Quantitative understanding of farmers' behaviour in pesticide use is critical to enhance sustainability of chemical pest control and protect farmers' health and the environment. However, reports on ...the levels of knowledge and awareness of farmers and the practices of pesticide use are often insufficient. Here, we conducted a comprehensive analysis on the effects of knowledge and awareness of farmers as well as the influence of the associated stakeholders (i.e. pesticide retailers and the government) on farmers' behaviour in pesticide use by using a detailed survey of 307 agricultural households (79 grain farms, 65 fruit farms, 53 vegetable farms and 110 mixed-crop farms) in the Wei River basin in northern China. Eight protective behaviours (PBs) were exhibited by farmers. Careful and safe storage of pesticides, changing clothes or showering after applying pesticides, and reading instructions of the container labels before application were the most frequent PBs. Vegetable and fruit farmers had higher levels of education and knowledge than grain farmers, but the former were less willing to reduce pesticide use because of fear of low profits and lack of trust in the government and pesticide retailers. The PBs of farmers were strongly affected by the perception of the consequences of their behaviour (standardised path coefficient, SPC=0.42) and the level of farmers' knowledge (SPC=0.33). Pesticide retailers and the government had a moderate and weak influence, respectively, on farmers' PBs, suggesting a large gap of trust among farmers, pesticide retailers, and the government. Training and supervising retailers, educating farmers, and improving information transparency across farmers, pesticide retailers and the staff of the Agricultural Extension and Technology Service are recommended for bridging the gap of trust between farmers and the associated stakeholders as well as for promoting the use of PBs among farmers.
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•Pesticide use among farmers and actions of related stakeholders were studied.•Farmers practised inadequate protective behaviours when using pesticides.•Actions of pesticide retailers and the government were found ineffective.•A large gap of trust existed between farmers and actions of related stakeholders.•Improving communication and trust among players could bridge the large gap.
ABSTRACT Compaction is one of the main physical factors of the soil to affect plant development. The aim of this study was to evaluate root and shoot development in winter plants grown in soils of ...different textures under varying degrees of soil compaction (DSC). The experiment was conducted in a greenhouse of the State University of Ponta Grossa, in the south of Brazil. Wheat (Triticum aestivum) and an intercropping system of black oats (Avena strigosa) and forage turnip (Raphanus sativus) were tested in a sandy loam Cambisol and a clayey loam Latosol under a DSC of 85%, 90%, 95% and 100% of the maximum bulk density in a completely randomised design with four replications. Each plot consisted of one PVC column, 0.1 m in diameter and 0.2 m in height, comprising three cylinders placed one on top of the other, with a respective height of 0.08, 0.04 and 0.08 m. The sub-surface layer (0.08-0.12 m) was compacted, and corresponded to the middle cylinder. In t he compacted sub-surface layer, the intercropped black oats and forage turnip presented 28.5% more root dry matter (RDM) than did the wheat. The total RDM decreased by 32% for an increase of 85% to 100% in the DSC, where both the compacted sub-surface layer (0.08-0.12 m) and the layer below that (0.12-0.2 m) were most affected, with a reduction of 45.2% and 53%, respectively. Considering the conditions of this study, which evaluated soils that offer no water or chemical restrictions on the plants, shoot dry matter (SDM) was less affected than the roots, decreasing by 12% for an increase of 85% to 100% in the DSC. There was no difference between the types of soil on crop response due to the variation in the DSC.
