|Main authors:||Oene Oenema, Meindert Commelin, Piet Groenendijk, John Williams, Susanne Klages, Isobel Wright, Morten Graversgaard, Irina Calciu, António Ferreira, Tommy Dalgaard, Nicolas Surdyk, Marina Pintar, Christophoros Christophoridis, Peter Schipper, Donnacha Doody|
|FAIRWAYiS Editor:||Jane Brandt|
|Source document:||»Oenema, O. et al. 2018. Review of measures to decrease nitrate pollution of drinking water sources. FAIRWAY Project Deliverable 4.1, 125 pp
In this article we provide overviews of the measures and practices that decrease nitrate losses to groundwater and surface waters. We discuss the (cost) effectiveness of the measures as reported in literature and the mechanisms and rationales of the measures and practices.
The actual vulnerability of a site to N losses 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 for ensuring 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 nitrates.
|1. Summary overview of main documents|
|2. Measures used in the FAIRWAY case studies|
|3. Good agricultural practices of the EU Nitrates Directive|
Our overview is largely based on data and information provided by Osterburg et al (2007); Anonymous (2011); Newell Price et al (2011); Bittmann et al (2014); Van Boekel (2015). These reports provide comprehensive overviews of a wide range of measures and practices, based on literature reviews and expert judgement.
Osterburg et al (2007) made a comprehensive overview of 49 measures to decrease the potential for nitrate leaching to groundwater and surface waters for Germany within the context of the EU Water Framework Directive (Table 7). The measures were compiled and assessed qualitatively for various farm types and environmental conditions on the basis of literature review, interviews and expert judgement. They used three indicators, namely,
- the soil N balance (N surplus),
- the amount of soil mineral N (0-90 cm) in autumn, and
- the net N load that is lost to groundwater or surface waters.
The cost-effectiveness of the 49 measures are summarised in Figure 19 for the indicator soil mineral N (0-90 cm) in autumn (Herbst-Nmin). The median cost of most measures ranges from 1 to 5 euro per kg N, but the uncertainty of the estimates is large for most of the measures (range 0 to 40 euro per kg N).
Table 7. Summary overview of the estimated effectiveness, efficiency, applicability and acceptance of 49 reviewed measures (Osterbrug et al., 2007).
|Nr||Measure||Effectiveness Kg N/ha||Efficiency Euro/kg N||Applicability||Acceptance|
|1||Cover cropping, early plough down||20-60||0.7-5.0||++||+++|
|2||Cover cropping, late plough down||30-60||0.7-4.0||++||+++|
|3||Growth of rapeseed before winter wheat||20-40||1.5-3.0||++||++|
|4||Growth of winter hardiness cover crop||30-60||1.2-4.3||++||++|
|5||Growth of cover crop in between cereals||10-40||1.3-12.5||++||+|
|6||Growth of annual grass fallow crop, with plough down in autumn||30-60||1.5-5.0||+++||++|
|7||Growth of two-year grass fallow crop, with plough down in autumn||30-70||1.6-6.7||+++||++|
|8||Growth of many-years grass fallow crop, with plough down in autumn||40-80||1.5-8.8||+++||+|
|9||Crop rotation; growth of less N demanding crops||10-30||5.0-35.0||++||++|
|10||Early harvest of maize followed by cover crop||20-40||7.5-15||++||+|
|11||Growth of cover crop after rapeseed||30-70||1.7-8.3||++||+|
|12||Growth of cover crop after potato||30-60||1.0-8.3||++||+|
|13||Growth of cover crop after vegetables||40-80||1.5-6.3||++||+|
|14||Crop rotation; growth of less N demanding crops||0-20||2.5-9999||+||++|
|15||Increasing planting density of maize||0-15||1.7-9999||++||+|
|16||Mulching of crop residues||0-20||2.0-9999||++||++|
|18||Minimum tillage after rapeseed||0-40||0.6-9999||+++||+|
|19||No soil cultivation in autumn after harvest of cereals||0-20||1.0-9999||+++||++|
|20||No soil cultivation in autumn after harvest of maize||0-20||1.0-9999||+++||++|
|21||Intensification of grassland||0-20||4.0-9999||++||+|
|22||Restricted grazing in autumn||0-40||1.3-9999||+||++|
|23||No reseeding and cultivation of grassland||40-80||0.3-1.3||++||++|
|24||Small reduction of N fertilization of arable crops||0-10||5.0-9999||0||+|
|25||No N fertilization of arable crops in late summer and autumn||0-20||1.0-9999||0||++|
