Water and Nutrient Balance Model J2000-S

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Das Wasser- und Stofftransportmodell J2000-S ermöglicht die Simulation des Wasser- und Stickstoffhaushaltes von Mesoskaligen Einzugsgebieten. Das Modell stellt eine Erweiterung des Modells [[Hydrologisches_Modell_J2000|J2000]] dar mit denen es die meisten Komponenten zur Beschreibung des hydrologischen Kreislaufs teilt. Zur Beschreibung des Stickstoffhaushalts werden die zusätzlichen Komponenten Bodentemperatur, Bodenstickstoffhaushalt, Landnutzungsmanagement, Pflanzenwachstum und Grundwasserstickstoffhaushalt beschrieben werden. Weitere Module wurden für die Erfordernisse des Stickstoffhaushalts angepasst.
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[[de:Wasser-_und_Stofftransportmodell_J2000-S]]
 +
The water and nutrient balance model J2000-S offers a simulation of the water and nitrogen balance of meso scale catchment areas. The model is an extension to the [[Hydrological_Model_J2000|J2000]] model with which it shares most of the components for the description of the hydrologic cycle. The additional components, soil temperature, soil nitrogen balance, land use management, plant growth as well as ground water nitrogen balance, are described for the specification of the nitrogen balance. Further modules are adapted for the demands of the nitrogen balance.  
  
  
 
----
 
----
−
==Bodenstickstoffmodul==
+
==Soil Nitrogen Module==
  
  
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Die Beschreibung des Bodenstickstoffhaushalts erfolgt analog zu der im Modell SWAT (Arnold et al. 1998). Hierbei werden in den einzelnen Bodenhorizonten die 5 Stickstoffpools für Nitrat, Ammonium, stabile organische Substanz, aktive organische Substanz, frische Pflanzenrest Biomasse unterschieden. Die Flüsse und Transformationen zwischen den Pools und außerhalb des Bodens: Nitrifikation, Denitrifikation, Mineralisation, Volatilation, Pflanzenaufnahme und Auswaschung, werden durch empirische Beziehungen in Abhängigkeit der Bodenfeuchte und Bodentemperatur berechnet. Der Nitratfluss wird äquivalent zum Wassertransport durch ein Routingverfahren zwischen den Teilflächen und zum Vorfluter weitergegeben (vgl. Abbildung 1).
+
The description of the soil nitrogen balance is carried out similarly to the SWAT model (Arnold et al. 1998). Within the individual soil horizons the five nitrogen pools for nitrate, ammonium, stable organic substances, active organic substance and fresh plant remains as biomass are distinguished. The fluxes and transformations between the pools and outside the soil, like nitrification, denitrification, mineralization, volatilation, plant uptake and eluviation, are calculated via the empirical relations against the soil humidity and soil temperature. The nitrogen flux is passed as well as the water transport via a routing method between the subareas to the receiving stream (see figure 1).  
  
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Der Stickstoffeintrag über Düngung und Bestandesabfall wird, ebenso wie der Entzug durch die Pflanzen, vom Pflanzenwachstums- und Landnutzungsmanagementmodul bereitgestellt. Die mineralischen Einträge werden dem Ammoniumpool oder direkt dem Nitratpool zugeführt.
+
The nitrogen input caused by fertilization and Bestandesabfall as well as the removal through the plants is provided by the plant growth module and the land use management module. The mineral inputs are allocated to the ammonium pool or directly to the nitrate pool. The organic nitrogen is either allocated to the Bestandesabfall pool or the active organic pool. The latter is poised with the stable organic pool. The nitrate pool is the central allocation section for the discharge as eluviation, plant uptake and denitrification. The processes described in the module take place in free parameterizable soil horizons. Here, the delivery of organic substances and fertilizer as well as the removal of nitrogen with the surface runoff are limited to the top horizon.
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Der organische Stickstoff geht entweder in die Pools für den Bestandesabfall oder in den aktiven organischen Pool ein. Der Abbau des Bestandesabfalls geht in Abhängigkeit vom C/N-Verhältnis in Anteilen in den Nitratpool oder in den aktiven organischen Pool ein. Der aktive organische Pool steht im Gleichgewicht mit dem stabilen organischen Pool. Der Nitratpool stellt die zentrale Verteilstelle für die Austräge in Form von Auswaschung, Pflanzenaufnahme und Denitrifikation dar. Die im Modul beschriebenen Prozesse finden in verschiedenen frei parametrisierbaren Bodenhorizonten statt. Hierbei beschränken sich die Zuführung von organischer Substanz und Dünger und die Abfuhr von Stickstoff mit dem Oberflächenabfluss auf den obersten Horizont.  
+
  
  
Line 16: Line 16:
 
