Methane pulse spray and irrigation promote seed germination and seedling growth of common vetch.

Background: Grazing livestock emits methane through rumen intestinal activity, however, its impact on plant growth in grassland while grazing still has not been explored in detail. Therefore, the study examined the effects of methane pulse spray (MPS), according to grazing intensity, at four grazing intensities (0, 3.6, 5.0, and 6.5 sheep·hm^- 2 yr^- 1) on seed germination and seedling growth of common vetch (Vicia sativa), while two irrigation rates (35 and 53 ml d^- 1) were employed to simulate the precipitation.

Results: The study revealed significant interactions between MPS and irrigation rate on seed germination and seedling growth parameters. Under moderate MPS intensities (0.74 and 1.04 mol m^- 2), seed germination rate, potential, index, and vigor index improved, especially at higher irrigation rates (53 ml d^- 1). Conversely, excessive MPS (1.33 mol m^- 2) inhibited particularly at the germination rate and growth,. The seedling growth dynamics fitted a logistic model, with MPS advancing the rapid growth phase and increasing maximum growth rates.

Conclusions: This study demonstrates that low to moderate levels of MPS from ruminants can promote seed germination and seedling growth of common vetch, while excessive MPS inhibits these processes. Irrigation enhances plant sensitivity to MPS, with wetter conditions (620 mm yr^- 1) facilitating a more pronounced response. The findings introduce a new model elucidating plant responses to external perturbations, which can inform grazing management strategies in diverse ecosystems. In wetter regions, moderate grazing intensities may leverage MPS benefits, while arid regions require careful grazing regulation to maintain grassland-livestock balance.