|26||Use enhanced efficiency fertilizers, including nitrification inhibitors||0-20||1.3-9999||++||++|
|27||Use of CULTAN; injection of liquid fertilizers||0-20||1.3-9999||+++||++|
|28||Improved fertilizer spreading||0-10||1.8-9999||++||++|
|29||Band application of fertilizer with potato||0-15||1.7-9999||+||++|
|30||Precision N fertilization||0-20||0.5-9999||+++||+|
|31||Covering manure storages||1-3||0.7-4.0||+++||++|
|32||Low-emission manure application||0-20||0.8-9999||+++||+++|
|33||Improved application technique for solid manure||0-10||3.5-9999||+++||+++|
|34||No manure application to land after 15 September||20-40||0.3-1.5||++||++|
|35||Ban on manure application from 1 October to 15 February||10-20||1.3-2.5||++||++|
|36||Lowering the maximum manure application rate to 150 kg per ha||?||?||++||++|
|37||Low-protein feeding of pigs||?||?||+++||+++|
|38||Low-protein feeding of poultry||?||?||+++||+++|
|39||Transformation of arable land into grassland||30-70||5.3-20.0||+++||0|
|41||Contour cropping on sloping land||?||?||+++||0|
|43||Introduction of riparian zones||50-300||0.4-20.0||+++||0|
|44||Re-introduction of wetlands||50-300||0.4-20.0||+++||0|
|45||Transformation to organic farming||20-80||1.0-10.0||+++||+|
|46||Nutrient management planning||0-30||0.3-9999||+++||+++|
|47||Using soil mineral N analyses for nutrient management planning||0-30||0.7-9999||+++||++|
|48||Using plant N analyses for nutrient management planning||0-20||1.0-9999||+++||+++|
|49||Using manure N analyses for nutrient management planning||0-40||0.1-9999||+++||++|
Effectiveness is expressed in terms of reduction in soil mineral N in autumn (kg N per ha), efficiency is expressed in euro per kg soil mineral N reduced, applicability is qualitatively estimated: low: +, medium: ++, high: +++. Acceptance by farmers is also qualitatively estimated, ranging from no: 0, low: +, medium: ++, high: +++.
Anonymous (2011) describe the background and rational of the measures of the EU Nitrates Directive in Annexes II and III, based on literature review and expert judgement. This study includes also maps for the EU-28 showing the vulnerability of the landscapes for nitrate losses to groundwater and surface waters. Evidently, the vulnerability differs greatly across EU-28 and hence, site-specific timing and implementation of the measures are important.
Newell Price et al (2011) made a comprehensive overview of 83 measures to decrease the potential for nitrate and phosphorus leaching to groundwater and surface waters and for decreasing the emissions of ammonia and greenhouse gases to the atmosphere for United Kingdom within the context of the EU Water Framework Directive, the UNECE Convention on Long-Range Transboundary Air Pollution (the Gothenburg Protocol), the EU National Emission Ceilings Directive (NECD), and the Kyoto Protocol. The emission mitigation options for reducing diffuse water pollution, air pollution and greenhouse gas (GHGs) emissions, were compiled on the basis of literature review and expert judgement. The aim is to help users in developing policies and selecting suitable mitigation methods. The cost of the measures range from a few hundred British pounds to more than a few thousands of British pounds per farm per year. Table 8 provides a summary overview of the estimated effectiveness, economic cost, applicability and adoptability of 42 reviewed measures. Effectiveness was expressed in relative decreases of nitrate losses to groundwater and/or surface waters, using four classes
- negative, i.e. losses increase,
- low; losses decrease by on average 10% (range 1-30%),
- moderate; losses decrease by on average 40% (range 20-80%), and
- high; losses decrease by on average 70% (range 50-90%).
Costs were expressed in British pounds per farm, which have been transferred into euro per farm. Applicability was evaluated from low to high, based on expert judgement. Adoptability was also evaluated from low to high, based on expert judgement. Land use changes were most effective but had low adoptability scores. Quite a few measures had unknown effectiveness score but relatively high costs. Enhanced efficiency measures had relatively high adoptability but the effectiveness was scored as low (to moderate).