Figure 1: Structure of the soil nitrogen module
 
Figure 1: Structure of the soil nitrogen module
  
−
The here applied nitrogen module contains some simplifications. Thus, no Pflanzenaufnahme from the ammonium pool is offered. Furthermore, the decomposition of organic substances is directly simulated to nitrate without any detour via ammonium. The N immobilization from mineral to organic nitrogen in the soil zone is neglected completely. The water transport of nitrogen is shown very generalized. Thus, a complete mixing of nitrogen in the individual storages takes place instead of advection and dispersion. The individual processes are described in the model as follows:
+
The here applied nitrogen module contains some simplifications. Thus, no plant uptake from the ammonium pool is offered. Furthermore, the decomposition of organic substances is directly simulated to nitrate without any detour via ammonium. The N immobilization from mineral to organic nitrogen in the soil zone is neglected completely. The water transport of nitrogen is shown very generalized. Thus, a complete mixing of nitrogen in the individual storages takes place instead of advection and dispersion. The individual processes are described in the model as follows:
  
  
−
===Pflanzenaufnahme===
+
===Plant Uptake===
  
−
At first, the plant’s demands (potential Pflanzenaufnahme) which shall be met by the soil nitrogen storage per day t0 are generated:  
+
At first, the plant’s demands (potential plant uptake) which shall be met by the soil nitrogen storage on the day t0 are generated:  
 
    
 
    
 
<math> potNup= BioNopt - BioN \! </math> [1]
 
<math> potNup= BioNopt - BioN \! </math> [1]
Line 27: Line 27:
 
with:
 
with:
  
−
'' <math>potNup\!</math>  = potential Pflanzenaufnahme [kgN/ha]''
+
'' <math>potNup\!</math>  = potential plant uptake [kgN/ha]''
  
 
'' <math>BioNopt\!</math> = optimal biomass  [kgN/ha]''
 
'' <math>BioNopt\!</math> = optimal biomass  [kgN/ha]''
Line 33: Line 33:
 
'' <math>BioN\!</math>    = actual biomass [kgN/ha]''
 
'' <math>BioN\!</math>    = actual biomass [kgN/ha]''
  
−
Afterwards, the proportions of the soil horizons which lie within the effective root zone are generated. At this, the horizons which lie completely within the root zone are taken into account completely (partroot = 1). However, the horizon which lies only partly in the root zone is only considered partly:  
+
Afterwards, the proportions of the soil horizons which lie within the effective root zone are generated. At this, the horizons which lie entirely within the root zone are taken into account completely (partroot = 1). However, the horizon which lies only partly in the root zone is only considered partly:  
  
 
<math> partroot[i] =  \frac {rootdepth - layerdepth[i - 1]}{layerdepth[i] - layerdepth[i - 1]} \! </math> [2]
 
<math> partroot[i] =  \frac {rootdepth - layerdepth[i - 1]}{layerdepth[i] - layerdepth[i - 1]} \! </math> [2]
Line 51: Line 51:
 
with:  
 
with:  
  
−
'' <math>i\!</math> = Horizont [-] ''
+
'' <math>i\!</math> = horizon [-] ''
  
 
'' <math>partroot\!</math> = proportion of the horizon at the root zone [-]''
 
'' <math>partroot\!</math> = proportion of the horizon at the root zone [-]''
Line 57: Line 57:
 
'' <math>layerdepth\!</math> = lower threshold of the soil horizon [-]''
 
'' <math>layerdepth\!</math> = lower threshold of the soil horizon [-]''
  
−
'' <math>potNup\!</math>  = potential Pflanzenaufnahme [kgN/ha]''
+
'' <math>potNup\!</math>  = potential plant uptake [kgN/ha]''
  
−
'' <math>potNup_z\!</math> = potential Pflanzenaufnahme in the individual horizons [kgN/ha]''
+
'' <math>potNup_z\!</math> = potential plant uptake in the individual horizons [kgN/ha]''
  
−
'' <math>uptake\!</math> = potential Pflanzenaufnahme which has been taken from upper horizons already [kgN/ha]''
+
'' <math>uptake\!</math> = potential plant uptake which has been taken from upper horizons already [kgN/ha]''
  
−
'' <math>\beta_{Ndist}\!</math> = distribution parameter of the Pflanzenaufnahme; default value = 1.0; possible values 1 - 15 [-]''
+
'' <math>\beta_{Ndist}\!</math> = distribution parameter of the plant uptake; default value = 1.0; possible values 1 - 15 [-]''
  
−
For the calculation of the potential Pflanzenaufnahme which is covered by upper horizons already, the following connection is applied:  
+
For the calculation of the potential plant uptake which is met by upper horizons already, the following connection is applied:  
 
<math> uptake = uptake + potNup_z[i] \! </math> [4]
 
<math> uptake = uptake + potNup_z[i] \! </math> [4]
  
−
'' <math>potNup_z\!</math> = potential Pflanzenaufnahme in the individual horizons [kgN/ha]''
+
'' <math>potNup_z\!</math> = potential plant uptake in the individual horizons [kgN/ha]''
  
−
'' <math>uptake\!</math> = potential Pflanzenaufnahme which has been taken from upper horizons already [kgN/ha]''
+
'' <math>uptake\!</math> = potential plant uptake which has been taken from upper horizons already [kgN/ha]''
  
  
Line 87: Line 87:
 
