




































African Journal of Pig Farming Vol. 1 (1), pp. 001-010, September, 2013. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

 
 
 

Full Length Research Paper 
 

Nitrogen and phosphorus management on pig farms in 
Northwest Germany – nutrient balances and 

challenges for better sustainability 

 
D. Otten* and H. F. A. Van den Weghe 

 
Department of Animal Sciences, Division: Process Engineering, Georg-August University of Goettingen,  

Universitaetsstr. 7, D-49377 Vechta, Germany. 
 

Accepted 26 September, 2013 
 

The study analyses the nutrient flow of nitrogen (N) and phosphorus (P) on six intensive pig farms in 
Northwest Germany over a period of 5 years. The study investigated the farmers’ management of 
nutrient flows associated with intensive pig farming, focusing especially on the management of 
manure. It could be shown that in intensive pig production, high performance and performance-related 
feeding positively affects nutrient flow efficiency. However, on the crop production side of the farms, 
there existed a great disharmony between the farmers’ perception of manure used as (N, P) fertiliser on 
their crops and the real quantity of nutrients produced by their intensive pig farming. The farmers were 
unable to estimate the fertiliser effect of their manure correctly [underestimation N = 7.6% (10.6 kg/ha), 
P = 33.6% (11.6 kg/ha)]. The application of nutrients by mineral fertiliser was underestimated also [N by 
4.1% (8.1 kg/ha), P by 12.7% (1.5 kg/ha)] and were inadequately attuned to the large amount of manure 
produced by their intensive pig production. As a result, the farms had large nutrient losses (104.5 kg N/ 
ha; 11.7 kg P/ha) and were unable to fulfil the minimum German legal requirements for fertiliser 
application. The study evaluated the critical aspects of nutrient management and discusses possible 
improvements for the future. 

 
Key words: Nutrient management, intensive pig production, Northwest Germany 

 
 

 
INTRODUCTION 
 
Sustainable food production places a great deal of 
responsibility on farm management to ensure a well-
balanced nutrient flow (Koelsch and Lesoing, 1999). 
Nutrient management must always be considered with 
respect to the prevalent production conditions: The farm 
structure (e.g. husbandry, type of farmland, 
infrastructure), the biophysical conditions (e.g. climate, 
soil), the prevalent socio-economic conditions (e.g. 
availability and cost of intermediate goods or techniques) 
and other dependent variables. The ideal management 

 
 
 
 

 
strategy always depends on the individual situation 
(Bosshard, 2000; Koelsch and Lesoing, 1999).  

Bearing this in mind, the nutrient flow management in 
an Intensive Livestock Area (ILA) is associated with 
exceptional challenges. ILAs are regions with a very high 
livestock concentration and often also with a higher 
productivity and degree of business organisation in 
livestock farming. Pig farms in such regions often have a 
greater productivity, size and degree of specialisation 
than farms in other regions. This leads to a higher 

 
*Corresponding author. E-mail: dennis.otten@agr.uni-goettingen.de. Tel: 0049-4441-15524.  



Otten  et al.         002 
 
 

 
material flow of individual nutrients per farm. In addition, 
ILAs have a very high regional turnover of nutrients and 
the excessive production of manure is becoming an 
increasingly important regional challenge and 
environmental risk (Ilea, 2009; Warnecke et al., 2009; 
Berkhoff, 2005; Abdalla, 2002; Tilman et al., 2002; Wing 
and Wolf, 2000).  

In the past, various authors have concerned 
themselves with nutrient flows in intensive pig production. 
Abdalla (2002) has given a general historical overview 
about the industrialisation of livestock farming and its 
conflicts and discussed the consequences from a broader 
institutional economic perspective. Cahoon et al. (1999) 
described the eutrophication threat to the river basins and 
other areas with expanding animal populations from the 
potential large nutrient loadings in North Carolina. Mc 
Sweeny and Shortle (1989) analysed the fertilisation 
problems from the perspective of a crop yield response to 
nitrogen application and the nitrogen content of manure in 
ILAs. They analysed the effects of various policy 
prescriptions on fertilisation decisions by such farmers 
and showed the importance of understanding producer 
behaviour for the design of economically sound policies.  

The N and P consumption, utilisation and losses in pig 
production have also been analysed in the Netherlands 
(Van der Peet-Schwering et al., 1999; De Boer et al., 
1997; Breeuwsma et al., 1995), France (Basset-Mens 
and Van der Werf, 2005; Dourmad et al., 1999) and 
Denmark (Nielson and Kristensen, 2005; Fernandez et 
al., 1999). The various authors evaluated the overall 
status for reducing the environmental problems 
associated with pig production by using feeding and other 
management measures. They also discussed N and P 
management in relation to legislative measures.  

Tamminga (2003) described the pollution caused by 
nutrient losses and its control in European animal 
production and suggested a combination of a better on-
farm nutrient management and a maximum stocking 
density of 2.0 livestock units / hectare (LU/ha) (LU = 
livestock units; 1 LU = 500 kg). The German Fertiliser 
Ordinance prescribes this maximum stocking density 
also. Additionally, a maximum overload (input – output) of 

60 kg N/ha and 20 kg P2O5 (8.73 kg P)/ha is allowed. 

