Land use changes from cropland to orchards in Eastern China have raised serious concerns about the regional nitrogen (N) cycle and greenhouse gas balance. We measured soil nitrous oxide (N₂O) emissions and methane (CH₄) uptake using manual static chambers in an apple orchard. The primary aims were to assess the effect of N fertilizer application on gas fluxes and quantify the site-specific N₂O emission factor (EF_d). Field experiments were arranged in a randomized block design with three N input rates (0, 800 and 2600/2000 kg N ha⁻¹ year⁻¹). We found that orchard soils were a negligible CH₄ sink (−1.1 to −0.4 kg C ha⁻¹ year⁻¹). Annual N₂O emissions responded positively to N input rates, ranging from 34.1 to 60.3 kg N ha⁻¹ year⁻¹. EF_d ranged from 1.00% to 1.65% with a mean of 1.34%. The extremely large background emissions of N₂O (34.1–34.3 kg N ha⁻¹ year⁻¹) most likely originated from nitrate accumulation in the soil profile because of historical overuse of N fertilizer. We conclude that (1) site-specific EF_d is suitable for assessing regional direct N₂O emissions from upland orchards; and (2) conventional fertilization regimes must be avoided, and reduced N input rates are recommended in the study region.

Mild organic substitution is advantageous for sustainable agricultural development. In order to determine the proper fertilization strategy, it is essential to investigate the impact of substituting chemical fertilizers with varying levels of organic manure on soil nutrients, microbial communities, and crop productivity. Four treatments were implemented: no fertilizer, sole chemical fertilizer, 20% organic manure substitution, and 40% organic manure substitution. Bacterial and fungal communities were characterized through high-throughput sequencing of the 16S rRNA gene V3–V4 region and the V4 region, respectively. The 20% and 40% organic manure substitutions increased soil organic matter (SOM) content, total nitrogen (TN) content, and reduced soil pH compared to the control (CK). The 20% organic manure substitution showed the most significant improvements in soil alkaline phosphatase, urease, and invertase activities. Soil nutrient enhancement increased bacterial alpha diversity, with a milder impact on fungal alpha diversity compared to bacteria. Different fertilization treatments elevated the relative abundance of bacterial Bacteroidetes (8.11%, 21.25%, and 1.88%), Actinomycetes (12.65%, 26.36%, and 15.33%), and fungal Ascomycota (16.19%, 10.44%, and 12.69%), known for degrading recalcitrant organic matter. The sole chemical fertilizer treatment increased the pathogenic Cheatotryiales. Shared species, primarily from bacterial Actinomycetes, Firmicutes, Proteobacteria, and fungal Ascomycota phyla, were found at 20% and 40% organic manure substitution levels. Specifically, the 20% organic manure substitution level promoted the relative abundance of beneficial plant growth-promoting taxa, Oxalobacteraceae and Massilia, and suppressed pathogens, with an increase in the relative abundance of the Purpureocillium genus and Mortierellomycota. These findings suggest that a 20% OF substitution can maintain crop yield, enhance soil nutrients and enzyme activities by fostering beneficial soil bacteria, inhibiting soil-borne pathogens, and refining microbial community structure.

The partial substitution of chemical fertilizers with organic manure is an important strategy for improving agricultural sustainability. However, its effect on heavy metal (HM) pollution and its potential risk to human health remain unclear. Therefore, a field study was conducted to evaluate the effects of partial organic fertilizer substitution (0, 10%, 20%, 30%, and 40%) on health risks posed by HMs, including Zn, Cu, Ni, Cd, Pb, As, and Cr. The results showed that organic fertilizer substitution significantly increased Cu, Cd, Pb, and As accumulations in the soil. The Zn, Cu, Pb, and As contents were significantly higher in grains grown under organic fertilizer substitution (40%) conditions. The HM contents in the soil and grains were below the safety threshold limits in all treatments. Furthermore, the health risk caused by the exposure to As, Cu, and Zn accounted for 86% of the hazard index (HI) value. The HI value was significantly greater at a substitution ratio of 40% than in the no-nitrogen fertilizer treatment. Ingestion of the wheat grains grown at substitution ratios ≥ 30%) increased the carcinogenic risk of As and the total carcinogenic risk. In conclusion, organic fertilizer substitution at high ratios significantly increased the non-carcinogenic and carcinogenic risks associated with ingesting wheat grain. The optimal organic fertilizer substitution ratio (20%) maintained crop yields and improved soil fertility without increasing the non-carcinogenic or carcinogenic risks to human health. These findings highlight the importance of understanding the impacts of optimal organic fertilizer management in wheat growing systems.

