| Reducing the amount of chemical fertilizers used in agricultural production,reducing the comprehensive greenhouse effects,and improving the efficiency of agricultural production are the key to achieving the sustainable development of modern agriculture and soil.This study took barrel-grown rice as the research object,adopted the controlled irrigation mode for water management,and was based on a single factor experiment of combining bio-organic fertilizer and chemical fertilizer.Applied to study the effects of different fertilization modes on paddy soil greenhouses gas emissions,the variations of habitat indicators,rice yields and economic benefits,with a view to discovering the impacts of bio-organic fertilizers on paddy soil greenhouse gas emissions and the relationships between soil habitat indicators and greenhouse gas emissions.It could provide a scientific theoretical reference for determining emission reduction technology suitable for the controlled irrigated paddy fields in this area.The experiment was carried out at the Kunshan Drainage and Irrigation Experimental Research Bas.Three fertilization modes were set up in the experiment:(1)100%chemical fertilizer(CK),(2)50%chemical fertilizer+50%bio-organic fertilizer(T1),(3)100%biological organic fertilizer(T2).The research results and conclusions are as follows:1.Bio-organic fertilizer can significantly reduce the emission flux of N2O(Nitrous Oxide)and CH4(Methane)in the paddy soil and the cumulative emission throughout the growth period,and at the same time can increase the emission level and cumulative emission of CO2(Carbon Dioxide)in the paddy soil.During the whole growth period of rice,the average N2O emission flux of T2 treatment was decreased by 80.65%-87.14%compared with CK and T1 treatments(P<0.05),and the average CH4 emission flux of T2 treatment was reduced by 31.14%-48.84%compared with CK and T1 treatments(P<0.05).The cumulative emissions of N2O and CH4 under T2 treatment were 83.00%-89.11%and 26.37%-26.45%lower than CK and T1 treatments,respectively.While the average emission flux of CO2 in T2 treatment was increased by 13.20%-25.49%,compared with CK and T1 treatments(P<0.05),and the increased range of corresponding cumulative emission was 12.85%-23.06%.Combined application of bio-organic fertilizer can inhibit the comprehensive greenhouse effects of paddy soil N2O,CH4 and CO2 more efectively in comparison with single application of chemical fertilizer.During the whole growth period of rice,the GWP of T1 and T2 treatments were 18.92%and 45.87%lower than the CK,respectively.The larger input ratio of bio-organic fertilizer,the more obvious inhibitory effects on the comprehensive greenhouse effect of paddy soil.The GWP of T2 treatment was significantly reduced by 33.24%compared with T1(P<0.05).2.There was a significant positive correlation between the emission fluxes(CH4 and N2O)and WFPS(Soil Pore Water Content)in the combined application of bio-organic fertilizer treatments during the whole growth period of rice.Among the first soil dehydration and the milky period of rice,the N2O emission fluxes of each treatment and WFPS showed a significant positive correlation.Among them,the N2O emission flux of CK and T1 treatments showed the extremely significant positive correlations with WFPS,while the CH4 emission flux and WFPS only presented the extremely significant positive correlations under the T1 and T2 treatments.After the rice yellow maturity period began,the influence of WFPS on CH4 and N2O emission fluxes was no longer significant.There was no significant correlation between the CO2 emission flux and the variation of WFPS in the paddy fields.3.When the input proportion of bio-organic fertilizer was larger,the content of soil organic carbon was significantly increased and so as the emission flux of CH4 and CO2 in the paddy soil.The improved effect of combined application of bio-organic fertilizer with chemical fertilizer on soil organic carbon content was lower than that of applying chemical fertilizer or bio-organic fertilizer singly.The change of soil organic carbon content had a significant regulation on the CO2 emission flux in the paddy fields.During the whole growth period of rice,the average organic carbon content of T2 treatment was 8.90%and 11.41%higher than that of CK and T1 treatments,respectively.Among them,the cumulative emission of CH4in T2 treatment was 0.19%and 35.95%higher than that in the CK and T1 during the whole growth period,and the cumulative CO2 emissions were 23.06%and 12.85%higher than those of CK and T14.Bio-organic fertilizer can significantly reduce the contents of nitrate nitrogen and ammonium nitrogen in the soil,and can reduce the N2O emission of paddy fields.When the input proportion of bio-organic fertilizer was larger,the N2O emission flux of paddy fields could be stabilized at a certain low level.During the whole growth period of rice,the average contents of nitrate nitrogen and ammonium nitrogen were always lower under T1 and T2 treatments in comparison with CK.The nitrate nitrogen contents of T1 and T2 treatments were decreased by 45.32%and 26.86%respectively compared with CK.The contents of ammonium nitrogen in T1 and T2 treatments were reduced by 21.06%and 2.51%respectively,compared with CK.Therefore,the corresponding cumulative emissions of T1 and T2 treatments were reduced by 35.96%and 89.11%respectively compared with CK during the whole growth period of rice(P<0.05),and the value in T2 treatment was lower than T1 by 83.00%(P<0.05).5.The application of bio-organic fertilizer can reduce the level of catalase activity in the soil and inhibit N2O emission in paddy fields.During the jointing and booting stage of rice,the catalase activity of T2 treatment decreased by 19.75%and 8.75%compared with CK and T1.The cumulative N2O emission of T2 treatment was 93.04%and 79.30%lower than CK and T1,respectively.The bio-organic fertilizer promoted the activity level of soil hydrolase.The soil invertase activity of each treatment showed obvious synchronization with the CH4 emission flux from paddy fields among the late tillering stage to the early jointing booting stage.The cumulative emissions of CH4 in the T1 and T2 were lower and the decrease was 71.20%and 12.01%in comparison with CK.The improved effects of bio-organic fertilizer on soil urease and phosphatase activity levels were mainly concentrated in the rice turning stage and the late tillering stage,and the fertilization mode of single application of bio-organic fertilizer had the best improvement effect on soil urease and phosphatase activities.The soil urease of T2 treatment was 22.44%and 39.38%higher than CK and T1,and the soil phosphatase of T2 was increased by 20.01%and 39.01%compared with CK and T1,respectively.The corresponding cumulative CO2 emissions(T2)increased by 33.07%and 20.43%in comparison with CK and T1.6.The full application of bio-organic fertilizer mode is the best emission reduction technology suitable for the reduction of N2O and CH4 emissions from rice fields in this area.While reducing the GWP of the rice fields,it can increase rice production and achieve optimal economic benefits.Compared with CK and T1,T2 treatments increased the yields of rice harvest of 68.74%and 73.83%,the rice output value of 6185 and 6448 yuan/ha,and the net income of 6226.2 and 6434.8 yuan/ha respectively.The ratios of production to investment also increased by 71.55%and 73.04%in comparison with CK(P<0.05),it also effectively reduces the input cost from the growth and development stage of rice to the harvest period.In addition,T2 treatment increased the combined effect scores of 57.50%and 61.86%compared with CK and T1 respectively.Considering the combined effects of bio-organic fertilizers on rice yield and economic benefits,and the comprehensive effects of rice fields,full application of bio-organic fertilizers is the most suitable fertilizer solution for controlling greenhouse gas emission reduction in irrigated rice fields in this area.Therefore,the fertilization mode of bio-organic fertilizer in this study was more effective in reducing greenhouse gas emissions in paddy fields,increasing rice yields and improving economic benefits.The research conclusions could provide scientific and theoretical basis for exploring the most suitable combined application method of crop-soil-fertilizer to achieve high-efficiency and sustainable-development of controlled irrigated paddy fields agricultural production in this area in the future. |
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