Landcare Research Ltd, Hamilton, New Zealand.
J Environ Qual. 2011 May-Jun;40(3):923-30. doi: 10.2134/jeq2010.0463.
A well-drained soil in N-fertilized dairy pasture was amended with particulate organic carbon (POC), either sawdust or coarse woody mulch, and sampled every 4 wk for a year to test the hypothesis that the addition of POC would increase denitrification activity by increasing the number of microsites where denitrification occurred. Overall mean denitrifying enzyme activity (DEA), on a gravimetric basis, was 100% greater for the woody mulch treatment and 50% greater for the sawdust treatment compared with controls, indicating the denitrifying potential of the soil was enhanced. Despite differences in DEA, no difference in denitrification rate, as measured by the acetylene block technique, was detected among treatments, with an average annual N loss of ∼22 kg N ha yr Soil water content overall was driving denitrification in this well-drained soil as regression of the natural log of volumetric soil water content (VWC) against denitrification rate was highly significant ( = 0.74, < 0.001). Addition of the amendments, however, had significant effects on the availability of both C and N. An additional 20 to 40 kg N ha was stored in POC-amended treatments as a result of increases in the microbial biomass. Basal respiration, as a measure of available C, was 400% greater than controls in the sawdust treatment and 250% greater than controls in the mulch. Net N mineralization, however, was significantly lower in the sawdust treatment, resulting in significantly lower nitrate N levels than in the control. We attribute the lack of measured response in denitrification rate to the high temporal variability in denitrification and suggest that diffusion of nitrate may ultimately have limited denitrification in the amended treatments. Our data indicate that manipulation of denitrification by addition of POC may be possible, particularly when nitrate levels are high, but quantifying differences in the rate of denitrification is difficult because of the temporal nature of the process (particularly the complex interaction of N availability and soil water content).
在施氮肥的奶牛牧场中，将颗粒状有机碳（POC）（木屑或粗木片）添加到排水良好的土壤中，并在一年中的每 4 周进行采样，以检验以下假设：添加 POC 将通过增加发生反硝化作用的微生境数量来增加反硝化活性。基于重量的总体平均反硝化酶活性（DEA），木质碎屑处理比对照处理高 100%，木屑处理高 50%，表明土壤的反硝化潜力增强。尽管 DEA 存在差异，但在乙炔阻断技术测量的反硝化速率方面，处理之间没有差异，平均每年 N 损失约为 22 kg N ha。土壤含水量是这种排水良好的土壤中反硝化作用的主要驱动因素，因为体积土壤含水量（VWC）的自然对数与反硝化速率的回归高度显著（= 0.74，< 0.001）。然而，添加改良剂对 C 和 N 的有效性都有显著影响。由于微生物生物量的增加，在添加 POC 的处理中，额外储存了 20 到 40 kg N ha。作为可用 C 的衡量标准，基础呼吸在木屑处理中比对照高 400%，在覆盖物中比对照高 250%。然而，净氮矿化作用在木屑处理中显著降低，导致硝酸盐氮水平显著低于对照。我们将反硝化速率测量中的无响应归因于反硝化的高时间变异性，并认为硝酸盐的扩散可能最终限制了改良处理中的反硝化。我们的数据表明，通过添加 POC 来控制反硝化是可能的，特别是在硝酸盐水平较高时，但由于该过程的时间性质（特别是 N 有效性和土壤含水量的复杂相互作用），量化反硝化速率的差异是困难的。
