Vegetable Fields Research Articles

Environmental Parameters Determine the Structure of Soil Bacteria under Different Land use Types in Tailings Area

Soil microorganisms contribute substantially to a wide range of services and thereby improve recovery in ecosystem restoration. However, there is relatively limited information on how microbial communities respond to different land-use types with similar plant species and their potential roles in supporting soil restoration in mine tailings. To understand the importance of the response of soil microbial communities to the stress of tailings area in different soil habitats, this article selected three different land use types (Tailings area, Buffer zone and Vegetable field) as the variables in the Yanzibian tailings area in Ningqiang, Shaanxi Province, China. Soil physicochemical properties and heavy metal concentrations of the different land use types were compared. Illumina MiSeq. 2500 Sequencing Technology was used to analyze the abundance and structural diversity of the microbial community in soil samples. The results showed that most of the soil samples were unsafe with multiple metals. All soil samples in the buffer zone and tailings ponds were acidic. With the acidity decreased, bacterial community richness and diversity increased significantly. Briefly, different environmental factors and soil microbial communities were significantly distinct across different land-use types. Cu, Zn, Pb, pH, MC (Moisture content), TN (Total nitrogen), TP (Total phosphorus), and TK (Total potassium) were essential factors affecting the abundance and structural diversity of soil microbial communities across three different land-use types. As a result, Actinobacteria, Alphaproteobacteria, and Gammaproteobacteria were the top dominant classes in the buffer zone and Vegetable field soils, while Sulfobacillia dominated in tailings pond soils. Further, we found that with the continuous decline of the pH, the dominant genera transferred from norank_f__norank_o__Vicinamibacterales, Bacillus and Nocardioides to the norank_f__norank_o__Gaiellales and norank_f__norank_o__Acidobacteriales, then to Sulfobacillus. These confirmed that the responses of microbiota to heavy metals stress varied in different land-use types. Together, this study provides important information on the occurrence and distribution of soil microbiomes in tailings areas and their potentially beneficial roles in soil restoration.

Effect of Soaking Tubers in Potassium Humate and Foliar Application of Nano-Calcium Fertilizer on some Growth Traits of Two Potato Cultivars

In the spring of 2022, researchers from the University of Mosul’s Faculty of Agriculture and Forestry conducted an experiment on a vegetable field. In this experiment, we looked at three variables: first, the effects of two different potato cultivars (Montreal and EL-Beida). For the second part, we soaked potatoes in a solution of potassium humate with a concentration of (0, 0.5, 1 g L-1). Therefore, the experiment had 18 treatments (2 3 3), with the third factor being Nano-calcium fertilizer with three concentrations of (0, 1.5, and 2.5 g L-1) applied to plants at three stages of plant growth: the first 20 days after full germination, the second and third stages, with a 20-day interval between addition and another. Cultivars were positioned in the primary plots, with the interaction between two additional variables located in sub-plots, as part of a factorial experiment inside a split-plot utilizing the Randomized Complete Block Design with three repetitions. Duncan’s multiple range test for comparing means was used to analyze the data at a 5% significance level. This leads to the following conclusion: Of the cultivars tested, the Montreal variety performed best when soaked in potassium humate at two different concentrations, increasing both leaf area and dry matter percentage in the vegetative development (0.5 and 1). both total chlorophyll content and leaf area were significantly increased by g.L-1. The best statistically significant data for plant height, number of aerial stems, and leafy area were obtained after spraying calcium Nano-fertilizer at two doses.

Variability and Expectant Genetic Advance for Yield and its Components in Radish (Raphanus sativus L.)

