Guoyuan Zou

Long-term excessive chemical fertilization threatens the sustainability of wheat–maize rotation systems in the North China Plain. Organic substitution is a promising alternative to sustain crop productivity and soil health, yet its underlying mechanisms require clarification. This study investigated the effects of six fertilization treatments (unfertilized [CK], chemical nitrogen [N] alone at 180 kg N ha⁻¹ season⁻¹ [NPK], chemical N 25% substituted by chicken manure per season [NPKM], full manure substitution per season [CM], chemical N 25% substituted by straw return under no tillage per season [NT] and chemical N 25% substituted by straw return under rotary tillage per season [ST]) on soil fertility and crop productivity in a long-term wheat–maize rotation field experiment initiated in 2007. All treatments followed a randomized complete block design with three replicates per treatment. Wheat and maize plants were randomly collected from each plot at the harvest stage of each season, and weighed and measured for yield and N uptake, while soil samples were randomly collected from each plot at maize harvest stage for chemical and enzyme activity analyses. Compared to NPK, organic substitution maintained grain yields while significantly enhancing key soil fertility indicators: soil organic carbon (C) (up to 53.8%), and labile C and N pools including readily oxidizable C (by 120.0%), ammonium N (by 23%) and microbial biomass C (up to 164.5%). It also strongly stimulated the activities of C-acquiring (e.g., β-glucosidase and cellobiohydrolase) and N-cycling (e.g., β-N-acetylglucosaminidase and urease) enzymes by up to 278.7% and 256.3%, respectively. Multivariate analyses identified these enzymes as primary drivers of soil C and N dynamics, with direct positive links to crop yield. In conclusion, long-term organic substitution, particularly full manure substitution, improved yield stability and soil fertility predominantly through an enzymatic-driven stimulation of nutrient cycling and organic matter accumulation, offering a viable strategy to reduce chemical fertilizer inputs and enhance crop production sustainability.

Biodegradable mulch film (BDM) is regarded as a key solution to combat plastic mulch film pollution due to its ability to degrade completely into CO₂ and H₂O through environmentally friendly microorganisms. However, commercial BDM often fails to degrade fully after use, leading to the accumulation of BDM residues in soil and their transformation into microplastics (MPs) via various processes, posing a threat to the soil ecosystem. Given these discrepancies between the theoretical and practical degradation performance of BDM, there is an urgent need to understand the impacts of BDM residues on plant growth and soil health. This research conducted pot experiments spanning the entire growth cycle of Chinese cabbage to evaluate the impact of PBST-BDM raw material (R), PBST-BDM residues (M), and PBST-BDM composting product (P) on crop growth and soil quality. The findings revealed that R treatments had a slight effect on Chinese cabbage growth (e.g., a 5.80% increase in emergence rate in R 1% treatment, p < 0.05), while M treatments significantly hindered the emergence rate, plant height, leaf area, and biomass accumulation of Chinese cabbage by 30.4% (p < 0.05), 2.71 cm (p < 0.05), 39.0% (p < 0.05), and 1.86 g (p < 0.05) in the M 1% treatment compared to the control group (CK). In contrast, P treatments enhanced Chinese cabbage growth, with greater improvements at higher weight ratios, resulting in increases of 8.89% (p < 0.05), 4.96 cm (p < 0.05), 36.3% (p < 0.05), and 2.31 g (p < 0.05) in the P 1% treatment. Microbial network topology in the M 1% treatment is highly variable, with the increased proportion of positive correlations in the P 1% treatment hinting at stronger symbiotic interactions between species (p < 0.05). Analysis results of PCoA and PLS-DA showed significant differences in microbial community and soil metabolites between M 1% treatment and CK (p < 0.05). These findings suggest that, although composting post-use BDM may reduce their negative ecological effects, possibly via accelerating the early breakdown of residues, the feasibility and scalability of this approach require further validation under real-world field conditions.

Acidic additives have garnered significant attention due to their ability to reduce ammonia (NH₃) emissions, enhance nitrogen retention, and balance function with cost-effectiveness. This study aimed to investigate the potential of oxalic acid (OA) in reducing gas emissions, promoting compost humification, and enhancing nutrient retention during the co-composting of chicken manure. Moreover, the comparative analysis of the effects and the economic benefits was conducted among OA groups with varying concentrations (OA1: 0.03 mol·kg⁻¹, OA2: 0.10 mol·kg⁻¹, and OA3: 0.15 mol·kg⁻¹) and a sulfuric acid (SA) group (SA1: 0.03 mol·kg⁻¹). The results indicated that the addition of OA can extend the thermophilic phase to some extent and achieve the required composting maturity. As the amount of OA increased, the NH₃ emissions (p < 0.05) and the total nitrogen loss rate was decreased; however, this also increased the cost. No significant difference in the total nitrogen loss rate was observed between SA1 and OA1 (p < 0.05). It is worth noting that the addition of SA increased the SO₄²⁻ content, leading to an increase of 113.52% in H₂S emissions. In contrast, the addition of OA resulted in a reduction in H₂S emissions by 29.92–45.90%. In terms of economic analysis, OA1 was the most effective (OA1 > OA2 > OA3 > SA1). Thereby, OA was proved to be a good alternative for SA in the co-composting of chicken manure, and 0.03 mol·kg⁻¹ OA is recommended.

Introduction: Improvement of root architecture is crucial to increasing nutrient acquisition.Methods: Two pot experiments were conducted to investigate the effects of different concentrations of urea ammonium nitrate solution (UAN) and ammonium polyphosphate (APP) on lettuce root architecture and the relationship between roots and nitrogen (N) and phosphorus (P) absorption.Results: The results showed that lettuce yield, quality, and root architecture were superior in the APP4 treatment compared to other P fertilizer treatments. The N480 treatment (480 mg N kg^-1 UAN) significantly outperformed other N treatments in terms of root length, root surface area, and root volume. There were significant quantitative relationships between root architecture indices and crop uptake of N and P. The relationships between P uptake and root length and root surface area followed power functions. Crop N uptake was significantly linearly related to the length of fine roots with a diameter of -1 for stimulating the root system. Above this threshold, a rapid increase in root absorption of P. UAN can promote extensive growth of fine roots with a diameter less than 0.5 mm. Applying appropriate rates of APP and limiting UAN application to less than 400 mg N kg^-1 can improve root architecture to enhance N and P absorption by lettuce. These results highlight a new possibility to improve nutrients use efficiency while maintaining high yields.

The one-time application of blended urea (BU), combining controlled-release urea (CRU) and uncoated urea, has proven to be a promising nitrogen (N) management strategy. However, the long-term sustainability of blending urea remains largely unexplored. To assess whether a single application of blended urea could effectively replace split uncoated urea applications, a long-term field experiment was conducted in the North China Plain (NCP). The results indicated that, when compared to common urea (CU) at the optimal N rate (180 kg N ha⁻¹), BU achieved comparable grain yields, N uptake and NUE (61% vs. 62). BU exhibited a 12% higher 0–20 cm soil organic nitrogen stock and a 9% higher soil organic carbon (C) stock. Additionally, BU reduced life–cycle reactive N (Nr) losses and the N footprint by 10%, and lowered greenhouse gas (GHG) emissions and the C footprint by 7%. From an economic analysis perspective, BU demonstrated comparable private profitability and a 3% greater ecosystem economic benefit. Therefore, BU under the optimal N rate has the potential to substitute split applications of common urea in the long–term and can be regarded as a sustainable N management strategy for wheat and maize production in the NCP.