The win-win effects of nitrification inhibitors on soil-crop systems: Decreasing carbendazim residues but promoting soil bacterial community diversities and stabilities and crop yields

Four birds with one stone: applying nitrification inhibitor on the basis of percarbamide restores yield, decreases fungicide residue, enhances soil multifunctionality and stimulates bacterial community

BACKGROUND

Fungicide residues were frequently detected in vegetables and soils, which severely affected crop yields and qualities. Reasonable nitrogen management might promote yields and decrease fungicide carbendazim residues in plant-soil systems. Current study explores comprehensive relationships among carbendazim residues, crop yields, soil multifunctionalities and endophytic and soil bacterial communities after applying nitrification inhibitors (3,4-dimethylpyrazole phosphate and dicyandiamide) and percarbamide to different soils.

RESULTS

Combined nitrification inhibitor and percarbamide additions produced multi-effects on restoring yields, declining fungicide residues, promoting soil multifunctionalities and stimulating bacterial communities. Relative to the control, percarbamide application promoted carbendazim dissipations in upland soils but decreased bacterial community diversities and stabilities in different soils. Compared to exclusive percarbamide, extra dicyandiamide applications decreased carbendazim residues by 25.8% in upland soils and 70.2% in paddy soils, declined carbendazim residues in carrots via improving soil pH, ammonium nitrogen (NH4 +-N) and Proteobacteria ratios. Relative to percarbamide application alone, extra dicyandiamide addition promoted the dry carrot yields by 133.2% in upland soils and 33.5% in paddy soils via promoting soil NH4 +-N, Acidobacteriota and Actinobacteriota ratios and bacterial community diversities and stabilities. Upland soil multifunctionality improvements diminished soil carbendazim residues via promoting soil pH and NH4 +-N, and paddy soil multifunctionalities and endophytic bacterial community structures generated negative influences on carrot carbendazim residues.

CONCLUSION

Our study suggested that nitrification inhibitor on the basis of percarbamide generated multi-effects on the different crop-soil systems: restoring carrot yields, reducing carbendazim contents, promoting soil multifunctionalities and stimulating bacterial community diversities and stabilities. © 2024 Society of Chemical Industry.

Dicyandiamide Applications Mitigate the Destructive Effects of Graphene Oxide on Microbial Activity, Diversity, and Composition and Nitrous Oxide Emission in Agricultural Soil

The widespread production and utilization of graphene oxide (GO) raise concerns about its environmental release and potential ecological impacts, particularly in agricultural soil. Effective nitrogen (N) management, especially through nitrification inhibitors like dicyandiamide (DCD), might mitigate the negative effects of GO exposure on soil microbes via N biostimulation. This study quantified changes in soil physicochemical properties, nitrous oxide (N2O) emissions, microbial activity, biomass, and community after treatments with GO and DCD. The GO exposure significantly reduced bacterial 16S rRNA gene abundance and the biomass of major bacterial phyla. It also stimulated pathways linked to human diseases. However, DCD application alleviated the negative effects of GO exposure on soil bacterial biomass. While DCD application significantly reduced soil N2O emission, the GO application tended to hinder the inhibiting performance of DCD. Our findings highlight the hazards of GO exposure to soil microbes and the potential mitigation strategy with soil N management.

Response of earthworm enzyme activity and gut microbial functional diversity to carbendazim in the manured soil

The effect of pesticide pollution on environmental microorganisms in soil has become the focus of widespread concern in society today. The response of earthworm gut and surrounding soil microbial functional diversity and enzyme activity to carbendazim (CBD) was studied in a soil-earthworm ecosystem amended with manure. In the experiment, CBD was added to the manured soil (MS). Meanwhile, the pesticide treatment without manure and the control treatment without pesticides were also set up. The activities of catalase (CAT) and acetylcholinesterase (AChE) were measured to evaluate the toxicity of CBD. The Biolog method was used to assess the functional diversity of the microbial community. In the 2 mg/kg CBD treatment, earthworm AChE activity decreased significantly in the MS after 14 d, which occurred earlier than in the un-manured soil (NS). The changes of earthworm CAT activity in the pesticide treatments showed a trend of initially increasing and then maintaining at a high activity level. However, the CAT activities at 28 d in the manured soils were clearly lower than that at 7 d for both the CBD treatments, while they remained stable in the control treatments. The carbon source utilization, Simpson index, Shannon index, and McIntosh index of soil microorganisms in the MS treatments were significantly higher than those in the NS treatments. The overall activity of earthworm gut microorganisms in the MS treated with 2 mg/kg CBD was higher than that in the control. Also, CBD treatment (2 mg/kg) increased significantly the Simpson index and McIntosh index of earthworm gut microorganisms. The results indicated that the enzyme activities in the manured soils increased before 7 d for the pesticide treatments. Furthermore, exposure to CBD at a high concentration in the MS not only led to the earlier inhibition of earthworm enzyme activity but also significantly improved the overall activity of earthworm gut microorganisms and microbial functional diversity. This study revealed the ecotoxicological effects of earthworms in response to pesticide stress following the use of organic fertilizers under facility environmental conditions, which can provide a theoretical basis for the remediation of pesticide pollution in soil in the future.

