Nitrous oxide emissions from cool-season pastures under managed grazing
Nitrous oxide emissions from cool-season pastures under managed grazing
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DOI：
10.1007/s10705-015-9685-6
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发表时间：
2015-02
影响因子：
3.1
通讯作者：
R. Jackson;L. Oates;W. Schacht;T. Klopfenstein;D. Undersander;M. Greenquist;M. Bell;C. Gratton
中科院分区：
文献类型：
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作者：
R. Jackson;L. Oates;W. Schacht;T. Klopfenstein;D. Undersander;M. Greenquist;M. Bell;C. Gratton
放牧牧场的高放牧密度可能会促进一氧化二氮（N2 O）从土壤中流失到大气中。然而，在北美冷季型牧场的N2 O通量的研究是缺乏的。我们进行了两个实验，其中测量的N2 O通量与重新采样（n = 100，10，000次迭代），这使我们能够生成一个经验分布的平均通量，以了解如何牧场管理策略可能会影响N2 O排放。在实验1中，N2 O通量估计在南部威斯康星州牧场轮牧，连续放牧，干草，没有农艺生产。在我们的研究农场，在轮牧下氧化亚氮通量显著为正[21.6（se = 10.3）μg m− 2 h −1]，但在其他三个处理或8个工作农场的轮牧围场下与零没有显著差异。在实验2中，我们测量了N2 O通量在内布拉斯加州东部之前，期间和之后两个旋转放牧事件下两个N-输入处理无机N肥和补充干酒糟和未施肥的控制。一氧化二氮的通量在降雨后的时期为正值（20-100 μg m− 2 h −1），但在其他方面与零没有显著差异。放牧后，N2 O排放量低于施肥或补充治疗的控制。这些实验表明，冷季牧场可以成为大气中N2 O的来源，但主要是在与大量降水相一致的放牧事件之后。然而，即使农场围场在不同的状态下从落叶中恢复，农场规模的排放量，虽然是偶发性的，可能是积极的，在年平均降水量以上。
High stocking densities on grazed pastures may promote nitrous oxide (N2O) loss from soil to the atmosphere. However, studies of N2O fluxes in cool-season pastures of North America are lacking. We performed two experiments in which measured N2O fluxes were bootstrapped with re-sampling (n = 100, with 10,000 iterations), which allowed us to generate an empirical distribution of mean fluxes to understand how pasture management strategies might affect N2O emissions. In Experiment 1, N2O fluxes were estimated in southern Wisconsin pastures under rotational grazing, continuous grazing, haymaking, and no agronomic production. Nitrous oxide fluxes were significantly positive under rotational grazing at our research farm [21.6 (se = 10.3) μg m−2h−1], but not significantly different than zero under the other three treatments or rotationally grazed paddocks across eight working farms. In Experiment 2, we measured N2O fluxes in eastern Nebraska before, during, and after two rotational grazing events under two N-input treatments—inorganic N fertilizer and supplemented dried distillers grains—and an unfertilized control. Nitrous oxide fluxes were positive (20–100 μg m−2h−1) in periods following rain, but otherwise not significantly different than zero. Post-grazing, N2O emissions were lower from the control than fertilized or supplemented treatments. These experiments show cool-season pastures can be a source of N2O to the atmosphere, but primarily following grazing events that coincide with significant precipitation. However, even though on-farm paddocks are in varying states of recovery from defoliation, farm scale emissions, although episodic, are likely to be positive in years with above average precipitation.