Herbicide Leaching Research Articles

Behaviour of ionic herbicides in different forestry soils derived from volcanic ash

Background: Weed control has been one of the most significant factors in forest establishment practices that can improve biomass production, and herbicides represent the most effective and convenient way to control weeds. The environmental concern about herbicides in this industry is because the herbicide-treated area is often located near water reservoirs or areas where rivers and creeks originate. This study aimed to determine the adsorption and degradation behaviours of seven ionic herbicides used in forestry production in five Chilean forestry soils and their relation to the leaching and to generate information to validate environmental predictive models. Methods: Adsorption and degradation of ionisable herbicides such as simazine, terbuthylazine, hexazinone, metsulfuron-methyl, indaziflam, flazasulfuron and glyphosate were studied in Andisol, Ultisol, Inceptisol, Entisol and Alfisol forestry soils, to be related to their leaching in 100-cm high and 11-cm diameter soil disturbed lysimeters. Herbicides were quantified using high-pressure liquid chromatography and gas chromatography. Relationships between soil physicochemical properties, herbicide adsorption and degradation, and herbicide leaching were determined. Results: In decreasing order, the herbicides were mobile in Entisol>Alfisol>Ultisol>Inceptisol>Andisol soils. On the other hand, the more leachable herbicides, from high to low, were: hexazinone, metsulfuron-methyl, simazine, glyphosate, terbuthylazine, flazasulfuron and indaziflam. The last two herbicides were not detected below 60 cm soil depth. In general, the maximum soil depth herbicide reached and the percentage mass leached up to 90 cm soil depth were inversely related to soil adsorption (1/Kd), soil porosity, humidity, silt, aluminium, and calcium soil content. Herbicide degradations were generally faster than referential published values. Conclusions: The environmental coefficients of ionic herbicides were more related to soil properties than their physicochemical properties. Persistence of herbicides in soil was smaller than that commonly reported in other studies or international databases and soil adsorption averages were generally higher than international reference values. The stronger relationship between ionic herbicide behaviour and forestry soil properties endorses the requirement to determine the environmental herbicides parameters in situ, avoiding using parameters estimated in other soils.

Are bioassays and Analytical Methods Equivalent to the Application of Herbicide Leaching to Sugarcane Crops?

Are bioassays and Analytical Methods Equivalent to the Application of Herbicide Leaching to Sugarcane Crops?

Herbicide Leaching in Soil with Different Properties: Perspectives from Commercial Formulations and Analytical Standards.

The leaching of herbicides into the soil is essential to control germinating seeds and parts of vegetative weeds. However, herbicide transportation to deeper soil layers can result in groundwater contamination and, consequently, environmental issues. In this research, our objective was to investigate differences in herbicide leaching between commercial formulations and analytical standards using three different soils. Leaching experiments were carried out for diuron, hexazinone, and sulfometuron-methyl herbicides isolated and in binary and ternary mixtures. The herbicide residue quantification was performed by ultra-high-performance liquid chromatography coupled to a mass spectrometer (LC-MS/MS). Diuron had less mobility in soils and was retained in the most superficial layers. Hexazinone and sulfometuron-methyl were more mobile and leached into deeper layers. The leaching process was more intense for hexazinone and sulfometuron-methyl. The additives present in the commercial formulation favored the leaching in soils of diuron, hexazinone, and sulfometuron-methyl herbicides isolated and mixture compared to the analytical standard. This fact highlights the importance of considering these effects for the positioning of herbicides in the field to increase the efficiency of weed control and minimize the potential for environmental contamination.

