Combining field incubation with nitrogen-15 labelling to examine nitrogen transformations in low to high intensity grassland management systems
Combining field incubation with nitrogen-15 labelling to examine nitrogen transformations in low to high intensity grassland management systems
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DOI：
10.1007/s003740050028
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发表时间：
2000-03
影响因子：
6.5
通讯作者：
D. Hatch;S. Jarvis;R. Parkinson;R. Lovell
中科院分区：
文献类型：
--
作者：
D. Hatch;S. Jarvis;R. Parkinson;R. Lovell
15N同位素稀释法与田间培养技术相结合，提供了三个长期畜群的氮周转毛率和净率的同时测量：未施肥(Z)，或作为三叶草的固氮(C)，或作为200 公斤化肥N ha-1年(F)。利用多点土壤注射器在4天的培养时间内测量土壤矿化/固定、周转和硝化作用，实现了土壤微区均匀的氮素富集化。净矿化速率在0.6~2.9 μg Ng-1day-1之间，三个处理的净矿化速率约为总矿化速率的一半。硝化速率在1.0~1.6 μg Ng~(-1)·d~(-1)之间。在F处理中，NH_4~+-N和NO_3~--N的周转周期分别为2天和4天，而在N限制处理(C和Z)中，NO_3~--N的周转速度比NH_4~+-N快一倍。因此，在C和Z处理中，有效氮得到了更有效的循环利用，而在F处理中，保持了更大的N池大小，这将更容易发生渗漏。增加的15N大部分被回收到土壤微生物量中，这意味着N的汇是植物生物量的4-5 倍。虽然C处理的土壤微生物量显著低于纯草处理，但微生物活性没有差异。总硝化速率沿氮素输入强度(即Z<；C<；F)的梯度增加，添加硝化抑制剂(C2H2)有增加微生物固定化的趋势，但不影响植物对N的吸收。在这项研究中，结合不同的技术来验证净化率的价值被证明，并且改进的土壤15N标记方法使得能够在自然田间条件下从相对未受干扰的土壤中获得测量结果。
The15N isotope dilution method was combined with a field incubation technique to provide simultaneous measurements of gross and net rates of N turnover in three long-term swards: unfertilized (Z) or receiving N either from N fixation as clover (C), or as 200 kg fertilizer N ha–1year–1(F). Uniform N enrichment of soil microplots was achieved with a multi-point soil injector to measure mineralization/immobilization turnover and nitrification over a 4-day incubation. Net rates of mineralization ranged between 0.6 and 2.9 μg N g–1day–1and in all three treatments were approximately half the gross rates. Nitrification rates (gross) were between 1.0 and 1.6 μg N g–1day–1. In the F treatment, the turnover of NH4+-N and NO3–-N pools was on a 2- and 4-day cycle, respectively, whereas in the N-limited treatments (C and Z) turnover rates were faster, with the NO3–-N pools turning over twice as fast as the NH4+-N pools. Therefore, available N was recycled more efficiently in the C and Z treatments, whereas in the F treatment a higher N pool size was maintained which would be more vulnerable to leakage. A large proportion of the added15N was recovered in the soil microbial biomass (SMB), which represented a 4–5 times larger sink for N than the plant biomass. Although the C treatment had a significantly lower SMB than the grass-only treatments, there were no differences in microbial activity. Gross rates of nitrification increased along the gradient of N input intensity (i.e. Z<C<F), and the addition of a nitrification inhibitor (C2H2) tended to increase microbial immobilization, but did not influence plant N uptake. In this study, the value of combining different techniques to verify net rates was demonstrated and the improved methodology for15N labelling of soil enabled measurements to be obtained from relatively undisturbed soil under natural field conditions.