Agricultural practices such as repeated fertilization impact carbon (C), nitrogen (N) and phosphorus (P) cycling and their relationships in the plant–soil continuum, which could have important implications for the magnitude of greenhouse gas emissions. However, little is known about the effect of C and N additions under contrasting soil P availability status on nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions. In this study, we conducted a field-based experiment that investigated the impact of long-term (23 years) P management (no (P0, 0 kg P ha⁻¹), low (P15, 15 kg P ha⁻¹) and high (P45, 45 kg P ha⁻¹) P inputs) on N₂O and CO₂ emissions following two C + N application events in two managed grassland ecosystems with loam and sandy loam soils. The magnitude of fluxes varied between the soil P availability levels. Cumulative N₂O emission was significantly higher in P0 soils (1.08 ± 0.09 g N₂O-N m⁻²) than P45 soils (0.63 ± 0.03 g N₂O-N m⁻²), with the loam soil (1.04 ± 0.04 g N₂O-N m⁻²) producing significantly higher emissions than the sandy loam soil (0.88 ± 0.05 g N₂O-N m⁻²). We conclude that P-limitation stimulates N₂O emissions, whereas P-enrichment promotes soil respiration in these temperate grassland sites. Our findings inform effective nutrient management strategies underpinning optimized use of N and P inputs to agricultural soils as mitigation measures for both food security and reducing greenhouse gas emissions.

Given their increasing trend in Europe, an understanding of the role that flooding events play in carbon (C) and nitrogen (N) cycling and greenhouse gas (GHG) emissions will be important for improved assessments of local and regional GHG budgets. This study presents the results of an analysis of the CO₂ and N₂O fluxes from a coastal grassland ecosystem affected by episodic flooding that was of either a relatively short (SFS) or long (LFS) duration. Compared to the SFS, the annual CO₂ and N₂O emissions were 1.4 and 1.3 times higher at the LFS, respectively. Mean CO₂ emissions during the period of standing water were 144 ± 18.18 and 111 ± 9.51 mg CO₂–C m⁻² h⁻¹, respectively, for the LFS and SFS sites. During the growing season, when there was no standing water, the CO₂ emissions were significantly larger from the LFS (244 ± 24.88 mg CO₂–C m⁻² h⁻¹) than the SFS (183 ± 14.90 mg CO₂–C m⁻² h⁻¹). Fluxes of N₂O ranged from −0.37 to 0.65 mg N₂O–N m⁻² h⁻¹ at the LFS and from −0.50 to 0.55 mg N₂O–N m⁻² h⁻¹ at the SFS, with the larger emissions associated with the presence of standing water at the LFS but during the growing season at the SFS. Overall, soil temperature and moisture were identified as the main drivers of the seasonal changes in CO₂ fluxes, but neither adequately explained the variations in N₂O fluxes. Analysis of total C, N, microbial biomass and Q₁₀ values indicated that the higher CO₂ emissions from the LFS were linked to the flooding-associated influx of nutrients and alterations in soil microbial populations. These results demonstrate that annual CO₂ and N₂O emissions can be higher in longer-term flooded sites that receive significant amounts of nutrients, although this may depend on the restriction of diffusional limitations due to the presence of standing water to periods of the year when the potential for gaseous emissions are low.

Nitrogen fertiliser application represents the largest anthropogenic source of nitrous oxide (N₂O) emissions, and the magnitude of these emissions is dependent on the type of fertilisers applied in the agroecosystems. Despite N-P-K compound fertilisers being commonly used in agricultural soils, a lack of information exists regarding their effects on N₂O emissions. This study aims at examining the effects of different commonly used N-P-K compound fertiliser formulations with contrasting nitrate to ammonium ratios (0.05 to 0.88) on N₂O emissions, yield, and nitrogen use efficiency (NUE) in temperate grassland and to compare these variables with common straight N fertilisers. Compound fertilisers with varying NPK inclusion rates (18-6-12, 10-10-20, 24-2.2-4.5, and 27-2.5-5), and calcium ammonium nitrate (CAN) and urea + N-(n-butyl) thiophosphoric triamide (NBPT) were applied at 80 kg N ha⁻¹ to experimental plots in managed grassland on two occasions in a growing season. Fluxes of N₂O during the experiment period, yield and NUE following two harvests were measured. The cumulative N₂O emission from urea + NBPT, 18-6-12, 10-10-20, and 24-2.2-4.5 treatments were significantly reduced by 44%, 43%, 37%, and 31% compared with CAN treatment under conducive soil moisture condition. Under the same soil condition, 18-6-12 and 10-10-20 treatments showed higher yield, N uptake, and NUE although did not significantly differ from the other fertiliser treatments. Our results suggest that ammonium-based compound fertilisers have a potential to reduce N₂O emissions while maintaining yields. Further long-term study is needed to capture the full magnitude of variations in N₂O emissions, including ammonia (NH₃) volatilization from nitrate and ammonium-based compound fertiliser applications from multiple soil types and under different climatic conditions.

Given their increasing trend in Europe, an understanding of the role that flooding events play in carbon and nitrogen cycling and greenhouse gas (GHG) emissions will be important for improved assessments of local and regional GHG budgets. This study presents the results of an analysis of the CO₂ and N₂O fluxes from a coastal grassland ecosystem affected by episodic flooding that was of either a relatively short or long duration (SFS and LFS sites, respectively). Compared to the SFS, the annual CO₂ and N₂O emissions were 1.4 and 1.3 times higher at the LFS, respectively. Mean CO₂ emissions during the period of standing water were 144 ± 18.18 and 111 ± 9.51 mg CO₂-C m⁻² h⁻¹, respectively, for the LFS and SFS sites. During the growing season, when there was no standing water, the CO₂ emissions were significantly larger from the LFS (244 ± 24.88 mg CO₂-C m⁻² h⁻¹) than the SFS (183 ± 14.90 mg CO₂-C m⁻² h⁻¹). Fluxes of N₂O ranged from −0.37 to 0.65 mg N₂O-N m⁻² h⁻¹ at the LFS and from −0.50 to 0.55 mg N₂O-N m⁻² h⁻¹ at the SFS, with the larger emissions associated with the presence of standing water at the LFS and during the growing season at the SFS. Overall, soil temperature and moisture content were identified as the main drivers of the seasonal changes in CO₂ fluxes, but neither adequately explained the variations in N₂O fluxes. Analysis of total Carbon (C), Nitrogen (N), microbial biomass and Q₁₀ values, indicated that the higher CO₂ emissions from the LFS were linked to the flooding-associated influx of nutrients and alterations in soil microbial populations. These results demonstrate that annual CO₂ and N₂O emissions can be higher in longer-term flooded sites that receive significant amounts of nutrients and where diffusional limitations due to the presence of standing water is limited to periods of the year when the temperatures are lowest.