氮肥及硝化抑制剂配合施用对石灰性土壤二氧化碳释放的影响

为研究施用氮肥对同时含有有机碳及无机碳石灰性土壤碳释放的影响,在陕西杨凌进行田间试验,比较了不同施氮量(0、160、220 kg·hm~(-2))及其与硝化抑制剂(DCD)配合(N160、N220及N160+DCD、N220+DCD)对土壤pH值、矿质态氮含量和二氧化碳(CO_2)释放量的影响。结果表明:施用氮肥显著降低了耕层土壤pH;配施DCD后土壤pH降低幅度小于未加DCD处理;加入DCD使氮肥的硝化过程推迟了约20 d;未加DCD处理的土壤CO_2释放量随施氮量增加而增加,试验结束时(施肥37 d后)土壤CO_2累积释放量最高达到167.1 g·m~(-2)。与N0处理相比,N160和N220处理的土壤CO_2累积释放量显著增加,增幅分别为20.9%和25.7%;N160+DCD和N220+DCD处理显著降低了土壤CO_2累积释放量,比对应相同施氮量处理分别降低了13.5%和11.0%。上述结果说明施用氮肥会同时影响石灰性土壤有机碳及无机碳的释放,施用氮肥引起的土壤无机碳的释放值得关注。

Effects of application of nitrogen fertilizer and nitrification inhibitor on carbon dioxide emissions from calcareous soil

A field trial was conducted to study the effects of adding nitrogen(N) fertilizer and nitrification inhibitor(DCD) on CO₂ emissions from calcareous soil in Yangling, Shaanxi. The treatments included a control to which no N fertilizer was added(N0) and two N fertilizer rates(160 and 220 kg N·hm^-2, represented as N160 and N220, respectively) and their combinations with DCD(N160+DCD and N220+DCD, respectively). The soil pH, contents of mineral N(NH₄⁺-N, NO₃^--N), and CO₂ emissions were measured. The results showed that the application of N fertilizer significantly reduced soil pH in comparison with N0. The decreasing rates of soil pH were less when N fertilizer was added with DCD. Addition of DCD delayed the nitrification of the N fertilizer by about 20 days. The CO₂ emissions from different N fertilizer treatments increased as the N rate increased when no DCD was added. Moreover, the maximum CO₂ emissions from soil after the experiment(37 days after adding N fertilizer) was as high as 167.1 g·m^-2. Compared with the N0 treatment, the amount of CO₂ emissions from the N160 and N220 treatments increased by 20.9% and 25.7%, respectively. When DCD was combined with the N160 and N220 treatments, CO₂ emissions from the soil decreased by 13.5% and 11.0%, respectively. This indicates that the application of N fertilizer affected both the release of organic carbon and inorganic carbon from the calcareous soil. Thus, the effect of N fertilizer on the release of inorganic carbon from soil needs more study.