UCD School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland; UCD Earth Institute, University College Dublin, Belfield, Dublin 4, Ireland; Teagasc, Environmental Research Center, Johnstown Castle, Wexford, Ireland.
Teagasc, Environmental Research Center, Johnstown Castle, Wexford, Ireland.
Sci Total Environ. 2020 Jun 20;722:137780. doi: 10.1016/j.scitotenv.2020.137780. Epub 2020 Mar 6.
Increased emissions of NO, a potent greenhouse gas (GHG), from agricultural soils is a major concern for the sustainability of grassland agriculture. Emissions of NO are closely associated with the rates and forms of N fertilisers applied as well as prevailing weather and soil conditions. Evidence suggests that multispecies swards require less fertiliser N input, and may cycle N differently, thus reducing N loss to the environment. This study used a restricted simplex-centroid experimental design to investigate NO emissions and soil N cycling following application of urea-N (40 kg N ha) to eight experimental swards (7.8 m) with differing proportions of three plant functional groups (grass, legume, herb) represented by perennial ryegrass (PRG, Lolium perenne), white clover (WC, Trifolium repens) and ribwort plantain (PLAN, Plantago lanceolata), respectively. Swards were maintained under two contrasting soil moisture conditions to examine the balance between nitrification and denitrification. Two NO peaks coincided with fertiliser application and heavy rainfall events; 13.4 and 17.7 g NO-N ha day (ambient soil moisture) and 39.8 and 86.9 g NO-N ha day (wet soil moisture). Overall, cumulative NO emissions post-fertiliser application were higher under wet soil conditions. Increasing legume (WC) proportions from 0% to 60% in multispecies swards resulted in model predicted NO emissions increasing from 22.3 to 96.2 g NO-N ha (ambient soil conditions) and from 59.0 to 219.3 g NO-N ha (wet soil conditions), after a uniform N application rate. Soil N dynamics support denitrification as the dominant source of NO especially under wet soil conditions. Significant interactions of PRG or WC with PLAN on soil mineral N concentrations indicated that multispecies swards containing PLAN potentially inhibit nitrification and could be a useful mitigation strategy for N loss to the environment from grassland agriculture.
农业土壤中一氧化二氮（NO）排放的增加是草原农业可持续性的主要关注点，因为一氧化二氮是一种强有力的温室气体（GHG）。NO 的排放与所施用的氮肥的速率和形式以及当时的天气和土壤条件密切相关。有证据表明，多物种草地需要较少的肥料氮投入，并且可能以不同的方式循环氮，从而减少氮向环境的损失。本研究使用受限单纯形-重心实验设计，调查了在八种不同植物功能群（草、豆科植物、草本植物）比例的实验草地（7.8 米）上施尿素氮（40kgN/公顷）后 NO 排放和土壤氮循环，这些草地分别由黑麦草（Lolium perenne）、白三叶草（Trifolium repens）和车前草（Plantago lanceolata）代表。在两种不同的土壤水分条件下维持草地，以检查硝化和反硝化之间的平衡。两次 NO 峰值与施肥和强降雨事件同时发生；在环境土壤水分条件下，分别为 13.4 和 17.7gNO-N/公顷/天，在湿润土壤水分条件下，分别为 39.8 和 86.9gNO-N/公顷/天。总的来说，在湿润土壤条件下，施肥后累积的 NO 排放量更高。在多物种草地中，豆科植物（WC）比例从 0%增加到 60%，模型预测的 NO 排放量从 22.3 增加到 96.2gNO-N/公顷（环境土壤条件），从 59.0 增加到 219.3gNO-N/公顷（湿润土壤条件），在统一的氮施用量下。土壤氮动态表明，反硝化作用是 NO 的主要来源，特别是在湿润土壤条件下。PRG 或 WC 与 PLAN 对土壤矿质氮浓度的显著相互作用表明，含有 PLAN 的多物种草地可能抑制硝化作用，并且可能是减少草原农业向环境中氮损失的有用缓解策略。
