Changfeng Ding

Prediction Model for Cadmium Transfer from Soil to Carrot (Daucus carota L.) and Its Application To Derive Soil Thresholds for Food Safety

At present, soil quality standards used for agriculture do not fully consider the influence of soil properties on cadmium (Cd) uptake by crops. This study aimed to develop prediction models for Cd transfer from a wide range of Chinese soils to carrot (Daucus carota L.) using soil properties and the total or available soil Cd content. Path analysis showed soil pH and organic carbon (OC) content were the two most significant properties exhibiting direct effects on Cd uptake factor (ratio of Cd concentration in carrot to that in soil). Stepwise multiple linear regression analysis also showed that total soil Cd, pH, and OC were significant variables contributing to carrot Cd concentration, explaining 90% of the variance across the 21 soils. Soil thresholds for carrot (cultivar New Kuroda) cropping based on added or total Cd were then derived from the food safety standard and were presented as continuous or scenario criteria.

Declined soil suppressiveness to Fusarium oxysporum by rhizosphere microflora of cotton in soil sickness

Cotton yield and quality have been severely compromised by soil sickness throughout the primary cotton-growing regions of China. The aim of this study was to gain insight into the role of rhizosphere microbial community in governing soil sickness of cotton. Plant growth, disease resistance, root exudates, and the composition of the rhizosphere microbial community of cotton were analyzed in two different (4- and 15-year) monocropped soils and in a fallow agricultural soil (control). The monocropped soils significantly influenced cotton growth and root exudates and reduced soil suppressiveness to Fusarium wilt in bioassay experiments. Additionally, pyrosequencing of the whole internal transcribed spacers (ITS1 and ITS2) and 16S rRNA gene amplicons demonstrated clear variations in the microbial composition of cotton rhizosphere between monocropped rhizosphere soils and control soil. Specifically, monocropped soils were characterized by an increase in the abundance of fungal pathogens, including Fusarium oxysporum f. sp. vasinfectum and Verticillium dahliae, relative to the rhizosphere of control soil. Some plant-beneficial and disease-suppressive bacterial taxa, including Xanthomonadaceae, Comamonadaceae, Oxalobacteraceae, and Opitutaceae, were associated with healthy cotton. A significant correlation existed between the presence of certain amino acids (e.g., glutamic acid and alanine) and the above identified taxa, indicating that some constituents in root exudates influenced the microbial compositions of the cotton rhizosphere to manage the disease status of plant in monocropped soils. Collectively, these results suggest that pathogenic fungal build-up and a reduction in the abundance of beneficial rhizobacteria in the rhizosphere contribute to changes in soil suppressiveness to soil-borne pathogens in monocropped soils, resulting in an aggravated level of soil sickness.

Effects of soil type and genotype on lead concentration in rootstalk vegetables and the selection of cultivars for food safety

Lead (Pb) contamination of soil poses severe health risks to humans through vegetable consumption. The variations of Pb concentration in different parts of rootstalk vegetables (radish, carrot and potato) were investigated by using twelve cultivars grown in acidic Ferralsols and neutral Cambisols under two Pb treatments (125 mg kg(-1) and 250 mg kg(-1) for Ferralsols; 150 mg kg(-1) and 300 mg kg(-1) for Cambisols) in a pot experiment. The Pb concentration in edible parts was higher in Ferralsols under two Pb treatments, with range from 0.28 to 4.14, 0.42-10.66 mg kg(-1) (fresh weight) respectively, and all of them exceeded the food safety standard (0.1 mg kg(-1)) recommended by the Codex Alimentarius Commission of FAO and WHO. The Pb concentration in edible parts was significantly affected by genotype, soil type and the interaction between these two factors. The variation of Pb concentration in different cultivars was partially governed by Pb absorption and the transfer of Pb from aerial to edible part. The results revealed that caution should be paid to the cultivation of rootstalk vegetables in Pb-contaminated Ferralsols without any agronomic management to reduce Pb availability and plant uptake. For Cambisols with slight to moderate Pb contamination, growing potato cultivar Shandong No.1 and Chongqing No.1 was effective in reducing the risk of Pb entering human food chain. The results suggest the possibility of developing cultivar- and soil-specific planting and monitoring guidelines for the cultivation of rootstalk vegetables on slight to moderate Pb-contaminated soils.

