铵态氮肥对黄土高原典型土壤氮素激发效应的影响

以黄土高原从北向南不同地区典型土壤类为对象，采用Bremner淹水培养法，研究铵态氮肥对黄土高原典型土壤氮素的激发效应。结果表明，在测定NH4+-N的激发效应时，只有考虑粘土矿物对有机氮矿化产物或者添加NH4+-N的固定，才可获得可靠结果。在培养20 d和60 d时，NH4+-N对不同土类氮素激发效应存在极显著和显著的影响（P≤0.01和0.05）；培养40 d时，尽管不同土类氮素激发效应也存在很大差异，但统计检验不显著。从整体评价，NH4+-N对土垫旱耕人为土和黄土正常新成土表现出正的激发效应，而对干润砂质新成土表现出负的激发效应，对简育干润均腐土在培养20 d和40 d时无激发效应，而在培养60 d时，表现出显著的负激发效应。结果还看出，在培养40 d和60 d时，NH4+-N对农田土壤表现出负激发效应，对林地和裸地土壤表现出正激发效应，而草地土壤在培养40 d时为正激发效应；培养20 d和60 d时无激发效应。添加有机物料在培养20 d和40 d时对激发效应的影响不显著（P=0.0872和0.1641），培养时间延长至60 d时影响显著（P＝0.049）。添加紫花苜蓿(Medicago sativa)后，NH4+-N在培养40 d时表现出正的激发效应，而添加长芒草(Stipa bungeana Trin.)却在培养20、40和60 d时均表现出负的激发效应，不添加有机物料在培养20、40和60 d时均无激发效应。

Priming effect of ammonium nitrogen fertilizer on soil nitrogen in typical soils of Loess Plateau

Typical soils collected from north to south on loess plateau were chosen to study the priming effect of ammonium nitrogen fertilizer on soil nitrogen by the Bremner incubation method. The results showed that the sequestration of clay to NH₄⁺-N must be considered in order to get reliable results when measuring the priming effect of NH₄⁺-N on soil nitrogen. The priming effects of NH₄⁺-N on soil nitrogen in different soils were significantly different on 20 d and 60 d (P≤0.01 and <0.05), respectively. On 40 d, priming effect of different soil types was different, but not significant. NH₄⁺-N had positive priming effect on soil nitrogen of Eum-Orthic Anthrosols and Los-Orthic Entisols, but negative effect on that of Ust-Sandiic Entisols, NH₄⁺-N had no priming effect on soil nitrogen of Hap-Ustic Isohumisols on 20 d and 40 d, but had significant negative priming effect on 60 d. Generally speaking, on 20 d and 40 d NH₄⁺-N had negative priming effect on farmland, positive effect on forest and bare land and positive effect on grassland soil, whereas no priming effect on 60 d.The influence of organic material on priming effect was not significant on 20 d (P=0.0872) and 40 d (P=0.1641), but significant on 60 d (P=0.0490). NH₄⁺-N had positive priming effect when alfalfa was added on 40 d, and nopriming effect on 20 d and 60 d, negative piming effect existed when Stipa bungeana was added on 20 d, 40 d and 60 d, while it did not have any priming effect when no organic material was added on 20 d, 40 d, and 60 d.