Interaction of straw amendment and soil NO3− content controls fungal denitrification and denitrification product stoichiometry in a sandy soil
Interaction of straw amendment and soil NO3− content controls fungal denitrification and denitrification product stoichiometry in a sandy soil
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DOI：
10.1016/j.soilbio.2018.09.005
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发表时间：
2018-11
影响因子：
9.7
通讯作者：
M. Senbayram;R. Well;R. Bol;D. Chadwick;David L. Jones;Di Wu
中科院分区：
文献类型：
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作者：
M. Senbayram;R. Well;R. Bol;D. Chadwick;David L. Jones;Di Wu
农作物残茬的归还对于保持甚至提高土壤肥力至关重要。然而，施用量对反硝化及其相关的气态氮排放的影响还没有完全了解。我们进行了一个完全自动化的连续流培养实验，使用氦/氧气氛超过30天，以检查玉米秸秆施用率的影响：i）反硝化速率，ii）反硝化产物的化学计量N2 O/（N2 O +N2），和iii）真菌反硝化N2 O通量的贡献。使用过筛的、重新包装的桑迪质地土壤建立了五个处理：i）未改良的对照，ii）仅施用硝酸盐，iii）低比例的秸秆+硝酸盐，iv）中等比例的秸秆+硝酸盐，和iv）高比例的秸秆+硝酸盐（n = 3）。我们同时测量了NO，N2 O以及直接N2排放量，并使用N2 O 15-N的网站偏好签名的土壤排放N2 O区分N2 O生产真菌和细菌反硝化。独特的是，在整个培养过程中也进行了土壤NO3−测量。在试验初期（0-13 d），N2 O的排放量随秸秆还田量的增加而几乎呈线性增加，但几乎不产生N2 O。秸秆还田量与N2 O排放量呈负相关，与后期（13-30 d）N2排放量呈正相关。在所有处理中，土壤NO3−含量被确定为负责从N2 O产生到N2 O减少的转变的主要因素。秸秆还田立即降低了来自细菌反硝化的N2 O比例，这意味着更多的N2 O排放来自真菌（对照组为18 ± 0.7%，高秸秆量处理组在前13天内高达40 ± 3.0%）。然而，当土壤NO3−含量下降到<40 mg NO3−-N kg− 1土壤时，在中等秸秆量处理中产生的N2 O的N2 O 15 N位点偏好值在实验开始后15天显示出急剧下降的趋势，从而表明N2 O明显转向更占主导地位的细菌源。我们的研究突出了土壤NO3−动力学，作物残留物掺入，真菌反硝化和N2 O/（N2 O + N2）比之间的复杂相互关系。总体而言，我们发现，作物秸秆施用对土壤N2 O和N2排放的影响主要取决于土壤NO3−含量，因为NO3−是反硝化的N2 O/（N2 O + N2）产物比的主要调节剂。此外，秸秆残体的施用增强了真菌反硝化作用，但只有当土壤NO3−含量足以为反硝化菌提供足够的电子受体时。
The return of agricultural crop residues are vital to maintain or even enhance soil fertility. However, the influence of application rate of crop residues on denitrification and its related gaseous N emissions is not fully understood. We conducted a fully robotized continuous flow incubation experiment using a Helium/Oxygen atmosphere over 30 days to examine the effect of maize straw application rate on: i) the rate of denitrification, ii) denitrification product stoichiometry N2O/(N2O+N2), and iii) the contribution of fungal denitrification to N2O fluxes. Five treatments were established using sieved, repacked sandy textured soil; i) non-amended control, ii) nitrate only, iii) low rate of straw + nitrate, iv) medium rate of straw + nitrate, and iv) high rate of straw + nitrate (n = 3). We simultaneously measured NO, N2O as well as direct N2emissions and used the N2O15N site preference signatures of soil-emitted N2O to distinguish N2O production from fungal and bacterial denitrification. Uniquely, soil NO3−measurements were also made throughout the incubation. Emissions of N2O during the initial phase of the experiment (0–13 days) increased almost linearly with increasing rate of straw incorporation and with (almost) no N2production. However, the rate of straw amendment was negatively correlated with N2O, but positively correlated with N2fluxes later in the experimental period (13–30 days). Soil NO3−content, in all treatments, was identified as the main factor responsible for the shift from N2O production to N2O reduction. Straw amendment immediately lowered the proportion of N2O from bacterial denitrification, thus implying that more of the N2O emitted was derived from fungi (18 ± 0.7% in control and up to 40 ± 3.0% in high straw treatments during the first 13 days). However, after day 15 when soil NO3−content decreased to <40 mg NO3−-N kg−1soil, the N2O15N site preference values of the N2O produced in the medium straw rate treatment showed a sharp declining trend 15 days after onset of experiment thereby indicating a clear shift towards a more dominant bacterial source of N2O. Our study singularly highlights the complex interrelationship between soil NO3−kinetics, crop residue incorporation, fungal denitrification and N2O/(N2O + N2) ratio. Overall we found that the effect of crop residue applications on soil N2O and N2emissions depends mainly on soil NO3−content, as NO3−was the primary regulator of the N2O/(N2O + N2) product ratio of denitrification. Furthermore, the application of straw residue enhanced fungal denitrification, but only when the soil NO3−content was sufficient to supply enough electron acceptors to the denitrifiers.