Effects Of Combined Controlled-released Nitrogen Fertilizer On Greenhouse Gas Emissions From Dry Farmland Under Different Mulching Patterns

In recent years,controlled-release nitrogen fertilizer has been widely used in farmland management for its advantages of high efficiency,durability and labor saving.However,under different mulching patterns from dry farming,the effect of combined controlled-release nitrogen fertilizer and conventional urea on greenhouse gas emissions from farmland has rarely been reported.In order to solve above-mentioned problems,field experiments applied with three different nitrogen treatments on spring maize including no nitrogen fertilizer（N0）,100%conventional urea at a rate of 225 kg N ha^-1（N1）,controlled-release nitrogen fertilizer and normal urea with a ratio of 1:2 applied at rate of225 kg N ha^-1（N2）under plastic film mulching（F）and corn straw mulching（S）,which were used static chamber-gas chromatograph technique,were conducted at Changwu Agricultural and Ecological Experimental Station from 2016 to 2018 to study the greenhouse gas emission characteristics and influence factors of spring maize from dry farmland.The main research progress is as follows:（1）Under plastic film mulching,there was no difference for the cumulative N₂O emissions between treatment combined application of controlled release nitrogen fertilizer and treatment applied with 100%conventional urea;under corn straw mulching,the cumulative N₂O emissions for treatment combined application of controlled release nitrogen fertilizer were significant lower than that of 100%conventional urea.There was extremely significant and positive correlation between N₂O emission and soil temperature from plastic film mulching.There was a significant and positive correlation between N₂O emission and soil temperature from corn straw mulching.There was a significant and positive correlation between N₂O emission and soil nitrate and ammonium nitrogen content for treatments applied with nitrogen fertilizer.（2）The CO₂ emission from farmland had obvious seasonality,which increased firstly and then decreased.Nitrogen fertilizer application significantly increased the average of the CO₂ emission flux and the annual cumulative CO₂ emissions.The cumulative CO₂emissions for the treatments combined application of controlled release nitrogen fertilizer in growth season and annual of maize were significantly lower than that of 100%conventional urea.Under the same nitrogen application conditions,the average of cumulative CO₂ emissions for treatments under corn straw mulching were higher than that under plastic film mulching in two years.There was no significant correlation between CO₂emission from farmland and soil water-filled pore space,but extremely significant and positive correlation with soil temperature.There was a significant and positive correlation between CO₂ emission flux and soil nitrate and ammonium nitrogen content for treatments applied with nitrogen fertilizer.（3）The average of the cumulative CH₄ uptake in two-year for treatments combined application of controlled release nitrogen fertilizer（FN2 and SN2）increased by 14.3%and14.6%,respectively,in two years,compared with conventional urea（FN1 and SN1）,and the difference was significant.The average of the cumulative CH₄ uptake（SN1 and SN2）for treatments under corn straw mulching increased by 9.7%and 12.9%,respectively,in two years,compared with that under plastic film mulching（FN1 and FN2）.There was extremely significant and negative correlation between CH₄ uptake in farmland and soil water-filled pore space.There was extremely significant and positive correlation between CH₄ uptake flux and soil temperature for treatments under plastic film mulching;significant and positive correlation between CH₄ uptake flux and soil temperature for treatments under corn straw mulching.There was significant and negative correlation between CH₄ emission flux and soil ammonium nitrogen content for treatments applied with nitrogen fertilizer,no significant correlation between CH₄ emission flux and soil nitrate nitrogen content.The contribution of all environmental factors to CH₄ uptake flux was WFPS>soil temperature>soil ammonium nitrogen.（4）Under plastic film mulching,treatments combined application of controlled release nitrogen fertilizer could not reduce the greenhouse gas warming potential,but significantly reduced the greenhouse gas intensity in the second year;under corn straw mulching,treatments combined application of controlled release nitrogen fertilizer significantly reduced the greenhouse gas warming potential and the greenhouse gas intensity.