CWA 17898:2022

SLOVENSKI STANDARD
01-september-2022
Metodologija za kvantifikacijo globalnega odtisa kmetijskih pridelkov, vključno z
vplivi tal
Methodology to quantify the global agricultural crop footprint including soil impacts
Methodik zur Quantifizierung des globalen Fußabdrucks landwirtschaftlicher
Nutzpflanzen einschließlich der Bodenbeeinflussung
Ta slovenski standard je istoveten z: CWA 17898:2022
ICS:
13.080.01 Kakovost tal in pedologija na Soil quality and pedology in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN
CWA 17898
WORKSHOP
June 2022
AGREEMENT
ICS 13.080.01
English version
Methodology to quantify the global agricultural crop
footprint including soil impacts
This CEN Workshop Agreement has been drafted and approved by a Workshop of representatives of interested parties, the
constitution of which is indicated in the foreword of this Workshop Agreement.

The formal process followed by the Workshop in the development of this Workshop Agreement has been endorsed by the
National Members of CEN but neither the National Members of CEN nor the CEN-CENELEC Management Centre can be held
accountable for the technical content of this CEN Workshop Agreement or possible conflicts with standards or legislation.

This CEN Workshop Agreement can in no way be held as being an official standard developed by CEN and its Members.

This CEN Workshop Agreement is publicly available as a reference document from the CEN Members National Standard Bodies.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members.

Ref. No.:CWA 17898:2022 E
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Measuring soil quality . 7
4.1 The methodology’s stakeholders . 7
4.2 General overview of the methodology . 7
4.3 Process analysis . 8
4.3.1 Crop exergy footprint (CEF) . 9
4.3.2 Impacts on soil (IoS) . 18
4.4 Parameter unification . 29
Annex A (informative) Example of use of the methodology . 30
A.1 General . 30
A.2 Crop exergy footprint (CEF) . 31
A.2.1 Mechanical processes . 31
A.2.2 Water . 32
A.2.3 Fertilization . 32
A.2.4 Total CEF1 . 33
A.2.5 Diffuse emission pool . 33
A.2.6 CEF in terms of production . 33
A.3 Impacts on soil (IoS) . 33
A.3.1 Nutrients Amendment . 34
A.3.2 Organic Matter Amendment . 35
A.3.3 Salinity Amendment . 35
A.3.4 Acidification Amendment . 35
A.3.5 Erosion soil losses . 36
A.3.5.1 Soil erosion . 36
A.3.5.2 Soil exergy . 37
A.3.5.3 Erosion soil losses exergy . 40
A.3.6 Total IoS . 41
A.4 Parameter unification . 41
Annex B (informative) Supplementary information . 43
B.1 Soil Erosión: RUSLE-USLE . 43
B.2 Soil Exergy . 47
B.2.1 Texture Input Option 2.1 . 47
B.2.2 Nutrients Input Option 2.2 . 48
B.2.3 Microorganisms Input Option 2.4 . 49
Bibliography . 50

