The excessive use of chemical fertilizers has resulted in a decline in soil quality, crop yield, and crop quality. Partial substitution of chemical fertilizers with organic fertilizers is a sustainable practice that can alleviate these issues. However, a comprehensive evaluation of the effects of partial organic substitution on muskmelon yield, quality, soil fertility, and economic benefits remains unclear. We conducted a greenhouse experiment with muskmelon production in Shandong, China, involving five treatments: no fertilization (CK); total chemical fertilizer (CON); only replacing base fertilizer with organic fertilizer (OPT); 15% (OF15) and 30% (OF30) organic substitution of chemical fertilizers based on optimized fertilization. Our results indicated that the partial organic substitution treatments (OF15 and OF30) improved yield by 5.60–11.9% compared to CON. Furthermore, the Vitamin C, soluble protein, and sugar content in muskmelon were higher in the OF15 and OF30 treatments than in the CON. Compared to the CON, organic substitution treatments significantly increased soil organic matter, total N, total K, alkaline-hydrolyzable, available P, and available K. Additionally, the economic benefit analysis revealed that OF15 and OF30 increased net benefits by 5.60–14.9% respectively, compared to CON. Collectively, these findings suggest that partial substitution of mineral fertilizer with organic fertilizer improves muskmelon productivity, enhances soil nutrients, and increases economic benefits.

The application of biogas slurry in agriculture production is regarded as a sustainable method for mitigating the environmental impacts of fertilization. To investigate the effects of biogas slurry application on soil nitrogen loss and crop yield, a field plot experiment was conducted within a wheat–maize rotation system. This study assessed the effects of three levels of biogas slurry nitrogen substitution, 50% (BSF), 100% (BS), and 150% (EBS), on the yield of silage maize and wheat, nitrogen use efficiency, and soil nitrogen loss. The findings revealed that in the first year (characterized by high rainfall), the application of the biogas slurry led to increased NH₃ emissions and nitrogen leaching, resulting in a notable rise in the annual nitrogen loss. Additionally, it was observed that as the amount of applied biogas slurry increased, the nitrogen loss also rose correspondingly. However, in the second year (a period of drought conditions), despite the elevated NH₃ emissions from the biogas slurry, there was a significant reduction in nitrogen leaching, which resulted in reductions of 14.2% and 20.0% in annual nitrogen loss for the BSF and BS treatments, respectively, with comparable nitrogen input to the fertilizer treatment. Throughout both years, the application of biogas slurry did not decrease the yield of silage maize and wheat, and notably, the BS treatment even enhanced the crop nitrogen utilization efficiency. Compared with other nitrogen fertilizer treatments, the EBS treatment did not increase crop yield even with an increased nitrogen application rate; it also reduced the nitrogen utilization efficiency and N loss. In conclusion, employing biogas slurry to replace chemical fertilizer (equivalent nitrogen substitution) during drought years can enhance nitrogen utilization efficiency, reduce nitrogen loss, and sustain crop yield. When applying biogas slurry in years with substantial rainfall, effective measures should be implemented to mitigate nitrogen loss.

The North China Plain (NCP) serves as a critical grain-producing region in China, playing a pivotal role in ensuring the nation’s food security. A comprehensive analysis of the carbon footprint (CF) related to the cultivation of major grain crops within this region and the proposal of strategies to reduce emissions through low-carbon production methods are crucial for advancing sustainable agricultural practices in China. This study employed the lifecycle assessment (LCA) method to estimate the CF of wheat, maize, and rice crops over a period from 2013 to 2022, based on statistical data collected from five key provinces and cities in the NCP: Beijing, Tianjin, Hebei, Shandong, and Henan. Additionally, the Logarithmic Mean Divisia Index (LMDI) model was utilized to analyze the influencing factors. The results indicated that the carbon footprints per unit area (CF_A) of maize, wheat, and rice increased between 2013 and 2022. Rice had the highest carbon footprint per unit yield (CF_Y), averaging 1.1 kg CO₂-eq kg⁻¹, with significant fluctuations over time. In contrast, the CF_Y of wheat and maize remained relatively stable from 2013 to 2022. Fertilizers contributed the most to CF composition, accounting for 48.8%, 48.0%, and 25.9% of the total carbon inputs for wheat, maize, and rice, respectively. The electricity used for irrigation in rice production was 31.8%, which was much higher than that of wheat (6.8%) and maize (7.1%). The LMDI model showed that the labor effect was a common suppressing factor for the carbon emissions of maize, wheat, and rice in the NCP, while the agricultural structure effect and the economic development effect were common driving factors. By improving the efficiency of fertilizer and pesticide utilization, cultivating new varieties, increasing the mechanical operation efficiency, the irrigation efficiency, and policy support, the CF of grain crop production in the NCP can be effectively reduced. These efforts will contribute to the sustainable development of agricultural practices in the NCP and support China’s efforts to achieve its “double carbon” target.