The study was carried out with the aim of estimating some of the genetic parameters represented by variations, broad sense heritability and expected genetic advance and evaluating the genetic performance for some of the growth and yield characteristics of the five varieties of radish (Raphanus sativus L.) are (Local red, Local black, Turkish red, Syrian red and Turkish white) during the growth season 2019- 2020 in the vegetable field at Horticulture and Landscape Department College of Agriculture and Forestry-Mosul University within the design of using Randomized Complete Block Design (R.C.B.D.) with three replicates. Results of the analysis of variance for the studied traits showed that there were significant differences between the five varieties of all studied traits. The local black variety significantly superior compared the other variety in the Leaf fresh weight, and the syrian red variety in the root weight and total yield. The phenotypic, genotypic variations and broad sense heritability was high for the plant height, Leaf fresh weight, root weight and total yield. Which it means that most of the phenotypic variation between varieties was due to genetic variations. As for the expected genetic advance was high for the plant height, Leaf fresh weight, root weight, the ratio of the root / leaf ratio and total yield. Which indicates the importance of selection for improving these characters.

Effect of Cultivars, Apical Pinching and Copper Nano-Fertilizer on 1-Characteristics of Vegetative Growth of Broad Bean (Vicia faba L.)

Research was conducted at the vegetable field of the University of Mosul’s Department of Horticulture and Landscape Engineering (in the College of Agriculture and Forestry) (2021). The experiment included a study of three factors, the first of which was the use of three different bean sprout cultivars (Spanish, American, and Dutch), the second of which was the condition of apical pinching (apical pinching and without pinching), and the third of which was the use of copper Nano-fertilizer at three different concentrations (zero, one, and 1.5 gm L-1) (2 x 3 x 3). Field research was conducted utilizing a factorial experiment with split-plots in R.C.B.D. Varieties were planted in the main plots, and the correlation between pinching and copper Nano-fertilizer concentrations was observed in the sub-plots. The Duncan multiple range test was used to compare the means of the groups, and a significance threshold of 5% was used for the study. Here’s a rundown of the A- The significant effect of the plants of the three cultivars varied in the characteristics of the vegetative growth, as the plants of the Spanish and American cultivars were significantly superior in plant height and percentage of dry matter, while the plants of the Dutch and Spanish cultivars excelled in the number of branches, while no significant differences were observed between the cultivars in terms of chlorophyll and leaf area. B- The treatment of apical pinching excelled in terms of the number of branches and leaf area compared to the treatment of not pinching. C- The use of copper Nano-fertilizer in two concentrations resulted in significant effects on all vegetative growth traits compared to comparison plants. D- Most of the effects of the binary and triple interaction of the studied factors were consistent with the single effect of each factor for most of the previous characteristics.

Genetic Material as a Component of IPM for Vegetable Field Bean Pod Borer Complex

Genetic Material as a Component of IPM for Vegetable Field Bean Pod Borer Complex

Effect of N20 P20 K20 Nano-Fertilizer on Quantitative and Qualitative Yield of Two Potato Cultivars

The study was conducted in the vegetable field of the Department of Horticulture and Landscape Design, College of Agriculture and Forestry, University of Mosul, during the 2021 agricultural season, in order to study the effect of spraying Nano-fertilizer N 02P 02K02 at concentrations of 1, 2, 3 and 4 g·L−1 compared to control treatment, in some components and quality of two potatoes varieties (Florice and Montreal). The experiment was conducted in a split - plot system within RCBD Design with three replications, cultivars factor arranged in the main plots and the concentrations of Nano-fertilizer in the sub plots. After recording the data and analyzing it statistically, the results were as follows: Florice variety was significantly superior in the total number of tubers, while Montreal variety was significantly superior in the percentage of dry matter, starch content of tubers and the specific weight of tubers. The use of the Nano-fertilizer at concentration of 2 g·L−1 led to a significant increase of the number of total, and marketable tubers by 4.65 tubers by plant and 11.10 tubers by plant, respectively compared to unfertilized control. The concentration of 3 g·L−1 led to a significant increase of the mean tuber weight, plant yield, marketable tubers yield, and tuber firmness to 108.54 g, 1189.38 g and 63.434 t·ha84. 10dna kg·cm−2 respectively, compared to unfertilized control. The interaction treatment between Florice cultivar and Nano-fertilizer administered in concentration of 2 g·L−1 led to a significant increase in the number of total and marketable potato tubers. The treatment of Montreal cultivar with a concentration of 3 g·L−1 Nano-fertilizer led to a significant increase of the mean tuber weight, plant yield, total yield of tubers and TSS in tubers, percentage of dry matter and starch in the tubers and the specific weight of the tubersd