Agar-gelatin-derived hydrogel-based controlled delivery devices for linuron herbicide to prevent environmental hazards

Innovation in agriculture chemicals and delivery systems is essential for the production of food for sustainable development. Herein, natural polymers and agar-gelatin-derived controlled delivery devices for linuron herbicide to prevent environmental and health hazards. These hydrogels were designed by the graft-copolymerization reaction of poly(methacrylamide) [poly(MAAm)] on agar-gelatin for use as controlled-release formulations (CRF). Copolymers were characterized by Copolymers were characterized scanning electron micrographs (SEM), Atomic force microscopy (AFM), X-ray diffraction (XRD) Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (NMR), and thermogravimetric analysis -differential thermogravimetry (TGA-DTG) techniques. SEM shows the uneven surface morphology, and AFM showed a rough surface with an average roughness value of 137.50 nm in the polymeric matrix. The amorphous nature of the polymer was confirmed with XRD techniques. Grafting of the poly(MAAm) on the agar and gelatin was confirmed by FTIR and 13C NMR spectra. Agar-gelatin-cl-poly(MAAm) hydrogels absorbed water at 4.05 ± 0.32 g per gram, which is useful for soil water retention. Release of the linuron herbicide occurred in a controlled manner during 72 h of observations and followed non-Fickian diffusion mechanism. The slow release of the linuron from the hydrogel is a useful observation for preventing leaching and evaporation loss of herbicide. In the soil column, the release of linuron occurred in a slow and sustained manner for 240 h. A soil adsorption study showed a decrease in ground water ubiquity score (GUS) for linuron-encapsulated hydrogel as compared to commercial formulations. It can reduce groundwater contamination risk due to the leaching of the linuron herbicide. Degradation of CRF may improve micronutrient and soil quality.

New Advances in Nano-Enabled Weed Management Using Poly(Epsilon-Caprolactone)-Based Nanoherbicides: A Review

The number of effective herbicides available to farmers is steadily decreasing due to increasing herbicide resistance. It seems very important to address and effectively deal with the main weed management challenges (low crop yield and environmental pollution) by investigating the potential of newly introduced materials, such as biocompatible polymer-based nanoparticles. The current review aims to encourage agricultural or environmental researchers to conduct new research on the synthesis and application of modified herbicides, such as nanoherbicides, for application in weed management and to provide a comprehensive foundation on the topic. Such nanosystems could help with the promotion of the controlled release of active ingredients and extend their action time, resulting in a reduction in dose and application number; improve the physical and chemical characteristics of the herbicide to increase foliar adhesion; prevent degradation that results from environmental factors (such as sunlight, temperature, microorganisms, or pH); and decrease herbicide leaching and contamination of the environment. Furthermore, it has been indicated that some polymeric nanocarriers can penetrate biological barriers, including membranes and plant cell walls, and translocate across vascular tissues, resulting in a more efficient delivery of active ingredients. Poly(epsilon-caprolactone) is a biocompatible material that is easily decomposable by enzymes and fungi. PCL nanoparticles could be applied as nanocarriers of herbicides in agriculture due to their low toxicity, their potential for large-scale synthesis from inexpensive materials, their ability to dissolve herbicides, their high loading capacity, and their ability to help minimize the chemical decomposition of herbicides.

Multicriteria assessment of alternative cropping systems at farm level. A case with maize on family farms of South East Asia

CONTEXTIntegration of farms into markets with adoption of maize as a cash crop can significantly increase income of farms of the developing world. However, in some cases, the income generated may still be very low and maize production may also have strong negative environmental and social impacts. OBJECTIVEMaize production in northern Laos is taken as a case to study how far can farms' performance be improved with improved crop management of maize with the following changes at field level: good timing and optimal soil preparation and sowing, allowing optimal crop establishment and low weed infestation. METHODSWe compared different farm types' performance on locally relevant criteria and indicators embodying the three pillars of sustainability (environmental, economic and social). An integrated assessment approach was combined with direct measurement of indicators in farmers' fields to assess eleven criteria of local farm sustainability. A bio-economic farm model was used for scenario assessment in which changes in crop management and the economic environment of farms were compared to present situation. The farm model was based on mathematical programming maximizing income under constraints related to i) household composition, initial cash and rice stocks and land type, and ii) seasonal balances of cash, labour and food. The crop management scenarios were built based on a diagnosis of the causes of variations in the agronomic and environmental performances of cropping systems, carried out in farmers' fields. RESULTS AND CONCLUSIONSOur study showed that moderate changes in crop management on maize would improve substantially farm performance on 4 to 6 criteria out of the 11 assessed, depending on farm types. The improved crop management of maize had a high economic attractiveness for every farm type simulated (low, medium and high resource endowed farms) even at simulated production costs more than doubling current costs of farmers' practices. However, while an improvement of the systems performance was attained in terms of agricultural productivity, income generation, work and ease of work, herbicide leaching, improved soil quality and nitrogen balance, trade-offs were identified with other indicators such as erosion control and cash outflow needed at the beginning of the cropping season. SIGNIFICANCEUsing farm modelling for multicriteria assessment of current and improved maize cropping systems for contrasted farm types helped capture main opportunities and constraints on local farm sustainability, and assess the trade-offs that new options at field level may generate at farm level.

