Biochar application has the potential for mitigating N₂O emissions from agricultural soils and has been suggested as a management practice to ameliorate soil fertility and increase crop productivity. Nevertheless, the influence of biochar addition on N₂O emissions from soils with different pH levels is not yet clear, which results in a poor understanding of the mechanisms regarding biochar application to soil N₂O mitigation. A 40-day incubation experiment was carried out in the present study to investigate the impact of biochar on N₂O emissions from soils with different natural pH. Four treatments (control, nitrogen fertilizer application, biochar amendment, and N plus biochar amendment) were set up separately in soils with three different natural pH levels (acidic vegetable soil, neutral rice soil, and alkaline soil). Our results showed that adding biochar significantly decreased N₂O emissions by 20.8% and 47.6% in acidic vegetable soil for both N and no N addition treatments, respectively. For neutral and alkaline soils, the reduction of N₂O emissions by biochar amendment was only significant for N addition treatments in alkaline soil. Soil pH and NO₃⁻-N concentration were significantly affected by biochar amendment (soil pH increased by 1.43–1.56, 0.57–0.70, and 0.29–0.37 units for acidic vegetable soil, neutral rice soil, and alkaline soil, respectively). Thus, biochar amendment could be used as an effective management practice for mitigating N₂O emissions from acidic and alkaline soils.

This study aimed to explore the effects of straw compost with different proportions as replacement to chemical fertilizer on soil microorganisms as well as rice growth yield and quality. The rice variety Quan9you 063 in Fengyang, Anhui province was employed as the research subject. Four experimental treatments were set: local conventional fertilization as a control (CK) and compost substituting chemical fertilizer at 10% (T1), 20% (T2), and 30% (T3) to investigate the effects of straw composting. Our findings revealed that T1 treatment had the best rice yield-increasing effect (p < 0.05). Compared with CK, the rice yield, grain number per panicle, and rice polishing rate increased by 6.43%, 21.60%, and 0.47%, respectively; the chalkiness and chalky grain rate decreased by 25.77% and 55.76%, respectively. The T1 treatment achieved significantly higher relative abundance of β-Proteobacteria, Sideroxydans, Methanoregula, and Candidatus Nitrosocosmicus, indicating that the compost replacing 10% chemical fertilizer notably increased the microbial diversity. Hence, the replacement of 10% of chemical fertilizers with compost can enhance the rice yield.

Harnessing an ammonia-oxidizing microbiome has become an increasingly attractive form of management for mitigating greenhouse gas emissions in rice paddies; however, the relationship between greenhouse gas emissions and ammonia-oxidizing microbiomes, using a nitrogen application and irrigation regime, has not been well investigated. To decipher which of (and how) the specific mmonia-oxidizing bacterial species drive the greenhouse gas CH₄ and N₂O emissions, a field experiment with varying nitrogen application and irrigation regimes was initiated to investigate the succession of key bacterial consortia associated with GHG emissions. The results showed that water-saving irrigation (AWD) significantly increased NO₃-N and NH₄⁺-N concentrations, compared with conventional irrigation (FDF), whereas (total nitrogen) TN was little higher in FDF (1.38 g kg⁻¹) compared with the AWD (1.36 g kg⁻¹). During the rice-growing season, CH₄ emissions ascended speedily, and emissions peaked at maximum values of 3.32 and 4.41 ug mg⁻² h⁻¹ on day 5 in FDF and AWD irrigation regimes, respectively, and then they rapidly decreased during the midseason period, maintaining a relatively low emission rate until the rice was harvested. The patterns of N₂O emission fluxes had the same tendencies with N fertilization. Putative key taxa, such as Flavobacterium, Massilia, Arenimonas, Novosphingobium, Pseudomonas, exhibited significant positive relationships with higher GHG emissions, suggesting that they make particularly obvious contributions to N₂O emissions. These putative taxa should be considered when designing a high nitrogen application and irrigation strategy. As such, the nitrogen application of N180, and the irrigation regimes of water-saving irrigation, are recommended methods for N conservation and the mitigation of greenhouse gas emissions in rice paddies.

(1) Background: We investigated the effects of nutrient levels on rice yield and nitrogen uptake, with the aim of improving rice yield and nitrogen use efficiency. (2) Methods: A 3-year field experiment was conducted using the rice variety Changliangyou Fuxiangzhan, with six treatments: no nitrogen application (CK), conventional fertilization (FP), single basal application of 60-day slow-release urea (CRU1), single basal application of urea combined with 40-day and 90-day slow-release urea (CRU2), partial substitution of chemical fertilizer with bio-organic manure (FPM), and conventional fertilization combined with straw return (FPS). (3) Results: Different nutrient management regimes significantly affected rice yield and nitrogen uptake and use, as well as soil nitrogen content. CRU2 achieved the highest performance across most indicators, with grain yield averaging 9.6% higher than that of FP and 36.4% higher than that of CK, alongside consistently greater effective panicle numbers. It also significantly enhanced nitrogen uptake, with higher grain and straw N accumulation, and showed the best nitrogen use efficiencies. Soil responses varied by treatment: FPS and FPM increased total nitrogen, while CRU2 and CRU1 had the highest inorganic nitrogen, and microbial biomass nitrogen peaked under FPM, CRU2, and FPS. Despite these benefits, CRU2 showed the largest negative nitrogen balance, averaging −33.0 kg ha⁻¹ over 3 years. (4) Conclusions: The CRU2 treatment achieved efficient synchronization between nitrogen supply and demand, with the highest yield, nitrogen uptake, and soil nitrogen levels.

Long-term reliance on mineral fertilizers may degrade soil structure and weaken carbon and nitrogen retention in rice–wheat rotation systems. Organic amendments combined with mineral fertilizers can provide organic substrates, promote aggregate formation, and improve soil C–N retention, but the contrasting effects of plant- and animal-derived amendments remain unclear. A long-term field experiment initiated in 2012 in Chaohu, China, compared no fertilization (CK), chemical fertilizer alone (CF), chemical fertilizer plus oil cake (OC), and chemical fertilizer plus cattle manure (CM). At wheat maturity in 2025, soil aggregate distribution, stability, aggregate-associated soil organic carbon (SOC) and total nitrogen (TN), C and N contribution rates, and yield components were determined; wheat yield was further evaluated using annual records from 2021 to 2025. Compared with CK, OC and CM increased water-stable macroaggregates (>0.25 mm) by 17.35% and 17.94% and reduced aggregate destruction by 54.61% and 53.57%, respectively. In large macroaggregates (>2 mm), OC and CM increased SOC by 58.30% and 84.83% and TN by 141.76% and 200.00%, respectively. Five-year mean yield increased by 208.09%, 240.78%, and 225.15% under CF, OC, and CM, respectively, relative to CK, but did not differ significantly among fertilized treatments. Overall, oil cake showed a numerical advantage in maintaining wheat yield, whereas cattle manure had greater potential to improve aggregate-scale C–N retention and soil structural stability.