Rice Physiology And Yield And Microbial Ecology In Paddy Soil Under Different Irrigation Methods And Fertilization

In order to study physiological response of rice and vartiation of microbial ecology in paddy soil to water-saving irrigation in depth, pot and field experiments were carried out to investigate the physiological response, yield component and water use of different rice varieties under different irrigation methods, the effect of irrigation method and fertilization level on photosynthetic physiology, root growth, N metabolism of rice and the effect of irrigation method and combined application of organic and inorganic N fertilizer on microbial ecology in paddy soil, rice growth, yield component and water use. Two irrigation methods (controlled irrigation, CIR and flooding irrigation, FIR) and three rice varieties (two line super hybrid rice combination:zhongzheyou1, three line hybrid rice combination:teyou63and conventional rice variety:youzhan8) were investigated in the field experiment. Pot experiment1designed three irrigation methods (CIR; Intermittent Irrigation, IIR; FIR) and three fertilization levels (higher fertilization level, FH; lower fertilization level, F1; no fertilization level, F0). Pot experiment2designed three irrigation methods (CIR, IIR, FIR) and three ratios of organic to inorganic nitrogen (N)(60%inorganic N+40%organic N (F1),80%inorganic N+20%organic N (F2) and100%inorganic N (F3). Main results were shown as the following:1. Field experiment shows that controlled irrigation reduced total water consumption of three rice cultivars by60%-75%when compared to flooding irrigation, no significant difference in leaf water potential, the contents of malonaldehyde and soluble protein, and the activities of superoxide dismutase, peroxidase and catalase after the booting were found between two irrigation methods. And there are also no significant difference in panicle length, effective panicle number per plant, thousand kernel weight, grain-straw ratio, seed setting rate and yield between two irrigation methods. Compared to the flooding irrigation, the controlled irrigation can save irrigation water greatly although it did not increase rice yield significantly.2. The pot experiment1shows that compared to FIR treatment, CIR and IIR treatments could increase Pn obviously, improve photosynthetic capacity of strong light and accommodate itself to weak light, enhance light saturation point. Thus the utilization rate of light was raised significantly. At the same time, CIR, IIR treatment increased the content of photosynthetic pigments and delayed the degradation of photosynthetic pigments at3growth stage when compared to FIR. In addition, in certain fertilization level, fertilization could increase the photosynthetic capacity of zhongzheyou1under saving-water irrigation method.3. The pot experiment1also shows that CIR and IIR treatments enhanced root activity of zhongzheyou1, root number per plant, root length per plant, root dry weight per plant, root volume per plant and the activity of nitrate reductase (NR), glutamine synthetase (GS) and solution protein content of Zhongzheyou1. Compared to FO, FH and Fl enhanced root activity of zhongzheyou1, root number per plant, root length per plant, root dry weight per plant, root volume per plant and the activity of NR, GS and solution protein content of Zhongzheyou1.4. The pot experiment2shows that CIR and IIR treatments saved irrigation water by31.3%,15.9%over whole growth stage of rice and reduced rice yield by31.9%,15.9%respectively when compared to FIR treatment, therefore water use efficiency (WUE) was not enhanced. Compared to F3, Fl and F2increased rice yield by20.1%,14.2%; F1and F2enhanced by37.3%,25.5%in FIR treatment respectively. Path analysis shows that number of productive ear, grains per ear and thousand kernel weights were the main component of rice yield in different irrigation methods and ratio of organic to inorganic N treatments. The principal component analysis shows that under the same total N application,40%inorganic N could decrease irrigation water and increase rice yield in IIR treatment appropriately. 5. The pot experiment2also shows that the enzymatic activity, the number of microorganism and the contents of microbial biomass C (MBC) and microbial biomass N (MBN) in soils were increased from booting to heading stages and peaked at the heading stage, but decreased from the heading to milky stages. Compared to FIR treatment, CIR and IIR treatments generally increased the enzymatic activity, the number of microorganism and the contents of MBC and MBN in soils. Combined application of organic and inorganic N generally had higher enzymatic activity, the number of microorganism and contents of MBC and MBN in soils when compared to only inorganic N. Thus water-saving irrigation method (CIR and IIR) could effectively enhance the microorganism activity of paddy soil under combined application of organic and inorganic N fertilizer.6. The16s rDNA analysis results of different paddy microbial community composition in the pot experiment2show that the CIR and IIR treatments had different paddy microbial community at the heading and milky stages from FIR treatment, and soil microbial community in ratio of organic to inorganic N were different with that of the single application of inorganic fertilizer.