Groundwater monitoring and leaching of sulfonylurea herbicides and transformation products

Screening of sulfonylurea herbicides (SUHs) in water is important due to their widespread usage and residual activity. Thus, it is essential to develop simple, sensitive and cost-effective pre-treatment method with minimal matrix interferences for quantification of SUHs from water. In present study, sample pre-treatment parameters using salting out liquid liquid extraction (SALLE) method for determining SUHs and their transformation products (TPs) were optimised for improved accuracy and selectivity. A mathematical model representing relationship between the variables and response (percent recovery) was developed using Box behnken design. The developed method has mean percent recovery of 89.80 to 101.20% with relative standard deviation < 10%. Based on greenness evaluation tools viz. Analytical Eco-Scale, GAPI and AGREE metrics, developed SALLE method falls under the category of green analytical methods. To determine the probability of contamination of groundwater by studied herbicides, leaching studies were carried out. About 0.035 ± 0.011 to 0.11 ± 0.013, 0.012 ± 0.014 to 0.042 ± 0.015, 0.009 ± 0.012 to 0.031 ± 0.011, 0.009 ± 0.012 to 0.015 ± 0.011 and 0.01 ± 0.014 to 0.017 ± 0.013 µg mL−1 residues of iodosulfuron methyl, metsulfuron methyl, ethoxysulfuron, 2-amino-4,6-dimethoxypyrimidine and 2-amino-4-methoxy-6-methyl-1,3,5-triazine, respectively were detected in leachates indicating their high potential to contaminate ground water resources. The herbicide residues in real water samples were below permissible limit (<0.01 µg g−1) imposed by World Health Organization and European Protection Agency for drinking water quality.

Sustainability assessment of cropping systems: A field-based approach on family farms. Application to maize cultivation in Southeast Asia

Maize cropping has often become the only way for many family farmers in Southeast Asia to rapidly obtain a cash income. However, the intensification of maize-based cropping systems is raising concerns about its environmental sustainability. This study contributed to field-based approaches for ex post sustainability assessment of current cropping systems on farms and for the design of more sustainable prototypes, in conditions where the information required for estimating sustainability indicators are not readily available. A 3-year regional agronomic diagnosis was combined with a multicriteria assessment and a prototyping procedure. The latter aimed to increase the performances on the indicators that showed critical levels on current systems. A local diversity of maize fields in Laos was used to test the approach. We defined and used indicators representing farmers’ socio-economic objectives and risks for the environment. Sustainability indicators were calculated using data extracted from farm surveys, direct measurements in fields managed by the farmers and crop modelling. Our analysis showed that the most frequent weaknesses in all current maize-based cropping systems were (i) low land and labour productivity, (ii) high susceptibility to weed infestation, (iii) high risk of herbicide leaching, (iv) risk of soil fertility depletion, (v) risk of soil erosion. None of the current cropping systems performed well simultaneously on both indicators of land/labour productivity and control of herbicide leaching. These sustainability issues mainly resulted from difficulties in mastering mechanised crop establishment. Taking the current cropping system as a starting point, prototypes with successful crop establishment thanks to well mastered mechanisation would significantly improve the following sustainability indicators: control of herbicide leaching (improved by 130–340%), yield (multiplied by 1.3–2.3), gross margin (multiplied by 1.3–2.2), weed control (improved by 180–430%) and labour productivity (multiplied by 1.4–3.4). However, it would increase erosion (erosion control divided by 1.6–7) and seasonal cash outflow would increase (multiplied by 1.1–2). Overall, improving crop establishment would increase sustainability (overall sustainability score multiplied by 1.1–1.6). Our results suggest that providing farmers with enhanced capacity to master crop establishment would not solve all sustainability issues of maize cultivation, but at least help avoid a catastrophic overuse of herbicides in that context.