A comprehensive and global evaluation of residual antibiotics in agricultural soils: Accumulation, potential ecological risks, and attenuation strategies

The occurrence of antibiotics in agricultural soils has raised concerns due to their potential risks to ecosystems and human health. However, a comprehensive understanding of antibiotic accumulation, distribution, and potential risks to terrestrial ecosystems on a global scale is still limited. Therefore, in this study, we evaluated the accumulation of antibiotics and their potential risks to soil microorganisms and plants, and highlighted the driving factors of antibiotic accumulation in agricultural soils based on 134 peer-reviewed studies (between 2000 and 2022). The results indicated that 56 types of antibiotics were detected at least once in agricultural soils with concentrations ranging from undetectable to over 7000 µg/kg. Doxycycline, tylosin, sulfamethoxazole, and enrofloxacin, belonging to the tetracyclines, macrolides, sulfonamides, and fluoroquinolones, respectively, were the most accumulated antibiotics in agricultural soil. The accumulation of TCs, SAs, and FQs was found to pose greater risks to soil microorganisms (average at 29.3%, 15.4%, and 21.8%) and plants (42.4%, 26.0%, and 38.7%) than other antibiotics. East China was identified as a hot spot for antibiotic contamination due to high levels of antibiotic concentration and ecological risk to soil microorganisms and plants. Antibiotic accumulation was found to be higher in vegetable fields (245.5 µg/kg) and orchards (212.4 µg/kg) compared to croplands (137.2 µg/kg). Furthermore, direct land application of manure resulted in a greater accumulation of TCs, SAs, and FQs accumulation in soils than compost fertilization. The level of antibiotics decreased with increasing soil pH and organic matter content, attributed to decreasing adsorption and enhancing degradation of antibiotics. In conclusion, this study highlights the need for further research on the impacts of antibiotics on soil ecological function in agricultural fields and their interaction mechanisms. Additionally, a whole-chain approach, consisting of antibiotic consumption reduction, manure management strategies, and remediation technology for soil contaminated with antibiotics, is needed to eliminate the potential environmental risks of antibiotics for sustainable and green agriculture.

Extraction and decontamination of microplastics from high organic matter soils: A simple, cost-saving and high efficient method

This article introduces a simple, cost-saving and high efficient for the extraction and separation of microplastics (MPs) from soil with a high organic matter (SOM) content. In this study, MP with particle sizes of 154–600 μm of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) were artificially added into the five Mollisols with the high SOM. Three flotation solutions were used to extract these MPs from soils, and four digestion solutions were used to digest the SOM. As well, their destruction effects on MPs were also examined. The results showed that the flotation recovery rates of PE, PP, PS, PVC and PET were 96.1%–99.0% by ZnCl2 solution, while were 102.0%–107.2% by rapeseed oil, were 100.0%–104.7% by soybean oil. The digestion rate of SOM was 89.3% by H2SO4:H2O2 (1:40, v:v) at 70 °C for 48 h, and this was higher than by H2O2 (30%), NaOH and Fenton's reagent. However, the digestion rate of PE, PP, PS, PVC and PET were 0.0%–0.54% by H2SO4:H2O2 (1:40, v:v), and this was lower than by H2O2 (30%), NaOH and Fenton's reagent. As well, the factors influencing on MP extraction was also discussed. Generally, the best flotation solution was ZnCl2 (ρ > 1.6 g cm−3) and the best digestion method was H2SO4:H2O2 (1:40, v:v) at 70 °C for 48 h. The optimal extraction and digestion method were verified by the known concentrations of MPs (recovery rate of MPs was 95.7–101.7%), and this method was also used to extract MPs from long-term mulching vegetable fields in Mollisols of Northeast China.

