黄土高原典型土壤有机氮矿化过程中非交换性铵态氮的变化

Change of Non-exchangeable Ammonium Nitrogen in the Process of Organic Nitrogen Mineralization of Typical Soils on Loess Plateau

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,研究黄土高原不同生境条件下土壤有机氮矿化过程中非交换性铵态氮的变化。结果表明:土壤非交换性NH4+-N随Bremner法淹水培养时间延长,含量增加。不同土壤类型在培养20 d时非交换性NH4+-N的增加量存在显著差异(p=0.022 9),而培养40 d和60 d时差异不显著(p分别为0.137 9和0.115 9)。培养期间非交换性NH4+-N的增加量均表现为以土垫旱耕人为土最大,其次是黄土正常新成土,简育干润均腐土和干湿砂质新成土较小;添加有机物料极显著影响培养期间的非交换性NH4+-N增加量(培养20 d、40 d和60 d时p分别为0.000 2,0.004和0.000 3),表现为紫花苜蓿和长芒草土壤非交换性NH4+-N的增加量均极显著高于不添加有机物料的对照土壤;在培养20 d、40 d和60 d时,加(NH4)2SO4土样非交换性NH4+-N的增加量显著大于不加(NH4)2SO4土样(p分别为0.003 7,0.003 3和0.002 7),这是土壤对(NH4)2SO4中NH4+-N固定的必然结果;不同植被类型土壤培养20 d时的非交换性NH4+-N增加量差异显著(p=0.043 4),培养40 d和60 d时差异不显著(p分别为0.737 8和0.537 5);长期秸秆和氮肥配施土壤非交换性NH4+-N增加量大于不施肥对照土壤,但差异不显著土壤黏粒、全氮和有机质与培养0 d、20 d、40 d和60 d时土壤的非交换性NH4+-N含量均呈极显著正相关;而非交换性NH4+-N的增加量与粘粒无相关性,但与全氮和有机质呈显著正相关。

In order to investigate the content change of non-exchangeable ammonium nitrogen during the process of soil organic nitrogen mineralization, the typical soils collected from north to south on Loess Plateau were chosen as the material, and the Bremner incubation method was conducted and the soils were incubated for 60 d. The results showed that the contents of non- exchangeable N H4^＋ -N increased with increasing the incubation time. The amount increased for non-exchangeable NH4^＋ -N existed significant difference （P=0. 022 9） among the different soil types after the 20d of incubation, however, it was not significantly different when incubation at 40 d （P=0. 1379） and 60 d （P=0. 115 9）. The increased amount of non--exchangeable NH4^＋ -N during the incubation indicated as the following tendency, namely, Eum-Orthic Anthrosols 〉 Los - Orthic Entisols 〉 Hap-Ustic Isohumisols 〉 Ust-Sandiic Entisols. Organic material influenced significantly the increased amount of non-exchangeable NH4^＋ -N （P was 0. 0002, 0. 0004 and 0. 0003 when incubated at 20 d, 50 d and 60 d, respectively）. NH4^＋ -N increased remarkably when Stlpa bungeana and Medicago sativa were added compared with no addition. The contents of non-exchangeable NH4^＋ -N increased significantly when added （NH4）2SO4 compared without addition at 20 d, 40 d and 60d of incubation and P was 0. 0037, 0. 0033 and 0. 0027, respectively. It was the result that the NH4^＋ -N from （NH4）2 SO4 was fixed within the soil. The increased amount of non-exchangeable NH4^＋ -N increased significantly for different soils, on which different vegetation types grew before the collection of soil samples, when incubated at 20 d （P=0.043 4）, but not significantly at 40 d and 60d （P=0. 7378 and 0. 5375）. The increased amount of non-exchangeable NH4^＋ -N in the soil, on which crop straw and nitrogen fertilizer had been incorporated for a long-term period, was larger than that of no addition, but it was not significantly different among these two fertilization models. Soil clay, total N and organic matter were positively correlated remarkably with the contents of non-exchangeable NH4^＋ -N, the increased amount of non-exchangeable NH4^＋ -N had no correlation with soil clay, whereas it had significantly positive correlation with total N and organic matter.