Agri-environmental indicator - risk of pollution by phosphorus


Data from August 2018

Planned update: April 2020

Highlights

The gross phosphorus balance for the EU was 1.2 kg per hectare per year in the period 2013-2015, down from 3.9 kg per hectare per year in the period 2004-2006.

The phosphorus surplus on EU agricultural land more than halved from 2004-2015.

Gross phosphorus balance on agricultural land, 3-years averages, kg P per ha, EU-28, 2004-2015
Source: Eurostat (aei_pr_gnb)

This article provides a fact sheet of the European Union (EU) agri-environmental indicator risk of pollution by phosphorus. It consists of an overview of recent data, complemented by all information on definitions, measurement methods and context needed to interpret them correctly. The risk of pollution by phosphorus article is part of a set of similar fact sheets providing a complete picture of the state of the agri-environmental indicators in the EU.


Full article

Key messages

  • Phosphorus is an important plant nutrient, essential for world-wide food security. It is used in agriculture as fertiliser, and the EU is strongly dependent on imports to fulfill its need. But phosphorus is used in an unsustainable way; via fertilisers, sewage and animal manure, phosphorus and other nutrients are lost to water bodies and cause pollution and euthrophication.
  • The indicator gross phosphorus balance provides an indication of the surplus of phosphorus (P) on agricultural land (kg P per hectare per year). It also provides trends on phosphorus inputs and outputs on agricultural land over time. The indicator is based on calculated input and output of phosphorus and not on soil sampling.
  • When calculated as 3-year averages to smooth out differences due to weather or input prices, the average gross phosphorus balance (GPB) per hectare of utilised agriculture area (UAA) in the EU-28 decreased from 3.9 to 1.2 kg P per ha UAA (see Figure 1) from 2004 to 2015. This means that the surplus is only around 30 % of what is was in the early 2000s and a significant decrease has been achieved.
  • The gross phosphorus balance decreased in most countries between 2004 and 2015 (Table 1). Slight increases were seen only in Cyprus, Latvia, Hungary and Austria. It is worth noting that the gross phosphorus balance of Hungary remains negative, which indicates a risk for soil depletion.
  • A negative phosphorus balance might be logical and sustainable if decades of excess phosphorus applications have built up large reserves of phosphorus in the soil. In this case, applying less than the crop requires is good practice and reduces environmental risk but not crop productivity. Thus some Member States/regions can run a negative balance ("phosphorus mining" ) for years without reducing crop yield potential. This may be the case with Italy and the Netherlands.
  • The quality and accuracy of the estimated gross phosphorus surplus per hectare depends on the quality and accuracy of underlying data and coefficients used. As methodologies (especially with regards to the coefficients) and data sources used in countries vary, the balances are only consistent within a country across time. The gross phosphorus balances are not consistent across countries, which means that data cannot be compared. However, trends can be compared between countries.

Analysis at EU level

The gross phosphorus balance for the EU-28 decreased from an estimated average of 3.9 kg P per ha per year in the period 2004-2006 to 1.2 kg P per ha per year in the period 2013-2015. The inputs of the gross phosphorus balance consist mainly of mineral fertilisers, organic fertilisers [1] and manure input, and other inputs like seeds and planting material. Mineral fertilisers and manure accounted for more than 93 % of the phosphorus input in EU-28 between 2010 and 2014 (country data are not complete for 2015, therefore 2014 values are used for this section). Annually on average 1.6 million tonnes came from manure, and 1.1 million tonnes from mineral fertiliser. Other organic fertilisers, such as compost, sewage sludge and industrial waste accounted for little more than 5 % of total phosphorus inputs. Data on other organic fertilisers are, however, lacking in many countries and, therefore, the significance of these fertilisers could be underestimated. Other inputs (e.g. seeds and planting material) represented only 1 % of total phosphorus input.