The maximum N fertilisation for manure is limited to 170 
kg N/ha [German Fertiliser Ordinance (Düngeverordnung 
– DüV) 2007].  

However, because of the dynamic regional 
concentration processes in ILAs at present and the 
increased requirements for sustainable animal 
production, the current development in such regions has 
to be checked with respect to on-farm material flow 
management. With this in mind, the present study had the 
following specific research objectives: (I) to describe the flow 
of N and P through the individual farm materials and identify 

the important factors affecting efficiency nutrient 
management; (II) to analyse the nutrient management of 
great quantities of manure; and (III) to use the results to 
discuss any possible opportunities to improve nutrient 

 

  
 
 
 
flow management in ILAs. 
 

 
MATERIALS AND METHODS 
 
For the investigation, the total N and P flow (inputs, intra-farm and 
outputs) of all the materials on six pig farms [2x piglet production, 
2x finishing pig production and 2x combination farms (piglet 
production and finishing pigs)] were analysed over a period of 5 
years. Due to this analysis of real farm data over a number of years, 
six farms were considered to be an adequate number of probands 
for a meaningful representation. In addition, it should be mentioned 
that a great deal of cooperation from the farmers is required to 
acquire all the data concerning a farm’s material flow and the 
farmer’s nutrient management.  

The six farms were located in Northwest Germany. Table 1 gives 
an overview of the average structure of the six farms and 
information about the average stocking density of the whole region 
of Northwest Germany over the study period. The abbreviations in 
front of the farm number represent the type of pig farm: PP = piglet 
production, FP = finishing pig production and CF = combination 
farm. These abbreviations will be used throughout this paper.  

The average number of animals per farm [329 sows (PP + CF); 
784 finishing places (FP + CF)] and the concentration of animals 
per unit area [2.73 LU/ ha (1 LU = 500 kg)] of the six farms reflected 
the regional conditions. Their production was also typical of this 
region [weaned piglets/ sow and year = 21.9 (PP + CF); daily 
weight increase/ finishing pig = 707 g (FP + CF)]. The average area 
of the six farms was 68.4 ha. The crop production primarily involved 
cereals (36.3 ha), maize (25.6 ha), small amounts of oilseed rape 
(5.4 ha) and other crops (1.1 ha). The farms’ texture of soil was 
sandy or clayey and of medium quality [German soil quality index = 
18-35; scale of index = 7-100 (BodSchätzG, 2007)].  

The analyses of the nutrient flow covered all the material inputs, 
the intra-farm transformations and the material outputs of all the 
farm’s goods. Table 2 provides an overview of the audited materials 
and the calculations used in the investigation.  

The information about the inputs via the animals, feed and 
mineral fertiliser (the amount used and composition) was provided 
by the bills of sale from the producer or the supplier/ purchaser. The 
N and P flows of the animals were budgeted according to the 
German Society of Nutritional Physiology (GfE, 2006). The values 
for the types and quantity of ammonia depositions in crop 
production (Builtjes et al., 2011) and the emissions leaving the pig 
production (Luft, 2002) were taken from other studies carried out in 
the region.  

In addition to the analyses of nutrient flow, the soil of each farm 
was analysed (VDLUFA, 1991) over a period of 15 years (annual) 
to determinate its mineral makeup and any changes over time. A 
total of 15 to 30 samples were taken per ha and were mixed to give 
one sample. The depth of soil sample corresponded with the 
ploughing depth on arable land; grassland no ploughing (arable 
land = 0-30 cm; grassland 0-10 cm). The samples were analysed by 
the Association of German Agriculture Analytic and Research 
Institutes (VDLUFA 1991) [ISO 11732 and 11885 (2005), DIN 
19684 (2000), DIN 38414 (1985)].  

The calculation period used for the pig production units was the 
standard German animal husbandry business year (01 July - 30 
June). For the crop production, each individual crop was analysed. 
The efficiency of the piglet production [output (piglets + slaughter 
sows) / input (lactation diet + gestation diet + piglet diet + gilts)] and 
the efficiency of the fattening pig production [output (fattening pigs) / 
input (fattening diet + piglets)] were calculated. The calculations for 
the combination farms included both these formulae. The efficiency 
of the crop production was also calculated [output (primary crops + 
secondary crops) / input (chemical fertiliser + manure + seeds + N 
deposition)]. 



003          Afr. J. Pig Farming 
 
 

 
Table 1. Structure of the six farms used in the study [PP: piglet production; FP: fattening pig production; CF: combination (piglets and 
fattening pigs)] 

 

Parameter 
 PP (I) 

1)
 PP (II) FP (I) FP (II) CF (I) CF (II) 

 

 

Mean ± Mean ± Mean ± Mean ± Mean ± Mean ±  

  
 

Region LU/ha 
2)

