双氢胺对土壤裂缝产生过程中N_2O释放的影响

Effects of adding DCD on N_2O emissions in soil cracking

模拟稻田土壤在加入不同量的(NH4)2SO4和双氢按(DCD)抑制剂的溶液后先进行淹水培养,然后让土壤自然蒸发变干,直至土壤产生裂缝到裂缝稳定,最后在裂缝稳定后的复水的连续培养试验。通过模拟对土壤进行复杂的、动态的水分含量变化过程中试验,探讨双氢胺抑制剂对其N2O释放的影响。每天监测土体释放的N2O通量,以及渗漏液中溶解的N2O浓度和pH值。这些监测结果表明:在相同的水分管理条件下,土壤中没有氮肥加入,只有DCD加入的A处理释放N2O气体最少,其平均释放通量为340.91μgm-2h-1;土壤中有高剂量的氮肥和DCD加入的E处理释放N2O最多,其平均释放通量为9280.23μgm-2h-1。裂缝产生稳定后的复水能减少N2O向空气中的释放。渗漏液中的N2O浓度都是过饱和的。当土壤中肥料(NH4)2SO4加入量(每千克土壤中外加N≤3g)相对较少的情况下,DCD抑制剂能抑制裂缝产生过程中的N2O释放;当土壤中肥料(NH4)2SO4加入量(每千克土壤中外加N≥6g)相对较多的情况下,DCD抑制裂缝产生过程中的N2O释放效果不明显。此外还得出(NH4)2SO4和DCD的加入量比是10:1时,其抑制N2O排放的效果比(NH4)2SO4和DCD的加入量比分别是10∶1.5和10∶2要好。土体释放的N2O通量和渗漏液中溶解的N2O浓度之间不存在相关性,土体释放的N2O通量和渗漏液中的pH值之间也不存在相关性。但是渗漏液中的NO浓度和pH值之间存在显著的正线性相关关系。

There is a flush of nitrous oxide （ N2O） emissions during cracking of clay paddy soils. The goal of the study was to control the high N2O emissions by adding nitrification inhibitor dicyandiamide （DCD） during the development of cracks. The specific objective of this study was to investigate whether DCD could inhabit N2O emissions during soil cracking and reirrigation. Soil columns incubation experiments were conducted by adding 5000 ml solution containing different amounts of （NH4） 2So4 and DCD to paddy soils. Thereafter, the soil columns were dried at 30 -32℃ in a greenhouse for 10 days. After the 10^1h day, the columns were re-irrigated with 5000 ml distilled water and left to dry again at 30 - 32℃ in the greenhouse. The dynamic changes of daily N2o emissions flux and the concentration of dissolved N2o and pH of leaching solution showed that the treatment with DCD addition and without nitrogen fertilizers （A treatment） had the lowest N2O emissions, the mean emissions flux was 340.91μg m^ -2 h^ -1 However, the treatment with high amount of DCD and nitrogen fertilizers addition （E treatment） had the highest emissions, the mean emissions flux was 9280.23 μg m^-2 h^-1. The results showed that after the crack development attained maxima, the re-irrigation inhibited the N2O emissions. The dissolved N2O was over-saturated in leaching solution. Moreover, the results indicated that DCD could inhibit the N2O emissions when low amount of （NH4 ）2SO4 was added, but DCD could not inhibit N2O emissions efficiently when high amount of （NH4 ）2 SO4 was added even though the ratio of （NH4）2SO4 and DCD was the same （10：1 ）. The inhibition of N20 emissions by DCD was more efficient when the ratio of （NH4）2SO4 and DCD was 10：1 than their ratio was 10：1.5 and 10：2. There was no significant correlation between N2O emissions flux and dissolved N2O in leaching solution. Similarly, no correlation was obtained between N2O emissions flux and pH of leaching solution either. While a positive significant （p 〈 0.05 ） linear correlation existed between dissolved N2O and pH of leaching solution, in general, the addition of DCD could inhibit N2O emissions under continuous and dynamic variance of water regimes during the incubation. The most efficient inhibition of the role of DCD as a N2O emission inhibitor was the added amount of commercial nitrogen fertilizer and the content of ammonium-nitrogen （NH4-N） in soils. Considering to reduce the N2O emissions, re-irrigation is one of the ways that can be used to control N2O emissions after cracks were produced in paddy soils.