Inemad improved Nutrient and Energy Management through Anaerobic Digestion Project/Contract number: 289712 Call identifier: fp7-kbbe-2011-5 Funding scheme: Collaborative project Document number
Net soil balance and geographical distribution of nitrogen/ phosphorus field surplus
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Net soil balance and geographical distribution of nitrogen/ phosphorus field surplus
Nutrient use efficiency should lead to zero surpluses in nutrients on agricultural soils. Most important nutrients are nitrogen and phosphor. Currently, the whole Flemish region is considered as a critical area for water pollution due to nitrates from agricultural purposes. As an overview, the following figure schematically represents the agricultural soil balance for Flanders for 2009. 
Figure : Agricultural soil balance for Flanders, in million kg N and P, for 2009 (Source: VMM Environmental Report Flanders, AMS based on Mestbank-ALV and VMM) An overview of the soil balance evolution over time for nitrogen and phosphor is presented in Figure and Figure . In 2008-2010, 76% of agricultural lands are presenting a phosphor concentration higher than the target value (Overloop et al., 2011).
Crop outflow Ammonia emission Biological N-fixation Atmospheric deposition Seeds and plant material Other fertilizer Manure
Mineral fertilizer influx influx influx outflow outflow outflow surplus surplus surplus 
Figure : Evolution of the soil balance in kg N, for 2007-2009 (Source: Lenders et al., 2012) Surplus Crop outflow Seeds and plant material Other fertilizer Manure Mineral fertilizer influx influx influx outflow outflow outflow surplus surplus surplus 
Figure : Evolution of the soil balance in kg P, for 2007-2009 (Source: Lenders et al., 2012) According to Gybels et al. (2009), the average nitrogen surplus in agricultural soils in Wallonia was 85 kg/ha in 2006, slightly less than half of total fertilizer inputs. This value depends on climate, atmospheric deposition of nitrogen and quantities exported with the harvest (and thus yields), which explains the quite marked variations from one year to another (Figure ). Gybels et al., 2009). gives an overview of nitrogen inputs and outputs and the soil surplus. The soil surplus decreased by 22% between 1990 and 2000. This is mainly due to the decrease of 9% in livestock N production and of 24% in inorganic fertilizer use. The atmospheric N deposition also decreased by 8%. Unfortunately no data regarding import, export and processing were available. Figure represents the soil surplus and some important N inputs and outputs in Wallonia, from 2000 until 2006. (Gybels et al., 2009). Table : Nitrogen inputs, outputs and soil surplus in Wallonia (2000-2006) (Source: Gybels et al., 2009)
Figure and Figure show an overview of the average content of available phosphorus in cropland in Wallonia (1998-2002). 83% of the croplands are below the limit value (deficiency value). 
Figure : Average content of available P in cropland in Wallonia (1998-2002) (Source : ASBL REQUASUD) 
Figure : Evolution of P available in cropland per agricultural area in Wallonia (1994-2004). (Source: ASBL REQUASUD)
The geographical distribution map for Flanders (Figure ) shows us that the nitrate limit is often exceeded in areas with high pig production. maximum concentration under 50 mg nitrate per litre maximum concentration exceeds 50 mg nitrate per litre river basing boundary
Legend 
Figure : MAP-measuring network for threshold of 50 mg nitrate per litre in winter year 2010-2011 per river basin (Source: VMM) There is no specific data available for Wallonia.
The European Nitrate Directive aims to protect water quality across Europe by preventing nitrates from agricultural sources polluting ground and surface waters and by promoting the use of good farming practices. The Nitrates Directive forms an integral part of the Water Framework Directive and is one of the key instruments in the protection of waters against agricultural pressures. Under the Directive, all Member States have to analyse their waters’ nitrate concentration levels and trophic state. Belgium, Malta and Denmark have the densest monitoring networks (see fig in 3.3.2). The threshold value is set on 50 mg NO3-/l. In Belgium the Nitrate Directive is transposed by VLM in the Flanders region and the Programme de Gestion Durable de l'Azote en agriculture (PGDA)in the Walloon region. Globally one can state that there has been a huge improvement in ground water quality since the implementation of the nitrate directive and the consequent MAP guidelines. In general a halving of MAP measuring points exceeding the guideline was reached over a period of 11 years. In 2002-2003 the first big improvements were visible, followed by a period of stabilisation between 2003-2007. For the period 2007-2010 again an improvement of the nitrate pollution was observed. In in 2010-2011 still 28% of measuring points still exceeded the guideline at least once. Important to notice is the clear connection between guideline exceedance and intensive farming, (ex West-Flanders, Kempen) and horticulture (ex Sint-Katelijne-Waver, Maasbekken, West-Flanders) (Source: VLM Voortgangsrapport 2011). Although these results are very encouraging a lot of effort is still needed as the novel action programme for the Nitrate Directive 2011-2014 aims at at least 84% of measurement points in the surface water below the 50 mg nitrate threshold by 2014 (MAP4). The ambition is to even ameliorate this percentage to 95% by 2018.