Table 8. Summary overview of the estimated effectiveness, economic cost, applicability and adoptability of 42 reviewed measures (after Newell-Price et al., 2011).
|1||Change the land use from arable cropping to unfertilised grassland (without livestock) and associated manure inputs||High||200 – 4000||Specific areas only||Low|
|2||Change the land use from arable cropping to permanent grassland, with a low stocking rate and low fertiliser inputs||High||1000-50000||Specific areas only||Low|
|3||Conversion of arable land to permanent woodland||High||500-1000||Specific areas only||Low|
|4||Convert land to biomass cropping (i.e. willow, poplar, miscanthus)||High||500-1000||Specific areas only||Low|
|5||Establish cover crops in the autumn||High||100-400||After specific crops only||Moderate|
|6||Establish autumn sown cover crops earlier||High||1000-15000||After specific crops only||Low|
|7||Plough out grassland in spring rather than the autumn||High||100-4000||Specific areas only||Low-moderate|
|8||Minimum tillage||Moderate||-4500- -500||Specific areas only||Low-moderate|
|9||Amelioration of compacted soils and cover cropping||Unknown||50-2000||Specific areas only||Moderate|
|10||Contour soil cultivation on sloping land||Unknown||50-600||Specific areas only||Moderate|
|11||Leave autumn seedbeds rough||Unknown||100-3000||Specific areas||Low|
|12||Use tines to disrupt tramlines (compacted soils)||Unknown||10-1000||Specific crops, areas||Low-moderate|
|13||Maintain and enhance soil organic matter||Unknown||-7000 - 1000||Moderate to high||Moderate to high|
|14||Establish grass buffer strips||Unknown||50 - 4000||Moderate to high||Low to moderate|
|15||Establish riparian buffer strips||Unknown||1000 - 12000||Specific areas||Moderate|
|16||Reduce surface runoff by loosening topsoil||Low||1000 - 2000||High||Moderate|
|17||Allow existing (old) drainage systems to naturally deteriorate i.e. cease to maintain them||Low or negative||50 - 2000||Specific areas only||Low|
|18||Actively maintain drainage systems||Unknown||500-3000||Specific areas only||Low|
|19||Clear out ditches regularly||Negative||0-1500||High||High|
|20||Use genetic resources to improve lifetime efficiency of livestock systems||Low||-9000- -2000||High||High|
|21||Develop new plant varieties||Low||-3000 – -150||High||High|
|22||Improve accuracy and spread patterns of fertiliser spreaders||Unknown||50-200||High||High|
|23||Use of a recognised fertilisation recommendation||Unknown||-4000 -500||High||Moderate|
|24||Use of a recognised fertilisation recommendation + make full allowance of nutrients from manure||Unknown||-8000 – -1000||High||Moderate|
|25||Reduce the amount of manufactured N and P fertiliser applied to crops below the economic optimum rate||Low||1200 - 54000||High||Low|
|26||Keep fertilisers away from water course||Low||20 - 4000||High||Moderate to high|
|27||Do not spread fertiliser on wet soils||Low||50-1000||High||Moderate to high|
|28||Place nutrients close to germinating or established crops to increase fertiliser N and/or P recovery||Low||20-100||High||Moderate to high|
|29||Use of nitrification inhibitors||High||500-4000||High||Low to moderate|
|30||Replace urea-based fertilisers by ammonium-nitrate based fertilizers||Low||-900- 200||High||Low|
|31||Use of urease inhibitor in urea fertilisers||Unknown||<1000||High||Low to moderate|
|32||Use of clover in grassland to replace N fertiliser||Moderate||<500||High||Moderate|
|33||Do not apply manufactured N and P fertilisers to soils when soil fertility levels are high||Unknown||<100||High||Moderate|
|34||Low-protein and low-P animal feeding||Low||1000-7000||High||Low to moderate|
|35||Phase feeding||Low||400-2000||High||Low to moderate|
|36||Extension of the grazing season||Negative||-1500- -6000||Moderate||Low to moderate|
|37||Extension of grazing when soils allow so||Unknown||-1500- 500||High||Low|
|38||Reduced grazing, especially on wet soils||Moderate||1000-6000||High||Low to moderate|
|40||Construct water troughs with a firm base to reduce poaching damage to the soil||Low||200-1000||High||Moderate|
|41||Reduce the total number of livestock on the farm i.e. the number of stock per unit of land area||Moderate||5000- 35000||High||Very low|
|42||Use of buffer strip to slow down water (and solute) transfer to surface water||Moderate||500 - 5000||Moderate||Low|
Bittmann et al (2014) made a comprehensive overview of 7 measures to decrease the emissions of ammonia to the atmosphere within the context of the UNECE Convention on Long-Range Transboundary Air Pollution. The measures have been described in detail for various farming systems and also the possible side-effects in terms of nitrate leaching and greenhouse gas emissions have been highlighted. Measure 1 relates to farm N management, with impact on basically all N loss pathways, including nitrate leaching losses. The cost of the measures are in the range of <1 to >5 euro per kg NH3-N per year. Management and feed measures are relatively cheap (<1 euro), and those for adaptation of buildings and manure storage relatively high (>5 euro per kg NH3-N per year).
