抄録
The supplementary report is made to determine optimum sowing date and pinching position of main stem by presumption of effective ripening date. Days of ripening (Y) are closely correlated with accumulated temperature (T) as presented by regression equation : T=-0.1535Y+33.7037. Using this equation we can calculate the maximum days of ripening by considering that at least 20°C in average temperature is necessary to get a mature fibre. Thus the maximurn days of ripening are estimated as 89 days, this theoretical value agrees well with above-mentioned thick solid line (at the harvest last decade November). The relation between the vertical position of bolls and seed cotton weight of them is indicated by the regression curves (Table 5.). It is shown the vertical position of boll haring a maximum seed cotton weight is 7.1, 7.6, 6.5, and 3.3 respectively for the different sowing dates, and these positions are situated at 2/3 from the base of the main stem. At upper 1/3 portion the seed cotton weight decreased rapidly by later sowings. From the data that pinching positions on the main stem were expected as 11.3, 10.3, 7.3 and 4.7 respectivey for the different sowing dates, it is considered that the pinching is not needed in the most desirable sowing period, May, while it may be effective in the late sowings. The relation between the vertical position of ripening bolls and lint weight of them is also shown by the regression curves. Again in this case it is shown the pinching may be more effective for later sowing.