'' <math>NO_3Pool\!</math> = soil nitrogen pool [kgN/ha]''
 
'' <math>NO_3Pool\!</math> = soil nitrogen pool [kgN/ha]''
  
−
'' <math>potNup_z\!</math> = potential Pflanzenaufnahme in the individual horizons [kgN/ha]''
+
'' <math>potNup_z\!</math> = potential plant uptake in the individual horizons [kgN/ha]''
  
 
If this demand is greater than 0, it can be met by the existing nitrogen storage with:  
 
If this demand is greater than 0, it can be met by the existing nitrogen storage with:  
Line 119: Line 119:
 
'' <math>NO_3Pool2\!</math> = soil nitrate pool after the time step [kgN/ha]''
 
'' <math>NO_3Pool2\!</math> = soil nitrate pool after the time step [kgN/ha]''
  
−
'' <math>potNupz\!</math> = potential Pflanzenaufnahme in the individual horizons [kgN/ha]''
+
'' <math>potNupz\!</math> = potential plant uptake in the individual horizons [kgN/ha]''
  
 
'' <math>partroot\!</math> = proportion of the horizon of the root zone [-]''
 
'' <math>partroot\!</math> = proportion of the horizon of the root zone [-]''
  
  
−
Anschließend berechnet sich die aktuelle Pflanzenaufnahme aus der potentiellen Pflanzenaufnahme und dem über die Horizonte summierten Bedarf:
+
Aterwards, the actual plant uptake can be calculated on the basis of the potential plant uptake and the demand that has been summed up via the horizons:
  
 
<math> N_{uptake} = potNup + \sum^{n}_{i=1}{demand[i]}  \! </math> [10]  
 
<math> N_{uptake} = potNup + \sum^{n}_{i=1}{demand[i]}  \! </math> [10]  
Line 132: Line 132:
 
'' <math>i\!</math> = horizon [-] ''
 
'' <math>i\!</math> = horizon [-] ''
  
−
'' <math>n\!</math> = proportion of the horizon of the root zone [-] ''
+
'' <math>n\!</math> = number of horizons in the root zone [-] ''
  
 
'' <math>demand\!</math> = demand which can be met by the soil nitrogen pool [kgN/ha]''
 
'' <math>demand\!</math> = demand which can be met by the soil nitrogen pool [kgN/ha]''
  
−
'' <math>potNup\!</math>  = potential Pflanzenaufnahme [kgN/ha]''
+
'' <math>potNup\!</math>  = potential plant uptake [kgN/ha]''
  
−
'' <math>N_{uptake}\!</math>  = actual Pflanzenaufnahme [kgN/ha]''
+
'' <math>N_{uptake}\!</math>  = actual plant uptake [kgN/ha]''
  
 
===Nitrate Rising by Evaporation===
 
===Nitrate Rising by Evaporation===
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'' <math>\eta_{temp}\!</math> = soil temperature coefficient [-]''
 
'' <math>\eta_{temp}\!</math> = soil temperature coefficient [-]''
  
−
'' <math>temp_{Layer}\!</math>  = temperatur of the soil layer [°C]''
+
'' <math>temp_{Layer}\!</math>  = temperature of the soil layer [°C]''
  
  
Line 187: Line 187:
 
with
 
with
  
−
'' <math> \eta_{water}\! </math> = soil humidity coefficient[-]''
+
'' <math> \eta_{water}\! </math> = soil humidity coefficient [-]''
  
 
'' <math>sto_{LPS}\!</math>  = maximum large pore storage of the horizon [l]''
 
'' <math>sto_{LPS}\!</math>  = maximum large pore storage of the horizon [l]''
Line 208: Line 208:
 
'' <math>layerdepth\!</math>  = layer depth of the horizon [cm]''
 
'' <math>layerdepth\!</math>  = layer depth of the horizon [cm]''
  
−
The total Gesamtumsatz of the ammonium pool can be calculated as follows:
+
The Gesamtumsatz of the ammonium pool can be calculated as follows:
  
 
<math> N_{nit + vol} = NH_4Pool * (1 - \exp(-(\eta_{water} \cdot \eta_{temp})-(\eta_{vol_z} \cdot \eta_{temp})))\!</math>
 
<math> N_{nit + vol} = NH_4Pool * (1 - \exp(-(\eta_{water} \cdot \eta_{temp})-(\eta_{vol_z} \cdot \eta_{temp})))\!</math>
Line 238: Line 238:
 
'' <math>frac_{vol}\!</math>  = fraction ammonium volatilation [-]''
 
'' <math>frac_{vol}\!</math>  = fraction ammonium volatilation [-]''
  
−
'' <math>nitri_{trans}\!</math> = amount of nitrifikation [kgN/ha]''
+
'' <math>nitri_{trans}\!</math> = amount of nitrification [kgN/ha]''
  
−
'' <math>volati_{trans}\!</math>  = amount of ammoniumvolatilation [kgN/ha]''
+
'' <math>volati_{trans}\!</math>  = amount of ammonium volatilation [kgN/ha]''
  
  
  