The influence of biochar pyrolysis temperatures on the efficiency of soil amendment for Imazapic sorption

Weeds are responsible for losses in sugarcane productivity, often requiring the application of herbicides to control their infestation in crops. One of the herbicides commonly used in sugarcane cultivation is Imazapic. However, this chemical can be leached into environmental compartments when applied to soil, contaminating it. Scientific research has shown that the soil amended with biochar can reduce the leaching of herbicides, avoiding environmental pollution. Therefore, the present work aimed to evaluate the adsorption efficiency of Imazapic in a dystrophic Yellow Ultisol amended with biochar cultivated with sugarcane. Biochars were produced with sugarcane bagasse by pyrolysis at temperatures of 300, 500, and 700ºC to evaluate the adsorption capacity of Imazapic by the soil amended with biochar. The experiments revealed an increase in Imazapic adsorption with soil amended with biochar and that the adsorptive potential is more significant for pyrolyzed biochars at higher temperatures. In this way, the biochars produced can reduce the risks of groundwater contamination by increasing the residence time of Imazapic in the surface layer of the soil, being subject to the action of microbial degradation and other forms of degradation.

Propisochlor retention and mobility in the presence of straw in Brazilian cropping systems

ABSTRACT Non-ionic herbicides, such as propisochlor, are more easily retained in organic soil fractions. The presence of straw in tropical cropping systems can affect herbicide transposition to the underlying seed banks and their environmental behavior. The aim of this study was to evaluate propisochlor soil retention in the presence of soybean and sugarcane straw (0, 5 and 10 t ha−1) through radiometric techniques. Most of the applied 14C-propisochlor was retained in the soil profile (18.2–39.4%) following an extreme rainfall simulation in the presence of straw. Decreased herbicide leaching was observed in the presence of sugarcane and soybean straw (0.7–0.5%), compared with soil without straw (1.8%). Hysteresis values ranged from 0.8 to 1.0, indicating that propisochlor sorption was reversible allowing for soil seed bank effects, as well as environmental dissipation. These findings indicate that propisochlor can overcome straw barriers, although representing low groundwater contamination risks. Because of this, reduced environmental impacts following the application of this herbicide are noted for tropical cropping systems containing straw mulch.

The leaching behaviour of herbicides in cropping soils amended with forestry biowastes

Leaching of herbicides in cropping soils not only impacts the groundwater sources but also reduces their effect in controlling weeds. Leaching studies were carried out in two cropping soils and two forestry biowaste media, wood pulp and sawdust with two herbicides, atrazine and bromacil in a packed lysimeter with simulated rainfall. The hypothesis was that high organic matter forestry biowaste soil amendments reduce the leaching of herbicides through the soil profile. Results from the experimental setups varied due to the impact of the simulated rainfall on the surface structure of the media. Organic carbon content, pH and structure of the media were all factors which affected the leaching of the two herbicides. The hypothesis was true for wood pulp, but for sawdust, organic matter content had less bearing on the leaching of the herbicides than other over-riding factors, such as pH, that were media specific. In sawdust, its large particle size and related pore volume allowed preferential flow of herbicides. Overall, the data indicated that both forestry biowastes were retentive to herbicide leaching, but the effect was more pronounced with wood pulp than sawdust.