 2.3 / 2.0 / 3.4 / 3.4 / 3.4 / 3.4 / 
 

Farm LU/ha 4.5 / 2.0 / 3.7 / 2.0 / 1.6 / 2.6 / 
 

Area of farm ha 83.3 7.2 67.6 0.3 50.1 3.1 33.7 0.8 106.8 2.5 68.9 3.5 
 

Crop production              
 

Cereals ha 36.1 8.8 42.7 3.6 17.3 3.6 19.8 0.7 52.4 1.6 49.6 5.8 
 

Maize ha 47.2 8.6 7 4.6 29.8 2.8 12.7 1.3 46.7 3.3 10.6 5 
 

Oilseed rape ha / / 16.2 2.9 / / / / 7.7 3.9 8.2 2.5 
 

Other ha / / 1.8 2.6 3 3.2 1.1 / / / 0.6 0.9 
 

Pig husbandry              
 

Pig breeding Units 637.2 39 236.5 9     173.3 13.8 270.7 7.7 
 

Fattening Units     1238 19 560 0 1143.3 222 199 18.5 
 

Production              
 

Weaned piglets Sow and year 23.7 1.1 22.1 1     20.8 0.4 21.1 0.6 
 

No. of litters Sow and year 2.4 0.0 2.2 0.1     2.6 0.4 2.3 0.03 
 

Body weight increase g/day     713 8.9 642 29 786.7 7.8 684 25.6 
 

Finished pigs/ unit p. a. 
3)

     2.6 0.1 2.4 0.1 3.1 0.0 2.8 0.1 
  

1)
 (I) and (II) are defined as farm one and two of the respective production system (PP, FP or CP). This definition is used throughout this study. 

2)
 

LU = livestock units; 1 LU = 500 kg. 
3)

 p.a.: per annum. 
 
 
 
Particular attention was paid to the farmers’ management of their 
manure. Using a questionnaire about their crop production 
management, the farmers were asked about how many kg N and P 
they believed they were applying per hectare to each field. These 
values were then compared with the true audited amounts from the 
pig production and the differences determined (Table 2). The 
differences between the perception of how much N (kg/ha) and P 
(kg/ha) were applied with mineral fertiliser and the true amount 
were determined also.  

Subsequently, a stepwise linear regression was carried out to 
determine which factors significantly affected nutrient efficiency in 
the various forms of production (P < 0.05). In this procedure, the 

factors were implemented until there was no further increase in R
2
. 

The respective efficiency in the piglet production and the crop 
production were the independent variables and the different 
materials included in the nutrient flows the dependent ones. The 
factors were tested for their statistical significance (P< 0.05). The 
variables were standardised in order to analyse which ones had the 
greatest influence (standardised beta coefficient). The statistical 
analysis was carried out with the software program SPSS, Version 
19 (PASW Statistics — SPSS 19. for Windows). 
 
 
RESULTS 
 
The N and P flows and the important factors affecting 
their efficiency will be described, firstly with respect to the 
pig production and then to the crop production. Lastly, the 
farmers’ management of the large amount of manure 
produced by their pig production will be elucidated. 

 
 
 
Pig production 
 
Table 3 illustrates the N and P flows in the pig production. 
The results for each type of pig production system [PP, 
FP and CF] over the whole study period have been 
summarised.  

The average total annual turnover [total (N, P) input; 
total (N, P) output] per sow in the piglet production varied 
between 54.7 kg (PP) and 54.9 kg (CF) for N, and 
between 10.5 kg (PP) and 10.6 kg (CF) for P. The 
average values per unit (place) in the finishing pig 
production ranged from 17.7 kg (CF) to 18.0 kg (FP) for N 
and 3.3 kg (FP) to 3.4 kg (CF) for P. The manure 
production was between 29.3 kg N/ sow (PP) and 29.6 kg 
N/ sow (CF) and 6.8 kg P/ sow (PP) and 7.0 (CF) kg P/ 
sow in the piglet production and 7.2 kg N/ unit (FP) to 7.6 
kg N/ unit (CF) and 2.0 kg P/ unit (FP) to 2.2 kg P/ unit 
(CF) in the finishing pig production. The efficiency in the 
piglet production [N = 0.35 (PP) to 0.34 (CF); P = 0.34 
(PP) to 0.33(CF)] was lower than in the finishing pig 
production [N = 0.39 (FP) to 0.36 (CF); P = 0.39 (FP) to 
0.34 (CF)].  

In the piglet production, the N and P concentrations of 
the different diets were rather similar on all six farms 
(Table 3). This is typical of intensive pig farming in 
Northwest Germany as all the diets were industrially 
produced. Since the mounting intensification of livestock 



Otten  et al.         004 
 
 
 
Table 2. The audited materials, the data sources and the calculations used in the inventory. 
 
