| Concerns with environmental issues are nowadays increasing considerably in every agricultural sector. Rice (Oryza sativa L.) production cause many environmental problems for instance the use of fertilizers increases pollution of the ecosystem; greenhouse gases are generated, especially methane gas, when flooding of rice fields cuts off oxygen supply, then anaerobic microorganisms ferment the organic matter in the soil, causing the production of methane carbon dioxide etc. Despite its environmental effects and the changes of the world ecology the production of rice must continue because it is the world's most important staple food crop with more than half of the world's population relying on it as the major daily source of calories and protein. To preferably avoid, or at least reduce the environmental impacts, no-tillage is becoming a more popular agricultural practice. It reduces erosion, conserves and improves water quality, and stores more carbon in the soil than plowed land. Hence it improves soil quality and helps reduce carbon inputs to the atmosphere that are thought to be the cause of global warming. No-tillage therefore provides an opportunity to rapidly expand production while protecting paddy soil against erosion, GHG emission, increasing soil microbial biomass (MB) and soil enzyme activities. The objectives of this study were to determine the environmental impacts on the ecosystem; no-tillage system might have particularly by assessing GHG and GWP order to suggest the conservation options in the rice producing areas. The study was carried out by analyzing the results of soil methane, CO2 and N2O, water and microbial biomass (MB) and soil enzymes under No-tillage with no fertilizer (NTO), Conventional tillage with no fertilizer (CTO), No-tillage with compound fertilizer (NTC) and Conventional tillage with compound fertilizer (CTC) systems from rice cultivation.1. In case of the effects of no-tillage on soil physical and chemical properties the results shows that:NTC was 25.87%> than CTC (p<0.05) for soil NH4+ at 10-20 cm soil depth; CTC was 32.24%> than NTC (P<0.05) for soil NO3- at 5-10 cm soil depth; NTO was 20%> than CTO (p<0.05) for soil TN at 0-5cm soil depth; NTO was 9.84%> than NTC (p<0.05) for SOC at 10-20 cm soil depth and NTC was 36%> than CTC for soil AP (Olesen P) at 5-10 cm soil depth. Therefore at the three soil depths (0-5,5-10, 10-20 cm) no-tillage had no significant effect for the soil pH, SON, TSN and TP. Soil water stable aggregate for<0.002 mm of soil textures in NTO was 16.27%> than NTC (P<0.05) at 0-5cm soil depth. Soil textures of 0.25-0.1,0.02-0.25,0.002-0.02 and <0.002 mm were not associated at three depths of soils in neither conventional tillage nor no-tillage.2. The difference in microbial biomass (MB) at three depths of the soil showed that NTC was 21.79%> higher than CTC (P<0.05) for MBC at 0-5 cm deep but no significant difference was observed at other two soil depths. Estimation of soil MBN in NTO at the soil depth of 0-5 cm was 25.21% and 5-10 cm was 81.98% greater (P<0.5) than CTO. No-tillage did not show any significant results for the 10-20 cm soil depths for MBN. Soil MBP in NTC was 33.68% > than CTC (P<0.05) at 5-10 cm deep but at 0-5 cm deep no difference. MBP at the soil depth of 10-20 cm was 19.18% greater compared to CTO treatment. There was correlation of MBC with soil nutrient, MBN, MBP and urease in NTO, CTO and CTC but not with NTC treatment. MBC with acid- phosphatase a significant negative correlation was found in NTC and CTC treatment. MBN with most of soil nutrients (except SOC), urease and acid-phosphatase:NTC and CTC founded significantly negative correlation. MBN with MBP a positive correlation found in CTO and NTC treatment. The positive correlations of MBN with urease and dehydrogenase were found in NTO treatment. MBP with soil nutrients no significant positive correlation found in NTC treatment. But it was only for SOC in CTC, was a positive correlation. MBP with dehydrogenase a positive correlation found in NTO treatment.3. The differences of soil enzymes:in the case of soil acidphosphatase enzyme at 0-5 cm soil depth NTC significantly retained 32.89% greater than CTC. In other two soil depths no significant differences in acidphosphatase. Soil enzyme dehydrogenase also retained by NTC was 27.42% greater than CTC (P<0.05) at 0-5 cm soil depth. In 5-10 cm soil depth no significance difference for dehydrogenase. But 10-20 cm deep dehydrogenase in NTO was 57.28% lower. For three depth of soil NTC was holding 3 to 9 fold (P<0.01) higher urease and 2 to 6 fold higher (P<0.01) dehydrogenase compared with NTO. The correlation co-efficients of soil enzymes with soil physical and chemical were also determined. Urease with soil NO3-, TSN and SON were positively correlated in all treatments. Urease with pH a positive correlation (P<0.01) found in CTO and with AP had positive correlation (P<0.01) in NTO and CTO treatments. NTO showed, acid phosphase with soil pH and soil NH4+ a negative correlation (P<0.05) but NTO showed, acid phosphase with dehydrogenase and TN a positive correlation (P<0.01). CTO not showed any significant relationship with soil nutrient and acid phosphatase. NTC showed only negative correlation (P<0.05) with acid phosphatase and dehydrogenase. CTC showed acid phosphatase with TP a positive (P<0.05) correlation, and acid phosphatase with dehydrogenase a negative (P<0.01) correlation. NTO showed, dehydrogenase with soil pH a negative correlation (P<0.05). CTO showed, dehydrogenase with TSN and SON a positive correlation (P<0.05). CTC showed a positive correlation:dehydrogenase with urease (P<0.01), SOC (P<0.05), TSN (P<0.05) and SON (P<0.05). NTC showed a positive correlation:dehydrogenase with urease (P<0.01), pH (P<0.05), TSN (P<0.05) and SON (P<0.05) but NTC also showed a negative correlation:dehydrogenase with NO3-(P<0.05).4. The pH of surface water in of the paddy field in NTO was 0.11 units lower than that in CTO. NTC and CTC had equal value of surface water pH, TP, NH4+ and NO3- value. The surface water AP in NTO and NTC were 20%(P<0.05) and 15.79% (P<0.05) respectively.5. For the leaching in the paddy field, TN, HN4+, NO3- increased from 45 to 278% in NTC and CTC treatments after the application of inorganic N (urea). TP, AP leached from 69 to 150% in same treatments when P2O5 was applied. No significant differences in nutrient leaching occurred between NTC and CTC treatments. In NTO and CTO treatment also not showed any significant differences except for the NO3-which in CTO was 16.39% greater (P<0.05) than in NTO.6. GHG and its contribution to integrated GWP from four tillage systems were drawn:NTO, CTO, NTC and CTC contributed equally to the CO2 emissions from the paddy fields. It was observed that emissions were significantly higher in CTO than in NTO and was also higher in CTC than in NTC in cumulative CH4 emissions. N2O emission was equal from NTO and CTO but significantly in CTC lower than in NTC. Moreover, GWPs based on these GHGs emissions were lower in NTO than in CTO (P> 0.05), and in NTC than in CTC (P<0.05). CTC had highest contribution to GWPs followed by NTC and least was NTO. NTC reduced a significant amount of GWP's (12%) compared to CTC.It can be concluded that no-tillage system positively affected soil nutrients, microbial biomasses and enzymes. Moreover it reduced greenhouse gases from rice fields thus it can be a conservation options in the rice producing areas such as in central China.
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