The water repellent behaviour of soils is a widely studied phenomenon given its implications for infiltration, runoff, erosion and preferential flow. However, the principles underlying the eventual ...penetration of water into affected soils remain poorly understood. Theoretical considerations of the energetics and kinetics involved as a water drop makes contact with a water repellent soil surface and eventually penetrates into the soil suggest three distinct stages in the overall process. These stages are 1) adhesional wetting as soil and water first make contact, followed by 2) a kinetic barrier transitional stage in which molecular reorganisation of organics on soil reduces the water-soil contact angle to allow the water drop to sit deeper over soil particles of initial contact such that there is contact with particles in directly underlying soil layers, and finally 3) branching interstitial wetting as water penetrates into the bulk soil. Studies presented here of optical microscopy, mass of soil initially wetted, penetration time through layers of soil of different thicknesses, and time-dependent measurements of contact angle, volume of water penetrated, and mass of soil wetted, all give results consistent with this model. However, only for highly water repellent soils can distinct stages in wetting be clearly resolved experimentally, presumably because only these soils have a high enough kinetic barrier in the transitional stage for good separation between stages. For less water repellent soils, while the general time dependent behaviour remains consistent with the model, the distinction between the three stages is not so easy to resolve experimentally. The roles of contact angle, particle size distribution and drop size in determining the rates of these stages is considered, and the implications of the model for understanding soil water repellency are discussed.
Soil and water losses due to agricultural mismanagement are high and non-sustainable in many orchards. An experiment was set up with rainfall simulation at 78mmh-1 over 1hour on 20 paired plots of ...2m2 (bare and straw covered) in new persimmon plantations in Eastern Spain. Effects of straw cover on the control of soil and water losses were assessed. An addition of 60% straw cover (75gm-2) resulted in delayed ponding and runoff generation and consequently reduced water losses from 60% to 13% of total rainfall. The straw cover reduced raindrop impact and thus sediment detachment from 1014 to 47g plot-1h-1. The erosion rate was reduced from 5.1 to 0.2Mgha-1h-1. The straw mulch was found to be extremely efficient in reducing soil erosion rates.
Summary
This review examines the interactions between soil physical factors and the biological processes responsible for the production and consumption in soils of greenhouse gases. The release of ...CO2 by aerobic respiration is a non‐linear function of temperature over a wide range of soil water contents, but becomes a function of water content as a soil dries out. Some of the reported variation in the temperature response may be attributable simply to measurement procedures. Lowering the water table in organic soils by drainage increases the release of soil carbon as CO2 in some but not all environments, and reduces the quantity of CH4 emitted to the atmosphere. Ebullition and diffusion through the aerenchyma of rice and plants in natural wetlands both contribute substantially to the emission of CH4; the proportion of the emissions taking place by each pathway varies seasonally. Aerated soils are a sink for atmospheric CH4, through microbial oxidation. The main control on oxidation rate is gas diffusivity, and the temperature response is small. Nitrous oxide is the third greenhouse gas produced in soils, together with NO, a precursor of tropospheric ozone (a short‐lived greenhouse gas). Emission of N2O increases markedly with increasing temperature, and this is attributed to increases in the anaerobic volume fraction, brought about by an increased respiratory sink for O2. Increases in water‐filled pore space also result in increased anaerobic volume; again, the outcome is an exponential increase in N2O emission. The review draws substantially on sources from beyond the normal range of soil science literature, and is intended to promote integration of ideas, not only between soil biology and soil physics, but also over a wider range of interacting disciplines.
•The existence of REVs in soils is often postulated but unclear.•We found REVs at this scale for the macroporosity in 25 undisturbed soil samples.•However, a measure for statistical homogeneity ...contradicted this finding.•We did not find REVs for connectivity measures.•Model approaches that take soil structure explicitly into account may be necessary.
Soil samples with a volume of approximately 100 mL are commonly used for measuring soil properties needed to parameterize continuum models of transport processes in soils. The necessary assumption that the sampled soil volume corresponds to a representative elementary volume (REV) has only been occasionally tested. Furthermore, the few studies so far have focused on bulk properties such as porosity and bulk density and have not investigated the scale-dependence of pore-space connectivity, which is fundamental for transport properties such as the permeability of soil. In this study, we investigated the scale-dependence of morphologic properties of the soil pore-space in 25 undisturbed soil columns sampled from five different depths (8, 23, 33, 53 and 73 cm) from a field site in southern Norway (Skuterud). We conducted the analyses of scale-dependence on regions of interests of 40 × 40 × 40 mm3 from binarized X-ray images with a resolution of 40 µm. We focused our evaluation on imaged porosity and three measures of pore-space connectivity (the connection probability, the Euler-Poincaré number and the critical pore diameter). As pore network connectivity is scale-dependent and because the connectivity of large pores has a very strong impact on the soil permeability, we conducted our analyses considering three contrasting minimum pore diameters, namely 80, 250 and 500 µm.