Bacteria are more sensitive than fungi to soil fertility in an intensive vegetable field

Partial substitution of chemical nitrogen (N) fertilizers with organic amendments is important for improving soil fertility and crop yield. Microorganisms play an important role in soil fertility by driving energy and nutrient cycles in the soil. However, there is limited information on the link between soil fertility and the microbial community under organic substitutions. Here, we investigated the soil fertility index and fertilization-sensitive operational taxonomic units (OTUs) of bacterial and fungal communities under different organic N substitution rates from 0 % to 100 % during four years of constant fertilization in an intensively-farmed vegetable field. Our results demonstrated that the 20 % and 50 % substitution rates could improve the soil fertility by 35.0 % and 27.5 %, respectively, compared with the 0 % substitution rate while ensuring crop yield. The 20 % to 100 % substitution rates significantly increased bacterial richness and diversity, as well as fungal diversity, compared with the 0 % substitution rate. Bacterial communities showed many more differences between the 0 % and other organic substitutions than in the fungal communities. Of the bacterial networks, the dominant sensitive OTUs are Phycisphaerae and Acidobacteria Subgroup_6 for the 0 % substitution rate and Gammaproteobacteria and Alphaproteobacteria for other organic substitutions. Of the fungal networks, Sordariomycetes and Pezizomycetes were the dominant sensitive OTUs in all fertilization treatments. The assembly patterns of bacterial and fungal communities were induced toward deterministic processes under chemical N fertilization, which were restrained from this process under organic N fertilization. Furthermore, soil fertility produced a significant influence on the bacterial community (dominated by deterministic processes) but not on the fungal community (dominated by stochastic processes). In conclusion, understanding the survival patterns of fertilization-sensitive microorganisms is fundamental to manage soil fertility, which will help to address the needs of targeted smart agriculture through the cultivation of specific microbial taxa in the future.

Soil heavy metal(loid) pollution and health risk assessment of farmlands developed on two different terrains on the Tibetan Plateau, China

The quality of farmland soils on the Tibetan Plateau is important because of the region's ecological vulnerability and their close link with local food security. Investigation on the pollution status of heavy metal (loid)s (HMs) in the farmlands of Lhasa and Nyingchi on the Tibetan Plateau, China revealed that Cu, As, Cd, Tl, and Pb were apparently enriched, with the soil parent materials being the primary sources of the soil HMs. Overall, the farmlands in Lhasa had higher contents of HMs compared to those in Nyingchi, which could be attributed to the fact that the former were mainly developed on river terraces while the latter were mainly developed on the alluvial fans in mountainous areas. As displayed the most apparent enrichment, with the average contents in the vegetable field soils and grain field soils of Lhasa being 2.5 and 2.2 times higher compared to those of Nyingchi. The soils of vegetable fields were more heavily polluted than those of grain fields, probably due to the more intensive input of agrochemicals, particularly the use of commercial organic fertilizers. The overall ecological risk of the HMs in the Tibetan farmlands was low, while Cd posed medium ecological risk. Results of health risk assessment show that ingestion of the vegetable field soils could pose elevated health risk, with children facing greater risk than adults. Among all the HMs targeted, Cd had relatively high bioavailability of up to 36.2% and 24.9% in the vegetable field soils of Lhasa and Nyingchi, respectively. Cd also showed the most significant ecological and human health risk. Thus, attention should be paid to minimize further anthropogenic input of Cd to the farmland soils on the Tibetan Plateau.

Spatio-temporal distribution of organochlorine pesticides in agricultural soils of southeast China during 2014-2019

Organochlorine pesticides (OCPs) are organic pollutants that are persistent and undegradable in the environment. To investigate their residual concentrations, spatial and temporal distributions, and the relationship with the crops planted, 12 individual OCPs in 687 soil samples from Jiangsu, Zhejiang and Jiangxi provinces of southeast China were examined. The detection frequencies of OCPs in the studied areas were 1.89%–64.9%. The concentrations of dichloro-diphenyl-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and endosulfans ranged from 0.01 to 5659 μg/kg, 0.03–3.58 μg/kg, and 0.05–3235 μg/kg, respectively. Jiangsu was mainly contaminated by p,p'-DDT, p,p'-DDD and endosulfan sulfate, Zhejiang was more polluted by OCPs except δ-HCH, and Jiangxi was more vulnerable to the contamination of OCPs except o,p'-DDE. The partial least-squares discrimination analysis (PLS-DA) model with RX2 36.3–36.8% revealed that compounds with similar chemical properties tended to appear in the same year and month. All crop lands were polluted by DDTs and Endosulfans. The highest concentrations of DDTs and Endosulfans were found in citrus and vegetable fields, respectively. This study offers new insight into the layout and partitioning of OCPs in agricultural land and into insecticide management on public health and ecological safety.

