Soil Nitrification, Denitrification And Factors In Shanghai Suburbs

Soil nitrification and denitrification is an important greenhouse gas N2O produced by biological processes, and is the ecosystem approach in the potential N losses. Different soil properties, different land use types, different management practices affected soil nitrification and denitrification process. Through analysis and compare with different types of agricultural land, different types of urban land use in soil nitrification and denitrification,we can explore the impact mechanism, which contribute to analysis of soil nitrogen transformation rates and forecast farm greenhouse gas emissions.This paper uses BaPS system and analyses of different types of agricultural land soil nitrification and denitrification process; monitors Peach garden, Horticulture and Forestry, greenhouse vegetables, the open-air vegetable soil nitrification and denitrification of the seasonal changes of temperature environmental factors and their influence soil properties, and uses gas chromatography simultaneous to monitor of greenhouse and open-air vegetable BaPS system during the experiment N2O concentration; and monitors Pujiang Town's different type of land use including urban land, soil nitrification and denitrification and N2O concentration in Shanghai; compares the Shanghai suburbs, such as determination of Baoshan District, Chongming Town, Nanhui District, Fengxian District, Pujiang Town, greenhouse vegetable nitrification and denitrification; in order to explore the soil nitrification and denitrification of the mechanisms, and their relative N2O emissions contribution rate.The major findings of this paper are:(1) Different types of agricultural land soil gross nitrification rates and denitrification rates were significantly different. The soil of the total nitrification rate:Greenhouse Vegetable> Open Vegetable> Vineyard> Taoyuan> Gardening forest. The soil of the denitrification rate: Greenhouse Vegetable> Open Vegetable> Vineyard> Gardening forest> Taoyuan. Greenhouse vegetables soil gross nitrification rates and denitrification rate was the highest, respectively,422.43Nugkg-1h-1 and 466.59 Nug-kg-1·h-1, which is other agriculture use type 2-3 time and 1-2 times.The total rate of soil nitrification and denitrification rates was close. Gross nitrification rates and soil water content, total nitrogen, C/N, NO3--N is closely related to. Denitrification rate and soil moisture, NO3--N, total nitrogen is closely related to. Moderate soil moisture is conducive to soil nitrification and denitrification. In the middle range of soil moisture, affecting soil nitrification, denitrification of the environmental factors become more diverse and complex. The modest improvement of soil aeration conditions were conducive to nitrification and denitrification.(2) Peach garden soil gross nitrification rate, denitrification rate was significantly seasonal changes. In 15℃～35.5℃temperature range of soil temperature, Taoyuan gross soil nitrification and denitrification rate showed significant negative correlation with soil temperature. Taoyuan soil gross nitrification rates, denitrification rate and soil water content was significantly positively related to. Soil moisture and temperature changes affect the seasonal factors. Other soil properties of Peach garden, such as soil organic matter, nitrate, total nitrogen, carbon and nitrogen ratio, pH, soil bulk density effect on the Peach garden gross nitrification rate, denitrification rate of seasonal change was weakly.In different seasons, Horticulture and Forestry soil of total nitrification rate difference was significant difference and denitrification rate difference was not significant. N loss in forest gardening, the soil nitrification and denitrification contribution rates were 39.6%,60.4%. Horticulture and Forestry gross nitrification rates and soil temperature were significantly positively. Gross nitrification rates was correlated with soil water content significantly negatively, which may be higher gardening soil moisture, inhibit soil nitrification. Gardening forest soil gross nitrification rates and soil organic matter was significantly negatively correlated with nitrate showed significant positive correlation. The influence of total porosity, soil bulk density, total nitrogen, carbon and nitrogen ratio, pH value on the total nitrification was weak.Greenhouse vegetables in different seasons of the soil gross nitrification rate, denitrification rate were significantly different. In 2009 Spring,gross soil nitrification and denitrification rates of the highest value, respectively 1122.17Nug·kg11·h-1,1725.03Nug·kg-1·h-1. In 2009 Fall,soil gross nitrification and denitrification rates was lowest, respectively,191.15 Nug-kg~-1·h-1,231.57 Nug-kg-1·h-1. Greenhouse vegetable soil N2O emission rates in 2009 Spring was most of the emissions. Greenhouse vegetable soil gross nitrification rates and denitrification rates and N2O emission rates with soil was significantly correlated. Nitrogen losses in greenhouse vegetable soil nitrification and denitrification of the contribution rate were 40.68%,59.32%. Soil properties such as soil