−
====Pre-calculation for the Influence of the Environmental Conditions====
+
====Pre-calculation for the Influence of Environmental Conditions====
  
−
In order to show the influence of the soil temperature and the soil humidity in the different transformation processes, the following coefficients are calculated beforehand: U
+
In order to show the influence of the soil temperature and soil humidity in the different transformation processes, the following coefficients need to be calculated beforehand: U
  
 
<math> \gamma_{temp} = 0.9 \cdot \frac {temp_{Layer}} {temp_{Layer} \cdot \exp(9.93 - 0.312 \cdot temp_{Layer}} + 0.1 \! </math> [1]  
 
<math> \gamma_{temp} = 0.9 \cdot \frac {temp_{Layer}} {temp_{Layer} \cdot \exp(9.93 - 0.312 \cdot temp_{Layer}} + 0.1 \! </math> [1]  
Line 272: Line 272:
  
 
'' <math>act_{MPS}\!</math>  = actual middle pore storage of the horizon [l]''
 
'' <math>act_{MPS}\!</math>  = actual middle pore storage of the horizon [l]''
 +
  
 
====Transfer between the Organic Pools====
 
====Transfer between the Organic Pools====
Line 281: Line 282:
 
with
 
with
  
−
'' <math>N_{Hum_{trans}}\!</math>  = transfer rate between the active and the stable organic pool [kgN/ha]''
+
'' <math>N_{Hum_{trans}}\!</math>  = transfer rate between the active and stable organic pool [kgN/ha]''
  
−
'' <math>\beta_{trans}\!</math>  = transfer constant between the active and the stable organic pool; default value= 0.00001 [-]''
+
'' <math>\beta_{trans}\!</math>  = transfer constant between the active and stable organic pool; default value= 0.00001 [-]''
  
 
'' <math>N_{activ_{pool}}\!</math>  = active organic pool [kgN/ha]''
 
'' <math>N_{activ_{pool}}\!</math>  = active organic pool [kgN/ha]''
Line 293: Line 294:
 
The transfer rate is here subtracted from the active pool whereas it is added to the stable pool.
 
The transfer rate is here subtracted from the active pool whereas it is added to the stable pool.
  
−
====Mineralisierung des aktiven Pools====
+
====Mineralization of the Active Pool====
  
−
Der aktive Pool wird unter Auslassung der Nitrifikation direkt zu Nitrat mineralisiert. Die Rate wird hierbei wie folgt berechnet:
+
The active pool is mineralized to nitrate directly without taking the nitrification into account. The rate is calculated as follows:
  
 
<math>N_{actmin} = \beta_{min} \cdot \sqrt{\gamma_{temp} \cdot \gamma_{water}} \cdot N_{activ_{pool}}\!</math>
 
<math>N_{actmin} = \beta_{min} \cdot \sqrt{\gamma_{temp} \cdot \gamma_{water}} \cdot N_{activ_{pool}}\!</math>
  
−
mit
+
with
  
−
'' <math>N_{actmin}\!</math>  = Transferrate zwischen aktiven organischen und dem Nitratpool [kgN/ha]''
+
'' <math>N_{actmin}\!</math>  = transfer rate between the active organic and the nitrate pool [kgN/ha]''
  
−
'' <math>\beta_{min}\!</math>  = Transferkonstante zwischen aktiven organischen und dem Nitratpool; Vorgabewert = 0.002 [-]''
+
'' <math>\beta_{min}\!</math>  = transfer constant between the active organic and the nitrate pool; default value = 0.002 [-]''
  
−
'' <math>N_{activ_{pool}}\!</math>  = Aktiver organischer Pool [kgN/ha]''
+
'' <math>N_{activ_{pool}}\!</math>  = active organic pool [kgN/ha]''
  
−
'' <math>\gamma_{water}\!</math>  = Bodenfeuchtekoeffizient [-]''
+
'' <math>\gamma_{water}\!</math>  = soil humidity coefficient [-]''
  
−
'' <math>\gamma_{temp}\!</math>  = Bodentemperaturkoeffizient [-]''
+
'' <math>\gamma_{temp}\!</math>  = soil temperature coefficient [-]''
  
−
Die Transferrate wird hierbei vom aktiven Pool subtrahiert währen sie zu dem Nitratpool hinzuaddiert wird.
+
The transfer rate is subtracted from the active pool whereas it is added to the nitrate pool.
  
