Nitrogen (N) addition is an important nutrient strategy for alpine grassland in northwestern China to improve productivity for livestock needs. A field experiment was conducted in a semi-arid alpine grassland in northwestern China to investigate the effect of N addition rates on soil N₂O emissions over the growing seasons of 2017 and 2018. Treatments included six N addition rates (0, 10, 30, 60, 120, 240 kg N ha⁻¹ y⁻¹), which were applied before each growing season. The N₂O fluxes increased with N addition rates and showed different episodic changes between the two growing seasons. In 2017, the maximum N₂O flux rate occurred within 2 weeks following N addition. In 2018, however, the maximum N₂O flux rate occurred later in the growing season due to a heavy rainfall event. Growing season cumulative N₂O emissions ranged between 0.32 and 1.11 kg N ha⁻¹, and increased linearly with N addition rates. Increasing N addition rates over 60 kg N ha⁻¹ yr⁻¹ did not further increase plant above-ground biomass. The inter-annual variability of N₂O flux suggests the importance of soil moisture in affecting N₂O emissions. It is particularly important to avoid over-applying N nutrients beyond plant needs to reduce its negative effect on the environment while maintaining livestock productivity. The N₂O flux rate increased with soil dissolved organic carbon (DOC) and soil pH. These results suggest the optimal N addition rate to the livestock grassland in this region should be 60 kg N ha⁻¹ yr⁻¹.

Few studies have investigated how the reclamation of the desert to cropland affects soil nitrous oxide (N₂O) emissions. A study site was initiated in 2005 at the southern Taklimakan Desert by establishing four fields along the desert−oasis ecotone. Three fields were reclaimed as croplands for continuous cotton (Gossypium hirsutum L.) production and received (1) high, (2) low, and (3) no fertilizer inputs and the fourth field remained as a native desert. Static-chamber monitoring of N₂O flux was conducted from April 2019 to March 2021. N₂O emissions occurred in cropland mainly after drip fertigation during the growing season. The two−year N₂O emissions in the desert, no fertilizer, low fertilizer, and high fertilizer were 248, 670, 2232, and 3615 g N ha⁻¹, respectively. The native desert was a weak source of N₂O emissions, with the non−growing season emissions accounting for 66% of the annual emissions. N₂O emissions from farmland mainly occurred over the growing season, accounting for 73−98% of the total annual emissions. The N₂O flux was positively related to soil NO₃⁻−N concentration and soil water−filled pore space (WFPS), highlighting the importance of soil N availability and moisture in affecting N₂O emissions in extremely arid areas. Our results demonstrate that land reclamation from the desert to cropland significantly increased N₂O emissions due to high nutrient inputs. Thus, appropriate fertilizer management in the reclaimed land is essential for maintaining yield, improving soil quality, and reducing N₂O emissions for continuous cotton production.