行政院農業委員會台南區農業改良場  研究彙報第13號

水稻不同成熟度收割對產量米質及發芽率之影響

莊商路 鄭義雄 林深林

摘  要

本試驗之目的在探求水稻在不同的成熟度收割,對產量和米質及發芽率之影響,以供農民作為提早或延後收割可行性之參考。經65年第一期作起連續四期作在臺南區農業改良場(以下稱本場)嘉義分場試驗,以嘉南5號為材料,成熟度自齊穗後20天起分成六次收割處理,每次間隔五天,每次收割四小區,每小區2.5m2,以逢機區集法排列,收後脫粒,日晒,調製後調查產量及米質,發芽率等,茲將兩年4期作試驗結果簡述如下:

1.谷產量:第一期作以齊穗後30∼35天收割者最高,第二期作在齊穗後45天以前,愈晚收割者愈高。

2.碾米率:呈現隨日數增加而碾米率昇高之趨勢,但至齊穗後40日起又開始下降。

3.谷容重:增加趨勢和碾米率相似,唯其頂點為齊穗後35日,以後又下降。

4.谷千粒重:隨日數增加而千粒重增加,但到齊穗後30日過後則突然小幅度下降,再漸漸回昇。可回昇至齊穗後30日時之重量或更高。

5.稔實率:稍有隨日數增加而稔實率增加之趨勢,但第一期作收割處理間稔實率差異極顯著,而第二期作則不顯著,推斷第二期作是因後期病蟲害所致。

6.穗重:雖有隨日數增加而增重之趨勢,但收割處理間差異不顯著,其原因尚待進一步考證。

7.青米:顯示規則性地隨日數增加而減少,早收割者青米多,晚收割者少。在齊穗後35日及以後收割者減少量差異不顯著。

8.死米:和青米減少趨勢同,而在其齊穗後30日及以後收割者減少量差異不顯著。

9.碎米:以齊穗後30∼35日收割者碎米量最少,較早或較晚收割碎米量均增加。

10.完好米:完好米量是100公克糙米減去前三項青米、死米及碎米所餘商品價值高之米,其量隨日數增加而增加,且第一期作齊穗後30日以後收割者及第二期齊穗後35日以後收割者之完好米在100公克粗糙米中所佔比率已達90%。

11.發芽率:浸種期的不同對發芽率所生的差異不大,即表示在收割後一個月內稻種無論何時收割者其發芽能力,都不會急劇衰退,但是收割期早晚之發芽率則有差異,以齊穗後25日及其以前收割者,稻種發芽率均較其他各處理顯著降低。表示用作稻種者,最好在齊穗後30日以後收割。

12.發芽勢:發芽勢之分散度,在同一浸種期隨割期之延後而縮小,且峰度亦是愈晚收割者較高,峰度頂點則晚收割者較早出現,同收割期而不同浸種期則發芽勢差異不大。


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

Summary

        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.



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