Figure : Overview of the results for the MAP network surface water for the winter year 2010-2011 (Source: VLM Voortgangsrapport 2011) In terms of the ground water quality one could up to 2005 see a deterioration of the quality, with up to 40% of measuring points exceeding the guideline. From 2005 on a slight improvement could be observed with an average status quo of 38% exceedance. According to the trend seen in the period 2007-2010 it is expected that some zones will not reach the ground water targets of 2014. Therefore, from 2012 onwards focal zones of ground water will be defined in which more stringent nitrate residue threshold values will be applied. On the positive side, in 2010 an average nitrate exceedance of 35.4% was observed, which forms a slight amelioration. If the current positive trend continues it is expected that the MAP4 target of max 36 mg nitrate per litre in the upper filter by 2014 could nevertheless be reached (Source: VLM Voortgangsrapport 2011)
Figure : Evolution of the weighted average nitrate concentration for the 3 filters in the freatic ground water measuring network from 2007 on, including a trend interpolation towards the following periods (Source: VLM Voortgangsrapport 2011) In Wallonia, the first implementation of the Nitrate Directive (Directive 91/676/EEG of the Council of 12 December 1991) took place, with some delays, in 2002. Thereafter, in 2007, a second program of nitrogen sustainable management (PGDA) was developed by the Minister of Environment and Agriculture (B. Lutgen), the thematic experts and the actors involved in this subject (and gathered into the structure Nitrawal). The Nitrate Directive was very criticized because of the implicit constraints for the farmers. This could explain the difficulty to implement it. The program was revised in 2011: changes concern mainly periods for fertilizers spreading. In the agriculture sector, this Sustainable management of nitrogen program (PGDA) requires (CRA-W, 2010):
In Wallonia, for one year and over the entire surface area of the farm, organic nitrogen inputs are not allowed to be greater than 115 kg/ha of crops and 230 kg/ha of grassland, while total inputs of (mineral and organic) nitrogen are not allowed to be greater than 250 kg/ha of crops and 350 kg/ha of grassland. Table : Average annual inputs of Nitrogen authorized in Wallonia (Sources: DGARNE, 2008; Nitrawal, 2007) 
On a field and for a rotation period (2 to 5 years), the average of organic nitrogen inputs can’t be greater than 115 kg/ha of crops (but the maximal input of organic nitrogen is limited, for one year, to 230 kg/ha) and 230 kg/ha of grassland. In vulnerable area, for one year and over the entire surface of the farm, organic nitrogen inputs are limited to an average of 170 kg/ha/year. Following some strong specifications, it is possible until this year to obtain derogation but the maximal quantities of 115 kg/ha of crops and 230 kg/ha of grassland remain valuable. These quantities are controlled, for each farm, by the soil linkage rate (LS), i.e. the ratio between the organic nitrogen produced by the herd and the spreading capacity (spreading norm*agricultural area). This ratio has to be lower than one. When a farm has a soil linkage rate higher than one, a solution consists of exporting manure through spreading contracts.
The estimated amounts of nitrogen produced per animal are a requirement for the calculation of the maximum amount of nitrogen on agricultural land where it is possible to spread. The Nitrates Directive in Annex III indicates that "Member States may calculate the amounts referred to in paragraph 2 (amount of manure applied each year) depending on the number of animals." Table shows the different values for the annual production of nitrogen per animal category after deduction of losses in storage and taking into account the crawlspace for pigs and poultry. These values were established on the basis of specific research. Table : Annual production of Nitrogen per animal category (Source: Moniteur Belge 26.04.2011)
The legislations regarding the conditions and periods for organic fertilizers spreading are compulsory on all the territory. The spreading conditions are summarized in and depend on the area (vulnerable or not), the kind of fertilizer (solid manure, compost, slurry and mineral nitrogen) and some external conditions, as the distance from waterways, the soil state (saturated in water, snowy, frozen, uncovered), the kind of culture (legume or others) and the slope. Table : Conditions for manure and mineral nitrogen spreading (Sources: Nitrawal, 2007; DGARNE, 2008; Moniteur Belge 26.04.2011)
The spreading periods depend on the parcel use (crop vs grassland) and on the kind of fertilizers (mineral, organic with fast action, organic with slow action). These periods are described in Table . Table : Spreading periods in Wallonia (Source: Moniteur Belge 26.04.2011)
In the Nitrate Directive, there are some specifications on crops and grasslands management for the vulnerable areas :
Other norms about this subject are included in the conditionality for the CAP aids :
These measures are for objective to ensure good compliance of agricultural practices. A control is performed every year in at least 3% of the farms in vulnerable areas: it is a measure of nitrates content in the upper layer of the soil before winter, when there is a big risk of leaching towards ground-water. If the results are bad, the farm must start a program of two years in order to improve its situation. If after three years the results remain negative, the farmer has to pay a fine in a range between 20 to 120€ per hectare. In the Walloon region there was in the period 1993-2002 a tendency for increased nitrate concentrations in the freatic waters within the territories that are now being considered as vulnerable areas. From 2003 on a stabilisation within nitrate concentrations was observed for the regions “Sables Bruxelliens” and “Crétacé de Hesbaye”. The same trend could however not be observed for he other vulnerable regions and it seems the measurements taken to improve the water quality have not yielded sufficient results yet. In Figure , the average nitrate concentration in the ground (left) and surface water (right) for the Walloon region is depicted.  
Figure : Visual representation of the average nitrate concentrations in ground water (period 2008-2010) (left) and surface water (period: 2010) (right) (Bron: www.nitrawal.be). The coloured region represents the vulnerable zone in the Walloon region.
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