土壤氮素矿化过程中非交换铵态氮的变化

Change of Non-exchangeable Ammonium Nitrogen During Procession of Soil Organic Nitrogen Mineralization

采用室内通气和淹水培养 ,研究了培养过程中土壤非交换铵态氮的变化及其对有机氮矿化量和微生物体氮的影响。结果表明 ,淹水培养过程中产生的铵态氮会被粘土矿物固定 ,使供试土壤非交换铵态氮显著增加(30 .0～ 14 2 .4 μg·g-1) ,从而导致有机氮矿化量的测定结果偏低。经过长期间歇淋洗通气培养后 ,在供试的 2 0个土样中 ,有 4个土样的非交换铵态氮增加 ,16个土样的非交换铵态氮减少 ;与培养前相比 ,2 0个土样非交换铵态氮平均下降 2 8.8μg·g-1(P <0 .0 1) ,显然 ,在长期间歇淋洗通气培养中有一部分非交换铵态氮释放出来 ,成为淋洗液中的矿质氮 ,从而使土壤有机氮矿化量测定结果偏大 :如果不考虑培养前后非交换铵态氮变化 ,培养 2 6 2d后累积的有机氮矿化量为 116 .0 μg·g-1;如果考虑非交换铵态氮变化 ,则有机氮矿化量为 87.2 μg·g-1,相差 2 8.8μg·g-1(P<0 .0 1)。在测定土壤微生物体氮时 ,熏蒸后接种土壤经过淹水培养 ,与未熏蒸土壤相比 ,形成大量铵态氮 ,导致非交换铵态氮增加 ,供试的 15个土壤平均增加 2 2 .2 μg·g-1(P <0 .0 1) ,相当于 88.7μg·g-1的微生物体氮。因此 ,仅用淹水培养后熏蒸与不熏蒸土样K2 SO4浸取态铵态氮的差值计算微生物体氮 ,结果偏低。

Changes of soil non exchangeable nitrogen during the aerobic incubation and waterlogged incubation and their effects on the quantity of mineralization of soil organic nitrogen and microbial biomass nitrogen were studied. The results showed that NH 4 +-N produced during waterlogged incubation could be fixed by clay mineral, leading to increase of non exchangeable nitrogen, from 30.0 μg·g -1 to 142.4 μg·g -1 , and so that the mineralization quantity of organic nitrogen is lower than the actual quantity. After the long term interval leaching aerobic incubation, among the 20 soil samples examined, 4 soil samples' non exchangeable nitrogen increased, and the other 16 soil samples' decreased. Compared with the beginning of incubation the non exchangeable nitrogen of 20 soil samples decreased by 28.8 μg·g -1 on average ( P <0.01), and thus the quantity of mineralization of organic nitrogen was higher than the actual value. During the determination of soil microbial biomass nitrogen, because the killed micro rganisms in fumigation were intensely mineralized during waterlogged incubation compared with the soil that was not fumigated, and the former produced an large quantity of NH 4 +-N, and resulted the increase of non exchangeable nitrogen significantly, the non exchangeable nitrogen of 15 soil samples increased 22.2 μg·g -1 on average ( P <0.01), corresponding to 88.7 μg·g -1 microbial biomass nitrogen. To calculate the microbial biomass nitrogen by only using the N Flush of the K 2SO 4 extracting NH 4 +-N in fumigated and nonfumigated soil, the result was lower than the actual value.