Comparison between the Soil Conditions, Root Activities and Yields of the First and Second Rice Crops
|Keywords:||稻作區域性與期作性低產及增產措施之研究||Issue Date:||Dec-1984||Publisher:||台中：農業試驗所||Start page/Pages:||45-57||Source:||稻作區域性與期作性低產及增產措施之研究:||Abstract:||
Two crops of rice can be cultivated in a year in most part of Taiwan. The first crop is grown in the former half of a year, and the second crop is in the later half. However, the yield per unit area of the second crop is always about 20% lower than that of the first in the past years. The research was designed to elucidate the causes of low yield of the second rice crop especially concerning the roots and their growth environments. Results were summerized as follows.
Most of the root system distributed in the plowed soil, i. e., in a layer about 15 cm below the surface of the soil. It was found that before booting stage the temperature of this layer of the second crop was always higher than that of the first crop. And until dough stage, the Eh value of this layer of the second crop was always lower than that of the first crop. Moreover, in the earlier stage, the tendency was more clear.
The roots of the second rice crop always grew in more reduced and unfavorable environment of the paddy soil. Furthermore, their oxidizing abilites were always lower than those of the first crop. Therefore, their roots could more easily be damaged by reduced substances in the soil. It was also noticed that the elongation rate of the roots of the second crop was faster but the roots became thinner when they grew in a higher temperature during the early growth stage. The outer morphological appearance also showed that the ratio of rotten roots of the second crop was higher at later growth stage. The analyses of phophorus and potassium in rice leaves and paddy soil revealed that the absorption ability of the second crop was lower than that of the first crop. The above facts may be the main cause of lower percentage of fertile grain as well as lower grain weight, and consequently influence the yield in the second rice crop.
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