Researching On Nutrient Obstruction Factors And Dynamic In Waterlogged Paddy Field

In this dissertation, we researched the nutrient obstruction factors and dynamic in waterlogged paddy field through combination of space and time on the feature analysis of nutrient and microorganism. Information provided in this work may contribute to a better understanding of the major nutrient and microorganism feature and dynamic change in a year in waterlogged paddy field. Main original conclusions are shown as follows.1. The present study has analyzed the nutrient characteristic in soil sample of eight provinces which is the main distribution region of waterlogged soil in China. Compared with high-yield fields soil in the same area, some results were found as below:The contents of organic matters (13.76～59.65g/kg) and total phosphorus (0.28～1.14g/kg) in the waterlogged soil were higher than that in high-yield field soil, and a significant difference was found between them in some provinces(P<0.05). Total nitrogen contents (1.51～4.72g/kg) in the waterlogged soil were a little more than in high-yield fields soil, but there was no significant difference between them(P <0.05). The level of contents of available nitrogen (127.41～238.54mg/kg) in the waterlogged soil was a little lower than in high-yield fields soil and no significant difference was found between them in some provinces(P<0.05).The level of contents of available zinc(4.92-12.86g/kg) in the waterlogged soil was higher than in high-yield fields soil, and the difference was significant(P<0.05). The above nutrient characteristic in waterlogged soil indicated that the waterlogged soil had a higher level of potential productivity. But in waterlogged soil, the value of the pH(4.47-5.80) was significant lower than that in high-yield fields soil. And the levels of reducing sulfur (59.22～-613.87mg/kg) and ferrous iron (320.47～3236.42mg/kg) ion were significant higher than that in high-yield fields soil(P<0.05). At the same time, it was significant lack of available phosphorus (0.17-3.02mg/kg) and available potassium (1.33～111.67mg/kg) in waterlogged soil to some provinces. This suggested that above several nutrient indexes were the important obstruction factors which influence the productivity in waterlogged soil. 2. The present study has analyzed the microorganism characteristic in soil sample of eight provinces which is the main distribution region of waterlogged soil in China. Compared with high-yield fields soil in the same area, some results were found as below:The contents of microbial biomass carbon (70.98-356.61mg/kg) in the waterlogged soil were lower than that in high-yield field soil, and a significant difference was found between them(P<0.05); the average value of cultivable bacteria, fungi, actinomycetes, nitrogen-fixing bacteria, ammonification bacteria, cellulose decomposer in the waterlogged soil were59.26%、35.29%、36.45%、48.61%、57.89%、47.32%of those in high-yield field soil. The above microorganism characteristic indicated that the total quantity of microorganism and the microbial activity were all lower in waterlogged soil. But the quantity of sulfur-oxidizing bacteria (19.3×106per gram of the sample) and iron-reducing bacteria (9.3×107per gram of the sample) were higher than the quantity of sulfur-oxidizing bacteria (15.0×l06per gram of the sample)and iron-reducing bacteria(7.0×107per gram of the sample) in high-yield field soil. The result indicated that the concentration of ferrous iron and hydrogen sulfide were higher in waterlogged soil.3. Researching on the feature of nutrient dynamic change in a year and getting the follow results. The nutrient (total nitrogen, total phosphorus, organic matters and available zinc) existed seasonal variation in the waterlogged paddy field during the growing of double cropping rice, but contents of these three nutrients were total higher than in high-yield fields soil or had no significant difference between them. The value of reducing sulfur and ferrous iron also had significant seasonal variation and existed mutual suppression between them. But contents of these two factors were higher in a year. The level of available nutrients (available nitrogen, phosphorus, potassium) were significant lower than that in high-yield fields during the peak of rice growing, especially available phosphorus. The above nutrient seasonal variation characteristic in waterlogged soil indicated that improving supply of available nutrients during peak season of rice growing in waterlogged paddy field, controlling and fixing the activity of reducing sulfur and ferrous iron is one of the important approach to increase soil fertility in waterlogged paddy field. 4. Researching on the feature of microorganism dynamic change in a year and getting the follow results. The content of microbial biomass carbon in the high-yield field soil was higher than that in waterlogged soil during the growing of double cropping rice. And SMBC increase significantly in season of high temperature than in low temperature in these two soils. The feature of dynamic change of these three basic microorganism (bacteria, fungi, actinomycetes) and functional microorganism (nitrogen-fixing bacteria, ammonification bacteria, cellulose decomposer bacteria) were similar with SMBC in a year. But the contents of those above microorganism in the high-yield field were total higher than that in waterlogged soil. Although the seasonal variation of sulfur-oxidizing bacteria and iron-reducing bacteria were similar with above mentioned microorganism, the total quantity of these two microorganism in waterlogged soil were higher than that in high-yield field. These all microorganism seasonal variation characteristic in waterlogged soil indicated that improving microorganism activity is another important measure to increase rice yield in the waterlogged paddy soil.