Can soil type interfere in sorption-desorption, mobility, leaching, degradation, and microbial activity of the 14C-tebuthiuron herbicide?

Understanding the behavior in soil of herbicides applied PRE-emergence, such as tebuthiuron, is essential for more accurate weed management and less environmental impact. Thus, the objective of this research was to evaluate the effect of the physicochemical attributes of soils in 14C-tebuthiuron behavior. All studies were carried out by radiometric technique. The Kf and Kd values of 14C-tebuthiuron sorption were 30% and 35% higher in clay soil (1.15 mg(1–1/n) L1/n Kg−1 and 1.32 L Kg−1) compared to loamy sand soil (0.80 mg(1-1/n) L1/n Kg−1 and 0.85 L Kg−1, respectively). The desorbed amount was ∼19% higher in loamy sand soil compared to loamy sand soil, and this process was influenced by OC and clay content. The 14C-tebuthiuron leaching in clay soil was up to 10 cm depth, while in loamy sand soil was higher, up to 25 cm, and this difference can be explained by high mobility and low sorption of herbicide in loamy sand soil. 14C-tebuthiuron had a long persistence in both soils (DT90 of ∼385 and 334 d in loamy sand and clay soil, respectively). Although, the microbiological activity in soils differed little in the presence and absence of herbicide. Soil type interfered in 14C-tebuthiuron behavior, and then the application recommendation of this herbicide as a function of the physicochemical attributes of the soil is an alternative to increase efficiency in weed control and reduce the risk of environmental contamination.

Risk of environmental contamination due to the hexazinone application in agricultural soils in northeastern Brazil

The behavior of herbicides as organic and inorganic colloids in soils depends on the pHysicochemical characteristics of the compounds, soil properties, and climatic conditions. Studies involving sorption, desorption, leaching, and dissipation of herbicides are essential to evaluate weed control efficiency and knowledge of the potential for environmental contamination. Thus, this study evaluated the behavior of hexazinone in Brazilian soils with different physical and chemical properties. Three agricultural soils with contrasting textures were used: Cambisol (sandy clay), Ferrasol (sandy loam), and Arenosol (loamy sand) from areas exempt from herbicide application. The quantification of hexazinone was performed using ultra-high-performance liquid chromatography coupled to a mass spectrometer (LC-MS/MS). The sorption (Kfs) and desorption (Kfd) constants of hexazinone showed differing soils with contrasting textures. The Ferrasol had the highest Kfs (0.46 mg kg−1), followed by the Arenosol (0.39 mg kg−1) and Cambisol (0.16 mg kg−1), whose desorption followed in the same order. The half-life (t1/2) of hexazinone in the studied soils showed similar values, with t1/2 = 24 days for the Arenosol, t1/2 = 23 days for the Cambisol, and t1/2 = 22 days for the Ferrasol. The Cambisol showed greater leaching capacity, with a GUS index = 3.9, compared to the Arenosol and Ferrasol, which had a GUS index of 3.6 and 3.2, respectively. Soil pH and CEC were the main properties that influenced the sorption and desorption of hexazinone in the environment.

Effect of Conventional Tillage and Zero Tillage on Different Soil and Yield Parameters

Conservation and conventional tillage directly affects soil environment for crop production. Conservation tillage provides a layer of crop residue which increases soil fertility, soil erosion, leaching of fertilizer, pesticides and herbicides into the ground water. Studies conducted in different climate zones showed that no-tillage resulted in acidification of surface layer when continued for several years compared to conventional tillage. Some study shows Conservation tillage enhance water infiltration rate and reduce moisture evaporation from soil, while some other study stated slower water infiltration rate in no tillage soil then on tilled. surface tillage and no tillage instead of conventional tillage are to control soil erosion, enhance crop performance, and use energy more efficiently. Decomposition of crop residues kept on the soil surface possibly release allele-chemicals which further strengthen the inhibitory effects on weed seed germination and early growth and development of weed plant. As with impact of tillage on root distribution, no-tillage causes greater and deeper water accumulation in the soil profile and greater root growth. Higher labor, animal or equipment requirement is a major drawback of conventional tillage. Conservational tillage allows elimination of several operations, depending on the conservation tillage systems used. Observation of numerous studies reveals that zero-tillage is superior to conventional tillage resulting in higher yields. Similarly several studies reveals that crops grown under zero tillage have yields as similar as or better than those grown under conventional tillage.

