University of Southern Queensland, Toowoomba, 4350, Queensland, Australia.
University of Southern Queensland, Toowoomba, 4350, Queensland, Australia.
J Environ Manage. 2019 Oct 15;248:109278. doi: 10.1016/j.jenvman.2019.109278. Epub 2019 Jul 20.
Reducing nitrous oxide (NO) emissions from agriculture soils is crucial, as it accounts for 5.6-6.8% of global anthropogenic emissions. This study aims to understand the interaction among climate, soil nitrogen (N) and applied N on NO emissions from the irrigated cotton farming system and its implications on farm economics. We conducted simulations for 116 years (1900-2015) and assessed the effect of different N-fertiliser application rates, initial soil nitrate (NO) N levels and rainfall conditions on NO emissions, NO emission factors (EFs) and financial returns (with and without NO costs). Results showed the following. 1) The proportional impact of higher N fertiliser rates on soil NO emissions was greater when initial soil N level was lower (5 mg NO kg) than higher (35 mg NO kg). However, the volume of impact was greater under higher initial soil N levels. 2) The relationship between N fertiliser rates and the EFs (range 0.03-7.2%) was not linear but bell-shaped. 3) Fertiliser N requirements increased with rainfall and decreased with initial soil N. Accordingly, the cotton returns for the driest rainfall condition (<10th percentile) were maximum at 300, 250 and 150 kg N ha for initial soil N of 5, 20 and 35 mg NO kg. For the wettest rainfall condition (>90th percentile), these rates were 50 kg ha higher across the initial soil N conditions. Any additional application of N-fertiliser above these rates was counterproductive. 4) Inclusion of NO cost into farm economics reduced the annual returns by up to $39 ha, but the optimal fertiliser application rates remain the same. 5) Optimising N fertiliser rates to soil N and rainfall conditions increased the annual returns by up to $303 ha, with a further increase of $15 ha from fertiliser use efficiency when the Australian Government incentives under the $2.55 billion dollar Emission Reduction Fund program was considered. These findings suggest that N-fertiliser application rates and NO emission mitigation strategies need further refinements specific to prevailing soil and climate variabilities.
减少农业土壤中的一氧化二氮（NO）排放至关重要，因为它占人为排放的全球排放量的 5.6-6.8%。本研究旨在了解气候、土壤氮（N）和施氮之间的相互作用对灌溉棉花种植系统中 NO 排放的影响及其对农场经济的影响。我们进行了 116 年（1900-2015 年）的模拟，并评估了不同氮肥施用量、初始土壤硝酸盐（NO）N 水平和降雨条件对 NO 排放、NO 排放因子（EF）和经济回报（有和没有 NO 成本）的影响。结果表明：1）当初始土壤 N 水平较低（5mgNOkg）时，较高的氮肥施用量对土壤 NO 排放的比例影响大于初始土壤 N 水平较高（35mgNOkg）时。然而，在较高的初始土壤 N 水平下，影响的程度更大。2）氮肥施用量与 EF（范围 0.03-7.2%）之间的关系不是线性的，而是钟形的。3）随着降雨量的增加和初始土壤 N 的减少，对氮肥的需求增加。因此，在降雨量最低的条件（<10%分位数）下，对于初始土壤 N 为 5、20 和 35mgNOkg 的棉花回报分别在 300、250 和 150kgNha 时达到最大值。对于降雨量最大的条件（>90%分位数），在所有初始土壤 N 条件下，这一比例高出 50kgNha。任何超过这些水平的氮肥的额外应用都是适得其反的。4）将 NO 成本纳入农场经济减少了高达 39 美元/公顷的年度收益，但最佳施肥水平保持不变。5）根据澳大利亚政府在 25.5 亿美元减排基金计划下的激励措施，通过优化氮肥施用量到土壤 N 和降雨条件，使年度收益增加了高达 303 美元/公顷，再加上从肥料利用效率上增加了 15 美元/公顷。这些发现表明，氮肥施用量和 NO 减排策略需要进一步细化，以适应当前的土壤和气候变异性。