European foreword
This CEN Workshop Agreement (CWA 17898:2022) has been developed in accordance with the CEN-
CENELEC Guide 29 “CEN/CENELEC Workshop Agreements – A rapid prototyping to standardization” and
with the relevant provisions of CEN/CENELEC Internal Regulations - Part 2. It was approved by a
Workshop of representatives of interested parties on 2022-06-06, the constitution of which was
supported by CEN following the public call for participation made on 2022-03-02. However, this CEN
Workshop Agreement does not necessarily include all relevant stakeholders.
The final text of this CEN Workshop Agreement was provided to CEN for publication on 20222-06-07.
Results incorporated in this CWA received funding from the program Retos-Colaboración 2017, funded
by the Spanish Ministry of Science, Innovation and Universities under grant agreement No. RTC-2017-
5887-5 (project FERTILIGENCIA).
The following organizations and individuals developed and approved this CEN Workshop Agreement
• Ms. Bárbara Palacino, Spain - Chairperson
• UNE, Spain, Ms. Rosa Cepas - Secretary
• BIO3G, France, Mr. Olivier Klarzynski
• Düngekalk Hauptgemeinschaft in BVK, Germany, Mr. Reinhard Müller
• Fertinagro Biotech, Spain, Ms. Victoria Cadahía
• Fertinagro Fertesa, Spain, Ms. Azucena Mainar
• Fertinagro Nutrigenia, Spain, Mr. Marcos Caballero
• Fundación Circe, Spain, Ms. Sonia Ascaso
• Hello Nature International, Italy, Mr. Benoît Planques and Ms. Erica de Benedetti
• Institute of Environmental Engineering of the Polish Academy of Science, Poland,
Ms. Irena Twardowska and Mr. Sebastian Stefaniak
• NEN, Netherlands, Ms. Marleen Schoemaker
• Parque Tecnológico Aula Dei, Spain, Mr. Manuel Márquez
• Universidad de Zaragoza, Spain, Ms. Alicia Valero
Introduction
Loss of soil fertility and soil erosion are some of the threats facing mankind. Agricultural systems are
complex systems made up of physical, chemical, and biological properties. Soil parameters or factors
constitute these properties. A large number of factors involved in the cycles and processes occurring in
the soil makes it necessary to study them using different parameters. Due to the complexity of soils, there
is currently no consensus on how to assess loss of soil fertility and soil erosion, and they are not included
in the usual environmental impact assessment methodologies.
This CWA proposes to use the exergy methodology to evaluate all the impacts of an agroecosystem,
including those occurring in the soil. Exergy is a physical property based on the second law of
thermodynamics and unifies into a single indicator; all soil parameters relevant for soil fertility
assessment.
This CWA is an opportunity to further improve soil quality evaluation by introducing a thermodynamic
indicator that will contribute to a rigorous assessment of agricultural processes' impact. The
determination of a single comparable, reliable, accurate, and globally accepted indicator will be essential
in the near future for the evaluation of soil fertility and agricultural processes efficiency and
environmental sustainability.
1 Scope
This European CWA specifies a methodology for identifying, characterizing, and implementing a single
indicator to assess the quality and degradation of agricultural soils and the overall impact of the
agriculture processes. The agriculture impacts are assessed through the mechanical, fertilization and
irrigation activities associated. Furthermore, soil impacts is evaluated accounting with soil erosion and
parameters such as nutrients, texture, and organic matter. The developed methodology allows a simple
but robust assessment of soil biogeochemical processes and the loss of fertility and degradation.
This European CWA also provides, in Annexes A and B, informative guidance on its use.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 20951:2019, Soil Quality — Guidance on methods for measuring greenhouse gases (CO , N O, CH ) and
2 2 4
ammonia (NH ) fluxes between soils and the atmosphere
ISO 11063:2020, Soil quality — Direct extraction of soil DNA
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
exergy
the maximum amount of work that may theoretically be performed by bringing a resource into
equilibrium with its surrounding environment by a sequence of reversible processes
The exergy of a system gives an idea of its evolution potential for not being in thermodynamic equilibrium
or dead state with the environment. Unlike mass or energy, exergy is not conserved but destroyed by
irreversibilities and lost in all physical transformations until the system reaches a dead state.
Exergy is an extensive property with the same units as energy.
3.2
eco-exergy
the working capacity of organisms due to the genetic information they possess [1]
3.3
crop exergy footprint
CEF
the energy required, considering the irreversibility of the different processes, to carry out the different
activities involved in the agricultural process
3.4
impacts on soil
IoS
the energy required, considering the irreversibility of the different processes, to incorporate and
replenish substances from a state where the soil and its components have undergone modifications due
to the agricultural process to the initial state of the soil
3.5
life cycle assessment
LCA
a methodology for assessing environmental impacts associated with all the stages of the life cycle of a
commercial product, process, or service
4 Measuring soil quality
4.1 The methodology’s stakeholders
4.2 General overview of the methodology
The approach described is a comprehensive methodology for assessing the impacts of agricultural
