城市污泥堆肥中氮素在土壤中的矿化特征

Nitrogen Mineralization in Forest Soil Applied With Municipal Sludge Compost

采用室内好氧矿化培养实验方法，研究了城市污泥堆肥应用于林地土壤后其氮素的矿化特征，考察了环境因素对其矿化的影响，并通过与尿素对比，评价了污泥堆肥的供氮能力。结果表明，在8％～20％水分含量下，污泥堆肥的潜在可矿化氮量（N0）和一级反应速率常数（k0）均随水分含量升高先增加后降低，而尿素的N0和k0则随水分升高而增加。在10-30℃温度范围内，污泥堆肥的N0和k0均随温度升高而增加，而尿素的N0随温度升高先增加后降低，尿素的k0随温度升高而增加。对于净氮释放率，污泥堆肥随水分含量升高先增加后降低，随温度升高而增加；而尿素则随水分升高而增加，随温度升高没有明显变化。在同一施肥（以氮计）水平条件下，污泥堆肥和尿素的净氮释放率表现为尿素净氮释放率（93．67％～97．04％）〉污泥堆肥净氮释放率（67．93％-80．15％），污泥堆肥的肥效释放较尿素缓慢。污泥堆肥和尿素通过矿化作用释放出铵态氮，经硝化作用转化为硝态氮，在水分较高和温度较高时，更多的硝态氮在土壤中的累积，可能造成潜在环境风险。

An indoor experimental method of aerobic incubation was adopted to study the characteristics of nitrogen mineralization in soil of forestry land applied with municipal sludge compost （MSC） with an emphasis on the impacts of environmental factors on the mineralization. In addition, nitrogen supplying capacity of MSC was evaluated by comparison with that of urea. The experimental results suggested that when moisture in soil ranged between 8% and 20%, the content of potentially mineralizable nitrogen （No） and first-order rate constant （k0） of MSC at first increased and then decreased as moisture in soil increased, while for urea the situation was： No and k0 increased constantly with the increase of moisture in soil; when temperature ranged between 10 and 30 ℃, both No and k0 of MSC increased with the increase of temperature, while for urea, No was firstly increased and then decreased, and k0 increased constantly with the increase of temperature. Furthermore, the net nitrogen release rate was investigated regarding its relationship with moisture and temperature; the net nitrogen release rate from MSC （from 67.93% to 80.15%） were lower than those released from urea （93.67% to 97.04%） when equal nutrition （N amount） was added in soil but it had been showed that fertilizer in MSC released slower than that in urea. NH4＋-N could be released from the MSC and urea through biological mineralization, and then nitrified to NO3-, resulting in nitrate accumulation in soil, which would likely pose potential environmental risks.