Van Boekel (2015) reviewed the measures implemented to address nutrient problems of groundwater and surface water for countries in northwest Europe. A total of 7 mitigation options were selected and analysed. However, the requested data and information was not available for all countries. Table 9 presents a summary of the cost effectiveness of selected measures. Van Boekel (2015) concluded that there are large variations in cost and cost-effectiveness among the mitigations options and between country estimates. For some measures the cost and cost effectiveness are not known, because the amount of data is very low.
None of these review papers addressed measures that could be adopted by citizens. However, cities are increasingly targeted as centers for sustainable development and innovation of food systems. Urban agriculture (UA) is advocated by some as a multi-faceted approach to help achieve urban sustainability goals, as it is provides possible social, economic and environmental benefits. The role of UA in restoring resource cycles receives increased attention, especially with regard to assimilating urban waste. However, there is little information on how nutrients are managed in UA in developed countries. Wielemaker et al. (in review) examined nutrient management in 25 ground-based UA initiatives in the Netherlands on i) preferences for types of fertilizers, and ii) quantity, quality of fertilizers used including nutrient composition and organic matter content, and nutrient outputs in harvested products. Results show that mean nutrient inputs exceeded mean crop demand by 100-300% for nitrogen, by 600% for phosphorus and 260% for potassium. The need to improve nutrient management in urban agriculture is evident. Soil tests, harvest logging and book keeping of nutrient inputs would improve data quality and may help balance nutrient inputs with nutrient outputs.
In summary, these five reports provide comprehensive overviews of measures to decrease nitrate losses from agriculture to groundwater and surface waters. The findings presented in these reports have been summarized into the so-called long list of measures in Annex 1 of »Review of measures to decrease nitrate pollution of drinking water resources. Four categories of measures have been distinguished:
- Efficiency enhancing measures (19 measures)
- Land use management (12 measures)
- Soil management (10 measures)
- Water management (3)
Evidently, most measures relate to improving the use of available nitrogen sources in the soil or applied nitrogen on the land; the more N is taken up and removed by harvest crop, the less is available for leaching and surface runoff.
A review was made of all the measures used to decrease nitrate polluction of drinking water resources in the 10 FAIRWAY case studies where this (or has been) is a particular issue. Most of the measures relate to efficiency enhancing measures and land use management measures. Unfortunately, the effectiveness and efficiency at the sites are not yet well known at the study-sites. For details for 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
»La Voulzie, FR: Measures to decrease nitrate and pesticide pollution in drinking water
»Lower Saxony, DE: Measures to decrease nitrate pollution in drinking water
»North Greece, GR: Measures to decrease nitrate pollution in drinking water
»Overijssel, NL: Measures to decrease nitrate pollution in drinking water
»Vansjø, NO: Measures to decrease nitrate pollution in drinking water
»Baixo Mondego, PT: Measures to decrease nitrate and pesticide pollution in drinking water
»Arges-Vedea, RO: Measures to decrease nitrate pollution in drinking water
»Dravsko Polje, SI: Measures to decrease nitrate and pesticide pollution in drinking water
The notion of ‘good agricultural practices’ is probably as old as sedentary agriculture itself. Farmers have learned how to maximize the economic and social benefits from their land over time; in the beginning through trial and error and word of mouth, later through formal education and guidelines from extension services, institutions, governments and processing industries.
