Effects of time of final closing cut on seed yield and seed quality of Paspalum atratum in Thailand

The effects of time of final closing cut on seed production of Paspalum atratum were examined in 1999-2000 from 2 experiments conducted in Lampang province, northern Thailand. The results showed that the time of final closing cut had a significant effect on seed yields of P. atratum in both years. In Experiment 1, where plots were cut at 30-day intervals, plots closed in mid-June produced the highest seed yield of 1333 kg/ha, followed by plots closed in mid-May and mid-April. Plots closed in mid-July produced about one-third the seed yield of plots closed in mid-June, and plots closed in mid-August produced no seed. Severe lodging at seed harvest occurred in plots closed in mid-April, mid-May and mid-June, resulting in a decrease in seed yield. Experiment 2 was conducted to determine more accurately the most suitable date of final closing cut by comparing cutting at 15-d intervals during the critical period from June 1 to August 1. Seed yields were consistently high at over 1489 kg/ha from plots closed between June 1 and July 1, and yields then dropped in plots cut on July 15 to one-fifth the seed from plots cut on July 1. Plots closed on August 1 produced no seed. There were small differences in seed quality attributes among plots from both experiments, which produced good seed quality, averaging 88% seed germination, 3.01 g thousand-seed weight and 81% seed purity. From the results in both experiments, it was confirmed that final closing cut dote of P. atratum should not be delayed later than July 1.