|Main authors:||Meindert Commelin, Jantiene Baartman, Piet Groenendijk, Oene Oenema, Susanne Klages, Isobel Wright, Tommy Dalgaard, Morten Graversgaard, Jenny Rowbottom, Irina Calciu, Sonja Schimmelpfennig, Nicola Surdyk, Antonio Ferreira, Violette Geissen|
|FAIRWAYiS Editor:||Jane Brandt|
|Source document:||»Commelin, M. et al. 2018. Review of measures to decrease pesticide pollution of drinking water sources. FAIRWAY Project Deliverable 4.2, 79 pp|
Here we give a qualitative overview of the measures and practices that decrease pesticides losses to groundwater and surface waters. We discuss the mechanisms and rationales of these measures and practices to decrease these losses.
The actual vulnerability of a site to pesticide pollution via surface runoff and leaching depends on the pedo-climatic conditions and farming practices. As pedo-climatic conditions are largely defined by Mother Nature and are not easy to manipulate, they govern the available options for farming practices to ensure environmental protection. Farming practices will hence have to be adjusted to the pedo-climatic conditions, when the objective is to decrease the risk of water pollution with pesticides. Recommendations and regulations directed at the reduction of pollution risks should therefore ideally be tuned to these different situations. Farming practices refer to farm land management (type and nature of pesticide application, rate, timing and method of application) in close connection with the complementary farm management (e.g. crop type choice, dates of sowing and harvest, drainage and irrigation, crop rotation, livestock feeding and housing).
The effectiveness of measures to reduce pesticide pollution of surface waters and groundwater depends on the site-specific adjustments of these measures to the pedo-climatic conditions and farming systems. It is well-known that ‘blanket recommendations’ are not effective, because they are not specific. However, detailed top-down prescriptions of when, how and where to do what in all pedo-climatic (sub) zones are not effective either. The recommendations need to be made farm and site specific to become really effective. This may require the involvement of both local farmers and advisors.
|1. FAIRWAY case studies|
|2. Qualitative literature review of measures and practices|
1. FAIRWAY case studies
Measures to prevent and reduce the risk of surface runoff and leaching can be categorized according to the source-pathway-receptor concept, i.e., there are
- source-based measures,
- pathway-based measures, and
- receptor or effects-based measures.
Most agricultural measures are aiming at controlling the pathways by which pesticides move through the environment and which are described in »Processes and factors that transfer pesticides to drinking water resurces. However within the FAIRWAY case studies source-based measures are also implemented (see Table 3). Examples of source-based measures are appropriate storage of pesticides, pesticide application according to the rules of integrated farming, organic farming, and prohibition and restrictions on the application (types of) pesticides. Examples of pathway-based measures are buffer strips, tillage management and drift reducing technologies.
Of the 13 FAIRWAY case studies, 8 are being used to study pesticide pollution: to investigate the relation between pollution of drinking water and nitrate and pesticide use. In these case studies several agricultural measures are already applied or tested to minimize pollution by pesticides. The case studies are located all over Europe reflecting different pedo-climatic zones (Figure 13).
For details of the measures applied in each case study see:
»Island Tunø, DK: Measures to decrease nitrate and pesticide pollution in drinking water
»Aalborg, DK: Measures to decrease nitrate and pesticide pollution in drinking water
»Anglian Region, UK: Measures to decrease pesticide pollution in drinking water
»La Voulzie, FR: Measures to decrease nitrate and pesticide pollution in drinking water
»Derg catchment, UK: Measures to decrease pesticide pollution in drinking water
»Noord-Brabant, NL: Measures to decrease pesticide pollution in drinking water
»Baixo Mondego, PT: Measures to decrease nitrate and pesticide pollution in drinking water
»Dravsko Polje, SI: Measures to decrease nitrate and pesticide pollution in drinking water
Table 3 shows the implemented measures in the case studies including evaluation factors as local experts grade them. Source based measures aiming at safe storage are mainly effective for surface water safety, which is point source pollution and will reach surface waters by drainage from the storage/cleaning areas. However not much is known about the costs and possibility of implementation. In one case study biobeds are tested as measure against point source pollution. Other source based measures are aiming at the amount of pesticides used by farmers, these are implemented in several case study locations via laws (restrictions or prohibitions) or financial enforcements (increased taxes). These measure can be very effective in reducing the amount of used pesticides. In addition, this type of measure will reach many land managers because they are enforced on a higher level.