Figure 1: Gross phosphorus balance on agricultural land, 3-years averages, kg P per ha, EU-28, 2004-2015
Source: Eurostat (aei_pr_gnb)

Analysis at country level

The current balances are not comparable between countries due to differences in definitions, methodologies and data sources used. However, trends can be compared between countries. The average gross phosphorus balance per ha in 2013-2015 was highest in the Mediterranean countries Cyprus and Malta (Figure 2). Malta had a strong decrease in the phosphorus balance from the years 2004-2006 to the years 2013-2015, even if the latter average remains elevated. In Cyprus, the balance does not significantly change over time and remains around 30 kg P per ha UAA.

The balance was negative for Bulgaria, Estonia, Slovakia, the Czech Republic, Germany, Romania, Hungary and Italy. This can indicate a risk for negative effects on soil quality, since more phosphorus is removed from the soil than is added. A negative trend can also indicate that excess phosphorus applied during previous years is removed. In this case applying less phosphorus than what is removed is sustainable since it reduces environmental risk without reducing crop productivity. This may be the case for Italy and the Netherlands. This strategy is often referred to as "phosphorus mining" and is a recognised measure for reducing the risk of phosphorus loss to water. The opposite case is found in Ireland. Ireland has a positive phosphorus balance, but a large deficit in soil phosphorus levels in certain soil types. In fact, around 60% of soil samples have low to very low phosphorus status [2]. Consequently, there is a national campaign to increase phosphorus application to e.g. the intensively stocked grassland farms[3]. This appears to have increased the phosphorus balance (surplus). In fact, even more phosphorus should be applied to bring soils up to the optimum for production without significantly increasing the risk to water (the optimum phosphorus level for crops is below the threshold for serious risk of loss to water).

Increasing trends were very slight, and concerned Cyprus, Latvia, Hungary and Austria. However, as regards Hungary, the balance of phosphorus has remained negative since the beginning of the data collection (Table 1). An increasing trend in the phosphorus balance is in such cases a sign of improved management of the natural resource soil, upon which agriculture depends.

There are large differences between countries in the share of phosphorus input coming from manure or fertilisers. Phosphorus is not available to the plant at the same rate for different types of manure and fertilisers. Manure input in the gross phosphorus balance is calculated from livestock numbers and excretion factors. The agri-environmental indicator livestock patterns shows the livestock density in the EU-28. Malta, the Netherlands, Belgium, Denmark, Cyprus and Ireland have the highest livestock densities and also have the highest rates of manure input per ha (over 14 kg P per ha per year). Bulgaria, Estonia, Latvia, Lithuania and Slovakia have the lowest livestock densities and also belong to the countries with the lowest rates of manure input per ha (less than 6 kg P per ha per year). The countries with the highest livestock densities also belong to the countries with a high share (over 60 %) of manure in total nutrient input.


Table 1: Gross phosphorus balance on agricultural land, 3-year averages 2004-2015, kg P per ha UAA
Source: Eurostat (aei_pr_gnb)


Figure 2: Average gross phosphorus balance, kg P per ha UAA, 2013-2015
Source: Eurostat (aei_pr_gnb)

Source data for tables and graphs

Data sources 

Indicator definition

Potential surplus of phosphorus on agricultural land (kg P per ha per year).

Subindicator:

Vulnerability to phosphorus leaching/run-off (to be developed).

Links with other indicators

This indicator has links to a number of other AEI indicators that describe developments in some of the main contributory factors.

Data used and methodology

Due to missing data, nutrient balances have been estimated by Eurostat for several countries and several years (see Table 1). These estimations were based on data available in Eurostat's dissemination database, international public data collections, and published research, and were confirmed with the countries in question as reasonable estimates. For 2015, no detailed estimates have been made and therefore no detailed analysis covers this year.