  
−
====Dynamik der Residuenpools====
+
====Dynamics of the Residue Pools====
  
−
Die Dynamik des Abbaus frischer organischer Substanz (Residuen) aus Pflanzenresten und organischem Dünger erfolgt nur im obersten Bodenhorizont. Die Residuen werden hierbei in zwei Pools aufgeteilt, der Erste repräsentiert die Biomasse als ganzes und der Zweite den Stickstoffanteil der Residuen. Die Zufuhr zu den Residuenpools erfolgt über Pflanzenreste nach der Ernte und über die organische Düngung mit Hilfe der folgenden Gleichungen:
+
The dynamics of the decomposition of fresh organic substances (residue) from plant remains and organic fertilizer is carried out only in the top horizon. The residue are divided in two pools: the first one represents the biomass as a whole, the second represents the residue's amount of nitrogen. The supply to the residue pools is carried out via plant remains after the harvest and via the organic fertilization with the help of the following equation:
  
 
<math>Residue_{pool} = Residue_{pool} + inp_{biomass} + (fertorgN_{fresh} \cdot 10)\! </math>
 
<math>Residue_{pool} = Residue_{pool} + inp_{biomass} + (fertorgN_{fresh} \cdot 10)\! </math>
Line 322: Line 323:
 
<math>N_{residue_{pool}} = N_{residue_{pool}} + inpN_{biomass} + fertorgN_{fresh}\!</math>
 
<math>N_{residue_{pool}} = N_{residue_{pool}} + inpN_{biomass} + fertorgN_{fresh}\!</math>
  
−
mit
+
with
  
−
'' <math>Residue_{pool}\!</math>  =  Residuenpool [kg/ha]''  
+
'' <math>Residue_{pool}\!</math>  =  residue pool [kg/ha]''  
  
−
'' <math>inp_{biomass}\!</math>  =  Zugeführte Biomasse [kg/ha]''  
+
'' <math>inp_{biomass}\!</math>  =  inputted biomass [kg/ha]''  
  
−
'' <math>fertorgN_{fresh}\!</math> =  Über organische Düngung zugeführter Stickstoff [kgN/ha]''  
+
'' <math>fertorgN_{fresh}\!</math> =  inputted nitrogen via organic fertilization [kgN/ha]''  
  
−
'' <math>N_{residue_{pool}}\!</math> =  Stickstoffanteil des Residuenpools [kgN/ha]''
+
'' <math>N_{residue_{pool}}\!</math> =  residue pool's amount of nitrogen [kgN/ha]''
  
−
Der Abbau des Residuenpools findet in Abhängigkeit des Kohlenstoff- Stickstoffverhältnisses (C/N-Verhältnis) statt. Die Berechnung des C/N-Verhältnisses erfolgt wie in der nachstehenden Gleichung angegeben.
+
The decomposition of the residue pool is carried out against the carbon-nitrogen relation (C/N-relation). The calculation of the C/N-relation is carried out according to the following equation.
  
 
<math>\epsilon_{C/N} = \frac{Residue_{pool} \cdot 0.58} {N_{residue_{pool}} + NO_3Pool}</math>
 
<math>\epsilon_{C/N} = \frac{Residue_{pool} \cdot 0.58} {N_{residue_{pool}} + NO_3Pool}</math>
Line 345: Line 346:
  
  
−
mit
+
with
  
−
'' <math>\epsilon_{C/N}\!</math> =  C/N-Verhältnis [-]''
+
'' <math>\epsilon_{C/N}\!</math> =  C/N-relation [-]''
  
−
'' <math>\gamma_{ntr}\!</math> =  Residuenabbaufaktor [-]''
+
'' <math>\gamma_{ntr}\!</math> =  residue decomposition factor [-]''
  
−
'' <math>Residue_{pool}\!</math>  =  Residuenpool [kg/ha]''  
+
'' <math>Residue_{pool}\!</math>  =  residue pool [kg/ha]''  
  
−
'' <math>NO_3Pool\!</math>  =  Nitratpool [kgN/ha]''  
+
'' <math>NO_3Pool\!</math>  =  nitrate pool [kgN/ha]''  
  
−
'' <math>N_{residue_{pool}}\!</math> =  Stickstoffanteil des Residuenpools [kgN/ha]''
+
'' <math>N_{residue_{pool}}\!</math> =  residue pool's amount of nitrogen [kgN/ha]''
  
  
−
Aus <math>\gamma_{ntr}</math>, <math>\gamma_{water}</math>, <math>\gamma_{temp}</math> rechnet sich die Abbaukonstante des Residuenpools:
+
The decomposition constant of the residue pool is calculated with <math>\gamma_{ntr}</math>, <math>\gamma_{water}</math>, <math>\gamma_{temp}</math>:
  
 
'' <math>\delta_{ntr} = \beta_{rsd} \cdot \gamma_{ntr} \cdot \sqrt{\gamma_{water} \cdot \gamma_{temp}}\!</math>
 
'' <math>\delta_{ntr} = \beta_{rsd} \cdot \gamma_{ntr} \cdot \sqrt{\gamma_{water} \cdot \gamma_{temp}}\!</math>
  
  
−
mit
+
with
  
−
'' <math>\delta_{ntr}\!</math> =  Konstante der Rate des Residuenabbaus [-]''
+
'' <math>\delta_{ntr}\!</math> =  constant of the residue decomposition’s rate [-]''
  
−
'' <math>\gamma_{ntr}\!</math> =  Residuenabbaufaktor [-]''
+
'' <math>\gamma_{ntr}\!</math> =  residue decomposition factor [-]''
  
−
'' <math>\beta_{rsd}\!</math> =  Residuenabbaukoeffizient; Vorgabewert = 0.05 [-]''
+
'' <math>\beta_{rsd}\!</math> =  residue decomposition coefficient; default value = 0.05 [-]''
  