Characteristics of annual NH3 emissions from a conventional vegetable field under various nitrogen management strategies

High N-fertilizer applications to conventional vegetable production systems are associated with substantial emissions of NH3, a key substance that triggers haze pollution and ecosystem eutrophication and thus, causing considerable damage to human and ecosystem health. While N fertilization effects on NH3 volatilization from cereal crops have been relatively well studied, little is known about the magnitude and yield-scaled emissions of NH3 from vegetable systems. Here we report on a 2-year field study investigating the effect of various types and rates of fertilizer application on NH3 emissions and crop yields for a pepper-lettuce-cabbage rotation system in southwest China. Our results show that both NH3 emissions and direct emission factors of applied N varied largely across seasons over the 2-year period, highlighting the importance of measurements spanning entire cropping years. Across all treatments varying from solely applying urea fertilizers to only using organic manures, annual NH3 emissions ranged from 0.64 to 92.4 kg N ha−1 yr−1 (or 0.07–6.84 g N kg−1 dry matter), equivalent to 0.05–5.99% of the applied N. At annual scale, NH3 emissions correlated positively with soil δ15N values, indicating that soil δ15N may be used as an indicator for NH3 losses. NH3 emissions from treatments fertilized partially or fully with manure were significantly lower compared with the urea fertilized treatment, while vegetable yields remained unaffected. Moreover, full substitution of urea by manure as compared to the partial substitution further reduced the yield-scaled annual NH3 emissions by 79.0–92.4%. Across all vegetable seasons, there is a significant negative relationship between yield-scaled NH3 emissions and crop N use efficiency. Overall, our results suggest that substituting urea by manure and reducing total N inputs by 30–50% allows to reduce NH3 emissions without jeopardizing yields. Such a change in management provides a feasible option to achieve environmental sustainability and food security in conventional vegetable systems.

Dynamic characteristics of heavy metal accumulation in agricultural soils after continuous organic fertilizer application: Field-scale monitoring

Manure has been considered as a source of soil heavy metal (HM) pollution. However, the long-term impact of manure application on soil HM accumulation have not been well studied. This study tracked the long-term cumulative trends of soil copper (Cu), zinc (Zn), arsenic (As), and lead (Pb) in three soil-crop systems over 5–8 years’ application of commercial manure fertilizer. The contribution of different fertilization treatments (CF, chemical fertilizer; T1-T3, manure with different application dosages) to soil HMs pollution risk were assessed. There are accumulating tendencies for Cu, Zn, and Pb in paddy fields, Cu and As in orchard fields, and Zn, As, and Pb in vegetable fields, while the concentrations of As in paddy fields and Zn in orchard fields decreased over time. Manure application significantly influenced the accumulation of Cu, Zn, and As in soils rather than that of Pb. The modeling prediction subsequently revealed that the time required to reach the risk screening values (Cu: 50 mg kg−1; Zn: 200 mg kg−1) for HM content in paddy soil, according to GB15618-2018, decreased from 18.20 years to 7.20 years due to the introduction of Cu and Zn via manure use. Recommend annual manure application dosage was 7.73 t hm−2 y−1 to ensure a 20-year period of clean production in paddy soils, while it was 26.15 t hm−2 y−1 in the orchard soil and 16.23 t hm−2 y−1 in vegetable soil to ensure a 50-year period of clean production, respectively. Overall, the impacts of HMs input by manure application on soil HMs accumulation varied depending on the type of metal and the soil-crop system. The cumulative trends of HMs in soils play a crucial role in determining whether the input of HMs through manure application can lead to the risk of HM pollution.