Material Kind of calculation Data 
 
Diets 
 
 
 

 
Animals 
 
 
 
 
 
 
 
 
 
 
 

 
Primary 

crops,secondary 
crops, seeds 
 
 
 
 
 
 
 
 
 
 
 

 
Mineral fertiliser 
 

 
Ammonia emissions 
 
 
Ammonia deposition 
 
Losses and 
accumulation in soil 
 
 

 
Manure 

 
Bill of sale from producer or supplier 

about amount and concentrations 
 
 
 
Information from farmer (bill of sale) for 
number and weight of pigs. Then GfE 
2006 to calculate nutrient flow 
 
 
 
 
 
 
 
 
 
 
Information from producer or distributor 
about quantity (bill of sale). Then German 
Fertiliser Ordinance [Düngeverordnung - 
(DüV), 2007] to calculate nutrient flow (in  
g/kg) 
 
 
 
 
 
 
 
 
 
 
 
Bill of sale from producer or distributor 

about amount and product contents 

 
Technical Instructions on Air Quality 
Control (Luft, 2002) 

 
Builtjes et al. (2011) 

 
Audited 
 
 
 
 
Audited 

 
Average amounts and concentrations (Table 3) 

 
Protein quantity (kg/pig) : < 30 kg body weight = 169 g/ kg 
body weight; >30 kg bodyweight = 0.168 x body weight - 
0.0000914 x body weight² 

 
P quantity (kg/pig): <80 kg bodyweight = 5.0 g/ kg 
bodyweight; > 80 kg body weight = 4.5 g/ kg body weight 
 

Barley (12% CD
1
) = 16.5 N; 3.5 P  

Barley (13% CD) = 17.9 N; 3.5 P  
Rye (11% CD) = 15.1 N; 3.5 P  
Rye (12% CD) = 16.5 N; 3.5 P  
Triticale (12% CD) = 16.5 N; 3.5 P  
Wheat (12% CD) = 18.1 N; 3.5 P  
Wheat (14% CD) = 21.1 N; 3.5 P  
Crop straw = 5.0 N; 1.3 P  
Rape (23% CD) = 33.5 N; 7.9 P  
Grain maize (10% CD) = 13.8 N; 3.5 P  
Grain maize (11% CD) = 15.1 N; 3.5 P  
Silage maize (28% DM

2
) = 3.8 N; 0.7 P  

Silage maize (32% DM) = 4.3 N; 0.8 P  
Grassland 1 cut/ year = 13 N; 2.6 P  
Grassland 2 cuts/ year = 18 N; 3.1 P  
Grassland 3 cuts/ year = 22 N; 4.1 P  
Grassland 4 cuts/ year = 27 N; 4.4 P  
Grassland 5 cuts/ year = 28 N; 4.4 P 

 
Average amounts and concentrations (Table 3) 

 
Piglet production= 6.0 kg N/ sow (piglet production only) 

Fattening pig production = 3.6 kg N/ unit 

 
55 kg N/ha 
 
Input (mineral fertiliser + manure + seeds + deposition) - 
Output (primary + secondary crops) 
 
Input [different diets + animal inputs (piglets or gilts)] - 
Outputs: [animal outputs (sold animals and losses) + N 
emissions].  
For Input crop production: - (10% N pit losses) - (20% N 
losses during manure application) 

 
1)

 CD = Crude Protein; 
2)

 DM = Dry Matter. 
 

 
production in the mid-1990s, the farms have increasingly 
used crude-protein (CP) and phosphorus-reduced diets in 
order to reduce both N and P in the manure and the 
amount of ammonia emitted. The highest concentrations 

 
 
 
 
in the diets used on the six farms were lactation diet CP < 
16.5%, P < 0.55%; gestation diet = CP < 14%, P < 
0.45%; and piglet diet = CP <18%, P < 0.55%. 

Because of the similar concentrations in the different 



005          Afr. J. Pig Farming 
 
 

 
Table 3. The average (mean, SD) nitrogen (N) and phosphorus (P) flow in the animal production with their respective quantities (kg) and concentrations (g/ kg) 
over the whole study period. 

 
       Piglet production (PP)   Fattening pig production (FP)    Combination farm (CF)  

 

                     

 Element   
Unit  Amount  Concentration in  Amount  Concentration in  Amount  Concentration in 

 

    

N    

P product (g/kg) N   

P product  (g/kg) N   

P  product (g/kg)  

             
 

                          

 Input    "1) ±  " ± N P " ± " ± N P " ±  " ± N P 
 

 Lactation diet  kg/sow 11.2 2.2  5.3 1.1 26.8 12.6   54.9 17.7 24.2 7.8 7.6 1.7  3.6 0.8 26.4 12.4 
 

 Gestation diet  kg/sow 20.4 5.2  9.5 2.4 22.7 10.4       23.9 2.1  10.8 0.7 22.8 10.3 
 

 Piglet diet   kg/sow 21.9 1.6  8.7 0.7 28.0 12.6 18.0  7.7    22.4 2.7  9.4 0.8 27.9 11.8 
 

 Fattening diet  kg/unit        15.9 0.9 6.8 0.3 24.9 10.7 15.6 1.7  6.9 0.7 26.1 11.6 
 

 Gilts   kg/sow 1.2 0.2  0.5 0.1 24.5 10.3       1.0 0.3  0.4 0.1 24.6 10.3 
 

 Piglets   kg/unit 54.7   24.0    2.1 0.1 0.8 0.1 26.9 11.5 2.1 0.4  0.9 0.2 26.9 11.5 
 

 Output   total (kg) 54.7   24.0    18.0  7.7    72.6 2)  32.1 2)   
 

 Fattening pigs  kg/unit        7.0 0.3 3.0 0.1 24.2 10.3 6.3 1.0  2.7 0.4 24.2 10.3 
 