−
'' <math>\gamma_{water}\!</math>  = Bodenfeuchtekoeffizient [-]''
+
'' <math>\gamma_{water}\!</math>  = soil humidity coefficient [-]''
  
−
'' <math>\gamma_{temp}\!</math>  = Bodentemperaturkoeffizient [-]''
+
'' <math>\gamma_{temp}\!</math>  = soil temperature coefficient [-]''
  
−
Der Abbau des Residuenpools erfolgt anhand der Konstante der Rate des Residuenabbaus. Dabei wird der Stickstoffteil auf den aktiven organischen Pool, im Sinne einer Humifizierung und den Nitratpool im Sinne einer Mineralisierung, im Verhätnis 20 zu 80% aufgeteilt:
+
The decomposition of the residue pool is carried out with the constant of the residue decomposition’s rate. At this, the nitrogen part is allocated to the active organic pool, in terms of humification, and the nitrate pool, in terms of mineralization, in a ratio of 20:80.
  
 
<math>Residue_{pool}2 = Residue_{pool}1 - (\delta_{ntr} \cdot Residue_{pool}1)\!</math>
 
<math>Residue_{pool}2 = Residue_{pool}1 - (\delta_{ntr} \cdot Residue_{pool}1)\!</math>
Line 385: Line 386:
 
<math>N_{residue_{pool}}2 = N_{residue_{pool}}1 - (\delta_{ntr} \cdot N_{residue_{pool}}1)\!</math>
 
<math>N_{residue_{pool}}2 = N_{residue_{pool}}1 - (\delta_{ntr} \cdot N_{residue_{pool}}1)\!</math>
  
−
mit
+
with
  
−
'' <math>\delta_{ntr}\!</math> =  Konstante der Rate des Residuenabbaus [-]''
+
'' <math>\delta_{ntr}\!</math> =  constant of the residue decomposition’s rate [-]''
  
−
'' <math>Residue_{pool}1\!</math> = Residuenpool vor dem Zeitschritt [kgN/ha]''
+
'' <math>Residue_{pool}1\!</math> = residue pool before the time step [kgN/ha]''
  
−
'' <math>Residue_{pool}2\!</math> = Residuenpool nach dem Zeitschritt [kgN/ha]''
+
'' <math>Residue_{pool}2\!</math> = residue pool after the time step [kgN/ha]''
  
−
'' <math>N_{active_{pool}}1\!</math> = Aktiver organischer Pool vor dem Zeitschritt [kgN/ha]''
+
'' <math>N_{active_{pool}}1\!</math> = active organic pool before the time step [kgN/ha]''
  
−
'' <math>N_{active_{pool}}2\!</math> = Aktiver organischer Pool nach dem Zeitschritt [kgN/ha]''
+
'' <math>N_{active_{pool}}2\!</math> = active organic pool after the time step [kgN/ha]''
  
−
'' <math>NO_3Pool1\!</math> = Bodennitratpool vor dem Zeitschritt [kgN/ha]''
+
'' <math>NO_3Pool1\!</math> = soil nitrate pool before the time step [kgN/ha]''
  
−
'' <math>NO_3Pool2\!</math> = Bodennitratpool nach dem Zeitschritt [kgN/ha]''
+
'' <math>NO_3Pool2\!</math> = soil nitrate pool after the time step [kgN/ha]''
  
−
'' <math>N_{residue_{pool}}1\!</math> = Stickstoffanteil des Residuenpools vor dem Zeitschritt [kgN/ha]''
+
'' <math>N_{residue_{pool}}1\!</math> = residue pool's amount of nitrogen before the time step [kgN/ha]''
  
−
'' <math>N_{residue_{pool}}2\!</math> = Stickstoffanteil des Residuenpools nach dem Zeitschritt [kgN/ha]''
+
'' <math>N_{residue_{pool}}2\!</math> = residue pool's amount of nitrogen after the time step [kgN/ha]''
  
−
====Denitrifikation====
+
====Denitrification====
  
−
Denitrifikation findet statt wenn der Boden sich in einem nahezu wassergesättigten Zustand befindet. Die Rate ist dabei abhängig von dem Gehalt an organischem Kohlenstoff im Boden und der Bodentemperatur. Abweichend von SWAT (0,95) liegt der Grad der Wassersättigung bei dem Denitrifikation stattfindet mit 0,91 niedriger. Dies ist dadurch begründet, Dass SWAT die Luftkapazität des Bodens im Gegensatz zu J2000 nicht berücksichtigt und somit in J2000 das zu Grunde liegende Porenvolumen, bei der Berechnung der Wassersättigung größer ist. Es wird weiterhin sichergestellt, dass die Rate höchstens 1 kgN/ha*d beträgt, da höhere Raten im Freiland nicht zu erwarten sind.
+
Denitrification occurs when the soil is nearly water-saturated. The rate depends on the amount of organic carbon in the soil as well as on the soil temperature. In comparison to SWAT (0,95), the degree of water saturation is lower (0.91) when denitrification occurs. This is because SWAT - in contrast to J2000 - does not consider the soil's air capacity. Thus, the underlying pore volume for the calculation of water saturation is higher in J2000. Furthermore, it is ensured that the rate is at the most 1 kgN/ha*d since higher rates are not expected in open land.
  
