Plant growth promoting rhizobacteria can improve plant health by providing enhanced nutrition, disease suppression and abiotic stress resistance, and have potential to contribute to sustainable ...agriculture. We have developed a sphagnum peat-based compost platform for investigating plant-microbe interactions. The chemical, physical and biological status of the system can be manipulated to understand the relative importance of these factors for plant health, demonstrated using three case studies: 1. Nutrient depleted compost retained its structure, but plants grown in this medium were severely stunted in growth due to removal of essential soluble nutrients - particularly, nitrogen, phosphorus and potassium. Compost nutrient status was replenished with the addition of selected soluble nutrients, validated by plant biomass; 2. When comparing milled and unmilled compost, we found nutrient status to be more important than matrix structure for plant growth; 3. In compost deficient in soluble P, supplemented with an insoluble inorganic form of P (Ca
(PO
)
), application of a phosphate solubilising Pseudomonas strain to plant roots provides a significant growth boost when compared with a Pseudomonas strain incapable of solubilising Ca
(PO
)
. Our findings show that the compost system can be manipulated to impose biotic and abiotic stresses for testing how microbial inoculants influence plant growth.
The presence of agricultural pesticides in the environment and their effects on ecosystems are major concerns addressed in a significant number of articles. However, limited information is available ...on the pesticide concentrations released from crops. This study reports losses of new-generation fungicides by foliar wash-off from vineyards and their potential impact on the concentrations of their main active substances (AS) in surface waters.
Two experimental plots devoted to vineyards were treated with various combinations of commercial new-generation fungicide formulations. Then, up to sixteen throughfall collectors were installed under the canopy. Concentrations of sixteen different AS in throughfall were determined along nine rainfall episodes. Concentrations in throughfall far exceeded the maximum permissible levels for drinking water established by the European Union regulations. Dynamics of fungicide release indicated a first-flush effect in the wash-off founding the highest concentrations of AS in the first rain episodes after application of the fungicides.
This article shows that foliar spray application of commercial formulations of new-generation fungicides does not prevent the release of their AS to soil or the runoff. Concentration data obtained in this research can be valuable in supporting the assessment of environmental effects of new-generation fungicides and modeling their environmental fate.
•Throughfall was monitored in vineyards treated with new-generation fungicides.•Twelve active substances (AS) were detected in throughfall.•Concentrations widely exceeded the limits established by European regulations.•The release of some persistent AS continued after several rainfall episodes.
The continuous use of copper against fungal diseases and off-target effects causes major environmental and agronomic problems. However, the rain-induced removal of Cu-based residues is known only for ...a limited number of crops. We present the results of rain-induced removal of fungicides from two monitored vineyard plots which were sprayed with two widely used Cu-based formulations: copper-oxychloride (CO) and Bordeaux mixture (BM), respectively. Cu removal per growing season was 0.60±0.12kgha−1 (30% of the applied fungicide) for CO and 0.80±0.10kgha−1 for BM (70% of the applied fungicide). Fractioning the Cu in soluble (CuS) and particulate fractions (CuP) showed that most of the Cu was removed as CuP, but CuS concentrations found in throughfall collectors exceeded the regulatory threshold for toxicity in surface waters. The first few millimeters of rain caused most of the Cu removal. Our findings agreed with the data reported in the scientific literature, in which a significant fraction of the Cu-based formulation is loosely attached to the plant surfaces. In addition, we found that rainfall energy had a minor influence on the removal.
► Mussel shell amendment on mine soil raises pH proportionally to the shell dose used. ► Shell amendment clearly increased Cu, Cd, Ni and Zn retention in soil/shell mixtures. ► Retention decreases ...when increasing amounts of metal are added to un-amended soil. ► Shell amendment would favour remediation and restoration of contaminated acid soils.
Batch and column experiments are used to study the effects of ground mussel shell amendment on the retention of heavy metals in acidic mine soil. The soil pH increases proportionally with the mussel shell concentration employed. Mussel shell amendment increases Cu, Cd, Ni and Zn retention in mine soil when compared with unamended soil. In fact, Cu retention was 6480μmolkg−1 (43% of the total added) when the maximum metal concentration (1570μM) was added to the unamended soil, whereas retention reached 15,039μmolkg−1 (99.9% of the total Cu added) when soil was amended with 24gkg−1 mussel shell; in the case of Cd, adsorption increases from 3257μmolkg−1 (15% of the total added) for the unamended soil, to 13,200μmolkg−1 (87% of the total added) for the shell-amended soil; Ni retention increased from 3767μmolkg−1 (25% of the total added) corresponding to unamended soil, to 11,854μmolkg−1 (77% of the total added) for the shell-amended soil; and finally, Zn retention increased from 4684μmolkg−1 (31% of the total added), for unamended soil, to 14,952μmolkg−1 (98% of the total added) for shell-amended soil. The results of the constant flow transport experiments show that the addition of the 24gkg−1 mussel shells can retain Cu, Cd, Ni and Zn within the first few centimetres of the column length, indicating the usefulness of ground mussel shells to drastically decrease the mobility and availability of these pollutants and to facilitate soil remediation.
Copper lost in foliar wash-off from vine leaves treated with Cu-based fungicides was analyzed with a single-drop rainfall simulator. The temporal losses of the particulate Cu (CuP) and the solution ...Cu (CuS) from raindrop strikes on leaves were modeled using a Poisson point process. This model estimated maximum detachment rates of 0.82 ng CuP and 0.033 ng CuS per raindrop. The total amount of Cu (CuT) in the leaves before rainfall ranged between 0.4 and 4.4 g Cu kg−1 dry weight. Wash-off reduced the amount of CuT present in the leaves by 0.6 g kg−1. Particulate losses of CuT ranged from 75 to 90%, while soluble losses of CuT ranged from 10 to 25%. The kinetic energy of the raindrops influenced the loss of CuS but not the loss of CuP. The Poisson point approach can provide an interesting starting point to model non-point source pollution produced from agricultural chemicals washed-off by rain.