 Piglets   kg/sow 17.2 0.7  7.3 0.3 26.9 11.5       17.2 1.8  7.3 0.8 26.9 11.5 
 

 Slaughter sows  kg/sow 1.9 0.2  0.9 0.1 23.1 10.3       1.7 0.4  0.8 0.2 23.0 10.3 
 

 
Animal 

  kg/sow 0.3 0.1  0.1 0.0 25.1 11.1       0.4 0.1  0.2 0.0 25.0 10.9 
 

 losses        

0.1 0.03 0.05 0.01 26.3 11.5 0.1 0.0 
 

0.0 0.0 26.2 11.5 
 

    kg/unit         
 

 
Manure 

  kg/sow 29.3   15.6 1.3 3.0 1.3       29.6   15.9 0.9 4.4 1.6 
 

   
kg/unit 

       
7.2 

 
4.6 0.3 5.8 4.1 7.6 

  
5.1 0.8 4.5 2.3  

              
 

 Ammonia   kg/sow 6.0       10.8  3.0    6.0       
 

 emissions   kg/unit 25.4   8.3    3.6      3.6 ##  10.1 8.3 2.7  
 

 Efficiency  Total (kg) 54.7   24.0    18.0  7.7    72.6 2)  32.1 2)   
 

 Efficiency (PP) 3) 0.35   0.34          0.34       
 

 Efficiency (FP) 4)         0.39  0.39    0.36   0.34    
 

 Total animal production efficiency 0.35   0.34    0.39  0.39    0.35   0.34    
 

                           
=1)

 = Means; 
2)

 = Total Inputs and Outputs in CF: piglet production (PP): = 54.9 kg N, 24.2 kg P; fattening pig production 17.7 kg N, 7.9 kg P
3)

 = Output (piglets + slaughter 

sows)/ Input (lactation diet + gestation diet + piglet diet + gilts); 
4)

 = Output = (fattening pigs) / Input = (fattening diet + piglets) 
 
 

 
diets used on the farms, the stepwise 
regression showed that it was particularly the 
farmers’ feeding management of the different 
diets which affected the nutrient efficiency 
[(Model N 

 
 
 
efficiency: Y = - 1.434 * gestation diet - 0.746 * lactation  
diet - 0.347 * piglet diet, R

2
= 0.95; P efficiency model: 

Y = - 1.664 * gestation diet - 1.067 * lactation diet - 0.418 * 

piglet diet,  R
2
 = 0.85]. There was a  lower  use   of 

 
 

 
gestation diet (from 40 g down to 25 g N/ kg 
produced piglet and from 8.5 g down to 5.0 g P/ 
kg produced piglet) and a higher use of lactation 
diet (from 13.0 g up to 20.0 g N/ kg produced 



Otten  et al.         006 
 
 

 
Table 4. The average (mean, SD) nitrogen (N) and phosphorus (P) flows in the crop production with their respective quantities (kg) and concentrations (g/ kg) over the whole study period. 
 
    Piglet production (PP)   Fattening pig production (FP)   Combination Farm (CF)  

 

                    

 Material Unit  Amount  Concentration  Amount  Concentration  Amount  Concentration 
 

   N  P  (g/ kg) N  P  (g/ kg) N  P  (g/ kg)  
 

 Input  " 1) ± " ± N P " ± " ± N P " ± " ± N  P 
 

 Chemical fertiliser kg/ha 100.6 36 6.6 4.4 257.8 20.4 52.8 11.8 6.9 3.2 231.8 30.4 107.2 30.5 5.1 1.7 182.8  10.8 
 

 Manure kg/ha 85.0 11.7 33.8 5.1 3.0 0.6 85.3 27 36.6 6.7 5.8 1.8 100.6 7.77 36.2 1.5 4.4  0.7 
 

 Seeds kg/ha 1.6 0.3 0.3 0.1 17.0 3.5 1.4 0.4 0.3 0.1 15.8 3.2 1.6 0.2 0.3 0.0 17.1  3.5 
 

 N depositions kg/ha 55.0      55.0      55.0       
 

 Output Total (kg) 242.2  40.7    194.5  43.7    264.4  41.6     
 

 Primary crops kg/ha 106.1 13.3 23.9 3.1 16.6 3.7 108.1 16.2 25.1 3.9 9.7 2.0 130.5 12.6 28.0 2.3 0.0  25.6 
 

 Secondary crops 2) kg/ha 12.6 6.6 3.8 1.4 0.6 0.2 12.1 3.3 3.2 0.8 0.6 0.2 18.1 2.2 4.7 0.5 12.2  4.0 
 

 Losses  and  accumulations 
kg/ha 123.6  

13.0    
74.2  

15.4    
115.8  

8.9     
 

 in soil              
 

                     
 

 Efficiency Total (kg) 242.2 ## 40.7 27.   194.5 12 43.7 28.   264.4 ### 41.6 3.7    
 

 Total crop production efficiency 3) 0.49  0.68    0.62  0.65    0.56  0.79     
  1)

 = Means 
2)

 = Input (different diets + animal inputs; piglets or gilts) - Outputs (animal outputs; marked, losses + N emissions) - (10% N pit losses) - (20% N losses during manure ___application)]; 
3)

 = 
Output (primary crops + secondary crops) / Input (chemical fertiliser + manure + seeds + N-depositions). 