  
Line 418: Line 419:
 
</math>
 
</math>
  
−
mit
+
with
  
−
'' <math>NO_3Pool\!</math> = Bodennitratpool [kgN/ha]''
+
'' <math>NO_3Pool\!</math> = soil nitrate pool [kgN/ha]''
  
−
'' <math>denit_{trans}\!</math> = Denitrifikationsrate [kgN/ha]''
+
'' <math>denit_{trans}\!</math> = denitrification rate [kgN/ha]''
  
−
'' <math>\gamma_{water}\!</math>  = Bodenfeuchtekoeffizient [-]''
+
'' <math>\gamma_{water}\!</math>  = soil humidity coefficient [-]''
  
−
'' <math>\gamma_{temp}\!</math>  = Bodentemperaturkoeffizient [-]''
+
'' <math>\gamma_{temp}\!</math>  = soil temperature coefficient [-]''
  
−
'' <math>\beta_{denit}\!</math> =  Denitrifikationskoeffizient; Vorgabewert = 0.91 [-]''
+
'' <math>\beta_{denit}\!</math> =  denitrification coefficient; default value = 0.91 [-]''
  
−
===Stofftransport mit der Wasserbewegung im Boden===
 
  
−
====Stickstoffkonzentration des mobilen Wassers====
+
===Mass Transport with Water Movement in the Soil===
  
 +
====Nitrogen Concentration of Mobile Water====
  
−
Für die Simulation des Stofftransports mit der Wasserbewegung wird zunächst die Stickstoffkonzentration des mobilen Wassers bestimmt. Hierbei wird vereinfachend angenommen, dass ausschließlich der Stickstoff des Nitratpools mobil ist und somit in die Berechnung eingeht. Die Wassermenge bestimmt sich aus den Bodenspeichern und den den Horizont verlassenden Wasserflüssen.  
+
 
 +
For the simulation of the mass transport caused by water movement, the nitrogen concentration of the mobile water is defined. Here, it is simplified assumed that only the nitrogen of the nitrate pool is mobile and therefore is taken into account for the calculation. The amount of water is determined on the basis of the soil storages and the water streams that leave the horizon.  
  
  
Line 451: Line 453:
 
<math>concN_{mobile} = \frac {NO_3Pool * (1 - \exp \frac{- mobile_{water}}  {(1 - \theta_{nit}) * soil_{water}})}  {mobile_{water}}</math>
 
<math>concN_{mobile} = \frac {NO_3Pool * (1 - \exp \frac{- mobile_{water}}  {(1 - \theta_{nit}) * soil_{water}})}  {mobile_{water}}</math>
  
−
mit
+
with
  
−
'' <math>NO_3Pool\!</math> = Bodennitratpool [kgN/ha]''
+
'' <math>NO_3Pool\!</math> = soil nitrate pool [kgN/ha]''
  
−
'' <math>soil_{water}\!</math> = Bodenwassergehalt [mm]''
+
'' <math>soil_{water}\!</math> = soil water [mm]''
  
−
'' <math>mobile_{water}\!</math>  = Menge an Mobilem Wasser [mm]''
+
'' <math>mobile_{water}\!</math>  = amount of mobile water [mm]''
  
−
'' <math>\Beta_{NO_{3}}\!</math>  = Perkolationskoeffizient; Vorgabewert = 0.2 [-] ''
+
'' <math>\Beta_{NO_{3}}\!</math>  = percolation coefficient; default value = 0.2 [-] ''
  
−
'' <math>RD1_{out}\!</math> =  Oberflächenabfluss [mm]''
+
'' <math>RD1_{out}\!</math> =  surface runoff [mm]''
  
−
'' <math>RD2_{out}\!</math>  = Interflow [mm]''
+
'' <math>RD2_{out}\!</math>  = interflow [mm]''
  
−
'' <math>h_{perco}\!</math>  = Perkolation in tieferen Horizont bzw. Grundwasser [mm]''
+
'' <math>h_{perco}\!</math>  = percolation in deeper horizons or ground water [mm]''
  
−
'' <math>hor_{by_{infilt}}\!</math> =  Infiltrations Wasser, dass in einem Zeitschritt in tiefere Schichten vordringt und somit den aktuellen Horizont "bypasst" [mm]''
+
'' <math>hor_{by_{infilt}}\!</math> =  infiltration water that goes into deeper layers in a time step and therefore passes by the actual horizon [mm]''
  
−
'' <math>diff_{out}\!</math> =  Wasser, dass durch Diffusion den Horizont verlässt [mm]''
+
'' <math>diff_{out}\!</math> =  water that leaves the horizon via diffusion [mm]''
  
