Background: Much attention has been focused on the influences of residue returning on N₂O emissions. However, comprehensive quantification of the effect size on N₂O emission following crop residue returning in subtropical, tropical and warm temperate conditions remains untested. Methods: To identify site-specific factors that influence N₂O emission (kg N₂O-N ha⁻¹) in residue returning systems, we performed a meta-analysis involving 260 comparisons from 72 studies. Results: The data indicated that significant promoting effects were observed under residue returning by rotary tillage, no-tillage and mulch, whereas N₂O release was significantly inhibited by 8% under residue returning by plough. For other contributors, the stimulatory and significant effects occurred in upland fields, under short- and medium-term residue returning durations, acidic/neutral soils, medium organic C and clay content. Nitrogen fertilizer application significantly stimulated N₂O emission, even though application rate at 100–150 kg N ha⁻¹ was inhibitory. Although a negative correlation between residue C/N ratio and N₂O emission has been shown, residue returning could not reduce N₂O emission with a higher C/N ratio and amount. Conclusions: Some options, such as converting residue returning methods, decreasing N fertilizer application rate, and regulating soil C/N ratio could be adopted to mitigate soil N₂O emission following residue returning.

Water eutrophication caused by agricultural production has become one of the most important factors that impede sustainable rural environmental governance in China. As a result, the Chinese central and local governments want to reduce the use of nitrogen and phosphorus fertilizer and gain socioeconomical profit simultaneously by promoting crayfish and rice integrated system (CRIS) in the rural areas with abundant water resources. In this article, we investigated whether CRIS in Qianjiang, Hubei, the origin place of the system in China, contributes to fulfilling the governments’ expectations. We found that CRIS efficaciously cuts the fertilizer rate in rice production and boosts farmers’ incomes because crayfish has a demand for water quality and holds a large internal market requirement. However, higher profit encourages farmers to expand crayfish production and thus discourages the initiatives in rice production. The area of the ditch for crayfish production expands ceaselessly and exceeds the limit of regulation of CRIS. As a result, the CRIS in the areas has emerged as a practice of aquaculture but in farmland. This is a regulatory gap. The input–output analysis of CRIS by material balance method can also reveal that excessive feed for crayfish has become a new source of agricultural pollution. Beyond that, due to the changed irrigation system and increased water exchange frequency of CRIS, the pollution has transformed from passive distribution to active, which will increase the risk of water eutrophication on a large area.

This paper clarifies the farm applicability and feasibility of spreading biodegradable plastic film mulching for garlic production to ensure the green and sustainable development of the garlic industry. We set up a field trial of garlic planting with biodegradable plastic film mulching (BM) and plastic film mulching (PM), using no film mulching (CK) as the control, and measured CH₄ and N₂O emissions in the garlic fields. The yield-scaled global warming potential, carbon footprint, and net ecosystem economic benefit (NEEB) were used to assess the comprehensive impact of the different treatments. Compared to the CK, film mulching significantly increased CH₄ absorption, with significantly higher seasonal cumulative CH₄ emissions (20.5%) in BM than PM, but significantly increased N₂O emissions, with significantly lower seasonal cumulative N₂O emissions (23.53%) in BM than PM. Both BM and PM improved garlic yield, with PM significantly increasing garlic yield by 18.86% compared to the CK. Moreover, film mulching significantly decreased the yield-scaled global warming potential (by 52.06% and 40.82% in PM and BM, respectively). PM had a significantly higher carbon footprint than BM. Film mulching improved NEEB by 9.29–11.78%. Considering crop yields and environmental benefits, we propose BM as an effective method for a green and efficient garlic production.