 

 
piglet and from 2.9 g up to 3.2 g P/ kg produced 
piglet) on the farms with a high nutrient efficiency. 
With the piglet diet, 35 g N and 6.9 g P was 
needed for each kg produced piglet.  

In the fattening pig production, the diets were 
different between the farms and their average N 
and P concentrations had a greater importance for 
nutrient efficiency than the feed conversion: Model 
N efficiency: Y = - 0.894 * N amount in diet - 0.401 * feed 
conversion, R

2
 = 0.89; Model P efficiency: Y = - 0.881 

* P amount in diet - 0.453 * feed conversion, R
2
 = 0.89. With 

an average concentration of N= 25.5g/ kg and P = 
4.8 g/kg, the more efficient farms had lower 
average dietary concentrations of both N and P 
than the less efficient farms (N = 27.9 g/kg, P = 
5.1 g/kg). As in the piglet production, those factors 

 

 
which affected the N efficiency were rather similar 
to those affected the P efficiency. 
 
 
Crop production 
 
The material flow of the crop production on the six 
pig farms and their N and P quantities (kg) and 
concentrations (g/kg) are shown in Table 4. The 
average total annual turnover [total (N, P) input; 
total (N, P) output] per ha in the crop production 
over the whole study period lay between 233.7 kg 
N/ha and 42.3 kg P/ha, with an efficiency of 0.55 
for N and 0.69 for P. The differences between the 
different production systems (PP, FP, CP) were 
not significant. The input via mineral fertilisers was 

 

 
86.9 kg N and 6.1 kg P per ha. On average, 90.3 kg 
N and 35.5 kg P per ha was applied via manure. The 
average audited losses lay at 104.5 kg N and 11.7 kg 
P per ha and year. For the analysis of the factors 
affecting the nutrient efficiency in the crop 
production, the N and P flows will be described 
separately. 
 
 
N flows 
 
The stepwise regression showed that it was the 
inputs which particularly affected the N efficiency: 
Model N  efficiency: Y = - 0.508 * manure  - 0.449 * 

mineral fertiliser + 0.286 * primary crops (R
2
 0.87). Figure 1 

shows how the fertilisation affected the N overload 

  



007          Afr. J. Pig Farming  
 
 
 
 

250 
 

200 

h
a
) 

 
 

(k
g

/ 

150 
 

 
 

N
-I

n
p

u
t 

100 
 

 
 

 50 
 

 0 
  
0 20  40   60   80  100 120 140 160 180 200 

 
kg N Overload/ ha  (total Input - total Output) 

 
Total N fertiliser  
Manure  
Chemical fertiliser 
Maximum legal total N overload (60 kg N/ ha) 
Maximum legal total N fertilisation (170 kg N/ ha) 

 
Figure 1. Nitrogen (N) fertilisation on the farms (kg/ ha) and the 
legal thresholds for the maximum overload and maximum total 
fertilisation in Germany [German Fertiliser Ordinance 
(Düngeverordnung-DüV, 2007)]. 
 
 
 

 80                                        
 

                                       
 

 

70 
                                       

 

 

  

                                     
 

                                      
 

s 
o

 i
 l 60 

                                       
 

                                       
 

50 
                                       

 

                                       
 

1
0

 0
 g
                                         

40 
                                       

 

                                       
 

                                      

P
 /
 

30 

                                       
 

                                       
 

g
                                        

 

m
 20                                        
 

 
10                                        

 

 

0   
                                     

 

                                       

                                         

 1995 1997 1999   2001 2003 2005 2007 2009      
  

year 
 
Figure 2. Development of the soil P concentration (mg P/100 g 
soil) (median, 75% quartile, 25% quantile; maximum. minimum) on 
all 6 farms between 1995 and 20010. 
 
 

 
(losses). The figure also shows the thresholds for 
maximum N overload (loss) and N fertilisation (maximum) 
given by the German Fertiliser Ordinance 
(Düngeverordnung – DüV, 2007).  

There was a great deal of variation in the amount of N 
applied. The two legal thresholds overlap almost exactly 
by the total N input line. Taking the standard method of 
fertiliser application on the farms into consideration, 
whereby there is a large input of chemical fertiliser, only a 
very small amount of manure can actually be applied to 

 

 
the fields before the legal thresholds are exceeded. 
Looking at the intersection of the legal overload threshold 
and taking into consideration the farmers’ style of 
applying fertiliser, a maximum of 67 kg N/ha can be 
applied with chemical fertiliser in addition to 73 kg N/ha 
using manure (max. 140 kg/ha). 
 
 
 
P flows 

 
The P supply within the soil and its development over 
time is an important indicator for the evaluation of the P 
flow. Figure 2 shows the P supply on the six farms over a 
period of 15 years (1995-2009). It became obvious that in 
the mid-1990s the intensification of pig production led to a 
high accumulation of P in the soil. Since then, the soil P 
concentrations have been reduced over time so that they 
have almost reached optimum values at present (6 mg to 
12 mg/100 g soil; Fleischer 1998). In addition to the 
reduction in the mean P load of the farmland, there has 
also been a strong reduction in the variation (that is, 
standard deviation) in P load so that the farms have 
achieved a more uniform P condition in their soils.  