processes and their efficiency, including the evaluation of soil quality and its degradation during the
process. The approach is based on detailed exergy analysis of the pre-and post-process soil condition of
an agricultural production system for:
— studying the resources and allow their exergy calculation for subsequent analysis and evaluation of
the worsening or improvement of the agricultural system status;
— defining process constraints and requirements for maintaining or improving the quality of the
system;
— identifying the process parameters and select the critical process parameters for process control and
optimization.
To apply the methodology, the system boundaries for the main system and parameters shall be defined
to apply all steps based on the same scope to ensure comparable results.
In this methodology, Crop Exergy Footprint (CEF) and Impacts on Soil (IoS) are used to analyse and
evaluate the agricultural process, including the different activities carried out during cultivation, such as
tillage, fertilization, and application of amendments, irrigation, and erosion. By means of these factors, it
is possible to describe the state and quality of the soil in different operational states.
A detailed methodology to evaluate the exergy loss due to soil erosion is shown as part of IoS. Diffuse
emissions are also accounted for in CEF. The production obtained by the agroecological system is the
main output. Accordingly, this methodology evaluates agroecosystem processes considering all exergy
flows entering and leaving the system allowing for a detailed analysis of the parameters that may have
been affected by crop generation.
The impacts on the agricultural soil are evaluated by means of the Impacts on Soil (IoS), which assesses
the hypothetical cost to return the system from the final state to the initial state before the agricultural
process. Understanding the fertility of soils as an avoided cost that nature provides leads us to propose
exergy replacement cost as a tool for the assessment of the loss of soil fertility due to agriculture practices.
A methodology has been established to evaluate the system in order to reduce the number of variables
to be analysed to assess the quality and status of the system.
For an overview of the methodology, see Figure 1.
Figure 1 — Schematic overview of the methodology system
4.3 Process analysis
An essential step for the analysis and evaluation of soil quality and process impact is the definition of
subfactors, which can be increased or decreased in value depending on their nature (used as an objective
function for the evaluation). The methodology recommends the use of the following subfactors for the
evaluation: mechanical processes, fertilizers, pesticides and phytosanitary supplies, water, erosion and
soil losses and diffuse emissions in CEF. In the case of IoS, the use of the subfactors: nutrients amendment,
organic matter amendment, salinity amendment, acidification amendment and erosion soil losses are
recommended. These subfactors are described in the following sections and schematically represented
in Figure 2 and Figure 3.
Figure 2 — Illustration of variables used for process and soil study and evaluation
Figure 3 — Methodology concepts diagram
4.3.1 Crop exergy footprint (CEF)
4.3.1.1 General
The Crop exergy footprint (CEF) is the indicator that allows evaluating the energy needed to carry out
the activities involved in the cultivation process, considering all the irreversibilities of the processes. This
indicator is applied to the agroecosystem as a whole, evaluating all inputs and outputs to the field.
The following exergy inputs to the agricultural system are considered: water, fertilizers and other
phytosanitary products, and the energy required in the different mechanical processes.
Two sets of subfactors shall be used within the methodology: Input Subfactors, which focus on the direct
activities and processes that are performed on the cultivation system, and Output Subfactors, which focus
on environmental impacts associated with the agricultural activities.
Three Input Subfactors are proposed to constitute the main CEF in the methodology:
— Mechanical processes [MJ/ha].
— Fertilizers, pesticides, and phytosanitary products [MJ/ha].
— Water [MJ/ha].
CEF = Mechanical processes + Fertilizers, pesticides + Water
Where "ha" stands for hectare, which represents the quantity of the main soil of the process under study.
These subfactors provide information on the three main activities used: tillage, irrigation, and
fertilization. The exergy indicator alone covers all these processes and provides a quality-weighting
factor based on rigorous thermodynamics.
Output subfactors are proposed to constitute the CEF in the methodology:
— Diffuse emissions [kg Element/ha].
CEF = Diffuse emissions
This subfactor is selected to focus on the environmental impact of the agricultural processes. Diffuse
emissions complement the Input Factors and allow a joint and global evaluation of the whole process.
All of these subfactors are detailed in the following sections.
4.3.1.2 Mechanical processes
This subfactor is defined as the activities and tasks necessary to prepare the system and improve its
capacities and qualities before and after cultivation. Mechanical processes include tillage, sowing,
fertilizing, and harvesting. They are responsible to a great extent for the energy consumed in agriculture.
There are two options for the estimation, option 1: when energy consumption in terms of fuel is known;
option 2: when no energy consumption is known (Figure 4).

