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为了探明盐渍化土壤中尿素N的转化特征,通过室内模拟培养试验研究盐分和施氮量对新疆灰漠土尿素N转化及土壤酶活性的影响。结果表明:尿素N转化受土壤盐度和尿素施用量的影响显著。土壤铵态氮含量随尿素用量和土壤盐度增加而增加,施用尿素可明显提高土壤pH值,促进脲酶活性,加速尿素水解。不施氮肥土壤脲酶活性随土壤盐度增加而显著降低,施氮肥(尿素)土壤,低盐度对脲酶活性无影响,高盐度反而促进了脲酶活性。硝化作用受土壤盐度与施氮量交互作用的影响显著,尿素施用量越大,土壤盐度对硝化作用的抑制越强烈。土壤盐度对硝酸还原酶活性的影响较小,但对亚硝酸还原酶活性有明显的抑制作用。因此,盐度过高以及施用尿素引起的pH值增加可能会导致盐渍土壤中氮肥氨挥发损失增加。
In order to find out the transformation characteristics of urea N in salinized soil, the effects of salt and nitrogen rates on urea N conversion and soil enzyme activities in desert ash soil were studied through laboratory simulated cultivation experiments. The results showed that urea N conversion was significantly affected by soil salinity and urea application. The content of ammonium nitrogen in soil increased with the increase of urea dosage and soil salinity. The application of urea could obviously increase the soil pH, promote the activity of urease and accelerate the hydrolysis of urea. Soil urease activity decreased with the increase of soil salinity without applying nitrogen fertilizer. Soil nitrogen and urea had no effect on urease activity, while high salinity promoted urease activity. Nitrification was significantly affected by the interaction between soil salinity and nitrogen application rate. The greater the urea application, the greater the inhibition of soil salinity on nitrification. Soil salinity had little effect on nitrate reductase activity but significantly inhibited nitrite reductase activity. Therefore, excessive salinity and increased pH caused by the application of urea may result in increased loss of nitrogenous ammonia volatilization in saline soils.