中文摘要：

通过室内培养试验，研究双氰胺（DCD）对采自安徽郎溪和江西鹰潭的2种红壤中硝化反应的抑制作用，以及对氮肥引起的土壤酸化的抑制效果。结果表明，当不添加氮肥时，DCD抑制了土壤残留铵态氮的硝化作用及由此引起的土壤酸化，培养结束时添加DCD处理的安徽郎溪和江西鹰潭红壤pH值分别比不添加DCD处理高0．37和0．40。当添加尿素和碳酸氢铵时，DCD抑制了来自氮肥的铵态氮的硝化作用以及由此引起的土壤酸化；同时由于尿素水解和碳酸氢根与H^＋的缔合？肖耗质子，添加DCD还使2种氮肥对红壤酸度起到一定程度的改良作用。培养结束时，DCD＋尿素和DCD＋碳酸氢铵处理的安徽郎溪红壤pH值分别比单加尿素和碳酸氢铵处理提高0．62和0．46，江西红壤pH值分别比单加尿素和碳酸氢铵处理提高0．82和0．69。添加DCD处理土壤交换性酸含量也显著低于不添加DCD处理。因此，氮肥与DCD配合施用可以有效缓解氮肥引起的红壤酸化。

英文摘要：

Effects of dicyandiamide （DCD） inhibiting nitrification and soil acidification caused by nitrogen fertilizer in two Uhisol samples collected separately from Langxi of Anhui Province and Yingtan of Jiangxi Province were investigated through indoor incubation. Results show that when no nitrogen fertilizer was applied, DCD suppressed nitrification of resid- ual ammonium nitrogen in the soils and subsequent soil acidification, leading to rise in pH by 0.37 and 0.40 in the soils from Langxi and from Yingtan, respectively as compared with the controls at the end of the incubation. When urea or am- monium bicarbonate was added, DCD inhibited nitrification of the ammonium released from the nitrogen fertilizers and sub- sequent soil acidification. In addition to hydrolysis of urea and consumption of protons by the association of bicarbonate i- ons with H ＋ , the addition of DCD also offset to a certain extent the effect of the two fertilizers on red soil acidity. At the end of incubation, Treatments urea ＋ DCD and ammonium bicarbonate ＋ DCD was 0. 62 and 0. 46 higher in pH than their counterparts without DCD in the soil from Langxi, and 0. 82 and 0. 69 higher in the soil from Yingtan. The treatments with DCD were also significantly lower in content of exchangeable acids than their counterparts without DCD. It is, there- fore, concluded that combined application of nitrogen fertilizer and DCD can effectively alleviate red soil acidification caused by nitrogen fertilizers.