Enhancing pakchoi cabbage yield and quality but reducing human-disease risk of bacterial community from wastewater irrigation by combined nanoscale zerovalent iron and nitrification inhibitor

It was indispensable to seek effective and feasible measures to alleviate the adverse effects of wastewater irrigation. Nanoscale zerovalent iron (nZVI) and soil nitrogen management might enhance the vegetable yield and quality but mitigate the potential human-disease risks from wastewater irrigation. This study selected the nZVI and nitrification inhibitor as experimental objects. The planted pakchoi cabbage was irrigated with the tap water and wastewater and treated with nZVI and 3, 4-dimethylpyrazole phosphate (DMPP), respectively, the pakchoi cabbage yield and quality, soil enzyme activity and abiotic property, and human-disease risk of bacterial community were quantified. Compared with the control, the nZVI significantly enhanced the pakchoi cabbage yield by 51.5% but reduced the pakchoi cabbage nitrate content by 52.6% under wastewater irrigation condition. The nZVI alone had double-edged sword effects of increasing the pakchoi cabbage yield, reducing the pakchoi cabbage nitrate content and soil human-disease risk but inhibiting the system multifunctionality and soil bacterial community diversity and stability, under wastewater irrigation condition. The nZVI diminished human-disease risk via increasing the soil Firmicutes and Verrucomicrobiota ratios, and the extra DMPP could mitigate the negative effects of nZVI by increasing soil enzyme activity and stimulating soil Acidobacteria ratio. The combinations of nZVI and DMPP could not only enhance the pakchoi cabbage yield and quality but also reduce the human-disease risk of soil bacterial community from wastewater irrigation.

Global impact of enhanced-efficiency fertilizers on vegetable productivity and reactive nitrogen losses

Vegetables are the most consumed non-staple food globally, and their production is crucial for dietary diversity and public health. Use of enhanced-efficiency fertilizers (EEFs) in vegetable production could improve vegetable yield and quality while reducing reactive nitrogen (Nr) losses. However, different management and environmental factors has significantly distinctive impacts on the effectiveness of EEFs. In this study, a worldwide meta-analysis based on the data collected from 144 studies was performed to assess the impacts of EEF (nitrification inhibitor [NI] and polymer-coated urea [PCU]) application on vegetable yield, nitrogen (N) uptake, nitrogen use efficiency (NUE), vegetable quality and Nr losses (nitrous oxide [N2O] emissions, ammonia [NH3] volatilization, and nitrate [NO3-] leaching). The effects of the applied EEFs on vegetable yields and N2O emissions were assessed with different management practices (cultivation system, vegetable type and N application rate) and environmental conditions (climatic conditions and soil properties). Compared to conventional fertilizers, EEFs significantly improved vegetable yield (7.5-8.1 %) and quality (vitamin C increased by 10.7-13.6 %, soluble sugar increased by 9.3-10.9 %, and nitrate content reduced by 17.2-25.1 %). Meanwhile, the application of EEFs demonstrated a great potential for Nr loss reduction (N2O emissions reduced by 40.5 %, NO3- leaching reduced by 45.8 %) without compromising vegetable yield. The NI was most effective in reducing N2O emissions (40.5 %), but it significantly increased NH3 volatilization (32.4 %). While PCU not only significantly reduced N2O emissions (24.4 %) and NO3- leaching (28.7 %), but also significantly reduced NH3 volatilization (74.5 %). And N application rate, soil pH, and soil organic carbon (SOC) were the main factors affecting the yield and environmental effects of EEFs. Moreover, the yield-enhancing effect of NI and PCU were better at low soil N availability and SOC, respectively. Thus, it is important to adopt the appropriate EEF application strategy targeting specific environmental conditions and implement it at the optimal N application rate.

Asymmetries among soil fungicide residues, nitrous oxide emissions and microbiomes regulated by nitrification inhibitor at different moistures

Carbendazim residue has been widely concerned, and nitrous oxide (N2O) is one of the dominant greenhouse gases. Microbial metabolisms are fundamental processes of removing organic pollutant and producing N2O. Nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) can change soil abiotic properties and microbial communities and simultaneously affect carbendazim degradation and N2O emission. In this study, the comprehensive linkages among carbendazim residue, N2O emission and microbial community after the DMPP application were quantified under different soil moistures. Under 90% WHC, the DMPP application significantly reduced carbendazim residue by 54.82% and reduced soil N2O emission by 98.68%. The carbendazim residue was negatively related to soil ammonium nitrogen (NH4+-N), urease activity, and ratios of Bacteroidetes, Thaumarchaeota and Nitrospirae under 90% WHC, and the N2O emission was negatively related to NH4+-N content and relative abundance of Acidobacteria under the 60% WHC condition. In the whole (60% and 90% WHC together), the carbendazim residue was negatively related to the abundances of nrfA (correlation coefficient = -0.623) and nrfH (correlation coefficient = -0.468) genes. The hao gene was negatively related to the carbendazim residue but was positively related to the N2O emission rate. The DMPP application had the promising potential to simultaneously reduce ecological risks of fungicide residue and N2O emission via altering soil abiotic properties, microbial activities and communities and functional genes. ENVIRONMENTAL IMPLICATION: Carbendazim was a high-efficiency fungicide that was widely used in agricultural production. Nitrous oxide (N2O) is the third most important greenhouse gas responsible for global warming. The 3, 4-dimethylpyrazole phosphate (DMPP) is an effective nitrification inhibitor widely used in agricultural production. This study indicated that the DMPP application reduced soil carbendazim residues and N2O emission. The asymmetric linkages among the carbendazim residue, N2O emission, microbial community and functional gene abundance were regulated by the DMPP application and soil moisture. The results could broaden our horizons on the utilizations DMPP in decreasing fungicide risks and N2O emission.