Soil microbial communities as potential regulators of N2O sources in highly acidic soils

• Soil pH was a key driver of N2O emission and sources in acidic soils. • N2O emission was significantly positively associated with the ratio of ITS to 16S. • N2O was significantly correlated with bacterial and fungal community composition. • Fungi contributed to N2O in highly acidic tea plantations and vegetable fields. Acidic soil is a main source of global nitrous oxide (N2O) emissions. However, the mechanism behind the high N2O emissions from acidic soils remains a knowledge gap. The objective of this microcosm incubation study was to pin-point the microbial mechanisms involved in N2O production processes in acidic soils. For that purpose, the isotopic signatures and microbial community structure and composition of four soil samples were examined. The results showed that highly acid soils (pH = 3.51) emitted 89 times more N2O than alkaline soils (pH = 7.95) under the same nitrogen (N) inputs. Fungal denitrification caused high N2O emissions in acidic soils. ITS to 16S abundance ratio was positively correlated with cumulative N2O emissions from the tested soils. The highly acid soils (pH < 4.5) showed greater fungal nirK gene abundance and lower abundance of AOA-amoA, AOB-amoA, nirK, nosZ I and nosZ II genes. The unclassified Aspergillaceae fungi (63.65%) dominated the highly acidic soils and was the most strongly correlated genus with N2O emissions. These findings highlight that soil microbial community structures, denitrifying fungi in particular, shaped by low pH (pH < 4.5) lead to high N2O emissions from acidic soils.

Identification, Diversity, and Distribution of Meloidogyne spp. in Vegetable Fields of South Georgia, U.S.A.

Root-knot nematode (RKN; Meloidogyne spp.) is the most prevalent plant-parasitic nematode in vegetable fields of Georgia, with an incidence of 67.3%. Because aggressive RKN species are reported in the southeastern United States, molecular-based identification of RKN species was conducted on soil samples taken from a nematode surveillance study in 2018 from 292 RKN-infested vegetable fields in southern Georgia. The RKN-infested soil was potted with tomato cultivar Rutgers, and individual nematode females were isolated from galled roots and subjected to species-specific PCR and mitochondrial haplotype-based RKN species identification. The incidence (%), mean, and maximum relative abundance (second-stage juveniles per 100 cm3 of soil) of the five RKN species identified consisted of M. incognita (91.9, 486, 14,144), M. arenaria (36.0, 707, 14,144), M. floridensis (2.2, 909, 5,264), M. javanica (5.5, 352, 1,488), and M. haplanaria (0.7, 8, 14). A large proportion of fields (29%) had mixed populations of M. incognita and M. arenaria, which may reflect the region's long history of cotton and peanut cultivation. For unknown reasons, mixed populations of M. incognita and M. arenaria were associated with higher population densities. M. incognita is the most important RKN species in vegetable fields, followed by M. arenaria; therefore, pure or mixed populations of these species should be addressed in nematode management programs. Although at a lower incidence, the newly detected species, M. floridensis and M. haplanaria, have the potential to become a major threat since they reproduce on vegetables with Mi-resistant genes.

A Flashback to Cholera Outbreaks in Kurdistan region-Iraq

Cholera is a contagious acute diarrheal disease due to ingestion of contaminated water and food with Vibrio cholera, a Gram-negative bacterium that naturally inhabits coastal and estuarine ecosystems. Millions of cholera cases and thousands of deaths are annually reported worldwide. Cholera is endemic in Iraq with every 3-5 years interval. Meanwhile, cholera outbreaks have been reporting in Kurdistan region. However, the epidemiology of the disease has not been investigated. This study comprehensively reviewed the cholera outbreaks in Kurdistan region, depending on the WHO situation reports, online resources and scientific researches. The results showed seven reported cholera outbreaks from 1995 to 2022. The cholera epidemics happened at irregular intervals that makes the prediction of next outbreak difficult. Moreover, the trend of cholera is greatly decreasing from thousands to hundreds of cases throughout the outbreaks and in total about 30 people died. These might be the consequences of effective prevention measures, population health and natural acquired immunity against cholera. It was found that Sulaymaniyah is the most affected governorate in the region. This is probably related to the contamination of the main drinking water resource, little Zab river. Besides, the irrigation of the vegetable fields with untreated sewage could be another cause. Also, both Inaba and Ogawa serotypes of Vibrio cholera, O1, El Tor individually caused the outbreaks. Thus, cholera outbreak will be happening in Kurdistan region, particularly in Sulaymaniyah governorate. This definitely needs more scientific investigations, hoping to tackle the future outbreaks and total eradication of the disease.