Table 3: Applied measures within the FAIRWAY case studies, with indicated properties based on expert judgement by experts working in the case study.
|Safe pesticide cleaning and storage facilities||NL, UK-NI||+/-||+||?||++||-|
|Safe storage unit for pesticides||UK-NI||?||+||?||?||?|
|Vegetated buffer strips||FR, SI||?||++||€€||+||-|
|Crop rotation improvement||FR||++||?||€€€||+||-|
|Input reduction||FR, UK-EN||++||++||€€€||+||-|
|Alternative (pesticide or mechanical)||UK-EN, UK-NI||?||+||?||+||++|
|Integrated Pest Management2||UK-EN, DK||+++||+||€€||+||+|
|Obligatory reduced input||PT, DK, SI||+++||+++||€||+++||++|
NOTE: Symbols in the table indicate a scale from negative to positive with – is negative, +/- is neutral and +++ is very positive. For the cost three categories are made low (€), moderate (€€) and high (€€€). When there is no data a ? is shown.
1Network engagement: embedding information and communication at all levels from supply chain to agronomist to farmers to stimulate change of practice.
2Intergrated Pest management, is a holistic farm management method to reduce pesticide use, by using alternative mechanical and biologic pest management in combination with adjusted cropping and resource management.
3These measure increase the price of pesticides, which is intented as an extra incentive to look for alternative crop management methods.
The other measures implemented in the case studies are aimed at reducing transport of pesticides. Within the case studies the applied measure are ‘edge of field’ measures including buffer strips. These measures are evaluated as effective by experts, which is underpinned in literature (Arora, Mickelson, & Baker, 2003; Lerch, Lin, Goyne, Kremer, & Anderson, 2017; Reichenberger et al., 2007). Also crop rotation changes and Intergrated Pest Management are implemented as a measure. Integrated Pest Management (IPM) is a farm management measure and can be applied in almost any situation, if designed well it is a very effective measure, because it often includes measure described above in an optimal combination. The effectiveness of crop rotation changes depends a lot on the design of the rotation and on the climatic and farm specific conditions, so this type of measure can be effective but has a low adoptability because it needs changes in farming system (Balderacchi, Di Guardo, Vischetti, & Trevisan, 2008).
2. Qualitative literature review of measures and practices
Beside the results gathered in the case studies, literature sources were reviewed to gather qualitative data about the performance (effectiveness, costs, applicability and adoptability) of a range of measures. As starting point, major reviews from 2000 until present were used (Reichenberger et al., 2007; Rittenburg et al., 2015; Tang et al., 2012). Beside that there were some excellent reviews about specific measures in relation to pesticide pollution (Alletto, Coquet, Benoit, Heddadj, & Barriuso, 2010; Krutz, Senseman, Zablotowicz, & Matocha, 2005). From these reviews and extra literature that was collected for the quantitative analysis, a qualitative overview is made of the most used and studied measures to reduce pollution of ground and surface water (Table 4). The evaluation is based on results of these studies, which contain in general clear data to assess the effectiveness of the measures. However costs, applicability and adoptability were often not well documented. Costs vary per location and time, but are often reflected in the amount of adjustments needed and how complicated the measure is. Estimates presented are gathered from literature but indicate low, moderate or high costs without clear quantitative boundaries. Applicability and adoptability are defined in chapter two, however in the reviewed literature there is not sufficient data available to give reliable results. A more general practicability was more often found, indicating the ease of use and possibility to apply the measure in practice.