Looking at the correlations of the P load in the soil with 
the distance of the field from the livestock buildings 
(Table 5), it is apparent that in the 1990s the P supply 
within the soil was closely related to how near it was 
situated to the farm buildings: The manure was not 
distributed over the whole farm land evenly. With the 
intensification of animal production, the farmers tended to 
apply the manure to the closest fields, while the fields 
further away evinced little pollution. Table 5 shows the 
correlation between the distance of the fields from the 
farm buildings and the P concentration between the years 
1995 to 2009. The regressions make clear that the P 
concentration in soil has been improved; however, there 
is still a significant correlation between the distance of the 
field and the soil P concentration at present [(2007 – 

2009) = R
2
 0.19].  

For the present-day P efficiency in the crop production, 
the stepwise regression showed that the nutrient 
efficiency was especially affected by the inputs. P 
efficiency model: Y = - 0.677 * manure + 0.474 * secondary crops 
+ 0.187 * (R

2
  0.91).  It  is obvi ous that,  as  with 
 
the N efficiency, manure 
management had the greatest 

influence. In contrast to the N efficiency, however, the 
mineral fertiliser was not included in the stepwise 
regression. Figure 3 shows how the P fertilisation 
affected the P losses (overload). The minimum legal 
requirements in Germany are also illustrated [German 
Fertiliser Ordinance (Düngeverordnung-DüV, 2007].  

With a legal maximum threshold overload of 20 kg 

P2O5 (8.72 kg P), the farms can apply a total of 39.1 kg 
P/ha. At this threshold and the farmers’ present 
fertilisation practices, 33.2 kg P could be applied using 
manure and 5.9 kg P/ha using chemical fertiliser. 

 primary crops 

 



Otten  et al.         008 
 
 

 
 60           

 

 50           
 

h
a

) 

40           
 

(k
g

/ 

30 
          

 

P
-O

u
tp

u
t           

 

20           
 

           
 

 10           
 

 0           
 

 0 3 6 9 12 15 18 21 24 27 30 
 

 
kg P Overload/ ha (total Input - total Output) 

 
Total P fertiliser 

Manure Chemical 

fertiliser  
Maximum legal total P overload (20 kg P2Os / ha; 8.73 kg P/ ha) 

 
Figure 3. Phosphorus (P) fertilisation on the farms (kg/ ha) and 
the legal thresholds for the maximum overload in Germany 
[German Fertiliser Ordinance (Düngeverordnung-DüV) 2007)]. 

 
 
 

 
%       

P       

kg/ ha       

%       

N       

kg/ ha       

-60 -40 -20 0 20 40 60 

  Chemical fertiliser  Manure   
 

Figure 4. The underestimation of the nutrient application by 
chemical fertiliser and manure. Shown are the differences (% 
total, kg/ ha) in perception between the farmers’ declared fertiliser 
use and their true fertiliser use (mean, sd). 

 
 

 
The farmers’ perception of their application of 
nutrient via manure and/or mineral fertiliser 
 
From the crop production information, it is clear that the 
manure applications were very important for the nutrient 
efficiency. Figure 4 shows the differences between the N 
and P quantities the farmers thought they had applied via 
manure and the true calculated quantity produced by the 
pig production. The figure shows also the differences 
between the farmer’s estimation of N and P application by 
mineral fertiliser and the applied amount. 

 

  
 
 

 
Both the absolute differences (kg/ha) and the 

percentage differences (%) are illustrated. The figure 
summarises the information from all six farms over the 
whole study period.  

It is clear that the quantity of nutrient fertilisation – 
manure and mineral fertilisers – was underestimated. The 
farmers were unable to estimate the fertiliser effect of 
their manure correctly [underestimation N = 7.6% (10.6 
kg/ha) P = 33.6% (11.6 kg/ha)]. The application of 
nutrients by mineral fertiliser was underestimated also [N 
= 4.1% (8.1 kg/ha) P = 12.7% (1.5 kg/ha)]. The 
differences between the farms were not significant. The 
high degree of standard deviation seen emphasises the 
high potential for improvement in the farmers’ estimation 
of their fertiliser use. 
 
 
DISCUSSION 
 
The intensive pig production on the six farms had positive 
effects on the nutrient efficiency in their livestock farming. 
As in other studies (Aarnink and Verstegen, 2007; 
Fernandez et al., 1999; De Boer et al., 1997), it was 
particularly the high performance and the requirement-
related diets which affected the nutrient efficiency 
positively. Industrially produced diets with reduced crude 
protein and P contents or with supplements for better 
digestibility have been used for a long time in intensive 
pig production (Aanrink and Verstegen, 2007; De 
Fernandez et al., 1999; De Boer et al., 1997). The 
present study has been able to show that the farmers’ 
feeding management has the potential to improve nutrient 
efficiency even further.  

