Studies on the Growth Phase and Effect of Fertilizer Application to Rice Plants in Malaya : IV. Seasonal changes of transpiration, dry matter production and water requirement and their varietal differences

Abstract

The experiment was carried out by pot using five leading varieties for three seasons at Telok Chengai Padi Experiment Station of West Malaysia. Five varieties tested were classified into two, that is three short term varieties for double cropping and two local long term varieties. The results obtained are summarized as follows : 1. The maximum value for transpiration per day was obtained around the heading stage and lesser values were obtained during the early and later stage of growth in general (fig.1). The changes in the increase of dry matter per day was similar tendency to that of transpiration. Both the transpiration and increase of dry metter per day in the Off season (dry period) were greater as compared with those of Main season (wet period). A distinct correlation between the above two itemes was observed particularly in the short term varieties (fig.2). 2. The higher value for water requirement (water required to produce 1 gram of dry matter) was obtained during the early stage and the least in the mid-growth stage and highest were obtained during the ripening stage in general (fig.1). It was noted that the paddy plant utilized the water most efficiently when demand for water was greater (fig.2). This was particularly evident in the short term varieties. 3. The water requirement (y) and dry matter production were directly proportional to the number of days (x) from transplanting to harvest. The linear equations were shown in fig.3. From these equations, water requirement was calculated in the Main season to be as 250∼320 for the short term varieties and 430∼530 for the long term varieties. In the Bahagia (short term variety), the water requirement in the Off season was comparatively higher as compared with that of Main season. The figures in the short term varieties of Main season were not much different to that of Japan. 4. The longest term variety needed twice as much water as the shortest term variety. The grain yield was normally poorer in the long term varieties as compared with that of the short term varieties (fig.4). It can thus be concluded that the use of longer growing period variety is inadvisable as the grain yield does not commensurate with the water consumed. The findings mentioned above are rether similar to the results obtained by Mr. T. Murakami in Ceylon but partly inconsistent with the results obtained by Dr. S. Matsushima in Malaysia.