Effect Of Inhibitors On Urea Hydrolysis And Soil Nitrification

Nitrogen fertilizer plays a very important role in increasing crop yield and improving crop quality. It definitely has some apparent effects on increasing production after the application of nitrogen fertilizer at arable lands in China; however, the dependence of soil on nitrogen fertilizer is growing to a large extent. For some types of soil, nitrogen fertilizer is almost directly proportional to crop yield. But in recent years, it has no enough time for crops to take absorption of the excessive amount of nitrogen because more and more nitrogen fertilizer has been put into the soil. The nitrogen is lost by means of transformation, especially the excessive amount of residual nitrate in soil, and then will access to the air and water during the process of leaching, runoff and denitrification, which results in severe pollution of the soil, air and water.Therefore, controlling the process of transformation from ammonium such as urea to nitrate and reducing the residual nitrate in soil is the key step to reduce nitrogen loss and prevent environmental pollution in addition to reasonable application of nitrogen fertilizer. The main purpose of this experiment is to figure out the effect of soil inhibitors on reducing nitrogen loss and environmental pollution after detailed studies on ammonium and nitrate in different conditions of temperature and humidity with the application of urease inhibitors, nitrification inhibitors and urea. The results show that:1 Hydroquinone has a significant effect on the content of urea in soil in different soil temperature and moisture conditions. The content of both ammonium and nitrate are lower than the blank (which only with urea). At the same soil moisture level, the effect of Hydroquinone as a urease inhibitor performs better at soil temperature 25 degree than 15 degree and 35 degree; also at the same soil temperature level, the effect of Hydroquinone performs better at the field capacity 60% than 40% and 80%. Based on the research of the urease inhibition rate in soil, the combination of soil temperature 25 degree and the field capacity 60% has the optimal inhibitory effect of urease.2 In different soil temperature and moisture conditions, nitrification inhibitor Dicyanodiamide is the perfect inhibitor of nitrification. The content of nitrate in soil is significant lower than the control treatment, while the content of ammonium is higher than the control treatment. At the same soil moisture level, the effect of Dicyanodiamide as a nitrification inhibitor performs better at soil temperature 15 degree than 25 degree and 35 degree; also at the same soil temperature level, the effect of Dicyanodiamide performs better at the field capacity 40% than 60% and 80%. The research of the nitrification inhibition rate in soil suggests that: the performance of Dicyanodiamide as a nitrification inhibitor become lower when the soil temperature and humidity increase.3 New nitrification inhibitor Dimethylpyrazol phosphates (DMPP) is a nitrification inhibitor both functional and environmental-friendly. The research of DMPP in different soil temperature and humidity conditions shows that: nitrate content in soil corresponding to the lower concentration of DMPP treatment is lower than the control treatment. At the same level of soil humidity, the performance of DMPP as a nitrification inhibitor in different soil temperatures is C15℃>C25℃>C35℃; also at the same level of soil temperature but different soil humidity conditions, concentration of nitrate from high to low is C80%>C60%>C40%.4 The study of effect of Potassium humate on nitrification illustrates that the concentration of Potassium humate has no noticeable effect on the content of nitrate. But with the extension of time for soil cultivation, nitrate content increases during the process in different conditions of soil temperature and humidity. Potassium humate has positive effect on both Dicyanodiamide and DMPP in different environmental conditions.5 Each of these soil inhibitors has its own advantages and disadvantages. Based on the comprehensive comparison, they have different effects on soil urease hydrolysis and nitrification inhibition in different soil temperature and humidity conditions. The conclusion can be drawn safely that the application of the soil inhibitors should take fully consideration of the soil conditions.