Effects Of Biochar, Natural Biomass And Organic N Fertilizer Application On Soil Organic Nitrogen Mineralization In The Yellow River Delta Costal Wetland

The Yellow River delta coastal wetland is the youngest, largest new natural coastal wetland ecosystem in the warm temperate zone of China. Due to the climate change, unreasonable development and utilization, natural wetlands are seriously shrinking and degraded, soil salinization degree is high, level of nitrogen, phosphorus and other nutrients are low. For many years, measures of vegetation and hydrological regulation are effectively used to renew the Yellow River delta coastal wetland. However, to achieve the sustainable restoration and functional conservation of degraded wetland, measures must be fundamentally taken to improve wetland soils. In recent years, biochar (BC) provides a new way for improving sterile saline-alkali soil and implementing sustainable restoration and functional conservation of degraded wetlands.Biochar is a carbon-rich and porous-rich product from pyrolysis of renewable biomass in a closed system under low or absent oxygen atmosphere. Special abundant porous physical structures and rather high surface area of biochar can improve soil physical properties such as soil texture, structure, thus can maintain soil aeration, moisture and fertility. Biochar is an excellent soil conditioner. Meanwhile, biochar input had influence on wetland soil texture, nutrient cycling and crop yield. Thus, biochar application may have influences on costal wetland soil N mineralization. As nitrogen is always one of the most limiting nutrient in the Yellow River delta coastal wetland, low level of available nitrogen greatly impacts the primary productivity in wetland ecosystem, available nitrogen mainly come from soil N mineralization. In this study, a 150d incubation was designed and the treatments contain control (CK), 1%BC,3%BC,3%reed,3%reed+3%BC,0.3%urea,0.3%urea+1%BC, in order to evaluate the effects and possible mechanism of peanut biochar, reed and urea application on net N mineralization in the Yellow River estuary delta coastal wetland.Results showed that:(1) Two biochar addition treatments (1%BC,3%BC) decreased soil net mineralized N. Compared to control, biochar increased soil pH, TC, TN and C:N ratio significantly, decreased soil urease activities. Higher C:N ratio and lower urease activities inhibit soil N mineralization, decreased soil net mineralized N.(2) For two reed treatmens, biological fixation of soil mineralized N was dominant. Two reed treatments decreased soil pH, significantly increased soil urease activities. Reed stimulated N immobilization in a short time by the highest C:N ratio induced by reed. Biochar can relieve inhibitory effect of reed on soil N mineralization, but the difference was not significant.(3) Two urea treatments greatly increased soil net mineralized N. Urea significantly decreased soil C:N ratio, increased soil urease activities, thus improved soil N mineralization significantly. After 46d, two urea treatments significantly decreased soil pH, but soil urease activities were increased in the presence of biochar. Thus, biochar application stimulate N mineralization in a short time in the later stage.The conclusions suggested biochar application generally decreased N mineralization in the Yellow River estuary delta coastal wetland, but in the presence of reed and urea, increased N mineralization was appeared to a certain extent by biochar application in a short time.