Grazing and applications of nitrogen and phosphorus effects on herbage production and greenhouse gas emissions of pasture in an arid region

Abstract

To promote herbage nutritive yield under global warming, optimizing grazing and proper fertilizer application (nitrogen, N; phosphorus, P) are crucial for balancing herbage nutritive quality production and soil greenhouse gases (GHGs) emissions in the arid regions. We conducted a 3-year experiment in a sown grassland to determine the effects of N (0, 75, and 225 kg ha⁻¹) and P fertilizer (0, and 75 kg ha⁻¹) applications and grazing (grazed, and non-grazed) on soil GHGs emissions, herbage nutritive quality (crude protein, CP; dry matter digestibility, DMD; metabolizable energy, ME), and yield scale of global warming potential over different periods (early growing period, peak growing period, late growing period, and non-growing season) from 2020 to 2022. The results show that grazing had no significant effect on soil GHGs emissions. Moreover, fertilizer application significantly increased soil CH₄ uptake by 20.1 %, soil CO₂ emissions by 12.8 % and soil N₂O emissions by 59.1 %. Furthermore, the interaction of grazing and fertilizer application had an additive effect on soil CH₄ uptake, and an antagonistic effect on soil CO₂ emissions in early growing period. The results showed that grazing decreased herbage yield by 29.03 %, CP yield by 28.72 %, DMD yield by 35.4 %, and ME yield by 26.69 %, the fertilizer application increased herbage yield by 57.6 %, CP yield by 113.1 %, DMD yield by 62.2 % and ME yield by 46.3 %, respectively. In addition, the mean annual herbage, CP, DMD, and ME yield scale of GWP were 1.1 ∼ 7.5, 7.6 ∼ 65.4, 1.5 ∼ 15.7, 12.8 ∼ 84.3 t CO₂.eg t⁻¹ yield ha⁻¹, respectively, with the lowest value of the nutritive yield scale of global warming potential found at 225 kg N ha⁻¹ with 75 kg P ha⁻¹ with/without grazing. Moreover, the CP yield could well predict GWP over different periods. Overall, application of 225 kg N ha⁻¹ with 75 kg P ha⁻¹ was the appropriate management, which balanced the herbage nutritive quality yield and global warming potential in sown pasture in the arid regions.