The methodology of the phosphorus balances is described in the Eurostat/OECD Gross Nutrient Budgets Handbook. The handbook lists all inputs and outputs into and out of the soil and the gross phosphorus surplus is calculated as the difference between total inputs and total outputs. The gross phosphorus surplus per ha is derived by dividing the total gross phosphorus surplus by the reference area. The reference area is usually the UAA. It should be noted that some countries use slightly different methodologies; the United Kingdom and Spain fall into this group. This means that the time series are comparable within the countries, but the individual values should not be compared with other countries' individual values.

The inputs of the phosphorus balance are:

  • inorganic fertilisers,
  • organic fertilisers; sewage sludge, urban compost, industrial waste products and other products.
  • Gross manure input, which is calculated from:
  • manure production (phosphorus excretion);
  • manure withdrawals (manure export, manure processed as industrial waste, non-agricultural use of manure, other withdrawals);
  • change in manure stocks;
  • manure import.
  • Other phosphorus inputs, which consist of :
  • seeds and planting material;

The outputs of the gross phosphorus balance are:

  • Total removal of phosphorus with the harvest of crops (cereals, dried pulses, root crops, industrial crops, vegetables, fruit, ornamental plants, other harvested crops).
  • Total removal of phosphorus with the harvest and grazing of fodder (fodder from arable land, permanent and temporary pasture consumption).
  • Crop residues removed from the field.

The phosphorus inputs and phosphorus outputs are estimated for each item of the balance from basic data multiplied with coefficients to convert the data in phosphorus content. Basic data (fertiliser consumption, crop production, livestock number, agricultural area) are mostly derived from statistics. Coefficients are mainly estimated by research institutes and can be based on models, statistical data, measured data as well as expert judgements. They are either given by the country or estimated by Eurostat. A European uniform methodology and validation procedure to estimate coefficients would be necessary to ensure reliable and consistent estimations and comparability across countries. At present the estimation of coefficients varies between countries in methodology and in updating procedures. In order to take into account the effect of mitigation actions (other than reducing the level of production) in the estimations, coefficients need to be updated regularly to reflect any changes in farming practices.

Climatic conditions have a big impact on the balance through the impact on yield and therefore phosphorus output. Climate and weather conditions are beyond the control of the farmer. To dampen the effect of weather conditions on the balance the results presented in this fact sheet with regards to the nutrient balance are presented not referring to a particular year but as an average for a certain period.

Context

The gross phosphorus balance provides insight into links between agricultural phosphorus use, losses of phosphorus to the environment, and the sustainable use of soil nutrient resources. A persistent surplus indicates potential environmental problems, such as phosphorus leaching resulting in pollution of drinking water and eutrophication of surface waters. A persistent deficit can impair the resource sustainability of agriculture soil through soil degradation, or soil mining, resulting in declining fertility in areas under crop or forage production.

A sustainable use of phosphorus is needed to ensure food supply in the future and to reduce negative impacts of waste of natural resources on the environment. These include, among others, appropriate fertilisation practices, reduction of imbalances in phosphorus inputs and outputs to agricultural soils, recovery of phosphorus from sewage for fertilisation.

Policy relevance

The EU-28 depends strongly on imports of phosphorus, and there are only minor phosphate rock reserves (the main source for the production of phosphorous fertilisers) in the EU. Therefore, phosphorus and phosphate rock are defined as a Critical Raw Material for the EU[4]. Phosphate rock is a non-renewable natural resource and ways to improve its use and reuse should be found. The European Commission has made a legislative proposal on fertilisers[5] aiming to create a genuine single market for fertilisers made from secondary raw materials (in particular recovered nutrients), thereby turning waste management problems into economic opportunities. The proposed rules can make the fertilisers sector less dependent on imports of critical, primary raw materials such as phosphate, which can also be recovered from domestic organic waste. This proposal is a part of the Circular Economy Action Plan[6].

The 7th Environment Action Programme (EAP) calls for further efforts to manage the nutrient cycle in a more sustainable way and to improve efficiency in the use of fertilisers. Better source control, and the recovery of waste phosphorus are called for.

