Effects of Ripening Regulator on Rice Harvesting and Milling Quality

Abstract

Study on spraying Hom Mali 105 rice variety with dimethipin (2, 3-dihydro-5,6-dimethyl-1,4-dithiin 1, 1, 4, 4-tetraoxide) to accelerate ripening and reducing grain moisture content at harvest was carried out at Faculty of Agriculture, Chiang Mai University. Results of the study showed that the chemical could reduce grain moisture content significantly and rapidly. However, application it at 12 days before harvesting (12 DBH) resulted in grain yield reduction noticeably. Applying at 500 and 750 ml/ha at 8 and 4 DBH gave no effect on grain yield as compared to control. Spraying at 8 DBH with the rates 500 and 750 ml/ha gave no difference in term of moisture reduction and milling quality. In this experiment was found that% head rice of the sprayed plots was much superior to that of the unsprayed plots when the cut crop was milled without field drying. Spraying at 4 DBH with both rates gave the same results in grain yield and milling quality. Nonetheless, it was noted that when the unsprayed crop was field dried for 4 days after harvesting its milling quality improved greatly and statistically gave the same head rice percentage as those of the sprayed plots.