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Archive:Agri-environmental indicator - risk of pollution by phosphorus

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Data from August 2018

Planned update: April 2020

Highlights

The gross phosphorous balance for the EU decreased from 3.9 kg per hectare per year in the period 2004-2006 to 1.2 kg per hectare per year in the period 2013-2015.

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

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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

  • Phosphorous is an important plant nutrient and the EU is almost entirely dependent on imports to fulfill the need of this agricultural fertiliser.
  • The indicator gross phosphorous balance provides an indication of the surplus of phosphorous (P) on agricultural land (kg P per hectare per year). It also provides trends on phosphorous inputs and outputs on agricultural land over time.
  • 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 EU-28 decreased from 3.9 to 1.2 kg P per ha UAA (Figure 1) from 2004 to 2015. It means that the surplus is only around 30 % of what is was in the early 2000s and a significant decrease has been achieved.
  • The GPB 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 GPB of Hungary remains negative, which indicates a risk for soil depletion.
  • 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 mean that data cannot be compared between countries. Trends can be compared between countries.

Analysis at EU level

The GPB 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 of mineral fertilisers, organic fertilisers and manure input, and other inputs like seeds and planting material. Mineral fertilisers and manure accounted for more than 93 % of the P input in EU-28 between 2010 and 2014 (country data are not complete for 2015, therefore 2014 values are used for this section). Other organic fertilisers such as compost, sewage sludge, industrial waste accounted for little more than 5 % of total P inputs. Data on other organic fertilisers are however lacking in many countries, therefore the significance of these fertilisers could be underestimated. Other inputs (e.g. seeds and planting material) represented only 1 % of total phosphorus input.

Analysis at country level

As explained in the notes on the data and methodology used, the current balances are not comparable between countries due to differences in definitions, methodologies and data sources used. The average GPB per ha in 2013-2015 was highest in the Mediterranean islands Cyprus and Malta (Figure 2). The balance was negative for Bulgaria, Estonia, Slovakia, Czech Republic, Germany, Romania, Hungary and Italy (Figure 2). Increasing trends were very slight, and concerned Cyprus, Latvia, Hungary and Austria. However, as regards Hungary, the balance of phosphorous remains negative since the beginning of the data collection. This indicates a risk for negative effects on soil quality, since more phosphorous is removed from the soil than what is added.

There are large differences between countries in the use of inputs. Phosphorus is not available to the plant in the same rate for different types of manure and fertilisers. Manure input in the gross phosphorous balance is based on manure production, manure withdrawals and manure import where the manure production is calculated from livestock numbers and excretion factors. The agri-environmental indicator livestock patterns shows the livestock density in 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.



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 (Table 1). These estimations were based on data available in Eurostat's dissemination database, international public data collections, and published research, and 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 Eurostat/OECD Phosphorus Balance Handbook. The phosphorus balance lists all inputs and outputs into and out of the soil and calculates the gross phosphorus surplus 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. It 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 (excluding manure).
  • 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 P with the harvest of crops (cereals, dried pulses, root crops, industrial crops, vegetables, fruit, ornamental plants, other harvested crops).
  • Total removal of P with the harvest and grazing of fodder (fodder from arable land, permanent and temporary pasture consumption).
  • Crop residues removed from the field.

The P inputs and P outputs are estimated for each item of the balance from basic data multiplied with coefficients to convert the data in P 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 P 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 P inputs and outputs to agricultural soils, recovery of phosphorus from sewage for fertilisation.

Policy relevance

The EU-28 depends entirely on imports of phosphorus, and there are only minor phosphate rock reserves (the main source for the production of phosphorous fertilisers) in the EU[1]. Phosphate rock is a non-renewable natural resource. The European Commission has made a legislative proposal on fertilisersCite error: Closing </ref> missing for <ref> tag and the Birds Directive Cite error: Closing </ref> missing for <ref> tag. It has been estimated that 25 %[2] or less of P applied annually is actually taken up by the growing crop; the remaining 75 % becomes bond in the soil profile or is lost to water. The crop uptake of P 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 %[3]. Yield and therefore the uptake of P by crops is not only determined by inputs but also by uncontrollable factors like type of soil and climate.

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

The accumulated amount of P represents a larger actual risk for the environment than the amount of P which is applied yearly, or the surplus on today’s balance. However, the future risk is strongly influenced by the P balance of today and the near future, in combination with the capacity of a soil to bind P. This contrasts with nitrogen; the cumulative N balance of the past is much less relevant since N 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 P 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. P accumulation in soils might increase concentrations of dissolved and colloidal P in drainage. Reference is made to a 2005 study commissioned by the European Commission called Addressing phosphorus related problems at farm practice. Areas at risk of encountering potential phosphorus excess were indicated in the study 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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Visualisations







Gross Nutrient Balance (aei_pr_gnb)
Gross nutrient balance on agricultural land by nutrient (sdg_02_50)



Notes

  1. ↑ COM(2017) 490 final:Commission Communication on the 2017 list of Critical Raw Materials for the EU
  2. ↑ 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
  3. ↑ 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.
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