Table 4: Measures reviewed in literature with evaluated performance
|1. Buffer strips||+||+++||€€||?||Effectiveness depends on design, added ecological value||(Arora et al., 2003; Krutz et al., 2005; Lerch et al., 2017; Reichenberger et al., 2007)|
|2. Constructed wetlands||+||+++||€€€||-||Effectiveness depends on local design, drain systems, sufficient hydraulic capacity||(Moore, Schulz, Cooper, Smith, & Rodgers, 2002; Tournebize et al., 2017; Vymazal & Březinová, 2015)|
|3. Erosion reduction||-||++||?||+||(Fawcett, Christensen, & ... 1994; Sadeghi & Isensee, 2001)|
|4. Tillage methods||+||+||€||?||Effectiveness depends on local design||(Alletto et al., 2010; Ghidey et al., 2005; Tang et al., 2012)|
|5. Drainage optimization||?||+||€||+/-||(Dinnes et al., 2002; Flury, 1996)|
|6. Residue management/ Mulching||?||++||€||+||(Alletto et al., 2010)|
|7. Drift reduction; no spray zones||n/a||++||€€||+||High ecological value||(de Snoo & de Wit, 1998; Felsot et al., 2010)|
|8. Drift reduction; wind breaks||n/a||++||€||+||High ecological value||(S Otto et al., 2015)|
|9. Drift reduction: mechanical spraying optimization||n/a||+||€€||+||(S Otto et al., 2015; Zande et al., 2008)|
|10. Crop rotations||++||++||€€||?||(Brown & Van Beinum, 2009; Rittenburg et al., 2015)|
|11. Application rate reduction||+||+||€||+/-||(Reichenberger et al., 2007)|
|12. Alternative pesticide||?||?||?||++/-||Depends on choice||(Reichenberger et al., 2007)|
|Redesign farming system|
|13. Integrated Pest management||++||++||€€€||(Gentz, Murdoch, & King, 2010; Reichenberger et al., 2007)|
NOTE: Symbols in the table indicate a scale from negative to positive with – is negative, +/- is neutral and +++ is very positive. For the cost three categories are made low (€), moderate (€€) and high (€€€). An ? indicates that no clear data is available and the evaluation of the measure is still unknown.
The reviewed measures are divided into three groups, based on the management level;
- pathway modifications,
- input control and
- redesigning of the farming system.
Pathway modifications are often physical measures that are most studied (and implemented) on field scale. Input control and redesigning farming systems are farm level measures. In the reviewed literature the main focus was on diffuse pollution, or pollution from the field. Although point source pollution also occurs it is identified as less complex to control and as a less important pollution source (Bach, Huber, & Frede, 2001).
Pathway modifications are physical interventions in the transport route from the source of the pesticide towards ground or surface waters. The effectiveness of the measure is therefore greatly influenced by the local situation like field characteristics (slope, soil type) and climate. This is explained in more detail in »Processes and factors that transfer pesticides to drinking water resurces.
On locations where overland flow dominates (case A in Figure 11), effective measures can be grouped into two general categories:
- measures that increase the soil’s ability to infiltrate and store water, thus reducing overland flow, and
- measures that reduce the overland flow velocity when it is generated and prevent offsite transport (Rittenburg et al., 2015).
Vegetated buffers or filter strips have been shown to be effective in reducing overland flow and soil erosion (Krutz et al., 2005; Lerch et al., 2017). They reduce pesticide loss by
- facilitating the deposition of particles which sorb pesticides,
- enhancing pesticide retention / sorption by increasing the time available for infiltration,
- sorbing dissolved-phase herbicides to the grass, grass thatch and soil surface, and
- reducing the volume of overland flow containing dissolved and particulate-associated pesticides (Tang et al., 2012).
Vegetated buffer strips have been shown to have high removal efficiencies for pesticides and sediment (Arora et al., 2003; S. Otto, Vianello, Infantino, Zanin, & Di Guardo, 2008). Performance of the vegetated filter strips for pesticide trapping depends on the hydrological conditions (e.g. precipitation, infiltration and overland flow), the strip design; strip width, area ratio and type of vegetation cover (Krutz et al., 2005) and characteristics of the particles and pesticides (Tang et al., 2012). However, the environmental fate of the pesticides and their metabolites retained in the filter strips has rarely been evaluated, and the increased infiltration of pesticides in a buffer strip can enhance leaching to groundwater (Krutz et al., 2005).
If well designed and adjusted to local conditions, vegetated buffers are very effective measures. The costs are estimated to be moderate, including implementation and maintenance costs and loss of productivity on the area of the field that is used as buffer. The practicability is low because the buffers need specific design to be effective (Rittenburg et al., 2015) and the application is limited to fields where slopes are steep enough to give regular overland flow events.
Constructed wetlands are less studied than buffer strips but if well designed, maintained and implemented they can have be very effective with rates of pesticide reduction up to 100% (Tournebize, Chaumont, & Mander, 2017; Vymazal & Březinová, 2015). However the cost are high, and they the take a relative large surface of productive land to be installed.
