抄録
Using the new color chart which was developed based on the colorimetrical characteristics of actual leaves in rice plants, the authors investigated the usefulness of the leaf color diagnosis and the possibility estimating the number of spikelets per squarc meter by leaf color. Following results were obtained: 1. The newly developed color chart was easier to judge the leaf color grade (greenness) than the chart which was made of embroidery thread, because the new one had greater size in greenish parts (4 × 8 cm) and the equally plotted scale with reference to the lightness as compared with the old chart. 2. Observation values of leaf color highly correlated with the nitrogen content (%) in leaf blade of rice plants, and the percentage of the length of leaf sheaths stained by iodide solution to the whole length of them, which represented the degree of starch accumulation in these organs, showed highly negativc correlation to the nitrogen content (%) in leaf blade. Moreover, the ratio of thc observed values of leaf color to the percentage of stained length of leaf sheath showed higher correlation to the nitrogen content in leaf blade, compared with the case applying the two characteristics, the leaf color or the percentage of stained length of leaf sheath, individually. 3. High correlation existed between the number of spikelets per square meter and the product of the observed values of leaf color and the number of tillers at the stage of leaf number index, about 90. Accordingly, it was confirmed that the number of spikelets per square meter was able to be estimated based on the observed values of leaf color and the number of tillers per square meter. 4. The results mentioned above (in Tanashi) were also recognized in the experiments carried on at Fukuoka, Miyagi, Shiga and Toyama prefectural agricultural experlment station.