We found that the pore connectivity improved with scale, predominantly due to the presence of pores with diameters of less than 0.25 mm. This stresses the importance of image resolution in scale analyses. We moreover observed that both the mean and the standard deviation of the critical pore diameter increased with scale, which may explain why the mean and standard deviation of the saturated hydraulic conductivity are often found to increase with scale. We detected an REV range for the macroporosity between approximately 15 and 65 mm. This range decreased with an increase in the minimum pore diameter considered. However, we also found evidence contradicting the existence of the detected REV range for the macroporosity due to a lack of statistical homogeneity. No REV range could be found for the three investigated connectivity measures, probably because the evaluated scales were too small. Based on our results we conclude that larger soil samples should be used to measure soil properties and investigate processes that depend on the pore network connectivity, such as permeability or water flow and long-range solute transport. We recommend that future studies should investigate REVs for connectivity measures and investigate which REV criteria are most meaningful in a continuum modelling context. Such studies are needed to evaluate whether REVs for transport properties are common in soils. If not, flow and transport models that explicitly account for heterogeneity are necessary.
A significant number of emerging pollutants (EPs) resulting from point and diffuse pollution is present in the aquatic environment. These are chemicals that are not commonly monitored but have the ...potential to enter the environment and cause adverse ecological and human health effects. According to the NORMAN network, at least 700 substances categorized into 20 classes, have been identified in the European aquatic environment. In light of their potential impact action is urgently required.
In this study, we present a concept that shows the current state of art and challenges for monitoring programs, fate and risk assessment tools and requirements for policies with respect to emerging pollutants as a base for sustainable water resource management.
Currently, methods for sampling and analysis are not harmonized, being typically focused on certain EP classes. For a number of known highly hazardous EPs detection limits are too high to allow proper risk assessment. For other EPs such as microplastics method development is in its infancy. Advanced ultra-sensitive instrumental techniques should be used for quantitative determination of prioritized EPs in water, suspended matter, soil and biota. Data on EPs' and their metabolites' properties that determine their fate in the environment are often not available. National surveys on water quality often use different parameters for water quality assessment and often do not include EPs. A harmonized monitoring of surface and groundwater is not yet achieved and urgently required. Specific component integrated into models assessing the fate of EPs in a multi compartment environmental approach are missing and must be developed.
The main goal of risk assessment is the overall protection of ecological communities in the aquatic environment and human health. New methods for assessing the cumulative risks from combined exposures to several stressors, including mixtures of EPs in a multi-scale approach are required.
A combination of regulations and management measures with respect to use/emissions of EPs into the environment, as well as to their occurrence in the environment are fundamental to reach an efficient water resource management.
Bacterial cell-to-cell interactions are in the core of evolutionary and ecological processes in soil and other environments. Under most conditions, natural soils are unsaturated where the fragmented ...aqueous habitats and thin liquid films confine bacterial cells within small volumes and close proximity for prolonged periods. We report effects of a range of hydration conditions on bacterial cell-level interactions that are marked by plasmid transfer between donor and recipient cells within populations of the soil bacterium Pseudomonas putida. Using hydration-controlled sand microcosms, we demonstrate that the frequency of cell-to-cell contacts under prescribed hydration increases with lowering water potential values (i.e., under drier conditions where the aqueous phase shrinks and fragments). These observations were supported using a mechanistic individual-based model for linking macroscopic soil water potential to microscopic distribution of liquid phase and explicit bacterial cell interactions in a simplified porous medium. Model results are in good agreement with observations and inspire confidence in the underlying mechanisms. The study highlights important physical factors that control short-range bacterial cell interactions in soil and on surfaces, specifically, the central role of the aqueous phase in mediating bacterial interactions and conditions that promote genetic information transfer in support of soil microbial diversity.
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