Nitrous oxide (N₂O) is an overwhelming greenhouse gas and agricultural soils, particularly acidic soils, are the main source of its release to the atmosphere. To ameliorate acidic soil condition, liming materials are added as an amendment. However, the impact of liming materials has not been well addressed in terms of exploring the effect of soil pH change on N₂O emissions. In the present study, a soil with pH 5.35 was amended with liming materials (CaMg(CO₃)₂, CaCO₃, Ca(OH)₂ and CaO) to investigate their effects on N₂O emissions. The results indicate that application of liming materials reduced the magnitudes of N₂O emissions. The maximum reduction of soil N₂O emissions took place for Ca(OH)₂ treatment when compared to the other liming materials, and was related to increasing soil pH. Mineral N, dissolved organic C, and microbial biomass C were also influenced by liming materials, but the trend was inconsistent to the soil pH change. The results suggest that N₂O emission mitigation is more dependent on soil pH than C and N dynamics when comparing the different liming materials. Moreover, ameliorating soil acidity is a promising option to mitigate N₂O emissions from acidic soils.

The event scale method, employed for assessing changes in nitrogen (N) dynamics pre- and post-rain, provides insights into its transport to surface water systems. However, the relationships between N discharge in catchments dominated by different land uses and water quality remain unclear. This study quantified variations in key N components in ponds across forest, paddy field, and orchard catchments before and after six rainfall events. The results showed that nitrate (NO₃⁻-N) was the main N component in the ponds. Post-rainfall, N concentrations increased, with ammonium (NH₄⁺-N) and particulate nitrogen (PN) exhibiting significant elevations in agricultural ponds. Orchard catchments contributed the highest N load to the ponds, while forest catchments contributed the lowest. Following a heavy rainstorm event, total nitrogen (TN) loads in the ponds within forest, paddy field, and orchard catchments reached 6.68, 20.93, and 34.62 kg/ha, respectively. These loads were approximately three times higher than those observed after heavy rain events. The partial least squares structural equation model (PLS-SEM) identified that rainfall amount and changes in water volume were the dominant factors influencing N dynamics. Furthermore, the greater slopes of forest and orchard catchments promoted more N loss to the ponds post-rain. In paddy field catchments, larger catchment areas were associated with decreased N flux into the ponds, while larger pond surface areas minimized the variability in N concentration after rainfall events. In orchard catchment ponds, pond area was positively correlated with N concentrations and loads. This study elucidates the effects of rainfall characteristics and catchment heterogeneity on N dynamics in surface waters, offering valuable insights for developing pollution management strategies to mitigate rainfall-induced alterations.

Nitrogen application significantly affects microorganisms in agricultural ecosystems. However, it is still unclear how nitrogen application affects soil chemical properties and microbial communities in purple mudstone weathering products. In this study, a field soil column experiment was conducted in a typical purple soil area with four nitrogen fertilizer application gradients of 0 [CK], 280 [N1], 560 [N2], and 840 [N3] N kg ha⁻¹. Nitrogen addition decreased the bacterial chao1 value and increased the bacterial evenness index. For both α- and β-diversity, the effect of nitrogen addition on bacteria was much greater than that on fungi. Nitrogen addition significantly increased the relative abundance of Proteobacteria, Gemmatimonadetes, Bacteroidetes, and Ascomycota and decreased the relative abundance of Actinobacteria, Cyanobacteria, and Basidiomycota. Both pH and TC are the most important soil chemical properties influencing the bacterial and fungal communities. With the increases in the nitrogen application rate, the co-occurrence network complexity increased and then decreased. In summary, nitrogen fertilizer application could significantly change the soil chemical properties, microbial community diversity, composition, and co-occurrence network of purple mudstone weathering products. Among them, the N2 treatment (560 N kg∙ha⁻¹) can more effectively stimulate the soil nutrients, enhance microbial network complexity, and promote further weathering of purple mudstone.

Diatomite is useful in soil remediation and water purification. However, its impacts on methane (CH₄) and nitrous oxide (N₂O) emissions in paddy soils and the underlying mechanisms remain poorly understood. A pot experiment was set up with four treatments, including a non-amended control (CK), sole biochar (B), sole diatomite (D), and combined biochar–diatomite (BD) amendments, to compare their effects on CH₄ and N₂O emissions from paddy soil. Compared to CK, D and BD treatments reduced global warming potential (GWP) by 32.40% and 34.41%, respectively, significantly outperforming B treatment. All amendments reduced cumulative N₂O emissions by 50.0−62.3%, with no significant variations observed among the amended treatments. CH₄ was the primary contributor to GWP, and its emissions were most effectively reduced by diatomite. A random forest analysis found that the DOC/NO₃⁻-N ratio had a high relative influence on CH₄ emissions. B, D, and BD treatments significantly increased pmoA gene abundances by increasing redox potential and lowering the DOC/NO₃⁻-N ratio. B treatment significantly reduced mcrA gene abundances, whereas D treatment exhibited no significant effect. All amended treatments altered the methanogenic community; only D and BD affected the methanotrophic community. Overall, diatomite outcompetes biochar for reducing the GWP of rice cultivation because it more potently suppresses CH₄ emissions by improving soil aeration, favorably shifting microbial community structure and altering resource stoichiometry.