This study aimed to explore the impact paths on soil organic carbon and crop yield of completely or partially substituting chemical N fertilizer with organic fertilizers. A four-year field experiment was conducted and included four treatments: (i) N0, no N fertilization application; (ii) NF, only synthetic N fertilizer application; (iii) 1/2OF, organic fertilizer substituted for 100% of the synthetic N fertilizer, with the total N application amount being equivalent to half that of NF; and (iv) 1/3OF + 2/3NF, organic fertilizer substituted for 1/3 of the synthetic N fertilizer with the total N application amount from organic and synthetic fertilizer being equivalent to that of NF. Soil total organic carbon (TOC), labile organic-carbon fractions (microbial biomass carbon (MBC), dissolved organic carbon (DOC), particulate organic carbon (POC), and easily oxidized organic carbon (EOC)), the carbon pool management index (CPMI), soil aggregated distribution, and water-stable aggregate-associated organic carbon were determined. Structural equation modeling (SEM) was used to clarify the impact paths of TOC and garlic yield changes under different N fertilizer treatments. Results showed that compared with N0 and NF, 1/2OF and 1/3OF + 2/3NF significantly increased TOC contents by 14.1–20.6%. Soil MBC, DOC, and EOC under 1/2OF were significantly higher than under N0, whereas the 1/3OF + 2/3NF treatment had significantly greater POC. The CPMI was improved by organic fertilizer treatment, with 1/2OF treatment being significantly higher than N0 and NF. The proportion of soil aggregate mass with particle sizes >2 mm was significantly greater under N0, while 1/3OF + 2/3NF significantly increased the proportion of particle sizes of 0.5–2 mm. Soil water-stable aggregate-associated organic carbon showed a trend of first increasing and then decreasing, with the largest particle sizes being 1–2 mm. Moreover, organic fertilizer significantly increased soil water-stable aggregate organic carbon compared with N0 and NF. Similarly, the garlic yield increased with organic fertilizer treatment, while 1/3OF + 2/3NF significantly increased the yield by 37.2% and 15.3%, respectively, compared with N0 and NF. Furthermore, SEM analysis indicated that fertilizer regimes could directly affect TOC and labile organic carbon components by affecting aggregate-associated organic carbon. In particular, aggregates with particle sizes of 0.5–2 mm played an important role, indirectly affecting garlic yield and CPMI. These results indicate that organic fertilizer application has the potential to improve soil organic-carbon content and garlic yield; moreover, fully applying organic fertilizer can reduce N fertilizer input while still maintaining an increase in soil organic carbon and crop yield in the short term. However, caution is still needed regarding of the type and quantity of organic fertilizer added in different cropping systems, and with different soil textures.

Straw return and plastic film mulching are two critical management measures that not only maintain high and stable crop yields, but also have a significant impact on the ecological environment. However, there is still a lack of research on the comprehensive effects of straw return and different film mulching treatments on the ecological environment. Thus, a 2-year field experiment was conducted and six treatments, which included two main treatments, namely straw return (SR) and non-straw return (NR), and three sub-treatments, namely no film mulching (CK), plastic film mulching (PM) and fully biodegradable film mulching (BM), were applied in a garlic cropping system. Based on the life cycle assessment method, six endpoint damage categories, resource consumption, global warming potential, environmental acidification, eutrophication, human health, and ecotoxicity, were assessed. Furthermore, we also evaluated the costs and economic benefits of the six treatments and optimized the treatment of used mulch and straw off-farm. The results indicated that the environmental impacts of the six endpoint damages in the garlic cropping system were ranked as ecotoxicity, eutrophication, environmental acidification, global warming potential, human health, and resource consumption. The SR-BM treatment had the lowest life cycle environmental impact composite index at 27.68 per unit area, followed by SR-PM at 27.75. All six endpoint damage categories for the PM and BM treatments were lower than the CK treatment per t of yield, with the SR-BM treatment being the most economically efficient, yielding at 3691.03 CNY·t⁻¹ and exceeding that of the SR-CK treatment by 7.26%. Fertilizer inputs were the primary contributor to resource consumption, global warming potential, environmental acidification, eutrophication, and ecotoxicity, accounting for about 72.80% of these five environmental impacts. Crop protection significantly affected human health, and garlic mulching helped minimize pesticide use, thereby reducing potential health impacts. Compared to straw incineration and waste mulch power generation, straw power generation and waste mulch recycling granulation offered positive environmental benefits and were more effective offset strategies. In conclusion, straw return with biodegradable mulch is a synergistic cultivation measure that offers both environmental and economic benefits. For straw return with plastic film mulch, environmental impacts can be reduced by waste mulch recycling granulation.