water content, total porosity, bulk density, soil organic matter, nitrate nitrogen, total nitrogen, carbon and nitrogen ratio, pH value on greenhouse vegetable soil gross nitrification rates and denitrification rates are weak. This may be because of the special environment of greenhouse vegetables. Greenhouse environment is relatively confined in the nighttime that temperature and humidity high nitrification activity of bacteria and denitrifying bacteria are more stable.Different seasons of open-air vegetable soil gross nitrification rate, denitrification rate were significantly different. In 2009 Spring,gross soil nitrification and denitrification rates of the highest value, respectively 610.79Nug-kg-1·h-1,697.18Nug-kg-1·h-1. In 2009 Summer, soil gross nitrification and denitrification rates was lowest, respectively 129.96 Nug·kg-1·h-1,129.39Nug·kg-1·h-1. Open-air vegetable soil N2O emission rates in 2009 Spring was most of the emissions. Soil nitrification and denitrification losses of nitrogen contribution rates were 66.3%,33.7%. The total nitrification was the main source of soil N2O emissions. Soil gross nitrification rates and soil total porosity was significantly correlated with, and soil bulk density was significantly negatively correlated,but soil moisture correlation was not significant. Open-air vegetable soil denitrification rate and soil water content was significantly correlated. Other soil properties such as soil organic matter, nitrate, total nitrogen, carbon and nitrogen ratio, pH value on the open-air vegetable soil gross nitrification rate, denitrification rate was not obvious. Open-air vegetable soil N2O emission rates in May 2009 was most of the emissions. The total nitrification was the main source of soil N2O emissions. Open-air vegetable soil gross nitrification rate and denitrification rate with soil N2O emission rate showed significant positive correlation.(3) The variation of pH value about soil is between 4.71 and 8.23.Among of them, agricultural land takes on acidic, but Urban construction land shows alkaline. Compared with urban soil, except in Taoyuan and Horticulture and Forestry, other land use types, such as open-air vegetables, greenhouse vegetables and vineyards, soil nitrate content was high, especially in greenhouse vegetable land, which was much higher nitrate content to other land types. There are obvious phenomenon of nitrate accumulation. Soil organic matter content of agricultural use land are differences due to organic manure application vegetation types. Compared with other types of urban land, residential areas with high soil organic matter content and soil nitrate content was significantly higher, which was residential soil cultivation and fertilization management and rich source of organic material relevant.The land type denitrification rate significantly different, the size of the order of greenhouse vegetables, open-air vegetable land, industrial areas, vineyards, River Forest Park, residential areas, Taoyuan, Commercial, Chenhang Park, transportation of construction land, forest gardening. Although agricultural land in the plastic greenhouses and outdoor vegetable denitrification rate higher, the type of urban land use soil denitrification rate not lower than other types of agricultural land with low soil denitrification rate, which shows that urban soil denitrification activity exists, and its denitrification bacteria urbanization process of soil compaction and soil properties change to some extent contributed to soil denitrification. Factor analysis showed that soil water content, organic matter and nitrate had a significant effect on the denitrification of agricultural land, but only the physical and chemical properties of urban soil pH on soil denitrification had a significant effect on. Urban soil alkalization promoted denitrification role.In Pujiang Town, these types of N2O emission rates of land value Size: Greenhouse Vegetable > Open Vegetable> Commercial> Residential> Industrial area> Gardening woodland> Vineyards> Transportation construction projects> Chenhang Park> Taoyuan> River Forest Park. N2O emission rates of greenhouse vegetables was the highest, which was up to 11.88 ug-kg-1·h-1. But the types of urban land commercial, residential and other garden soil N2O emission rate higher than Taoyuan N2O emission rate. Urban soil N2O emissions should also be concerned about.(4)Different areas of the greenhouse vegetable soil gross nitrification rate, denitrification rate was significantly higher. With different areas of the total greenhouse vegetable soil nitrification rate Size:Baoshan> Chongming> Nanhui> Pujiang> Fengxian. The greenhouse vegetable in different areas of denitrification rate in decreasing order, Chongming, Baoshan, Fengxian, Nanhui, Pujiang. Factor analysis showed that soil bulk density and soil nitrate content in soil in greenhouse vegetable have a significant impact on soil gross nitrification rates. Soil moisture, organic matter, nitrate, carbon and nitrogen ratio on the plastic greenhouses of the significant effects of denitrification. Tillage, irrigation, fertilization is caused by soil nitrification and denitrification difference.