Comparison of agrochemicals allocation efficiency between greenhouse and open-field vegetables in China

Occurrence characteristics and ecological impact of agricultural soil microplastics in the Qinghai Tibetan Plateau, China

Plastic mulch is widely recognized as a significant contributor to microplastics (MPs) pollution in agricultural soil. However, its direct impact on remote areas with low population density remains uncertain due to multiple pollution sources. This study aims to investigate MPs pollution and its risks regarding agricultural soil in the Qinghai Tibetan Plateau (QTP) in China. The results revealed that soil samples from the study area exhibited a range of MPs abundance, varying from 16.67 to 950 items/kg, with the highest average abundance observed in Chengguan district (CG) soil samples (611.11 items/kg). Polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE) were identified as the predominant components of MPs in farmland soil. Furthermore, significantly higher levels of MPs were found in the facility agriculture soil compared to the control soil. Diversity and risk of MPs in different regions and cultivation conditions were significantly different. According to the employed risk assessment models, agricultural soil demonstrated a relatively high polymer risk (47 % of areas classified as level III). In addition to being influenced by exogenous factors, the diversity of MPs also plays an intrinsic role in regulating the risk of MPs pollution. This study contributes to an enhanced comprehension of the issue of MPs pollution in QTP farmland soil, providing valuable empirical evidence and theoretical underpinning for the development of efficacious control strategies.

Towards Sustainable Productivity of Greenhouse Vegetable Soils: Limiting Factors and Mitigation Strategies

Greenhouse vegetable production has become increasingly important in meeting the increasing global food demand. Yet, it faces severe challenges in terms of how to maintain soil productivity from a long-term perspective. This review discusses the main soil productivity limiting factors for vegetables grown in greenhouses and identifies strategies that attempt to overcome these limitations. The main processes leading to soil degradation include physical (e.g., compaction), chemical (e.g., salinization, acidification, and nutrient imbalances), and biological factors (e.g., biodiversity reduction and pathogen buildup). These processes are often favored by intensive greenhouse cultivation. Mitigation strategies involve managing soil organic matter and mineral nutrients and adopting crop rotation. Future research should focus on precisely balancing soil nutrient supply with vegetable crop demands throughout their life cycle and using targeted organic amendments to manage specific soil properties. To ensure the successful adoption of recommended strategies, socioeconomic considerations are also necessary. Future empirical research is required to adapt socioeconomic frameworks, such as Science and Technology Backyard 2.0, from cereal production systems to greenhouse vegetable production systems. Addressing these issues will enable the productivity of greenhouse vegetable soils that meet growing vegetable demand to be sustained using limited soil resources.

Shadow prices of agrochemicals in the Chinese farming sector: A convex expectile regression approach

The use of agrochemical inputs has significantly enhanced agricultural yields in China; however, their excessive utilization has also caused a range of environmental issues. This paper examines the costs associated with reducing agrochemicals by employing shadow prices, which represent the value of the marginal product of agrochemicals, to further develop cost-effective environmental policy measures for reducing their usage. To this end, the shadow prices of agrochemicals have been assessed by adopting a newly developed convex expectile regression approach and using statistical data from 31 provinces in China spanning from 2005 to 2020. Furthermore, the present study investigates the disparities between shadow prices and market prices for different agrochemicals across various regions in China. The findings suggest that the costs of reducing chemical fertilizers are higher than those of reducing pesticides and plastic films. Moreover, the results indicate that central China exhibits relatively high potential for decreasing agrochemical usage. Finally, these findings can inform the Chinese government's restructuring of producer support and environmental policy in a cost-effective way to mitigate agrochemicals use in the future. Additionally, the research method employed in this study holds potential for extension to other agrochemicals-dependent countries.

Regulating root structure of potted lettuce to magnify absorption from APP and UAN fertilizers

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 <0.5 mm.

Conclusion and discussion

The length of fine roots played a more prominent role in promoting N absorption, while overall root size was more important for P absorption. APP has a threshold of 9.3 mg P kg-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.

A comprehensive evaluation of influencing factors of neonicotinoid insecticides (NEOs) in farmland soils across China: First focus on film mulching

Neonicotinoid insecticide (NEO) residues in agricultural soils have concerning and adverse effects on agroecosystems. Previous studies on the effects of farmland type on NEOs are limited to comparing greenhouses with open fields. On the other hand, both NEOs and microplastics (MPs) are commonly found in agricultural fields, but their co-occurrence characteristics under realistic fields have not been reported. This study grouped farmlands into three types according to the covering degree of the film, collected 391 soil samples in mainland China, and found significant differences in NEO residues in the soils of the three different farmlands, with greenhouse having the highest NEO residue, followed by farmland with film mulching and farmland without film mulching (both open fields). Furthermore, this study found that MPs were significantly and positively correlated with NEOs. As far as we know this is the first report to disclose the association of film mulching and MPs with NEOs under realistic fields. Moreover, multiple linear regression and random forest models were used to comprehensively evaluate the factors influencing NEOs (including climatic, soil, and agricultural indicators). The results indicated that the random forest model was more reliable, with MPs, farmland type, and total nitrogen having higher relative contributions.