Optimizing organic fertilizer substitution is essential for enhancing the sustainability of agriculture and achieving a balance between crop productivity, nutritional quality, and environmental safety. Here, we conducted an 11-year field experiment to evaluate the effects of substituting 50% of mineral fertilizers with pig manure (PM) or cattle manure (CM) on the nutritional quality of wheat grain, heavy metal (HM) accumulation, and associated human health risks. The yield and protein content were highest in the mineral fertilizer (MF) treatment, and grain micronutrients (Fe, Mn, Cu, Zn) were 6.7–13.8% higher under organic substitution (PM/CM) than in the MF treatment. The Ni, Pb, and As contents were 35.4–43.0% higher in the PM treatment than in the MF treatment, which stems from the higher HM content in pig manure. Health risk assessments indicated that the Hazard Index (HI) for children exceeded 1 in the PM treatment, primarily due to As, which accounted for 69.6% of the HI. All treatments remained within safe thresholds, although As and Pb posed detectable carcinogenic health risks. The higher levels of Ni and As in pig manure likewise led to a significant increase in the health risk associated with the PM treatment compared to the MF treatment. We developed a novel Grain Quality Index (GQI) that combined nutrient and HM data, which indicated that the nutritional quality of wheat grain was similar in the CM and MF treatments. The GQI was 9.1% lower in the PM treatment than in the MF treatment. These findings suggest that the substitution of mineral fertilizer with cow manure can help achieve a balance between yield, nutrition, and safety, and more stringent regulation of HMs is required for the use of pig manure. Our findings provide actionable insights with implications for sustainable wheat production policies.

China produces 61.0% of the world’s watermelons, yet a life cycle assessment (LCA) of its production system is lacking. Here, we combined farmer surveys and field experiments to assess resource depletion and environmental impacts across North China (NC), Northwest China (NW), and Southwest China (SW), and to quantify the mitigation potential through optimized nitrogen (N) management. NC achieved the highest yield but also the highest resource use and emissions per hectare. In contrast, SW performed best per ton of fruit produced due to lower input intensity. Nitrogen fertilizer dominated greenhouse gas emissions and eutrophication potential, with over 85% of its impact arising during the field application stage. Grouping farms by yield and N partial factor productivity revealed a mitigation potential of 46.5–55.4%, enabling both high yield and high efficiency. Field experiments confirmed that reducing N input by 14.3–40.0%, as recommended regionally, stabilizes yield while significantly lowering environmental burdens. Our findings validate that region-specific N optimization is a key strategy for achieving sustainable watermelon production in China.

The global consumption of resources and environmental problems are becoming increasingly serious. China produces 61.0% of the world's watermelons, yet no comprehensive assessment of the resource consumption and environmental effects of China's watermelon production system has been reported. This study applies life cycle assessment (LCA), combining farmer surveys with field experiments, to systematically evaluate and verify the reduction potential of land occupation (LO), water depletion (WD), energy depletion (ED), global warming potential (GHG), acidification potential (AP), and eutrophication potential (EP), as well as the resource budget and environmental impact index (REI), in north China (NC), northwest China (NW), and southwest China (SW). The results reveal significant differences in resource consumption and environmental effects. The NC region was found to achieve the highest yield, 146% and 174% greater than the two other regions, but also to exhibit the highest resource use and emissions per unit area, with the lowest REI. By contrast, the SW region was found to achieve the most favorable performance in resource consumption and environmental emissions per unit yield. During the material stage (MS), more than 86.6% of energy and water resources are consumed, while in the farm stage (FS), 47.3% to 98.7% of total pollutants are emitted. Nitrogen (N) fertilizer is identified as the main contributor to GHG, WD, and EP, with field application accounting for more than 85% of the total impact. Although REI values across the three regions remain low, yield management and improved N fertilizer efficiency (PFPN) present a reduction potential of 46.5% to 55.4%, enabling both high yield and high efficiency. Field experiments further verify that reducing N fertilizer use by 14.3% to 40.0% can lower environmental impacts, which is of great significance for promoting green watermelon production.