Reducing P concentration in diets, strongly regulations 
(and controls of them) and strict fertilizing management 
were important factors for reducing the P load in soil in 
the past (Fernandez et al., 1999; De Boer et al., 1997). 
Additionally, the increased cultivation of maize could be 
responsible for partly reduction. The cultivation of barley 
and rye were replaced by maize at this time very much. 
On average, maize requires a little more phosphorus of 
growth. Because of a further reduction of P load is 
unnecessary in many places, the question arises as how 
much more P needs to be removed from diet. This 
reduction in P enables the farmers to have a higher 
stocking density and still be able to conform to the 
legislative requirements given by the German Fertiliser 
Ordinance (Düngeverordnung-DÜV, 2007). From a 
sustainable point of view, the removal of P from the input 
side of animal production (that is, the diet) is questionable 
because it can only be done by using (energy-) costly 
methods and then any necessary P would have to be 
reapplied to the farm using by mineral fertiliser.  

As in other studies in ILAs (Cahoon et al., 1999; 
Breeuwsma et al., 1995), there was a high accumulation 
of P in soil on the study farms with the increasing 
intensification of animal production in the middle of the 
1990s. The high influence of the distance of the fields 



009          Afr. J. Pig Farming 
 
 

 
Table 5. Development of the relationship between the distance of the fields from the farm buildings 
and the soil phosphorus concentration (mg P/ 100 g soil) between the years 1995 – 2009. 

 
 

Year 
regression function 

R2 F sig.  

 

Y= mx + b  

     
 

 1995 - 1997 [-]2.1854x [+] 34.09 0.18 12.01 0.001 
 

 1998 - 2000 [-]0.4363x [+] 14.20 0.09 3.84 0.035 
 

 2001 - 2003 [-]0.6405x [+] 18.10 0.04 2.13 0.150 
 

 2004 - 2006 [-]0.4984x [+] 18.32 0.08 6.91 0.100 
 

 2007 - 2009 [-]0.4857x [+] 11.91 0.19 10.4 0.002 
 

 
 
 
 
from the farm buildings on the soil P concentration in the 
1990s illustrated that with any increase intensification of 
pig production, emphasis should not only be placed on 
the application technique (e.g. towing hose, direct 
incorporation into the soil, etc.) as had been done by the 
local government in Northwest Germany (Ministry of 
Food, Agriculture, Consumer Protection and Regional 
Development, Lower Saxony, 2012). Appropriate 
technologies are also necessary in overcoming longer 
transportation distances of manure.  

The present study had shown that there is a great 
potential for improving the nutrient efficiency in crop 
production, too. Particularly, the contribution of the animal 
production (via the manure) to the nutrient supply in the 
crop production was not being taken enough into 
consideration with respect to determining the need for the 
mineral fertiliser input. This led to particularly high losses 
both of N (104.5 kg/ha) and P (11.7 kg/ha). With the 
present practise of fertiliser application on the study 
farms, a maximum of 68 kg N/ha could be applied by 
chemical fertiliser and 76 kg N/ha by manure to fulfil the 
legislative requirements of the German Fertiliser 
Ordinance (Figure 1). Using these values for the 
maximum fertiliser production (29.45 kg N/sow and 6.05 
kg N/unit fattening pig), the maximum stocking density 
would have to be at 2.3 sows/ ha or 11.2 units fattening 
pigs/ha (0.97 LU/ha for sows or 1.79 LU/ ha for fattening 
pigs; sow including piglet rearing = 0.42 LU; fattening pig 
= 0.16 LU). With respect to the requirements of P 

fertilisation (overload = 20 kg P2O5; 8.72 kg P) a 

maximum of 33.2 kg P/ha could be applied by manure 
(Figure 3). This corresponds to an equivalent of 4.8 sows/ 
ha (production = 6.9 kg N/sow) and 15.8 units/ ha 
(production = 2.1 kg P/unit) or 2.0 LU/ha for sows and 2.5 
LU/ha for fattening pigs.  

These calculations of the maximum stocking density at 
the farms’ present practise of fertiliser application show 
that the main limiting factor is N. This means that the 
present practise of fertilisation and the large mineral 
fertiliser inputs are not compatible with the stocking 
density on any of the six farms. The underestimations in 
perception of the fertiliser application illustrated in this 
investigation emphasise the large managerial mistakes 
being made in the crop production. 

 
 
 
 

Increasing ecological problems from pig production are 
also resulting at present from excessive N depositions 
from animal husbandry units. Current values are already 
at 55 kg/ha (Builtjes et al., 2011). Beside the depositions 
caused by manure application, the exhaust air from 
livestock buildings is the most important form of N 
emission (Dämmgen, 2009). Mitigating such emissions is 
associated with a lot more costs and must be combined 
with regulatory measures. A major challenge of the future 
will be to prevent or reduce these emissions.  

The present investigation has shown that with respect 
to sustainable development particular attention needs to 
be paid to nutrient management practises on the crop 
side. Even when economic advantages lie in the 
production of animals in ILAs, the great amount of 
manure produced makes it necessary that a high degree 
of managerial attention should be paid to the crop 
production side of the business. Amendments to the 
regulations governing fertiliser application would help to 
improve the situation. Any monitoring of the situation 
must include an effective and exact controlling of the 
amount of fertiliser applied to any given area. The legal 
obligations for recording fertilisation set out in the present 
German regulations (Düngeverordnung DÜV, 2007) do 
not fulfil this need. 
 
 
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