The notion of ‘good agricultural practices’ changed following increased awareness of the environmental consequences of the intensification of agricultural practices. The term ‘nutrient management’ was introduced in the second half of the 1980s; the term replaced in part fertilization and fertilizer management, and emphasized the importance of (i) including all sources of nutrients in fertilization recommendations, including animal manures, and (ii) nutrient losses to air and water. The term ‘best environmental management’ reflects the increased awareness of the environmental implications of modern farming probably even better.
The discussion on good and best management practices remained rather academic in the agricultural arena until the acceptance of the Nitrates Directives by the EU Member States in 1991. The aim of this Directive is
- to reduce water pollution caused or induced by nitrates from agricultural sources, and
- to prevent further such pollution.
For the first time in history a set of coherent measures was introduced to decrease nitrate losses from agriculture. It does so from a farm perspective as well as from a landscape perspective. The Nitrates Directive requires Member States
- to monitor nitrate pollution and eutrophication of groundwater and surface waters,
- to promote the implementation of Good Agricultural Practices (see Annex II of the Directive),
- to designate so-called Nitrate Vulnerable Zones (NVZs) where nitrate concentrations are higher than 50 mg per litre, and
- to establish Action Programmes with specific measures (see Annex III of the Directive) for NVZs to decrease nitrate pollution.
The measures of Annexes II and III of the Nitrates Directive are presented in Tables 10 and 11.
Table 10. Measures referred to in Annexes II of the Nitrates Directive; Code of Good Agricultural Practice
|1||Periods when the land application of certain types of fertilizer is prohibited or inappropriate.|
|2||The land application of fertilizer to steeply sloping ground.|
|3||The land application of fertilizer to water-saturated, flooded, frozen or snow-covered ground.|
|4||The conditions for land application of fertilizer near water courses.|
|5||The capacity and construction of storage vessels for livestock manures, including measures to prevent water pollution by run-off and seepage into the groundwater and surface water of liquids containing livestock manures and effluents from stored plant materials such as silage.|
|6||Procedures for the land application, including rate and uniformity of spreading, of both chemical fertilizer and livestock manure, that will maintain nutrient losses to water at an acceptable level.|
|7||Land use management, including the use of crop rotation systems and the proportion of the land area devoted to permanent crops relative to annual tillage crops.|
|8||The maintenance of a minimum quantity of vegetation cover during (rainy) periods that will take up the nitrogen from the soil that could otherwise cause nitrate pollution of water.|
|9||The establishment of fertilizer plans on a farm-by-farm basis and the keeping of records on fertilizer use.|
|10||The prevention of water pollution from run-off and the downward water movement beyond the reach of crop roots in irrigation systems.|
Table 11. Measures referred to in Annexes III of the Nitrates Directive, to be included in Action Programmes of Member States.
|A. The measures shall include rules relating to:|
|1||Periods when the land application of certain types of fertilizer is prohibited.|
|2||The capacity of storage vessels for livestock manure; this capacity must exceed that required for storage throughout the longest period during which land application in the vulnerable zone is prohibited, except where it can be demonstrated to the competent authority that any quantity of manure in excess of the actual storage capacity will be disposed of in a manner which will not cause harm to the environment.|
Limitation of the land application of fertilizers, consistent with good agricultural practice and taking into account the characteristics of the vulnerable zone concerned, in particular:
|B. These measures will ensure that, for each farm or livestock unit, the amount of livestock manure applied to the land each year, including by the animals themselves, shall not exceed a specified amount per hectare. The specified amount per hectare be the amount of manure containing 170 kg N. However|
|(a)||for the first four year action programme Member States may allow an amount of manure containing up to 210 kg N;|
|(b)||during and after the first four-year action programme, Member States may fix different amounts from those referred to above. These amounts must be fixed so as not to prejudice the achievement of the objectives specified in Article 1 and must be justified on the basis of objectives criteria , for example:
|C. Member States may calculate the amounts referred to in paragraph B on the basis of animal numbers.|
Although the Code of Good Agricultural Practices were implemented on a voluntary basis, and many Member States have been struggling with its implementation, it is clear that the notion of ‘Good Agricultural Practice’ has changed in the EU since the implementation of the Nitrates Directive. This is also related to the measures of Annex III of the Nitrates Directive, which have to be implemented in nitrate leaching vulnerable zones (NVZs) and are obligatory for all farmers in those areas. The scientific basis for codes of good agricultural practice was first presented in 1993 (Jordan, 1993) and then further elaborated in 2011 (Anonymous, 2011). Interestingly, the Nitrates Directive is only 8 pages (including the annexes), and the Code of Good Agricultural Practice covers only a half a page. Yet, it has far-reaching implications for agriculture in the EU. In contrast, the recent Commission report ‘Best environmental management practice for the agriculture sector - crop and animal production’ (Antonopoulos et al 2018) covers 628 pages, but will likely have less impact. The guidance document on ammonia mitigation cover 96 pages (Bittman et al., 2014).