Figure 4 — Diagram explaining the method of calculating the energy consumed during the
mechanical process based on the different possible starting data available
The exergy of the mechanical processes (Ex) is proportional to the amount of fuel used (Formula 1). If
this amount is known, the conversion to energy units will be performed.
   
kg MJ
Fuel l ·Density ·HHV
()
   
l kg
    
MJ
(1)
Ex =

ha

Land surface ha
( )
If the real amount of diesel used is unknown, the following values for the HHV (High Heating Value) and
density shall be used (Table 1).
Table 1 — High heating value (HHV) of fuels

Diesel
HHV (MJ/kg) 45.6
Density (kg/l) 0.84
Tillage processes demand the largest amount of energy, depending on the type of soil and depth of the
process. According to the study performed by IDAE [2], the exergy due to different types of tillage can be
found in Table 2; a simple classification is made according to texture, light (corresponding to sandy and
loamy textures), and heavy (corresponding to clay textures).
Figure 5 shows how the classification of textures is divided according to whether they are considered
light or heavy, showed in green or brown, respectively.
A classification is made according to the working depth, which can be either high or low, for depths higher
than 15 cm or lower than 15 cm, respectively. However, the classification of low or high depth will depend
on each tillage activity and on the working machinery and its technical specifications.

Figure 5 — Texture classification scheme, showing the division between light textures (green)
and heavy textures (brown)
In the case of fertilizer or amendment application processes and the seeding process in the cropping
system, a data collection shall be used (Table 2), distinguishing two consumptions, which are related to
the width of the implement and work in the labour or application rate of the product, called "Normal" and
"High". Exergy values according to the doses of product applied should be estimated, based on dose data
(kg/ha or l/ha) (Formula 2).
 
MJ MJ
Ex =∑ Machinery energy
(2)
 
ha ha
 
Regarding the machinery, within the group of harvesters, there are different types depending on the type
of crop (corn, cereal, sunflower, among others). Data are also available for balers, windrowers, and
mowers (Table 2).
Table 2 — Energy data on the consumption of tillage implements, seed drills, and harvesters
Energy (MJ/ha)
Light/low Light/high Heavy/low Heavy/high
Subsoiler 687,01 877,85 1 030,51 1 145,02
Mouldboard plow 687,01 839,68 992,35 1 145,02
Disc plow 572,51 725,18 877,85 1 030,51
Chisel plow 343,50 458,01 572,51 687,01
Rolling cultivator 458,01 534,34 687,01 763,34
Disc harrow 229,00 267,17 343,50 381,67
Spring tine cultivator 152,67 229,00 305,34 381,67
Vibrocultivators 229,00 229,00 229,00 229,00
Spike-tooth harrow 190,84 190,84 190,84 190,84
Energy (MJ/ha)
Normal High
Centrifugal spreader 57,25 28,63
Locator spreader 229,00 152,67
Row seed drill 267,17 152,67
Direct row seed drill 419,84 229,00
Single seed drill 248,09 171,75
Direct single seed drill 267,17 190,84
Inter-row cultivators - Spreader 171,75 133,59
Inter-row cultivators 171,75 133,59
Roller 190,84 152,67
Hydraulic spray 41,98 28,63
Spray pump 152,67 76,33
Manure distributor trailer 267,17 190,84
Dose (kg/ha o l/ha) Energy (MJ/kg)
Normal High
Centrifugal spreader 250,00 0,229 0,115
Row seed drill 140,00 1,908 1,090
Direct row seed drill 145,00 2,895 1,579
Inter-row cultivators - Spreader 200,00 0,859 0,668
Hydraulic spray 250,00 0,168 0,115
Spray pump 850,00 0,180 0,090
Energy (MJ/ha)
Normal High
Cereal harvester 572,51 343,50
Corn harvester 763,34 458,01
Sunflower harvester 305,34 152,67
Sugar beet leaf stripper 458,01 381,67
Sugar beet uprooter 343,50 267,17
Sugar beet loader 419,84 305,34
Potato harvester 1 259,52 954,18
Rotary mowers 286,25 229,0
Cutter bar 286,25 229,0
Mower conditioner 267,17 229,0
Fodder windrow rake 152,67 38,17
Packer (conventional) 381,672 209,92
Loading bales 45,80 30,53
Wrapping machine 95,42 76,33
Self-loading trailer 95,42 57,25
Hay combine harvester 954,18 763,34
Corn combine harvester 1 374,02 1 030,51
4.3.1.3 Fertilisers, pesticides and phytosanitary supplies
The exergy embodied in all the processes associated with the production of fertilizers, pesticides, and any
other phytosanitary supplies applied to the agroecosystem needs to be accounted for. The energy
consumed in the transport of the raw materials to the factory and then to the field are also considered. If
detailed information is known, this can be calculated for each situation following a life cycle assessment
approach (Figure 6). If not, this methodology provides average data for each nutrient obtained after a
careful revision of bibliography sources[3], [4], [13]–[15], [5]–[12]; Ecoinvent 3) furthermore a constant
transport distance of 500 km in rail and 400 km by trail is considered[16], [17] (Table 3).