Core Soil Microorganisms and Abiotic Properties as Key Mechanisms of Complementary Nanoscale Zerovalent Iron and Nitrification Inhibitors in Decreasing Paclobutrazol Residues and Nitrous Oxide Emissions

Agrochemical residues and nitrous oxide (N2O) emissions have caused considerable threats to agricultural soil ecology. Nanoscale zerovalent iron (nZVI) and nitrification inhibitors might be complementary to each other to diminish soil agrochemical residues and N2O emissions and enhance soil bacterial community diversities. Compared to the control, the nZVI application declined soil paclobutrazol residues by 5.9% but also decreased the bacterial community co-occurrence network node. Combined nZVI and Dicyandiamide applications significantly decreased soil N2O emission rates and paclobutrazol residues but promoted Shannon diversity of the bacterial community. The increased soil pH, ammonium nitrogen, and Actinobacteriota could promote soil paclobutrazol dissipation. The nZVI generated double-edged sword effects of positively decreasing paclobutrazol residues and N2O emissions but negatively influencing soil multifunctionalities. The nZVI and Dicyandiamide could be complementary to each other in diminishing soil agrochemical residues and N2O emission rates but promoting soil bacterial community diversities simultaneously.

Non-targeted effects of nitrification inhibitors on soil free-living nitrogen fixation modified with weed management

Biological nitrogen fixation and nitrification inhibitor applications contribute to improving soil nitrogen (N) availability, however, free-living N fixation affected by nitrification inhibitors has not been effectively evaluated in soils under different weed management methods. In this study, the effects of the nitrification inhibitors dicyandiamide (DCD) and 3, 4-dimethylpyrazole phosphate (DMPP) on the nitrogenase, nifH gene，and diazotrophic communities in soils under different weed management methods (AMB, weeds growth without mowing or glyphosate spraying; GS, glyphosate spraying; MSG, mowing and removing weeds and glyphosate spraying; and WM, mowing aboveground weeds) were investigated. Compared to the control counterparts, the DCD application decreased soil nitrogenase activity and nifH gene abundance by 4.5 % and 37.9 %, respectively, under the GS management method, and the DMPP application reduced soil nitrogenase activity by 20.4 % and reduced the nifH gene abundance by 83.4 % under the MSG management method. The application of nitrification inhibitors significantly elevated soil NH4+-N contents but decreased NO3--N contents, which had adverse impacts on soil nifH gene abundance and nitrogenase activity. The nifH gene abundances were also negatively impacted by dissolved organic N and Geobacter but were positively affected by available phosphorus and diazotrophic community structures. Nitrification inhibitors significantly inhibited Methylocella but stimulated Rhizobiales and affected soil diazotrophic communities. The nitrification inhibitors DCD and DMPP significantly altered soil diazotrophic community structures, but weed management outweighed nitrification inhibitors in reshaping soil diazotrophic community structures. The non-targeted effects of the nitrification inhibitors DMPP and DCD on soil free-living N fixation were substantially influenced by the weed management methods.

Linking Carbendazim Accumulation with Soil and Endophytic Microbial Community Diversities, Compositions, Functions, and Assemblies: Effects of Urea-hydrogen Peroxide and Nitrification Inhibitors

Fungicide carbendazim accumulation in soils and plants is a wide concern. Nitrogen (N) is a substantial nutrient limiting crop growth and affecting soil microbial activity and the community in degrading fungicides. We investigated the effects of urea-hydrogen peroxide (UHP) and nitrification inhibitors Dicyandiamide (DCD) and 3,4-dimethylpyrazole phosphate (DMPP) on carbendazim accumulation and soil and endophytic microbial communities. The UHP application had negligible influences on soil and plant carbendazim accumulation, but the combined UHP and DCD decreased soil carbendazim accumulation by 5.31% and the combined UHP and DMPP decreased plant carbendazim accumulation by 44.36%. The combined UHP and nitrification inhibitor significantly decreased the ratios of soil Firmicutes and endophytic Ascomycota. Soil microbial community assembly was governed by the stochastic process, while the stochastic and deterministic processes governed the endophyte. Our findings could provide considerable methods to reduce fungicide accumulation in soil-plant systems with agricultural N management strategies.