Impacts of the addition of biochar, biosolid and aluminum silicate on the leaching and bioavailability of 2,4-D + picloram in soil

The use of herbicides in high-yield crops is increasing, and their fate in the environment has become a primary environmental concern. The aim of this study was to evaluate the impacts of the use of biosolid, biochar, and aluminum silicate on the leaching dynamics of a mixture of 2,4-D + picloram herbicides, which is widely used in agricultural and non-agricultural areas. Three experiments were carried out, one for each residue, using the same methodological procedure. The tests were designed in randomized blocks with four replicates and split plots. Different proportions of the residues were incorporated in the pots at 0%, 10%, 20%, 30%, and 40% referring to the column volume, allocated in the subplots at different depths in the soil column (0–5, 5–10, 10–15, 15–20, 20–25, 25–30, 30–35, 35–40, and 40–45 cm). After the application of 2,4-D + picloram, 40 mm of rain was simulated in all columns. The plant bioindicator, Cucumis sativus , was sown in the profile. The increase in the biochar dose intensified 2,4-D + picloram leaching and grew C. sativus biomass in deeper layers of the soil profile. Regarding biosolids, an increased dose reduced the 2,4-D + picloram movement in soil and stimulated the growth of C. sativus . The addition of aluminum silicate to the soil did not influence the leaching of 2,4-D + picloram. However, it increased the biomass of C. sativus plants in the deeper layers of the soil profile. The addition of biosolids reduced the leaching of 2,4-D + picloram in the soil profile. However, the incorporation of biochar and aluminum silicate did not decrease the risk of contamination of the deeper layers of soil. • The addition of residues in soil versus the leaching 2,4-D + picloram was evaluated. • Bioassay carried out used on soil columns, with Cucumis sativus as the bioindicator. • Biosolid reduces herbicide leaching in the soil profile and environmental risk. • Biochar increases herbicide leaching and availability in deeper soil layers. • Aluminum silicate behaves as inert for the herbicide movement and availability.

Reducing herbicide use and leaching in agronomically performant maize-based cropping systems: An 8-year study

Irrigated maize-based Cropping Systems (CS) are questioned because of the high risk of herbicide transfer to water. An 8-year systemic experiment was conducted to i) compute a multi-performance comparison between a Conventional Maize Monoculture (MMConv) and four CS that aimed to reduce irrigation and herbicide leaching: MMLI, a low-input MM using cover crop and Integrated Weed Management (IWM) techniques; MMStill, a Strip-tillage MM using cover crop; MMCT, a Conservation Tillage MM with cover crop; Maize-MSW, an IWM Maize rotated with Soybean and Wheat and ii) determine the main drivers and evaluate the influence of CS on herbicide leaching in maize. Drainage water was collected through 1-m depth lysimeter plates and analysed for 6 herbicide molecules and 1 degradation metabolite.MMLI yielded 10.7 t ha−1 close to MMConv (11.5 t ha−1) despite a lower herbicide use (−57%) and irrigation (−21%). MMLI and Maize-MSW had less drainage events compared to MMConv. MMCT and MMStill both yielded less (respectively 7.6 t ha−1 and 6.2 t ha−1) while their herbicide use increased (both +24%). Mean annual herbicide losses were 0.5 ± 1.0 g ha−1 for MMLI, 0.7 ± 1.2 g ha−1 for Maize-MSW, 1.3 ± 2.1 g ha−1 for MMStill, 2.0 ± 4.8 g ha−1 MMConv and 3.0 ± 9.6 g ha−1 for MMCT. Herbicide leaching remained variable but was consistently and mostly influenced by drainage volume. According to the CS, only 1.5 to 6.0 drainage events were responsible for 90% of the herbicide losses. High leaching peaks were identified for mesotrione and glyphosate and may indicate that preferential flows occurred, especially under MMCT. Quantity applied had limited influence on herbicide leaching. To reduce the herbicide leaching risk, CS must concomitantly manage water quality and quantity through a combination of agroecological practices, as in MMLI, a CS able to reach other technical objectives. Present study recommends assessing CS through a diversity of performance indicators.