Most measures in Annexes II (Table 10) and III (Table 11) of the Nitrates Directives are source-based measures; these relate to the amount, method, and timing of manure and fertilizer applications. Examples of pathway-based measures are the irrigation measures, buffer strips, green covers, and land use management. Some measures though could be classified as a mixture of source-based and pathway-based. The Nitrates Directive does not explicitly demand for receptor or effects-based measures, but does not exclude such measures as creation of riparian zones and dredging could be considered part of land use management.
The list of measures of the Nitrates Directive is much smaller than the list of possible measures shown in Tables 7 and 8. Notably, precision fertilization is not mentioned
The Groundwater Directive, Water Framework Directive and Drinking water Directive do not prescribed specific measures as in the Nitrates Directive. Rather, these Directives require Member States ‘to take all necessary measures to ensure that water bodies are not polluted’ and that ‘the water intended for human consumption is wholesome and clean’.
Farmers make a myriad of tactical and operational decisions annually. From the early 1990s onwards they have to consider an increasing number of governmental constraints related to nitrogen use, which have their origin in the EU Nitrates Directive, EU Water Framework Directive, the EU National Emission Ceiling Directive and the UNECE Gothenburg Protocol (Oenema et al., 2011). All these Directives have paragraphs related to nitrogen management and to targets for nitrogen emissions. These regulations have made decision making of farmers much more complex. Suppliers and processing industries have also released a range of good and best management practices and guidelines, related to the environment and climate change, but also to product quality and production methods. These guidelines also affect the way nitrogen is used in agriculture.
Evidently, there is a wide range of possible measures to reduce nitrate losses from agriculture to groundwater and surface waters (Annex 1 and Annex 2 of »Review of measures to decrease nitrate pollution of drinking water resources). However, there is no “golden bullet” solution available, which would allow farmers to achieve high crop yields and at the same time reduce nitrate losses drastically. Yet, some measures are more effective than others. Reducing total N input was identified as the least cost-effective measure (on average 16 euro per kg N per year) in the study of Osterbrug et al (2007), while precision fertilization and timing, and using enhanced efficiency fertilizers were evaluated as cost-effective (1-3 euro per kg N per year) by Osterbrug et al (2007). They did not include a measure ‘comply with fertilization recommendations’. The DEFRA Guide Book does not include an option to reduce N input; rather they include the option ‘to comply with fertilizer recommendations’, which was evaluated as a cost-effective measure, as it give a net gain of 400 to 3000 British pounds per farm per year (Newell Price et al., 2011). Van Boekel (2015) did not identify N input control as a possible measure. In contrast, balanced N fertilization has been identified as the most effective measures of the EU Nitrates Directive (Velthof et al., 2009), although the cost of this measure is significant (Oenema et al., 2009). The diversity of possible and identified options to decrease nitrate losses from agriculture to the groundwater and surface waters may reflect differences in environmental conditions, notions of the N cycle and in culture. It may also reflect the wide variations in measured effectiveness.
