Ma Hongxiu, Sun Quan, Zhang Xiaojuan, Jiang Peng
College of Forestry and Prataculture, Ningxia University, Yinchuan, China.
Front Plant Sci. 2025 Jun 3;16:1598110. doi: 10.3389/fpls.2025.1598110. eCollection 2025.
Reducing emissions of the greenhouse gas nitrous oxide (NO) while improving forage yield and quality is essential for sustainable agriculture in the context of global warming. However, how to reduce NO emissions through water and nitrogen management in alfalfa planting is still unclear. In this two-year field experiment, the effects of three irrigation rates (W1, 375 mm; W2, 525 mm; W3, 675 mm) and five nitrogen (N) fertilizer application rates (N0, 0 kg N ha; N1, 75 kg N ha; N2, 150 kg N ha; N3, 225 kg N ha; N4, 300 kg N ha) on alfalfa yield, quality, resource use efficiency, and NO emissions were explored. The results showed that irrigation combined with N application resulted in greater NO emissions than irrigation alone. The cumulative NO emissions increased with the increase of irrigation rate, and the average maximum cumulative NO emissions of the W3 treatment (0.58 kg ha) increased by 94.14% and 57.38% compared with that of the W2 and W1 treatment, respectively. The cumulative NO emissions also increased with the increase of the N application rate, and the average cumulative NO emissions of the N4 treatment (0.69 kg ha) increased by 31.99%, 62.87%, 108%, and 173% compared with that of the N3, N2, N1, and N0 treatments, respectively. The variation of the average NO emission coefficient was similar to that of the cumulative NO emissions, and the W3 treatment (5.46) and N4 treatment (4.84) had the largest coefficients. Yield, crude protein, crop water productivity (WP), and NO emissions increased with the increase of N application rate, regardless of irrigation rate, with maxima occurring at N2 or N3 levels. These results suggest that the low NUE may be caused by the high cumulative NO emissions. Besides, the combination of the irrigation rate 525 mm and the N application rate 150-225 kg N ha could significantly increase alfalfa yield and crude protein content compared to other irrigation and nitrogen application treatments. However, further increasing irrigation and N rates failed to obtain further yield and crude protein increases, but led to NO emission increase and WP and NUE reductions. This may cause serious resource waste and environmental pollution.
在全球变暖背景下，减少温室气体一氧化二氮（N₂O）排放同时提高饲草产量和质量对可持续农业至关重要。然而，苜蓿种植中如何通过水分和氮素管理减少N₂O排放仍不清楚。在这项为期两年的田间试验中，研究了三种灌溉量（W1，375毫米；W2，525毫米；W3，675毫米）和五种氮肥施用量（N0，0千克氮/公顷；N1，75千克氮/公顷；N2，150千克氮/公顷；N3，225千克氮/公顷；N4，300千克氮/公顷）对苜蓿产量、质量、资源利用效率和N₂O排放的影响。结果表明，灌溉与施氮相结合导致的N₂O排放比单独灌溉更多。累积N₂O排放量随灌溉量增加而增加，W3处理的平均最大累积N₂O排放量（0.58千克/公顷）分别比W2和W1处理增加了94.14%和57.38%。累积N₂O排放量也随施氮量增加而增加，N4处理的平均累积N₂O排放量（0.69千克/公顷）分别比N3、N2、N1和N0处理增加了31.99%、62.87%、108%和173%。平均N₂O排放系数的变化与累积N₂O排放量相似，W3处理（5.46）和N4处理（4.84）的系数最大。无论灌溉量如何，产量、粗蛋白、作物水分生产率（WP）和N₂O排放均随施氮量增加而增加，在N2或N3水平达到最大值。这些结果表明，低氮利用效率可能是由于高累积N₂O排放量所致。此外，与其他灌溉和施氮处理相比，525毫米灌溉量与150 - 225千克氮/公顷施氮量的组合可显著提高苜蓿产量和粗蛋白含量。然而，进一步增加灌溉量和施氮量未能使产量和粗蛋白进一步增加，反而导致N₂O排放增加以及WP和氮利用效率降低。这可能会造成严重的资源浪费和环境污染。