Impact of rice straw biochar addition on the sorption and leaching of phenylurea herbicides in saturated sand column

The application of phenylurea herbicides (PUHs) may lead to the extensive distribution in soils, while the role of straw biochar as a soil amendment on the transport and sorption of PUHs are still unclear. Thus, the transport and sorption behavior of three typical PUHs with rice straw biochar (RSB) was studied in both adsorption simulation experiments of aqueous solution and packed column experiments. The sorption mechanism of RSB to herbicides was investigated through batch sorption studies with three influencing factors including dosage of RSB, pH, and ionic strength (IS) with orthogonal test. The sorption coefficients were improved significantly by increasing the dosage of RSB, while there was no obvious influence by enhancing the pH and IS value. The optimal sorption conditions (pH value at 3, IS at 0.1 M, and RSB dosage at 60 mg) of three herbicides were set and the maximum removal rates of Monuron, Diuron, and Linuron were 41.9%, 25%, and 56.8%, respectively. The co-transport process of RSB and PUHs were investigated under different RSB dosage, pH value, and IS value. The retention effect increased greatly with enhancing the RSB dosage and pH value. However, IS did not have a significant influence on the retention of RSB, and therefore it had little effect on the adsorption capacity, which was consistent with the results of sorption experiments. The breakthrough curves (BTCs) for co-transport were well simulated by the two-site non-equilibrium convection–dispersion equation (CDE). Most of the regression coefficients (R2) were above 0.99, which uncovered the co-transport in packed column were affected by physical absorption and chemical forces. According to the fitting parameters analysis, the RSB particles and PUHs were subjected to a greater resistance and a stronger stability by reducing pH value in porous media. The presence of RSB increased the amount of dynamic sorption sites in the entire co-transport system, which led to a significant promotion of the PUHs' sorption and interception.

Impact of long-term conservation agriculture induced changes in soil properties on persistence of pendimethalin under different cropping systems

Increasing use of herbicides in modern agriculture poses potential risks of crop phytotoxicity, contamination of land and water resources, and adverse impacts on human and ecosystem health. Apart from climatic conditions and soil properties, agronomic practices can significantly influence the persistence of herbicides in soil. Therefore, we assessed the impact of 13-year conservation agriculture (CA) on soil properties as well as on the fate (persistence and leaching) of pendimethalin herbicide in an alluvial sandy loam soil (Typic Haplustept) in comparison with an intensively tillage-based conventional system. The experiment involved two cropping systems (mungbean (Vigna radiata L.)–wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor L.)–wheat as summer and winter crops respectively) and three tillage practices: zero tillage with crop residue retention in both summer and winter seasons (ZT-ZT), conventional tillage in summer and zero tillage with residue retention in winter (CT-ZT) and conventional tillage in both seasons (CT-CT). The adoption of ZT-ZT system resulted in a 24% increase in infiltration rate, 13% greater moisture retention and 69% higher organic carbon content in surface (0–0.05 m) soil over CT-CT. In contrast, under the CT-ZT treatment, only a small change in the above soil properties was observed, which indicated that the benefits associated with CA were negated as soon as the soil was tilled in the subsequent season. In terms of herbicide leaching, under ZT-ZT, a greater fraction (4.1% vs 2.6%) of pendimethalin residues percolated down into the subsurface soil (0.15–0.30 m) than under the CT-CT system, most likely due to greater pore connectivity with the zero-till situation. However, there was a non-significant difference in the overall dissipation of the herbicide from the surface soil (0–0.05 m) under different systems. The field study illustrated that long-term adoption of CA under mungbean–wheat and sorghum–wheat cropping systems can lead to a significant change in soil properties and these in turn can influence the fate of herbicides in soils.