Soil fertility and landscape surrounding former arable fields drive the ecological resilience of Mediterranean dry grassland plant communities

IntroductionSemi-natural dry grasslands are among the species-richest and most diverse habitats in Europe especially in the Mediterranean Basin. They evolved with long-term severe environmental constraints, either biotic (e.g., grazing or mowing) or abiotic (e.g., dryness or oligotrophy). Their recovery after sever anthropogenic disturbance, such as cultivation is often very slow and incomplete. A deeper understanding of the processes driving the recovery would be of great benefit to better restore or conserve these grasslands. We used the filter model as a framework to assess the relative importance of dispersion, abiotic and biotic filters as drivers of this recovery.MethodsWe studied the medium-term dynamics of 37 Mediterranean dry grassland plant communities after an episode of cultivation in the plain of La Crau (Southern France) by two census: after 25 years of abandonment, and revisited 10 years later (35 years of abandonment). Our aims were to characterize the temporal medium-term dynamics of these communities, to measure their taxonomic resilience and to identify the drivers. We performed structural equation modeling to measure the importance of the various drivers, with cover of remnant dry grasslands surrounding each studied community as a proxy for the dispersion filter, soil pH and phosphorus content as proxies for the abiotic filter and cover of the most dominant species as a proxy for the biotic filter.Results and DiscussionOur results show that former arable field vegetation do not recover after more than 40 years. The three filters drive the recovery of dry grassland vegetation: former arable fields that have lower phosphorus content (abiotic filter) have a lower cover of dominant species (biotic filter), a higher species richness and a higher similarity with remnant dry grassland plant communities, especially if the former arable fields are surrounded by remnant dry grasslands (dispersion filter).

Effects of plastic film mulching and nitrogen fertilization on the emissions of greenhouse gases from vegetable field in Southwest China

This study identified the influence of plastic film mulching (FM) and nitrogen (N) fertilization on the CH4 emission, the global warming potential (GWP) and the greenhouse gas intensity (GHGI) in a summer-hot pepper and winter-radish rotation field from May 2014 to April 2017. The experiment had 8 treatments including no-mulching (NM) and plastic film mulching with four different N fertilization rates (0, 150, 300 and 450 kg N ha−1 and 0, 100, 200 and 300 kg N ha−1 in the respective hot pepper and radish growing periods). The results indicated that FM as well as N fertilization had insignificant effects on CH4 emissions in the hot pepper and radish growing periods (P > 0.05). Relative to NM, FM had little effect on GWP (P > 0.05) but lowered GHGI substantially (P < 0.05) during the hot pepper growing period. During the radish growing period, FM enhanced GWP and GHGI significantly (P < 0.05). Additionally, N fertilization significantly enhanced GWP and vegetable yields both in hot pepper and radish growing periods (P < 0.05). In hot pepper growing period, N fertilization increased GWP more significantly than yield which resulted in increased GHGI with N fertilization rate, and the promotion effect of N fertilization on hot pepper yield was strongest at 150 kg N ha−1 with a relatively low GHGI. However, in radish growing period, N fertilization increased yield more significantly than GWP which resulted in the decreasing effect of N fertilization on GHGI, and the promotion effect of N fertilization on radish yield was strongest at 300 kg N ha−1 with a relatively low GHGI. Therefore, FM with 150 kg N ha−1 and NM with 300 kg N ha−1 were respectively recommended for the hot pepper growing period and radish growing period to achieve high vegetable yields and mitigate greenhouse gas (GHG) emissions simultaneously under the present vegetable field condition in Southwest China.