Figure 6 — Diagram explaining the method of calculating the energy consumed during the
mechanical process based on the different possible starting data available
Formula 3 should be applied if option 1 is possible, through the data on the nutrient content of the
fertilizers used, the fertilizer dose applied, and the exergy involved in the production of the nutrient
(Table 3).
  kg Nut   kg comp 
MJ MJ
Ex = ∑ Nutrient content in compound ·Dose ·Exergy nutrient Table 3
( ) (3)
( )      ( )
ha kg Nut
kg comp ha
     
Table 3 — Average exergy contribution associated to the production and transport of nutrients
Inorganic nitrogen 67,8 MJ/kg N
Phosphorus 50,87 MJ/kg P
Potassium 15,06 MJ/kg K
Calcium 22,89 MJ/kg Ca
Magnesium 31,2 MJ/kg Mg
Copper 222,94 MJ/kg Cu
Iron 9,25 MJ/kg Fe
Manganese 73,08 MJ/kg Mn
Zinc 28,77 MJ/kg Zn
Gypsum 3,7 MJ/kg S
Limestone 2,3 MJ/kg Ca
In the case of pesticides, if detailed information is known, this can be calculated for each situation
following a life cycle assessment approach. If not, this methodology provides data for each pesticide
obtained after a careful revision of bibliography sources (Ecoinvent 3) (Table 4).
Table 4 — Average exergy contribution associated to the production of pesticides
Exergy (MJ/kg)
Carbofuran 118,36
Carbaryl 281,31
Cypermethrin 226,22
Chlordimeform 86,4
Malathion 348,57
Paration 232,07
4.3.1.4 Water
Water supplied by rain is not always enough for crop, and irrigation processes are needed. In this
methodology, the exergy of the water will be calculated as the energy consumed in the irrigation
processes associated. Irrigation processes consume large amounts of energy (Formula 4).

kWh
(4)
Ex MJ = Water consumption m·energy consumption ·,3 6
( )
( ) 
m
If data about the type of irrigation process is available, the energy consumption shown in Table 5 will be
used.
Table 5 — Energy consumption (kWh/m ) related to the type of irrigation carried out [18]
Capture Transport and treatment Total
3 3 3
(kWh/m ) (kWh/m ) (kWh/m )
Irrigation
Transport
system
Irrigated
Surface Underground Transfer Desalination Reuse and
land
treatment
Gravity 0 0,02 0,15 1,2 3,7 0,25 0,04 0,07
Sprinkling
and 0,24 0,05 0,25 1,2 3,7 0,25 0,35 0,35
automotive
Local 0,18 0,1 0,5 1,2 3,7 0,25 0,43 0,53
AVERAGE 0,14 0,06 0,30 1,20 3,70 0,25 0,27 0,32
If the type of irrigation process is unknown, average data will be obtained from Table 6.
Table 6 — Average energy consumption considered
Water cycle processes
Aspects considered
kWh/m
in agriculture
Surface water 0,555
Pump
Groundwater 0,633
Supply and transport General 1,200
Distribution General 0,232
Surface water 1,99
TOTAL
Groundwater 2,07
Analyzing the consumption of irrigation water and the number of different crops in Spain using INE
(Instituto Nacional de Estadística. Spanish National Statistical Institute) Table 7 was obtained. These data
shall be used if the amount of water used is unknown, but the crop type is available.
Table 7 — Water consumption according to a type of irrigation and crop
Area by Crop Groups and
Gravity area Sprinkling area Drip surface
type of Irrigation Spain
3 3 3
(m /ha) (m /ha) (m /ha)
Herbaceous 4.778 3.873 87
Potatoes and vegetables 573 716 254
Fruit trees 843 29 719
Olive grove and vineyards 422 56 1.540
Other crops type 285 20 64
TOTAL 6 901 4 695 2 663
If there is no knowledge of the type of irrigation and water consumption, it is possible to roughly estimate
the amount of water consumed per crop, irrespective of the type of irrigation (Table 8).
Table 8 — General water consumption, irrespective of the type of irrigation,
depending on the type of crop
Crop type Area General irrigation
(ha) 3
(m /ha)
Herbaceous 1 285 835 6 584
Potatoes and vegetables 379 119 6 812
Fruit trees 639 457 1 860
Olive grove and vineyards 1 208 058 1 428
Other crops type 211 726 7 234
TOTAL 3 724 195 23 918
Figure 7 describes the calculation process necessary to estimate the energy consumed during the
irrigation process, depending on the starting data available.
Figure 7 — Diagram explaining the method of calculating the energy consumed during the
irrigation process based on the different possible starting data available
4.3.1.5 Diffuse emissions
When nutrients are applied to soil, the generation of different emissions takes place. Nitrogen is the
leading emitter generating gaseous emissions of ammonium, nitrous, and nitrogen oxides.
Due to the diffuse character of the emission, its quantification is difficult. Values of emission factors
associated with different fertilizer products are not always available. The standard ISO 20951:2019
explains experimental methods to quantify the emissions. If it is not possible to obtain these values, the
methodology explained here shall be used (Table 9).
For ammonium, if a revised emission factor is not available, the factor proposed by [19] should be used.
Table 9 — Emission factor for each fertilizer
Fertilizer type Emission factor NH /N (%)
Ammonium nitrate 2
Ammonium sulfate 8
Urea 15
Multi-nutrient fertilizers (NPK-, NP-, NK-) 4
Urea ammonium nitrate 8,5
Liquid ammonium 3
-
Nitrogen emitted as NO to subterranean water depends on the climatology and period of the years as
it is very dependent on rainfall. If real data is not available, this methodology will use the following
formula [20], [21]:

kg N P

N =21,37+ 0,0037·,S+ 0 0000601·N− 0,00362·U
 (5)
org

ha··year c L

where
N 3-
is leached NO N (kg N /ha·year);
P is precipitation plus irrigation (mm/year);
c is clay content in percentage (%);
L is rooting deph (m);
S is nitrogen supply through fertilisers (kg N/ha);
U is nitrogen uptake by crop (kg N/ha);
N is nitrogen in organic matter (kg N/ha):
org

C
org

N = ·VD· / r·r
(6)
org b C Norg


N
where
V 3
is soil volumen (m /ha);
D is total density;
b
r is ratio C:N equal to 11 if not specific data is available [22];
C/N
r is ratio N organic/N total equal to 0,85 if not specific data is available.
Norg
N O is emitted into the air, and its estimation is very uncertain. If more specific data are not available,
the estimation proposed by [23] in Formula 7 shall be used.

kg N O
44 14 14 
2 −
N O · 0,01· N++N 0,01··NH+ 0,0075··NO
( ) (7)
 
2 tot cr 3 3

ha· year 28 17 62
 

where
N is total nitrogen in mineral and organic fertilizers (kg N/ha);

tot
N is nitrogen contained in harvest residues (kg N/ha);
cr
NH is nitrogen losses in the form of ammonia (kg NH /ha);
3 3
- -
NO is nitrogen losses as nitrate (kg NO /ha).
3 3
NO emitted is estimated as [22] (Formula 8):
x
=

