Effects Of Exogenous Carbon,nitrogen And Acetochlor Addition On Soil Nitrogen Transformation And Greenhouse Gas Emissions

The carbon storage of farmland soil is high,and it is affected by human factors.The stability and growth of the soil carbon pool will affect the soil microorganism and soil fertility,and then affect the crop yield.China is a big country in the application of nitrogen fertilizer,the using rate is increasing,but the utilization efficiency is very low,so a large amount of nitrogen fertilizer input will cause serious loss and ecological risk.In the farmland nitrogen mainly existed in organic matter,and between nitrogen fertilizer input and carbon pool has the coupling effect.So to study the effects of coupling effects on nitrogen can provide the basis for the stability of soil carbonpooland the improvement of nitrogen use efficiency.In this study,garden soils and the most common straw as carbon sources in Fuzhou were selected.And the effects of the carbon and nitrogen nutrition and their coupling relationship on the content of available nitrogen,denitrification loss and greenhouse gas emissions were analyzed.The following conclusions are obtained:(1)Only N fertilizer,there was no significant difference between nitrification and denitrification in 75 and 150mg·kg-1 nitrogen application.While,nitrification and denitrification were significantly enhanced by 300mg·kg-1,and the denitrification losses reached 1,3221ug·kg-1,which is 117 times of the control treatment.Acetochlor could inhibit the hydrolysis of urea in soil under 150 and 300mg·kg-1 nitrogen application rate,and the hydrolysis rate decreased by 9.8%-10.1%.And it had a significant inhibitory effect on denitrification loss under the nitrogen fertilizer amount of 300mg and kg-1,and the total loss was reduced by 18.2%(2)The emission of N2O and CO2 increased with the increase of nitrogen application rate.When the nitrogen is 300mg.kg-1,N2O and CO2 emissions were 8,640.24 and 1,592.84ug·kg-1 respectively.Compared with the single application of urea,the acetochlor can significantly reduce soil N2O and CO2 emissions(P<0.05),which was reduced by 33.94%and 11.60%respectively.(3)Straw addition could promote the hydro lysis of urea.The hydrolysis rate of urea was increased by 22.7%-30.5%and 181%-26.1%,respectively,when the Straw added amount is 4.44mg·kg-1 to 13.33mg·kg-1.The addition of straw in soil can significantly improve the hydrolysis rate of urea,which is more obvious than that of herbicide acetochlor.(4)Soil straw will produce retention effect on soil ammonium nitrogen and nitrate nitrogen,the fixing effect will be enhanced with the increase of the amount of straw,and acetochlor will produce different effects on the soil nitrate nitrogen content in the different time.(5)The addition of straw could promote denitrification loss,and the loss rate was significantly correlated with the amount of straw,while the acetochlor can inhibit soil denitrification losses.The inhibitory effect was the most obvious when the amount of straw was 8.88g·kg-1,and the inhibition of acetochlor was decreased by the addition of excess straw.(6)Adding straw could increase soil CO2 and N2O emission,and the emission increased with the increase of straw dosage.The acetochlor can inhibit the CO2 emission at 4.44 and 8.88 g.kg-1 straw addition significantly,and has no significant effect on N2O emission.(7)The effects of coupling on ammonium nitrogen and nitrate nitrogen are significant(P<0.01).High nitrogen fertilizer and straw are not conducive to accumulation of soil ammonium nitrogen and nitrate nitrogen.With the increase of N fertilizer amount and increase the amount of straw inputs can be effective in soil nitrogen release,Straw amount of 8.88g·kg-1 nitrogen application amount of 200mg·kg-1 under the conditions of the best slow-release effect,ammonium nitrogen and nitrate nitrogen reached the maximum sustained release.(8)The effect of carbon and nitrogen coupling on the denitrification of soil reached a significant level(P<0.01),and when the proportion of straw and nitrogen was changed,the main factors restricting denitrification were changed.The primary factors of denitrification were the carbon sources in early stage and the nitrogen source was the main factor of denitrification in the later period of culture.The coupling effect was main factor of denitrification in the medium term.Nitrogen fertilizer and straw returning can be through controlling the adding amount of straw quantity and nitrogen fertilizer to improve soil nutrient and reduce denitrification losses of greenhouse gas emissions.The reasonable control of carbon and nitrogen in the proportion of investment is to achieve soil fertility,increase nitrogen utilization and reduce environmental hazards.