The Habitats Directive [7] and the Birds Directive [8] aim to ensure biological diversity through the conservation of natural habitats and wild flora and fauna within the European territory. Farmers who have agricultural land in Natura 2000 sites may face restrictions in using their land, such as reduction in the use of fertilisers.

Within the Common Agriculture Policy, various agri-environment measures have been established throughout the European Union directly or indirectly addressing diffuse contamination by phosphorus. Some of these measures are directed at mitigating soil erosion such as crop rotations, mulch seeding retaining stubble after harvest and ploughing restrictions. Other measures tackle the problem of excess nutrients through reduced fertiliser use. All measures that impact soil erosion and nutrient balances ultimately result in a reduction of diffuse contamination by phosphates from agricultural land.

Agri-environmental context

The gross phosphorus balance indicates the total potential risk to the environment (water and soil). The input side of the balance counts all phosphorus supplied to the soil. The output side of the balance presents the nutrients removed from the field by agricultural production; harvest or grazing. Sustainability could be defined as preserving and/or improving the level of production without degrading the natural resources. The harvest and grazing of crops and fodder means that phosphorus is removed from the soil. To sustain soil fertility this removal of phosphorus should be compensated. Fertilisers and manure are therefore imperative to supply the crops with the necessary phosphorus for growing.

Excess of phosphorus interferes with uptake of other elements (iron, manganese, zinc) which are also crucial for sustainable agricultural management. Depending on the soil phosphorus capacity, excessive phosphorus can be stored in the soil. Part of phosphorus in fertilisers and manure is converted from active phosphorus to fixed phosphorus. Only a small part of the phosphorus compounds are directly available to the plant; more importantly, availability of phosphorus is determined by soil pH, the soil type and the mineral compound of soil. The active phosphorus pool is the main source of available phosphorus for crops, whereas the fixed phosphorus pool contains inorganic phosphate compounds that are very insoluble and organic compounds that are resistant to mineralisation by microorganisms in the soil. Phosphate in this pool may remain in soils for years without being made available to plants and may have very little impact on the fertility of a soil. Depleting the active pool through crop uptake may cause some of the fixed phosphate to slowly become active. The storage capacity of the soil, however, depends on soil characteristics like soil texture. An important aspect of the ability of a soil to hold phosphate is that a soil cannot hold increasing amounts of phosphate in the solid phase without also increasing soil solution phosphate. Increased amounts of phosphate in solution will potentially cause more phosphate to be lost to water running over the soil surface or leaching through the soil. Loading soils with very high levels of phosphate will generally not hurt crops but may result in increased phosphate movement to nearby bodies of water[9]. It has been estimated that 25 %[10] or less of phosphorus applied annually is actually taken up by the growing crop; the remaining 75 % becomes bound in the soil profile or is lost to water. The crop uptake of phosphorus is in sharp contrast to the crop use of nitrogen and potassium fertilisers, where the recovery in the season of application can be as high as 80 %[11]. Yield and therefore the uptake of phosphorus by crops is not only determined by inputs but also by uncontrollable factors like type of soil and climate.

The estimated phosphorus surplus represents the potential risks to water and soil. The actual phosphorus loss from agricultural land to surface waters is a complex function of climate, topography, soil type, soil phosphorus status, phosphorus fertilisation, and land management. These factors vary greatly in space and over the year, and the hydrological pathways for phosphorus losses also vary greatly in space and time. The effects of these individual factors on phosphorus loss from agricultural land to surface waters are rather well understood, but in combination the understanding is less well developed. As a consequence, current simulation models do not yet simulate the actual phosphorus loss from agricultural land to surface waters very accurately. Furthermore, the ecological effect of phosphorus from agricultural land in surface waters depends on the 'bio-availability' of the phosphorus. A significant fraction of the phosphorus from agricultural land that is lost to surface waters is particulate phosphorus and the availability of this phosphorus to growing organisms in surface waters is much less than dissolved reactive phosphorus, at least in the short term. Hence, ‘the pollution effect’ of phosphorus lost from agricultural land to surface waters does not depend on the total phosphorus loss but on the fraction 'reactive phosphorus'.