kg NO
x
NO = 0,21·N O
(8)
x 2

ha· year

4.3.2 Impacts on soil (IoS)
4.3.2.1 General
Understanding the fertility of soils as an avoided cost that nature provides without charge leads us to
propose Impacts on soil (IoS) as a tool for the assessment of the loss of soil fertility due to agriculture
practices. Exergy is used to calculate the energy embodied in a simulated replacement process that may
recover the impact on fertility.
This methodology proposes that the quality or fertility of soil can be restored with the proper recovery
of nutrients, organic matter, microorganisms, salinity, and acidification. This allows the measurement by
means of exergy of the reposition needed after an agricultural process. This term is added to the rest of
the agroecological process as the unifying unit used is exergy.
A set of subfactors shall be used within the methodology: The Amendment Subfactors, which focus on the
assessment of the state of the different selected parameters and their recovery to initial levels if they have
been minimized due to agricultural practices.
— Four Amendment Subfactors are proposed to constitute the main IoS in the methodology:
— Nutrients Amendment.
— Organic matter Amendment [MJ/ha].
— Salinity Amendment.
— Acidification Amendment.
IoS = Nutrients Amendment + Organic Matter Amendment + Salinity Amendment + Acidification
Amendment
These subfactors provide information on the main soil nutrient cycles and have been selected to focus on
the environmental impact of the agricultural processes.
— Output Subfactors, which focus on soil losses impacts associated with the agricultural activities
— Erosion soil losses [MJ/ha·year]
IoS = Erosion soil losses
The estimation of the IoS is needed to replenish the impacts of the agricultural process will be made by
comparing the final state of the soil with the initial state prior to the start of plowing. The quantity of each
selected factor will be analysed, and the need for replacement will be assessed. If the final state of the
factor is higher than the initial state, no replenishment will be necessary. If the final state is lower than
the initial state, the soil will have suffered a deterioration of its properties, and therefore, it will be
necessary to calculate the Impacts soil (IoS).
All of these factors are detailed in the following sections.
4.3.2.2 Nutrients Amendment
The flow of nutrients from the soil to the plants allows their growth. The movement of nutrients in the
soil is a complex process influenced by many soil and plant properties. An adequate level of each nutrient
in the soil is the first requisite. This is obtained using mineral or organic fertilizers. In this methodology,
the cost associate with the reposition of nutrients is calculated as the energy needed in the production of
the inorganic fertilizer, its transport, and distribution. Furthermore, the emissions generated due to the
application of the fertilizers in the field are considered.
Formula 9 should be used for the calculation of nutrient content needed for the quantity of amendment.
Formula 10 should be applied for estimate the Nutrient Amendment (MJ/ha) based on the result of
Formula 9, the fertilizer production cost (exergy, Table 10), mechanical fertilizer application process
(Table 2) and nutrient concentration of the fertilizer (Table 11).
m
kg  kg Nutrient  kgsoil
(9)
Nutrient = Variation content ·10.000 ·0,3m·1.400
  
ha kgsoil
   ha m
   
kg Nut MJ
Nutrient Amendment MJ/ ha = Nutrient · Fertilizer prod. Cost
( )
   
ha kg Nut
   
 MJ   kg Nut
Fert. mechanical process ·Nutrient (10)
   
kg fert ha
   
+
 kg Nut
Fertilizer nutrient concentration

kg fert
 
The most representative energy value for each nutrient is shown in Table 10:
Table 10 — Exergy needed for nutrients amendment
Nitrogen (inorganic) 67,8 MJ/kg N
Phosphorus 50,87 MJ/kg P
Potassium 15,06 MJ/kg K
Calcium 22,89 MJ/kg Ca
Magnesium 31,2 MJ/kg Mg
Copper 222,94 MJ/kg Cu
Iron 9,25 MJ/kg Fe
Manganese 73,08 MJ/kg Mn
Zinc 28,77 MJ/kg Zn
These data are the energy embodied in all the processes associated with the production of fertilizers.
Also, the energy consumed in the transport of the raw materials to the factory and then to the field [3],
[4], [13]–[15], [5]–[12].
In addition to these data, the cost of field distribution will also be estimated. This value will be calculated
from the energy consumption established for the normal centrifugal spreader (0,229 MJ/kg fertilizer)
and considering the quantity of fertilizer to be distributed. The amount of fertilizer is calculated from the
composition of each nutrient in the most used mineral fertilizers and with only one nutrient per
compound (Table 11).
Table 11 — Content for each nutrient in the most used fertilizers
Nutrient content
Product/Fertilizer
(kg element/kg compound)
Nitrogen
Urea 0,46
(inorganic)
Triple superphosphate (TSP) –
Phosphorus 0,144
single superphosphate (SSP)
Potassium Potassium chloride 0,498
Calcium Calcium nitrate 0,186
Magnesium Magnesium sulfate 0,0999
Copper Copper sulfate 0,25
Iron Iron sulfate 0,2
Manganese Manganese sulfate 0,32
Zinc Zinc sulfate 0,28
The calculation of Nutrients Amendment will be calculated based on the following formulas. For the
conversion of kg soil to hectares, a soil density of 1 400 kg/m and a depth of 0,3 m is considered as this
is a topsoil study.
4.3.2.3 Organic matter (OM) Amendment
Organic matter content is highly relevant in soil fertility because it influences the physical, chemical, and
biological properties of soil. Organic matter is linked to the structure, the nutrients cycles, cationic
exchange capacity, pH, and microorganism activity, among other aspects. Furthermore, the stability of
OM in soils is directly related to its capacity to store carbon, avoiding CO emissions.
Subproducts and wastes represent one of the main sources of OM that is applied to soils. It can be applied
directly or after a stabilization process as composting. Compost is selected as representative of the
repositioning of organic matter. Windrow composting, where long rows of OM are pile, is the most
representative one. The energy needed for this process is low (0,076 MJ/kg) and is mainly due to the
machinery needed to turn over the piles. However, in this case, transport is not considered as it will be
small as it is usually applied close to the point of production.
Formula 11 should be used for the calculation of organic matter content needed for the quantity of
amendment. Formula 12 should be applied for estimate the Organic Matter Amendment (MJ/ha) based
on the result of Formula 11, the compost exergy (Table 12) and mechanical fertilizer application process
(Table 2).
%Variation kg soil
  