Major controlling factors and prediction models for mercury transfer from soil to carrot

PurposeSoil-plant transfer models are needed to predict levels of mercury (Hg) in vegetables when evaluating food chain risks of Hg contamination in agricultural soils.Materials and methodsA total of 21 soils covering a wide range of soil properties were spiked with HgCl2 to investigate the transfer characteristics of Hg from soil to carrot in a greenhouse experiment. The major controlling factors and prediction models were identified and developed using path analysis and stepwise multiple linear regression analysis.Results and discussionCarrot Hg concentration was positively correlated with soil total Hg concentration (R2 = 0.54, P < 0.001), and the log-transformation greatly improved the correlation (R2 = 0.76, P < 0.001). Acidic soil exhibited the highest bioconcentration factor (BCF) (ratio of Hg concentration in carrot to that in soil), while calcareous soil showed the lowest BCF among the 21 soil types. The significant direct effects of soil total Hg (Hgsoil), pH, and free Al oxide (AlOX) on the carrot Hg concentration (Hgcarrot) as revealed by path analysis were consistent with the result from stepwise multiple linear regression that yielded a three-term regression model: log [Hgcarrot] = 0.52log [Hgsoil] − 0.06pH − 0.64log [AlOX] − 1.05 (R2 = 0.81, P < 0.001).ConclusionsSoil Hg concentration, pH, and AlOX content were the three most important variables associated with carrot Hg concentration. The extended Freundlich-type function could well describe Hg transfer from soil to carrot.

Rare earth element transfer from soil to navel orange pulp (Citrus sinensis Osbeck cv. Newhall) and the effects on internal fruit quality.

The effects of soil rare earth element (REE) on navel orange quality and safety in rare earth ore areas have gained great attention. This study investigated the transfer characteristics of REE from soil to navel orange pulp (Citrus sinensis Osbeck cv. Newhall) and examined the effects of soil REE on internal fruit quality in Xinfeng County, Jiangxi province, China. Path analysis showed that soil REE, pH, cation exchange capacity (CEC), and Fe oxide (Feox) significantly affected pulp REE concentrations. A Freundlich-type prediction model for pulp REE was established: log[REEpulp] = -1.036 + 0.272 log[REEsoil] - 0.056 pH - 0.360 log[CEC] + 0.370 log[Feox] (n = 114, R2 = 0.60). From the prediction model, it was inferred that even when soil REE and Feox were as high as 1038 mg kg-1 and 96.4 g kg-1, respectively, and pH and CEC were as low as 3.75 and 5.08 cmol kg-1, respectively, pulp REE concentrations were much lower than the food limit standard. Additionally, soil REE levels were significantly correlated with selected fruit quality indicators, including titratable acidity (r = 0.52, P < 0.01), total soluble solids (r = 0.48, P < 0.01) and vitamin C (r = 0.56, P < 0.01). Generally, under routine methods of water and fertilization management, the cultivation of navel oranges in rare earth ore areas of south China with soil REE ranging from 38.6 to 546 mg kg-1 had improved in internal fruit quality.

Phytotoxicity and accumulation of chromium in carrot plants and the derivation of soil thresholds for Chinese soils

Soil environmental quality standards in respect of heavy metals for farmlands should be established considering both their effects on crop yield and their accumulation in the edible part. A greenhouse experiment was conducted to investigate the effects of chromium (Cr) on biomass production and Cr accumulation in carrot plants grown in a wide range of soils. The results revealed that carrot yield significantly decreased in 18 of the total 20 soils with Cr addition being the soil environmental quality standard of China. The Cr content of carrot grown in the five soils with pH>8.0 exceeded the maximum allowable level (0.5mgkg(-1)) according to the Chinese General Standard for Contaminants in Foods. The relationship between carrot Cr concentration and soil pH could be well fitted (R(2)=0.70, P<0.0001) by a linear-linear segmented regression model. The addition of Cr to soil influenced carrot yield firstly rather than the food quality. The major soil factors controlling Cr phytotoxicity and the prediction models were further identified and developed using path analysis and stepwise multiple linear regression analysis. Soil Cr thresholds for phytotoxicity meanwhile ensuring food safety were then derived on the condition of 10 percent yield reduction.