Biochar's dual role in greenhouse gas emissions: Nitrogen fertilization dependency and mitigation potential

Biochar was popularly used for reducing greenhouse gas (GHG) emissions in vegetable production, but using biochar does not necessarily guarantee a reduction in GHG emissions. Herein, it's meaningful to elucidate the intricate interplay among biochar properties, soil characteristics, and GHG emissions in vegetable production to provide valuable insights for informed and effective mitigation strategies. Therefore, in current research, a meta-analysis of 43 publications was employed to address these issues. The boost-regression analysis results indicated that the performance of biochar in inhibiting N2O emissions was most affected by the N application rate both in high and low N application conditions. Besides, biochar had dual roles and showed well performance in reducing GHG emissions under low N input (≤300 kg N ha-1), while having the opposite effect during high N input (>300 kg N ha-1). Specifically, applying biochar under low N fertilization input could obviously reduce soil N2O emissions, CO2 emissions, and CH4 emissions by 18.7 %, 17.9 %, and 16.9 %, respectively. However, the biochar application under high N fertilization input significantly (P < 0.05) increased soil N2O emissions, CO2 emissions, and CH4 emissions by 39.7 %, 43.0 %, and 27.7 %, respectively. Except for the N application rate, the soil pH, SOC, biochar C/N ratio, biochar pH, and biochar pyrolysis temperature are also the key factors affecting the control of GHG emissions in biochar-amended soils. The findings of this study will contribute to deeper insights into the potential application of biochar in regulating GHG under consideration of N input, offering scientific evidence and guidance for sustainable agriculture management.

Pesticides in Greenhouse Airborne Particulate Matter: Occurrence, Distribution, Transformation Products, and Potential Human Exposure Risks

Pesticides are frequently sprayed in greenhouses to ensure crop yields, where airborne particulate matter (PM) may serve as a carrier in depositing and transporting pesticides. However, little is known about the occurrence and fate of PM-borne pesticides in greenhouses. Herein, we examined the distribution, dissipation, and transformation of six commonly used pesticides (imidacloprid, acetamiprid, prochloraz, triadimefon, hexaconazole, and tebuconazole) in greenhouse PM (PM1, PM2.5, and PM10) after application as well as the associated human exposure risks via inhalation. During 35 days of experiment, the six pesticides were detected in all PM samples, and exhibited size- and time-dependent distribution characteristics, with the majority of them (>64.6%) accumulated in PM1. About 1.0-16.4% of initially measured pesticides in PM remained after 35 days, and a total of 12 major transformation products were elucidated, with six of them newly identified. The inhalation of PM could be an important route of human exposure to pesticides in the greenhouse, where the estimated average daily human inhalation dose (ADDinh) of the six individual pesticides was 2.1-1.2 × 104 pg/kg day-1 after application (1-35 days). Our findings highlight the occurrence of pesticides/transformation products in greenhouse PM, and their potential inhalation risks should be further concerned.

Leaching and fractionation of phosphorus in intensive greenhouse vegetable production soils

Greenhouse vegetable production systems use excessive phosphorus (P) fertilizer. This study is set out to look into the P fractionation, mobility, and risk of P leaching in ten greenhouse soils. The mean P concentrations in leachates varied from 0.4 to 1.6 mg l-1 (mean of 30 days of soil leaching). Between 5.7 and 31.0 mg kg-1 of P was leached from soils during 30 days of column leaching. Organic matter (OM) and Olsen-extractable P (Olsen P) correlated strongly with cumulative P leached after 5, 10, 15, 20, 25, and 30 days of leaching. The high correlation between OM and Olsen P with cumulative P leached at 5 days of leaching suggests that in future leaching experiments, the leaching period should be extended to 5 days of leaching. The first two P fractions correlated significantly with the total P leached in the primary days of leaching. The pH had little effect on P leaching but had a significant impact on soluble and exchangeable P fraction, suggesting that P mobility would increase in these calcareous greenhouse vegetable soils as pH rose. The calculated change point (194 mg kg-1) was high, indicating that a high percentage (40%) of the studied greenhouse soils had exceeded the change point. In conclusion, due to the high degree of P saturation and change point in greenhouse vegetable soils, P mobilization is a significant risk, and the findings can be used to provide future direction for fertilizing greenhouse vegetable soils.

The widespread presence of triazole fungicides in greenhouse soils in Shandong Province, China: A systematic study on human health and ecological risk assessments

Triazole fungicides (TFs) are extensively used on greenhouse vegetables and are ubiquitously detected in the environment. However, the human health and ecological risks associated with the presence of TFs in the soil are unclear. In this study, ten widely used TFs were measured in 283 soil samples from vegetable greenhouses across Shandong Province, China, and their potential human health and ecological risks were assessed. Among all soil samples, difenoconazole, myclobutanil, triadimenol, and tebuconazole were the top detected TFs, with detection rates of 85.2-100%; these TFs had higher residues, with average concentrations of 5.47-23.8 μg/kg. Although most of the detectable TFs were present in low amounts, 99.3% of the samples were contaminated with 2-10 TFs. Human health risk assessment based on hazard quotient (HQ) and hazard index (HI) values indicated that TFs posed negligible non-cancer risks for both adults and children (HQ range, 5.33 × 10-10 to 2.38 × 10-5; HI range, 1.95 × 10-9 to 3.05 × 10-5, <1). Ecological risk assessment based on the toxicity exposure ratio (TER) and risk quotient (RQ) values indicated that difenoconazole was a potential risk factor for soil organisms (TERmax = 1 for Eisenia foetida, <5; RQmean = 1.19 and RQmax = 9.04, >1). Moreover, 84 of the 283 sites showed a high risk (RQsite range, 1.09-9.08, >1), and difenoconazole was the primary contributor to the overall risk. Considering their ubiquity and potential hazards, TFs should be continuously assessed and prioritized for pesticide risk management.