The EU Nitrates Directives includes 10 measures in Annex I (Table 10) and 5 in Annex III (Table 11), but two of the Annex III measures overlap with those of Annex II. Demanding measures are A3 (N application limits) and B (manure N application limit) of Annex III, especially for intensive agricultural systems. These measures (with slight modifications) are described in detail in »Further characterisation of key measures that decrease nitrate losses, because most of these measures have been implemented in all EU Member States, and because these measures seem highly effective (although not equally across EU-28), and are formulated in such a manner that they are applicable across EU-28.
Based on the review of measures discussed in this chapter, a priority list of measures was formulated; the so-called short list of measures (Table 12). This list serves two purposes,
- it provides a quick overview of effective measures, and as such is a first attempt to derive most promising measures and
- it was used to focus the literature research for the further in-depth analysis of the measures, based on experimental results.
The quantitative analysis of the literature results is further discussed in »Quantitative analysis of measures and practices.
Table 12. So-called shortlist of measures aimed at decreasing nitrate pollution of groundwater and surface waters,
based on literature review, expert judgement and joint discussions.
|Nr||Name of the measure||Characterization of the measures|
|1||Nitrogen fertilization; balanced nitrogen fertilization (dose of application)||Matching nitrogen input to the average nitrogen demand of the crop is termed balanced nitrogen fertilization. This measure includes terms like “reduction in fertilization”, nutrient management planning, and more drastic measures such as withholding nitrogen fertilizer inputs. Typically, this measure has been studied in nitrogen fertilizer trials. This measure includes also the combined use of synthetic fertilizers, animal manures, organic fertilizers, bio-based fertilizers, composts, etc. Evidently, crop type (crop rotation), soil type, soil tillage, etc. have to be specified as well.|
|2||Precision nitrogen fertilization (optimization in space and time)||Precision nitrogen fertilization builds on balanced fertilization, and includes “variable rate fertilization” and “split applications”. This includes measures like a ban on fertilization in winter, on sloping land, on frozen land, etc. Evidently, crop type (crop rotation), soil type, soil tillage, etc. have to be specified as well.|
|3||Enhanced efficiency nitrogen fertilizers||Enhanced efficiency fertilizers include various types of nitrogen fertilizers, with or without nitrification inhibitors, urease inhibitors, special coatings (slow-release fertilizers). Evidently, crop type (crop rotation), soil type, soil tillage, etc. have to be specified as well.|
|4||Changes in crop types and/or crop rotations||Changes in crop types and rotation (without much change in nitrogen fertilization input) may change the nitrogen output with harvested crop and thereby nitrogen leaching. This measure includes a change to high-yielding crop varieties, and energy crops Evidently, crop type (crop rotation), Nitrogen input, soil type, soil tillage, etc. have to be specified as well.|
|5||Cover crops||Cover crops or catch crops or green manures are grown after the harvest of the main crops, and serve to mop up residual mineral nitrogen from the soil and/or to improve soil quality. These crops may be sown in between the main crops (relay cropping) or after the harvest the main crop. Evidently, crop type, sowing/harvesting data, soil type, soil tillage, etc. have to be specified as well.|
|6||Mulching||Mulching refers to the covering of the soil with crop mulch or with plastic mulch, mainly to reduce evaporation, modify soil surface temperature, and suppress weed growth. Due to changes in crop yield and soil water flow and utilization, leaching may be suppressed.|
|7||Restricted grazing||Restricted grazing includes zero grazing, spring-season grazing only, and siesta-grazing. This measure refers to a decrease in the animal-grazing hours per year relative to year-round grazing or day-and-night grazing during the growing season.|
|8||Buffer strips||Buffer strips refer to the strips of land along water courses. These strips have adjusted management (fertilization, crops, tillage) and thereby minimize the leaching and overland flow to surface waters. The width and management of the strip are critical|
|9||Riparian zone||Riparian zones refer to wetland areas along water courses which intercept and scavenge nutrients from leaching and overland flow pathways before entering the water courses. It includes constructed wetlands. Special vegetation and management may increase the scavenging of nutrients and thereby the pollution of the surface waters|
|10||Irrigation||This measure includes sprinkler irrigation, drip irrigation, furrow irrigation, flood irrigation, and fertigation. Irrigation may both increase or decrease leaching, depending on irrigation practice, crop type, soil type and weather conditions.|
For these measures quantitative data and information have been collected from the literature, stored in the Excel tool and then statistically analysed.
Note: For full references to papers quoted in this article see