Effects Of No-Tillage And Application Of Fertilizer On Paddy Soil Biological Characteristics And Emissions Of The Greenhouse Gas

In this research, paddy field was selected under Cole-rice rotation system in the southeastern part of Hubei province. A series of experiments was conducted, in a range of soil tillage and application of fertilizer to identify dynamic variation of microbial biomass and soil enzyme activity at different soil depth during rice duration and the soil physico-chemical property, greenhouse gas emission and rice yield within seven treatments, such as No-tillage without fertilizer (NT₀), Cultivation tillage without fertilizer (CT₀), No-tillage with envelope urea (NTCU), No-tillage with and ammonium (NTA), No-tillage with stool (NTS), No-tillage with compound fertilizer (NTC) and Cultivation tillage with compound fertilizer (CTC). The mail results are as follow:1. The effect of No-tillage on soil microbial biomass(1) Microbial biomass carbon at 5 to 10 cm soil level and 10 to 20 cm soil level varied drastically under all treatments with fertilizer application, especially at top application stage during the whole rice duration compared with no-fertilizer. Fertilizer application increased the microbial biomass carbon at 0 to 20 cm soil level. At 0 to 5 cm soil level, the microbial biomass carbon under NTS was the highest, while it measured highest at 5 to 10 cm soil level and 10 to 20 cm soil level under NTC. No-tillage could improve the microbial biomass carbon at 0 to 5 cm soil level without fertilizer application compared with tillage treatments, but there was non significant difference when compound fertilizer was applied.(2) Microbial biomass nitrogen at all of the soil levels varied drastically during the whole rice duration under all treatments with fertilizer application compared with those with no-fertilizer, especially at top application stage. Fertilizer application increased the microbial biomass nitrogen at 0 to 20 cm soil level. The microbial biomass nitrogen was highest under NTS, NTC and NTA at 0 to 5 cm soil level, 5 to 10 cm soil level and 10 to 20 cm soil level, respectively. No-tillage could improve the microbial biomass nitrogen at 0 to 10 cm soil level without fertilizer application compared with tillage treatments, but there was non significant difference when compound fertilizer was applied.(3) Microbial biomass phosphate at 0 to 5 cm soil level and 5 to 10 cm soil level varied drastically during the whole rice duration under fertilizer treatments compared with no- fertilizer. No-tillage with fertilizer application increased the microbial biomass phosphate at 0 to 20 cm soil level, while tillage with fertilizer application increased it at 5 to 20 cm soil level. The microbial biomass phosphate was highest under NTA, NTC and NTCU at 0 to 5 cm soil level, 5 to 10 cm soil level and 10 to 20 soil levels, respectively. No-tillage could improve the microbial biomass phosphate at 5 to 20 cm soil level without fertilizer application compared under tillage treatments, but there was non significant difference when compound fertilizer was applied. Stratification seemed to be apparently for microbial biomass phosphate, which appeared mainly at 0 to 10 cm soil level and decreased as soil depth increased.2. The effect of No-tillage on enzymatic activity(1) Fertilizer application played an important role on urase and dehydrogenase activities in soil, while no-tillage did not. Urase and dehydrogenase activities at all of the soil levels varied drastically under fertilizer treatments compared with no-fertilizer treatments during the whole rice duration. Compared with non-fertilizer, fertilizer treatments increased the urase and dehydrogenase activities of soil at 0 to 20 cm level. Among all the fertilizer treatments, the urase activity of soil at 0 to 10 cm level under NTS was the highest, and it measured highest at 10 to 20 cm level under NTA. Whereas, the dehydrogenase activity of soil at 0 to 5 cm level under NTCU was highest, and it measured highest at 5 to 20 cm level under NTA.(2) The effect of tillage and fertilizer application on soil phosphotase activity performed differently. The variation of phosphotase at different soil level performed with great similarity and certain fluctuation occurred. NTS could significantly increase the phosphotase activity of soil at 0 to 5 cm level, and NTCU at 10 to 20 cm soil level, while NTA decreased significantly at 5 to 10 cm soil level compared with no-tillage and fertilizer-free treatments. CTC increased significantly the phosphotase of soil at 5 to 10 cm level compared with tillage and fertilizer-free treatments, and NTC increased it at 0 to 5 soil level compared with CTC.3. The effect of No-tillage on soil physico-chemical propertyFertilizer application did not significantly increase the soil volume weight irrespective of tillage or not compared with non-fertilizer, which was significantly decreased under NTS. Non significant difference was shown on soil pH between fertilizer treatments and non-fertilizers. No-tillage decreased the soil pH to some extent, with non significant difference, however.Fertilizer treatments increased the content of NH₄⁺ and NO₃^- compared with no-fertilizer treatments. Among all the fertilizer treatments, the content of NH₄⁺ under NTCU at 0 to 5 cm soil level was the highest, followed by soil at 10 to 20 cm level, and the content of NO₃^- at soil level of 5 to 10 cm was highest, either, compared with non-fertilizer. Besides, the soil content of NH₄⁺ decreased as the soil depth increased, while the content of NO₃^- varied differently, with the highest content at 5 to 10 cm level and the least at 10 to 20 cm level.Soil soluble total nitrogen content increased under NTS and NTC condition at 5 to 10 cm soil level, while CTC significantly increased the soil soluble total nitrogen content. NTS decreased it at 10 to 20 cm soil level, and NTCU decreased it at 5 to 10 cm soil level. Soil soluble total nitrogen and organic nitrogen contents varied as similarly as NO₃^-.4. The effect of No-tillage and fertilizer application on greenhouse gas emissionCH₄ emission under all treatments in the research followed the seasonal discipline, increasing firstly and then decreasing and the seasonal discipline of N₂O emission was not apparent. Fertilizer application increased the emission of CH₄ and N₂O. No-tillage and no-fertilizer significantly increased the emission of CH₄ and decreased the emission of N₂O compared with tillage no-fertilizer. Compared with tillage fertilizer, no-tillage fertilizer treatments decreased slightly the emission of CH₄ and increased slightly the emission of N₂O with non significant difference. Greenhouse effect analysis under two gases emission of CH₄ and N₂O in paddy field has demonstrated that no-tillage no-fertilizer increased the greenhouse effect to 25.9% compared with tillage no-fertilizer. While compared with tillage fertilizer treatments, no-tillage fertilizer decreased the greenhouse effects to 10.1%.5. The effect of No-tillage and fertilizer application on rice physiological characteristic index and yieldNearly all treatments with fertilizer application have increased the rice yield in the study with rice yield increase of 36.8%, 24.1% and 18.4% under NTC, NTS and NTCU, respectively, except NTA, under which the yield decreased 5.6%, compared with no-tillage no fertilizer treatment as a result of productive tillers, panicle length and plant height highest under NTC and NTCU, and lower than other fertilizer treatments under NTA with no-tillage and no-fertilizer the least. Compared with no-tillage no-fertilizer, tillage no-fertilizer increased yield by 34.3% because of high productive tillers per mu, panicle length, total spikelets m^-2 and plant height. Grain yield and each physiological index were non significantly different between no-tillage and tillage irrespective of fertilizer application.