Ammonia (NH₃) volatilized from agricultural production and its secondary aerosols contribute greatly to air pollution. Different long-term crop straw management practices may significantly affect the soil fertility and soil nitrogen cycle, however, the effect on NH₃ volatilization has not been well studied. Therefore, a one-year field experiment was conducted to evaluate the effect of straw incorporation on NH₃ volatilization from subtropical calcareous agricultural soil from a longterm perspective, including four treatments: synthetic fertilizer (CK); synthetic fertilizer incorporation with 100% or 50% of the previous season’s crop straw (SI1 and SI2, respectively); and synthetic fertilizer incorporation with 50% burned crop straw (SI2B). Soil NH₃ volatilizations were monitored through a wheat–maize rotation year by using a dynamic chamber method. The results demonstrated that NH₃ volatilization primarily occurred within 38 days and 7–10 days following nitrogen fertilization events for the wheat and maize seasons, respectively. Different crop straw management practices mainly impacted the NH₃ flux of the basal fertilization rather than the topdressing fertilization; long-term crop straw incorporation effectively lowered NH₃ loss (35.1% for SI1 and 16.1% for SI2 compared to CK; and the inhibiting effect increased with increasing straw amount, possibly contributed by the high straw carbon/nitrogen ratio, and enhanced microbial activity, which contributed to inorganic nitrogen immobilization and lower ammonium content in the topsoil. However, SI2B significantly increased (29.9%) the annual NH₃ flux compared with SI2, indicating that long-term 100% straw incorporation could be a promising straw management practice for mitigating NH₃ loss and increasing soil fertility.

Adoption of crop residue amendments has been increasingly recommended as an effective management practice for mitigating greenhouse gas emissions while enhancing soil fertility, thereby increasing crop production. However, the effect of biochar and straw on nitrous oxide (N₂O) and methane (CH₄) emissions in soils of differing pH remains poorly understood. Three treatments (control (i.e., no amendment), maize straw, and biochar derived from maize straw) were therefore established separately in soils with different pH levels, classified as follows: acidic, neutral, and alkaline. N₂O and CH₄ were investigated using a static chamber–gas chromatography system during 57 days of a mesocosm study. The results showed that cumulative N₂O emissions were significantly higher in acidic soils than in other experimental soils, with the values ranging from 7.48 to 11.3 kg N ha⁻¹, while CH₄ fluxes ranged from 0.060 to 0.089 kg C ha⁻¹, with inconclusive results. However, a weak negative correlation was observed between log N₂O and log NO₃-N in acidic soil with either biochar or straw, while the same parameters with CH₄ showed a moderate negative correlation, suggesting a likelihood that these amendments could mitigate GHGs as a result of the NO₃-N increase in acidic soils. It is also possible, given the alkaline nature of the biochar, that incorporation had a significant buffer effect on soil acidity, effectively increasing soil pH by >0.5 pH units. Our findings suggest that for the rates of application for biochar and straw used in this study, the magnitude of reductions in the emissions of N₂O and CH₄ are dependent in part on initial soil pH.