kg kg
OM = ·42 000 000
(11)
  
ha kg soil
100 ha
  
 
     
kg kJ kJ
OM · Compost + Fert. mechanical process
     
ha kg kg
     
 
(12)
Organic Matter Amendment MJ/ ha =
( )
kJ
1 000
MJ
The OM Amendment in soils is going to be calculated as the energy needed in the composting process, the
transport, and application in fields, considering a value of 10% assimilation rate of organic matter in the
soil. This factor is defined as the percentage of organic matter applied to the soil that decomposes and
recalcitrates to form part of the soil organic matter [24] (Table 12).
Table 12 — Exergy of organic matter amendment
Exergy (MJ/kg) Conversion factor
Compost 0,076 10 %
In addition to these data, the cost of field distribution will also be estimated. This value will be calculated
from the energy consumption established for the normal centrifugal spreader (0,229 MJ/kg fertilizer).
4.3.2.4 Salinity Amendment
In some lands, irrigation water contained salts that accumulate in soils. This effect is worse in arid
regions-high levels of sodium hamper plant growth. Among the different treatments to improve soil
salinity, gypsum addition is simulated to calculate the repositioning cost. Gypsum (CaSO ·2H O) addition
4 2
+ 2+
allows the exchange of Na ions by Ca decreasing salinity.
Formula 13 should be used for the calculation of sulphur content needed for the quantity of amendment
based on the EPS (Exchangeable Proportion of Sodium) calculated (Formula 15). Formula 14 should be
applied for estimate the Salinity Amendment (MJ/ha) based on the result of formula 13, gypsum
production exergy (Table 13), mechanical fertilizer application process (Table 2) and gypsum nutrient
content (Table 13).

EPS − EPS
final initial

kg

Sulphur = ·CEC·,8736
(13)

ha

 100

    
MJ kg MJ
Salinity Amendment Sulphur amendment ·. Fertilizer prod cost+
    
ha ha kg S
    
  
MJ kg
(14)
Fert.· mechanical process Sulphur amendment
  
kg fert ha
  
+
 
kg S
Gypsum nutrient content
 
kg compound
 
If the sodium proportion is high, the soil is defined as sodic (EPS >15). In this case, plant growth is
hindered. The growth of sensitive plants is affected when the EPS is around 5 [25]. The value of the
EPS factor is estimated from the following formula, where CEC is the cation exchange capacity of the
soil:
=
Na meq/ 100g
( )
EPS %·= 100
( ) (15)
CEC meq/ 100g
( )
This is applied when EPS>5 because sensitive plants decrease yield when the level of sodium is around
5 EPS. Due to the impurities in the gypsum and the inefficiency of the process in general, these quantities
are adjusted with an extra 30 % gypsum in practice to take into account that the reactivity is
not complete [25].
Table 13 — Exergy and sulphur content of gypsum
Exergy 3,7 MJ/kg S
Gypsum
Content 0,186 kg S/kg compound
The Salinity value will be calculated from the energy consumption established for the normal centrifugal
spreader (0,229 MJ/kg fertilizer) and considering the quantity of compound to be distributed (Table 13).
4.3.2.5 Acidification Amendment
Soil acidification affects a wide range of properties, from the capacity of plant roots to take up nutrients
to the activity of soil microorganisms. The oxidation o
...