The accumulated amount of phosphorus represents a larger actual risk for the environment than the amount of phosphorus which is applied yearly, or the surplus on today’s balance. However, the future risk is strongly influenced by the phosphorus balance of today and the near future, in combination with the capacity of a soil to bind phosphorus. This contrasts with nitrogen; the cumulative nitrogen balance of the past is much less relevant since nitrogen hardly accumulates in soils. This is why the main indicator on its own is not sufficient to indicate areas at risk of phosphorus pollution.

Vulnerability to phosphorus leaching - run-off

It would be more accurate if results of the main indicator could be interpreted in relation to the subindicator "vulnerability to phosphorus leaching/run-off". However, this subindicator has not been developed. The vulnerability to phosphorus leaching, or P-sensitivity, refers to the combined risk of phosphorus loss to the groundwater or to the surface water by combinations of low sorption capacity, high erosion risk and increased risk of drainage. Phosphorus can easily be leached from highly organic soils (e.g. peat) and from sandy soils with low retention capacity. Small amounts are lost from most soils, but when the soils become phosphate saturated, leaching will be enhanced. Phosphorus accumulation in soils might increase concentrations of dissolved and colloidal phosphorus in drainage. In a 2005 study commissioned by the European Commission called Addressing phosphorus related problems at farm practice [12], areas at risk of encountering potential phosphorus excess were indicated by estimating phosphorus balances and combining them with the proportion of vulnerable soils. The Netherlands and Slovenia display the highest rate of vulnerable soils and high balance surplus. In the Netherlands sensitive soils are prone to leaching, in Slovenia, erosion and run-off are the main agents of phosphorus loss.

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  • Agriculture and Environment, see:
Gross Nutrient Balance (aei_pr_gnb)
  • Agri-environmental indicators, see:
Gross nutrient balance on agricultural land by nutrient (sdg_02_50)

Notes

  1. Organic fertiliser other than manure are sewage sludge, urban compost, industrial waste products, and other products
  2. Teagasc 2016: National soil P fertility trends. In training material for FAS advisers
  3. NITRATES EXPLANATORY HANDBOOK for Good Agricultural Practice for the Protection of Waters Regulations 2018 https://www.agriculture.gov.ie/media/migration/ruralenvironment/environment/nitrates/2018Nitratesexplanatoryhandbook03042018.pdf
  4. COM(2017) 490 final:Commission Communication on the 2017 list of Critical Raw Materials for the EU
  5. COM(2016) 157 final: Proposal for a regulation on making available on the market of CE marked fertilising products
  6. COM(2017) 33 final: Report from the Commission on the implementation of the Circular Economy Action Plan
  7. Council Directive 92/43/EEC on the conservation of natural habitats and of wild fauna and flora
  8. Directive 2009/147/EC on the conservation of wild birds
  9. The Nature of Phosphorus in Soils, Lowell Busman, John Lamb, Gyles Randall, George Rehm, and Michael Schmitt, University of Minnesota
  10. Morgan, M.A., 1997. The behaviour of soil and fertiliser phosphorus. In: Tunney, H., Carton, O., Brookes, P. and Johnston, A. (eds.) Phosphorus loss from soil to water. CAB International, Oxon, UK
  11. Bomans E., Fransen K., Gobin A., Mertens J., Michiels P.,Vandendriessche H., Vogels N. Addressing phosphorus related problems in farm practice. Final report to the European Commission. Soil Service of Belgium.
  12. http://ec.europa.eu/environment/natres/pdf/phosphorus/AgriPhosphorusReport final.pdf