A large amount of vegetable waste generated by farms is currently damaging the environment and public health. Anaerobic fermentation is a mature technology that significantly contributes to the recovery of energy and resources from tail vegetables and the control of environmental pollution. However, most vegetable wastes have not been utilized due to poor performance of biogas production, lack of optimal solid contents, and multiple other reasons. Herein, the anaerobic digestion biogas production performance of tail vegetables treated with different total solid (TS) content was studied using solanaceous and leafy vegetables as raw materials. Results showed that there was no acidification in all trials except for treatment with TS of 6%. The optimal TS for anaerobic fermentation of vegetable waste was determined to be around 20% in terms of methane production and biogas production efficiency. The cumulative methane production per unit of volatile solids (VSs) reached 241.7 mL CH₄/g of VS, and the methane content was about 65% during the peak period of biogas production. Theoretically, the value of methane production based on anaerobic fermentation of tail vegetables is as high as 1.8 × 10¹³~4.6 × 10¹³ L in China. This research provides advice for screening specific and efficient parameters to promote the biogas production rate by tail vegetable anaerobic fermentation.

Anaerobic digestion is an important means to turn agricultural waste into resources and an important way to address the challenges in treating vegetable residues in China. In this study, the co-digestion of dairy manure with tomato residue was investigated to clarify the effect of the total solids (TS) of the digestion substrate on methane’s production and mechanism using the self-made anaerobic digestion device. The results showed that all treatments could rapidly ferment methane and that the daily methane production showed a trend of increasing first and then decreasing. The optimal concentrations of the digestion substrate for liquid anaerobic digestion (L-AD), hemi-solid-state anaerobic digestion (HSS-AD), and solid-state anaerobic digestion (SS-AD) were 10%, 18%, and 25%, respectively. Compared with SS-AD and HSS-AD, L-AD gas production peaked 3–6 days earlier. Treatment TS25 had the best cumulative methane production, reaching 117.4 mL/g VS. However, treatment TS6 had acid accumulation and a very unstable system. The cumulative methane production of SS-AD was higher than that of HSS-AD and L-AD. Firmicutes and Bacteroidetes were the dominant flora, and Methanoculleus, Methanosarcina, and Methanobrevibacter were the main archaeal groups. The TS significantly changed the microbial community composition of the digestion system, especially the low TS treatment. The results presented herein indicated that TS significantly changed the bacterial and archaeal community composition of the digestion system, and thus with the increase in TS from 6% to 25%, the methane yield increased.

This study compared the performance of singular, binary, and ternary mixing of feedstocks for anaerobic digestion. Three wastes, including organic fraction of municipal solid waste (OFMSW), dairy manure, and corn stover, were tested under the mesophilic condition. Results showed that the binary and ternary mixing stabilised digesters while solely processing OFMSW resulted in pH drop and over accumulation of volatile fatty acids. The highest methane yield of 302.3 L/kg-VS was achieved with 50% OFMSW, 33% corn stover, and 17% dairy manure, which was about 5 times of that obtained from digesting OFMSW alone. The binary and ternary mixing led to multiple peaks in daily methane production, which evened out methane production throughout the 50-day digestion process. Economic analysis showed that solid digestate price, direct fixed capital cost, and labour cost significantly affected net present value (NPV). Ternary mixtures had the highest NPV and internal rate of return and were financially attractive under analysis conditions.