Planting Date Study in Upland Rice

Abstract

An experiment to establish the most suitable planting date for puland rice was undertaken in each of three years at the Nong Hoi Highland Research Station, Chiang Mai during 1980 - 82. In 1980 four sowings were compared over the period May 20 to August 20; in 1981 six sowings were made between March 20 and june 20 and in 1982 eight sowings were compared between April 20 and June 30. Highest yields (up to 4 tons per hectare) were obtained from sowings in the period May 20 to June 10. sowings in late June (June 20 to 30) yielded between 25 and 45 per cent of the maximum yields achieved with earlier sowings. Generally the later the sowing date after June 10 the greater the yield reduction. Reduced night temperatures during the later stages of grwoth of the later sowings was considered to be a major factor contributing to the reduced yields. An added advantage of the sowings in the last week of May and first week of June was the reduced incidence of the disease brown spot (Helminthosporium oryzae).