Tillage is strongly related to runoff and infiltration processes on the field, and thus will influence the transport pathways of pesticides. In an extensive review Alletto (2010) reviewed the effectiveness of tillage methods on both overland and leaching transport of pesticides. In both cases changes in tillage methods can be effective, but local design and application are very important for success (Tang et al., 2012). Ghidey et al (2005) found that incorporation of applied pesticides below the upper 2-5 cm of the soil is one of the most effective ways to reduce overland flow of pesticides. The costs of changing tillage methods are generally low and practicability is good. However there is a risk that tillage methods will not remediate total pollution but only will change the transport route, because infiltration (leaching) and overland transport are often mutually exclusive (Flury, 1996). Tillage alters the soil hydraulic properties and thereby the transport pathways of water and related solutes such as pesticides (Alletto et al., 2010). If preferential flow is significant, tillage can reduce pesticide leaching by disrupting continuous macropore flowpaths. On the other hand, in soils where matrix flow is predominant, conventional tillage may enhance pesticide leaching as compared to reduced tillage or no-tillage (Tang et al., 2012). Conservation tillage (i.e. zero-tillage or reduced tillage) increases retention/sorption of pesticides in topsoil, particularly because of retarded degration of soil organic matter compared to tillage, while increasing the availability of pesticides for biological degradation, leading to enhanced persistence in soils. However, reduced tillage also reduces erosion and thereby the particulate transport with sediment (Alletto et al., 2010).
For situations/locations with mainly subsurface flow (case B1 in Figure 11), reduction of pesticide loss to surface and groundwater is challenging. Source input management (i.e.Intergrated Pest Management) is of course possible, but altering the pathway of water flow is difficult. Tile drainage may decrease the overland flow volume, but it may create subsurface flow paths which does not necessarily reduce overall pollutant transport (Rittenburg et al., 2015). Optimizing drainage is shown to be possibly effective but not regarded as the best approach to reduce pollution (Flury, 1996), however combined with other measures it can be used to be overall more effective.
Locations with deeply drained soils and thus posing a risk of leaching to groundwater (case B2 in Figure 11) benefit most from input control measures and increased residence time in the mixing layer (0-5 cm from the soil surface) to enhance degradation of the pollutant (Rittenburg et al., 2015). This second option can be obtained by mulching or crop rotation adjustments. Increased organic matter in the soil will give more sorbtion options for the pesticide, reducing the risk of transport by water (Alletto et al., 2010).
Drift is a transport route and pollution pathway that is isolated from the other pathways. Preventing drift is mainly studied by reducing the transport route from the spraying device to offsite areas including open water bodies. Input control is a very effective measure to reduce drift pollution, because if less or no pesticide is sprayed this relates directly to the potential pollution. This is mentioned in literature, but not tested because of the clear relation. The practicability of reduced input for drift pollution depends a lot on the local situation and solutions to combat the pests (Felsot et al., 2010). If the solutions are expensive or not available the practicability will be low.
Besides input reduction three main measures that are used to reduce drift pollution are no spray zones, windbreaks and mechanical drift reduction technology (Felsot et al., 2010; S Otto, Loddo, Baldoin, & Zanin, 2015). All three measures are effective. Beside that, no spray zones and windbreaks often have a high ecological value which within the EU is also rewarded within the Common Agriculture Policy (Reichenberger et al., 2007). This results in a good practicability for these measures. The mechanical drift reduction consists of a broad spectrum of technologies to reduce drift by changing spraying nozzles (vd Zande 2005) or ventilator design (Otto et al., 2015). Beside these agronomic measures also regulations are made to reduce drift, like restrictions based on weather conditions.
Reduced input and redesigning the farming system are sometimes referred to as ‘Good Agricultural Practices’ (GAPs) or ‘Best Management Practices’, which are agricultural management practices aiming at minimizing off site movement of pesticides to surface waters. Examples of such practices include band spraying on row crops, application restrictions for vulnerable soils and/or wet climates and keeping a certain distance from adjacent water bodies when spraying (Tang et al., 2012). Also the timing of pesticide application (with regards to e.g. forecast of heavy rainfall) or an integrated approach to pest management is important (Gentz et al., 2010). Integrated Pest Management (IPM) is a farm management measure and can be applied in almost any situation, if designed well it is a very effective measure, because it often includes measure described above in an optimal combination. However, the costs are high of IPM because the number of required changes on the farm. Moreover, reducing pesticides input often implies a (temporal) reduction in yields (Reichenberger et al., 2007).
It is evident that there is no single strategy to reduce pesticide losses. When aiming at transport reduction, site-specific plans that are well managed may provide greatest success (Rittenburg et al., 2015). A few factors, beside applied measure, seem to be of major importance in pesticide application management: applications should not coincide with large precipitation events and should be applied when crops can uptake the chemicals or when there is enough organic matter and residue in the soil to either immobilize or bind them allowing for biodegradation (Rittenburg et al., 2015).
Note: For full references to papers quoted in this article see