| Waterlogged paddy field refers to the rice field witch reserving amount of water in the winter break, widely distributed in southwest of our country. There are about 1.25 million hm2 waterlogged paddy field in southeast of Sichuan basin area. This kind of paddy fields were summarized as such characteristics:soil cold, poor air permeability, soil structure is bad, the soil is easy to be accumulated more poisonous and harmful substance, poor coordination between water, nutrients, air and heat energy, part of is lack of soil available nutrients, rice akiochi was induced frequently in waterlogged paddy field witch resulting in a decline in rice production by 10%-20%, seriously when rice yield could be reduced by more than 50%. Therefore, to carry out the research on rice akiochi of waterlogged paddy field, to find out the counter-measures and counter-ways of rice akiochi, improving the rice production, witch has important practical significance to solve the current limited arable land and improve the contradiction of grain production, and to ensure a steady income for the farmers. This study adopted the method of combining hydroponic experiment and pot experiment, researched the causes of inducing rice akiochi, discussed the effect of rational fertilization and adding various kinds of modifier on the counter-measures of rice akiochi, aimed to provide practical technique to solve rice akiochi. The main research results were as follows:1.The results of solution cultivation experiment indicated that, the critical concentrations of Fe2+, Mn2+ and S2- witch poisoning rice were Fe2+70 mg·L-1, Mn2+ 350 mg·L-1, S2- 5 mg·L-1. At the concentrations, Fe2+, Mn2+ and S2- began to affect the growth of rice, the biological production was suffered to decline was the mainly performance, but rice plants did not show any obvious symptoms from appearance. At high concentration of Fe2+ treatment, the Fe rice root absorbed would accumulate more in the root, and at high concentration of Mn2+ treatment, the Mn rice root absorbed would accumulate more in the straw.2.The results of pot experiment showed that, straw powder and sugar could greatly reduce Eh value of the early flooded paddy soil, and made the seeding rice new tillers appeared the phenomenon of death (rice akiochi), significantly inhibited the increase of tillers at the early stage of rice growth, eventually leaded to decrease of rice effective spike, delayed rice mature time, and biological yield was also decreased. But the rice growth was not affect by 100 mg·kg-1 Fe+, even was boosted a little.This showed that,100 mg Fe2+·kg-1 was not the cause of rice akiochi at the early stage of rice growth under the condition of soil cultivation, but was. rice akiochi could be due to a variety of restrainable type of allelochemicals witch was decomposed by the easy reducing organic matter (such as straw powder and sugar), and this restrainable type of allelochemicals significantly reduced the soil Eh value, thus it affected the growth of rice. Because of the shortage of labor force and transporting machinery in the area of waterlogged paddy field of Sichuan province, the rice straw was directly returned to field as soon as it was outputted, it was easy to cause local straw accumulation, and. then it leaded to soil Eh declined dramatically at the location of straw accumulated in early spring, rice akiochi was caused eventually.3.In the pot experiment, the treatments of added silicon fertilizer calcium, lime, magnesium sulfale and sodium tetraborate did not work on the prevention of rice akiochi Therefore, in order to effectively prevent rice akiochi in the area of waterlogged paddy field of Sichuan province, the level of easy reducing organic matter (include rice straw) was controlled to avoid excess application or local accumulation. This shows, rice straw should be returned evenly when rice was harvested. Besides, rice straw should be moved out of field as well when straw yield is large, these is a kind of effective counter-measure to solve rice akiochi. |
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