and August should be investigated.