Diverse effects of wetting and drying cycles on soil aggregation: Implications on pesticide leaching

The important effect of soil wetting and drying cycle (WDC) on soil structure, and the consequent effect on pollutant fate is underexplored. We thoroughly investigated the changes in soil structure and in leaching of Alion (indaziflam) and Express (tribenuron methyl), pre and post WDC, from two clayey soils and two loamy soils under different land uses (uncultivated, field crops, and orchards). Soil stability was quantified by an aggregate durability index we recently developed. WDC did not affect the stability of the sandy-loam soils, as expected. However, for the sandy-clay-loam with high CaCO3 content aggregation was observed. For the clayey soils with similar CaCO3, aggregation and disaggregation were obtained, for a soil with relatively low and high SOM, respectively. The stability trends are reflected by the ratio between the contents of inorganic carbon and soil organic matter (SOM), CaCO3/SOM, normalized to the clay content. Aggregation was explained by CaCO3 cementation, while disaggregation was attributed to high clay content and to alterations in SOM conformation post WDC. These opposite trends, obtained for the two clayey soils, were confirmed by analyzing changes in soil packing employing X-ray tomography (micro-CT). Our results clearly demonstrated that soil aggregation and disaggregation, induced by a WDC, suppresses and enhances herbicide mobility, respectively. However, the effect of WDC on herbicide leaching was not noticeable for Alion upon its high adsorption to a clayey soil, indicating that herbicide physical-chemical properties may dominate. Finally, WDC induces micron-scale changes in aggregate structure, which have a notable effect on pollutant mobility and fate in the environment.

Context matters: Agronomic field monitoring and participatory research to identify criteria of farming system sustainability in South-East Asia.

In the mountainous areas of South-East Asia, family farms have shifted from subsistence to input-intensified and market-oriented maize-based farming systems, resulting in a substantial increase in farm income, but also in new environmental threats: deforestation, biodiversity loss, soil erosion, herbicide leaching and soil fertility degradation. In this typical case study of cash-strapped farms, where the balance between socio-economic and environmental dimensions of sustainability is complex, we used participatory methods (serious games and Q-methodology), combined with agronomic field monitoring, to identify relevant farm and field-level criteria for sustainability assessment.Serious games at farm level showed that short-term socio-economic dimensions prevailed over environmental dimensions in farmers' objectives. However, farmers also greatly valued their capacity to transfer a viable farm to the next generation and avoid herbicide use. Serious games at field level showed that some farmers were willing to preserve soil fertility for future generations. The agronomic field monitoring showed that maize yield deviations from potential water-limited yield were primarily due to weed infestation favoured by low sowing density, due to uncontrolled moto-mechanized crop establishment. This technical failure at the beginning of the maize cycle led to herbicide overuse, poor returns on investment for fertilizer, and increased exposure to soil erosion.Combining the perspectives of scientists and farmers led to the following set of locally-relevant criteria: i) at farm level: farm income, diversity of activities, farmer autonomy, farmer health, workload peaks, soil fertility transfer between agroecological zones in the landscape, rice and forage self-sufficiency; ii) at field level: resource use efficiency, soil fertility, erosion and herbicide risks, susceptibility to pests, weeds and climate variability, biodiversity, land productivity, economic performance, labour productivity and work drudgery. Our approach helped to identify key relevant sustainability criteria and could be useful for designing alternatives to current maize-based cropping systems, and contributed to informing priority-setting for institutional development and agricultural policies in the region.