莊商路 鄭義雄 林深林
The Influence of Harvest at Different Degrees of Paddy Maturity on the Grain Yield, the Milling Quality and the Germination rate
S. L. Chuang, Y. H Cheng, S. L. Lin
The purpose of this study was to elucidate what is the relationship between the grain yield, the milling quality, as well as the germination rate and the different harvest dates after heading. It is expected that the results of this study can be used as reference to evaluate the feasibility of harvesting paddy earlier or later than the optimum time to escape the bad weather, meet the cropping pattern and the labor arrangement. This study had been carried out at the Chai-yi Branch Station of Tainan District Agricultural Improvement Station from 1976 to 1976, Tainan No. 5, the most popular rice variety in this island, was used as the tested material and was harvested at the interval of 5 days from 23 to 53 days after heading. The harvested grains were dried under natural sunshine. Meanwhile the grain yield, the milling quality and the germination rate were investigated in the laboratory. The results of this study are summarized as follows:
1. Grain yield: the harvests made from 33 to 35 days after heading have the highest grain yield in the first crop season. The harvests made before 48 days after heading in the second crop season showed the tendency of the later harvesting the better grain yield.
2. Percentage of milled rice: the percentage of milled rice was increased following the increase in the number of days after heading, but showed to decline at the 43rd day after heading.
3. Weight of grains per liter: the weight of grains per liter showed the same tendency as the percentage of milled rice, but it reached the top point at the 38rd day after heading instead of at the 43rd day.
4. Weight of 1000 grains: the weight of 1000 grains was increased following the increase in the number of days after heading, but once it reached the top point at the 33rd day after heading, the curve had a slight decline and then raised again. The results showed that it was possible for the curve to climb up to the point, which was higher than the peak on the 33rd day after heading.
5. Percentage of ripened grains: the percentage of ripened grains was also increased with increase in the number of days after heading. The differences in the percentage of ripened grains between those obtained on the different harvesting dates were highly significant in the first crop season but there was no significant difference between those in the second crop season.
6. Weight per panicle: Although there was a tendency which showed that the weight per panicle was increased with the increase in the number of days after heading, there was no significant difference in weight per panicle between those obtained on the difference in weight per panicle between those obtained on the different harvesting dates. A further study needs to be done to find the reasons for explaining this fact.
7. Green grain: the results of this study showed that there was a regular decline in the amount of the green grain following the increase in the number of days after heading. In other words, the earlier harvested the more green grain, or the later harvested the less green grain.
8. Dead grain: the dead grain had the same tendency as the green grain, but after 30 days from heading there were not much change till the grains were full ripened.
9. Broken grain: the harvests made in the period from 33 to o35 days after heading had the least broken grains. If the harvests which were made earlier or later than the optimum time showed the increase in the amount of the broken grains.
10. Head rice: the percentage of head rice was calculated by subtracting the green grain, the dead grain and the broken grain from the brown rice the then dividing the remains by the broken rice. There was an increasing tendency of head rice following the increase in the number of days after heading. The percentage of head rice had reached 90% if the harvests were made at the 33rd days after heading in the first crop season and at the 38rd day after heading in the second crop season.
11. Germination rate: there were no significant difference in germination rate between the different soaking time treatments but there were significant differences in germination rate between the harvests made at the different dates. The harvests made before 28 days after heading there was low germination rate of rice grains, therefore it was suggested that the harvests should be made at least after 33rd days from heading if the rice grains will be used as rice seed.
12. There was a general phenomenon in the germination shape that was the earlier the harvests the broader and flatter the distribution shape, and the later the harvests the narrower and higher the distribution shape. There were no significant differences in the germination shape between the results at the different soaking times within the same harvests.
In sum up, the best time for harvesting was from 32 to 37 days after heading in the first crop season, and the optimum time for harvest in the second crop season was at the 30rd after heading. If the harvests which were made earlier or later than the optimum time would show lower in grain yield and poorer in grain quality, since the rice was harvested to early it was not grown up to be ripened. If the rice were harvested too late the pest insects and diseases and the long raining time would spoil the rice yield and quality. When harvest should be made earlier or later than the optimum time to meet the cropping pattern, escape the pest insects and diseases, as well as the climatic conditions. Comparison should be made between the loss and the gain caused by harvesting not in the optimum time. Even the results obtained from this study showed that there were not much loss in yield and devaluation in quality when harvests were make later than the optimum time, but some rice varieties of which the shedding characters were easier than that of Tainan No. 5 or their agronomic characteristics were more susceptible to the bad weather and the pests insects and diseases would suffer from lose in the yield and devaluation in the quality.