Levels of heavy metal in soil and vegetable and associated health risk in peri-urban areas across China

Peri-urban vegetable field plays an essential role in providing vegetables for local residents. Because of its particularity, it is affected by both industrial and agricultural activities which have led to the accumulations of heavy metal in soil. So far, information on heavy metal pollution status, spatial features, and human health risks in peri-urban vegetable areas across China is still scarce. To fill this gap, we systematically compiled soil and vegetable data collected from 123 articles published between 2010 and 2022 at a national level. The pollution status of heavy metals (i.e., cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn)) in peri-urban vegetable soils and vegetables were investigated. To evaluate the levels of heavy metal pollution in soil and human health risks, the geoaccumulation index (Igeo) and target hazard quotient (HQ) were calculated. The results showed that mean concentrations of Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in peri-urban vegetable soils were 0.50, 0.53, 12.03, 41.97, 55.56, 37.69, 28.55, and 75.38 mg kg−1, respectively. The main pollutants in peri-urban vegetable soil were Cd and Hg, and 85.25% and 92.86% of the soil samples had Igeo > 1, respectively. The mean Igeo values of this regions followed the order of northwest > central > south > north > east > southwest > northeast for Cd and northeast > northwest > north > southwest > east > central > south for Hg. The mean Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn concentrations in vegetables were 0.30, 0.26, 0.37, 0.54, 1.17, 6.17, 1.96, and 18.56 mg kg−1, respectively. Approximately 87.01% (Cd), 71.43% (Hg), 20% (As), 65.15% (Pb), 27.08% (Cr) of the vegetable samples exceeded the safety requirement values. The vegetables grown in central, northwest, and northern China accumulated much more heavy metals than those grown in other regions. As the HQ values for adults, 53.25% (Cd), 71.43% (Hg), 84.00% (As), and 58.33% (Cr) of the sampled vegetables were higher than 1. For children, the HQ values were higher than 1 for 66.23% (Cd), 73.81% (Hg), 86.00% (As), and 87.50% (Cr) of the sampled vegetables. The findings of this study demonstrate that the situation of heavy metal pollution in peri-urban vegetable areas across China are not optimistic and residents who consume the vegetables are at high risk of health issues. To ensure soil quality and human health, strategies should be taken to guide vegetable production and remedy soil pollution in peri-urban areas with the rapidly urbanizing China.

Ammonia oxidizing archaea and bacteria respond to different manure application rates during organic vegetable cultivation in Northwest China

Ammonia oxidization is a critical process in nitrogen cycling that involves ammonia oxidizing archaea (AOA) and bacteria (AOB). However, the effects of different manure amounts on ammonia-oxidizing microorganisms (AOMs) over the course of organic vegetables production remains unclear. We used the amoA gene to evaluated AOMs abundance and community structure in organic vegetable fields. Quantitative PCR revealed that AOB were more abundant than AOA. Among them, the amoA copy number of AOB treated with 900 kgN ha−1 was 21.3 times that of AOA. The potential nitrification rate was significantly correlated with AOB abundance (P < 0.0001) but not with AOA, suggesting that AOB might contribute more to nitrification than AOA. AOB sequences were classified into Nitrosomonas and Nitrosospira, and AOA into Nitrosopumilus and Nitrososphaera. Nitrosomonas and Nitrosopumilus were predominant in treatments that received manure nitrogen at ≥ 900 kg ha−1 (52.7–56.5%) and when manure was added (72.7–99.8%), respectively, whereas Nitrosospira and Nitrososphaera occupied more than a half percentage in those that received ≤ 600 kg ha−1 (58.4–84.9%) and no manure (59.6%). A similar manure rate resulted in more identical AOMs’ community structures than greater difference manure rate. The bacterial amoA gene abundances and ratios of AOB and AOA showed significantly positive correlations with soil electrical conductivity, total carbon and nitrogen, nitrate, phosphorus, potassium, and organic carbon, indicating that these were potential key factors influencing AOMs. This study explored the AOMs’ variation in organic vegetable fields in Northwest China and provided a theoretical basis and reference for the subsequent formulation of proper manure management.