Derivation of soil thresholds for lead applying species sensitivity distribution: A case study for root vegetables

The combination of food quality standard and soil-plant transfer models can be used to derive critical limits of heavy metals for agricultural soils. In this paper, a robust methodology is presented, taking the variations of plant species and cultivars and soil properties into account to derive soil thresholds for lead (Pb) applying species sensitivity distribution (SSD). Three species of root vegetables (four cultivars each for radish, carrot, and potato) were selected to investigate their sensitivity differences for accumulating Pb through greenhouse experiment. Empirical soil-plant transfer model was developed from carrot New Kuroda grown in twenty-one soils covering a wide variation in physicochemical properties and was used to normalize the bioaccumulation data of non-model cultivars. The relationship was then validated to be reliable and would not cause over-protection using data from field experimental sites and published independent studies. The added hazardous concentration for protecting 95% of the cultivars not exceeding the food quality standard (HC5add) were then calculated from the Burr Type III function fitted SSD curves. The derived soil Pb thresholds based on the added risk approach (total soil concentration subtracting the natural background part) were presented as continuous or scenario criteria depending on the combination of soil pH and CEC.

Ecotoxicity of benzo[a]pyrene assessed by soil microbial indicators

The ecotoxicity of benzo[a]pyrene (BaP) to soil microorganisms was evaluated using the following microbial indicators: soil microbial biomass, respiration, nitrification, and Shannon index. Two soil types, udic ferrosols and aquic cambisols, were amended with 0 mg/kg, 1 mg/kg, 10 mg/kg, 100 mg/kg, 500 mg/kg, or 1000 mg/kg BaP; incubated at 25 °C; and tested on days 28, 60, and 180. The Shannon index was extremely insensitive to BaP. Microbial biomass and respiration could not be classified as sensitive indicators because of their relatively high 10% effect concentration (EC10) values. Nitrification was the most sensitive indicator in both soils and could be the preferred microbial indicator for testing the ecotoxicity of BaP. Higher toxicity of BaP was exhibited in udic ferrosols than in aquic cambisols, and the ecotoxicity of BaP decreased with incubation time. Extending the 28-d incubation time, which is suggested in the International Organization for Standardization and Organisation for Economic Co-operation and Development guidelines, to 60 d was recommended for future microbial toxicity tests of BaP. On day 28, the EC10 values for microbial biomass, respiration, and nitrification were 71 mg/kg, 43 mg/kg, and 3.4 mg/kg in aquic cambisols and 51 mg/kg, 22 mg/kg, and 1.3 mg/kg in udic ferrosols, respectively. On day 60, these values were 106 mg/kg, 59 mg/kg, and 19 mg/kg in aquic cambisols and 77 mg/kg, 40 mg/kg, and 6.9 mg/kg in udic ferrosols. These values could be used in combination to derive ecotoxicological soil screening levels of BaP.

Oxidation-reduction regimes in some Oxisols of tropical China

Abstract The oxidation-reduction regimes of some Oxisols of tropical China were investigated on the basis of the Eh values and the amounts of reducing substances, both measured by newly devised methods. The Eh values in the surface layers of soil profiles under natural forest and commercial forest were 400–550 mV, lower by 100–200 mV than the deeper horizons. The concentrations of reducing substances in the surface layers corresponded to 0.5–5.0 · 10−5M of Mn2+. In the cultivated layer of a submerged paddy soil the concentration of reducing substances was as high as 13·10−5M, with an Eh value of less than 100 mV. There was a negative correlation between the Eh value and the logarithm of the concentration of reducing substances, showing that the intensity aspect and the capacity aspect of the oxidation-reduction status of a soil are closely interrelated.

Comparison of the physiological characteristics of transgenic insect-resistant cotton and conventional lines

The introduction of transgenic insect-resistant cotton into agricultural ecosystems has raised concerns regarding its ecological effects. Many studies have been conducted to compare the differences in characteristics between transgenic cotton and conventional counterparts. However, few studies have focused on the different responses of transgenic cotton to stress conditions, especially to the challenges of pathogens. The aim of this work is to determine the extent of variation in physiological characteristics between transgenic insect-resistant cotton and the conventional counterpart infected by cotton soil-borne pathogens. The results showed that the difference in genetic backgrounds is the main factor responsible for the effects on biochemical characteristics of transgenic cotton when incubating with cotton Fusarium oxysporum. However, genetic modification had a significantly greater influence on the stomatal structure of transgenic cotton than the effects of cotton genotypes. Our results highlight that the differences in genetic background and/or genetic modifications may introduce variations in physiological characteristics and should be considered to explore the potential unexpected ecological effects of transgenic cotton.