•Loss of Cu-fungicides by rainfall can be modeled by means of a Poisson point process.•The model describes the time course of Cu expelled by drop strikes on vine leaves.•The model parameters were easily obtained by inverse modeling from experiments.•This mechanistic approach can be used to assess agricultural pollution risks.
► We study the adsorption of fungicides cyprodinil and fludioxonil in soils. ► We examine the influence of adjuvants present in commercial formulations in the adsorption. ► Adjuvants in the ...commercial formulation induce strong deviations in the adsorption isotherms regarding to experiments using the pure active ingredients.
The objective of this work was to assess the effect of adjuvants in the sorption in soils of the fungicides, cyprodinil and fludioxonil, usually applied together in a mixture commonly called ‘Switch’. Water suspensions of a commercial formulation of Switch were used in phase partition experiments for a set of selected soils from vineyards. A clean-up procedure of the supernatant was developed for the phase separation in presence of the adjuvants prior to quantification of cyprodinil and fludioxonil. The maximum sorption on the solid phase (which includes soil and other solids from the commercial formulation of Switch) was 2000
mg
kg
−1 for fludioxonil and 3000
mg
kg
−1 for cyprodinil after incubation with 800
mg
L
−1 of Switch. However, adsorption to soil particles were lower; fludioxonil concentrations adsorbed in soils range from 50 to 80
mg
kg
−1 of soil and cyprodinil concentrations range from 120 to 260
mg
kg
−1 of soil. Adjuvants increased the solubility of fludioxonil in pure water at 25
°C up to 5 times that of the pure substance (from 1.8 to 9
mg
L
−1 in control samples), and show a strong influence on the adsorption in soil. Soil pH, effective cation exchange capacity and copper content due to past anti fungal copper-based sprays, have also influence on the adsorption of the active ingredients in presence of adjuvants.
The upper horizons of old vineyard soils have substantial copper contents due to the traditional use of copper-based fungicides. Total copper levels in eight vineyard soils in the Rías Baixas area of ...Galicia (northwestern Spain) ranged from 60 to 560 mg kg-1 (mean ± SD = 206 ± 170 mg kg-1). The adsorption of the fungicides metalaxyl (pK a = 1.41) and penconazole (pK a = 2.83) by these soils was determined using fungicide solutions of pH 2.5 and 5.5, and desorption of fungicide adsorbed at pH 5.5 was also determined. In all cases, Freundlich equations were fitted to the data with R 2 > 0.96. Penconazole was adsorbed and retained more strongly than metalaxyl, with K F values more than an order of magnitude greater. In the desorption experiments, both fungicides exhibited hysteresis. Soil copper content hardly affected the adsorption of metalaxyl, but K F values for adsorption of penconazole increased at a rate of about 0.1 mL n (μg of penconazole)(1- n ) (μg of Cu)-1, which is attributed to the formation of Cu2+−penconazole complexes with greater affinity for soil colloids than penconazole itself. Because the dependence of K F for penconazole adsorption on copper content was the same at both pH values, complex formation appears not to have been affected by the solubilization of 6−17% of soil copper at pH 2.5. A similar copper dependence, or lack of dependence, was observed when 100−1000 mg kg-1 of copper was added as Cu(NO3)2·2H2O to the solutions from which the fungicides were adsorbed. Keywords: Soil contamination; metalaxyl; penconazole; adsorption−desorption; copper
Intensive use of copper-based fungicides in agriculture causes contamination of subsurface environment. While the transport of dissolved copper in porous media has been widely studied, transport ...mechanisms of particles of copper-based fungicides are poorly understood. This paper reports the results of tests involving the transport of colloid-size particles of a copper oxychloride-based fungicide (COF) in water-saturated quartz sand columns under varying electrochemical and hydrodynamic conditions. The effect of the ionic strength on colloid attachment and exclusion suggests that interactions of COF in water depend on the characteristics of the diffuse layer. Hydrodynamic shear influences the deposition of fungicide particles, indicating that attachment forces are weak. Particle deposition dynamics was well-fitted with the two-site kinetic attachment model, which reflects the heterogeneity of the quartz surface. Retention also occurs for unfavorable electrochemical conditions, which was attributed to stagnation zones arising from the physical and chemical heterogeneity of the quartz surface.
The mechanism of mediated transport of copper (Cu) by humic acids (HA) in pore water was studied taking account of colloid filtration theory and by means of breakthrough experiments of HA in ...water‐saturated columns filled with quartz sand. The influence of pH and Cu2+ concentration on Cu–HA binding and retention of Cu–HA complexes in the matrix were analysed with colloid‐surface attachment models. Experiments were performed for differing Cu concentrations (0–20 mg l−1) and pH (5–7). Copper binding to HA increased with pH and Cu2+ addition, according to ion–humic complexation theory. The zeta potential of the HA became less negative with increasing amounts of Cu, which led to less electrostatic repulsion and an increase in the retention of the HA in the column. A kinetic colloid transport model with a random sequential adsorption (RSA) blocking function was well fitted to the experimental breakthrough curves (BTCs). The model accounted for heterogeneity in the adsorption sites in the quartz sand for all of the electrochemical conditions. For pH = 7, the transport of Cu was coupled with the HA, while at pH = 5, the transport occurred mostly as free Cu2+. Models of the influence of dissolved soil organic matter and electrochemical conditions on the fate of trace elements in the soil may contribute to a quantitative exploration of strategies for soil remediation and disposal of contaminated soil containing excessive amounts of trace elements.
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