−
'' <math>\theta_{nit}\!</math> =  Fraktion des Porenvolumens von dem Anionen ausgeschlossen sind (durch positiven Ladungsüberschuss der Tonminerale); Vorgabewert = 0.05 [-]''
+
'' <math>\theta_{nit}\!</math> =  fraction of the pore volume from which anions are excluded (due to positive charge preponderance of the clay mineral); default value = 0.05 [-]''
  
−
'' <math> concN_{mobile}\!</math> = Stickstoffkonzentration des mobilen Wassers [kgN/ha*mm]''
+
'' <math> concN_{mobile}\!</math> = nitrogen concentration of the mobile water [kgN/ha*mm]''
  
−
Das der Einfluss des Infiltrations Wassers, dass dass in einem Zeitschritt in tiefere Schichten vordringt wird mit Hilfe eines Parameters (<math>infil_{conc_{factor}}</math>) wie folgt bestimmt. Dabei repräsentiert dieser Parameter in wie weit das "Bypasswasser" mit der Bodenmatrix interagiert oder in Makroporen an den durchflossenen Schichten vorbeifliest.
+
The influence of the water that expands into deeper horizons in a time step is determined with a parameter (<math>infil_{conc_{factor}}</math>). At this, the parameter represents to what extend the bypass water interacts with the soil matrix or bypasses the layers that are flown through in macro pores.
  
 
<math>hor_{by_{infilt}}[i-1] = \sum^{n}_{i}{hor_{by_{infilt}}} * infil_{conc_{factor}}  \!</math>
 
<math>hor_{by_{infilt}}[i-1] = \sum^{n}_{i}{hor_{by_{infilt}}} * infil_{conc_{factor}}  \!</math>
  
−
mit
+
with
  
−
'' <math>hor_{by_{infilt}}\!</math> =  Infiltrations Wasser, dass in einem Zeitschritt in tiefere Schichten vordringt und somit den aktuellen Horizont "bypasst" [mm]''
+
'' <math>hor_{by_{infilt}}\!</math> =  infiltration water that goes into deeper layers in a time step and therefore passes by the actual horizon [mm]''
  
−
'' <math>infil_{conc_{factor}}\!</math> =  Bypassparameter [mm]''
+
'' <math>infil_{conc_{factor}}\!</math> =  bypass parameter [mm]''
  
−
'' <math>i\!</math> =  Aktueller Horizont [-]''
+
'' <math>i\!</math> =  actual horizon [-]''
  
−
'' <math>n\!</math> =  Anzahl der Horizonte [-]''
+
'' <math>n\!</math> =  number of horizons [-]''
  
−
====Stickstofftransport in den Abflusskomponenten====
+
====Nitrogen Transport in the Runoff Components====
  
−
Basierend auf der Stickstoffkonzentration des mobilen Wassers werden für die einzelnen Horizonte die Stickstofffrachten für die Abflusskomponenten berechnet. Hierbei wird der Interflow in allen Horizonten und der Oberflächenabfluss nur im obersten Horizont berücksichtigt, während die Perkolation immer in den tiefer gelegenen Horizont bzw. in die Grundwasserspeicher erfolgt.  
+
For the individual horizons the nitrogen loads for the runoff components are calculated on the basis of the mobile water's nitrogen concentration. At this, the interflow is considered in all horizons whereas the surface runoff is only considered in the top horizon. However, the percolation occurs in the deeper horizons or in the ground-water reservoir.
 +
  
 
<math>N_{surface} = Beta_{NO_3} \cdot RD1_{out} \cdot concN_{mobile}\!</math>
 
<math>N_{surface} = Beta_{NO_3} \cdot RD1_{out} \cdot concN_{mobile}\!</math>
Line 500: Line 503:
  
  
−
mit
+
with
  
−
'' <math> concN_{mobile}\!</math> = Stickstoffkonzentration des mobilen Wassers [kgN/ha*mm]''
+
'' <math> concN_{mobile}\!</math> = nitrogen concentration of the mobile water [kgN/ha*mm]''
  
−
'' <math>hor_{by_{infilt}}\!</math> =  Infiltrations Wasser, dass in einem Zeitschritt in tiefere Schichten vordringt und somit den aktuellen Horizont "bypasst" [mm]''
+
'' <math>hor_{by_{infilt}}\!</math> =  infiltration water that goes in deeper layers and thus bypasses the actual horizon in a time step [mm]''
  
−
'' <math>N_{surface}\!</math> =  Stickstoff im Oberflächenabfluss [kgN/ha]''
+
'' <math>N_{surface}\!</math> =  nitrogen in the surface runoff [kgN/ha]''
  
−
'' <math>N_{interflow}\!</math> =  Stickstoff im Interflow [kgN/ha]''
+
'' <math>N_{interflow}\!</math> =  nitrogen in the interflow [kgN/ha]''
  
−
'' <math>N_{perco}\!</math> =  Stickstoff im Perkolationswasser [kgN/ha]''
+
'' <math>N_{perco}\!</math> =  nitrogen in the percolation water [kgN/ha]''
  
−
'' <math>RD1_{out}\!</math> =  Oberflächenabfluss [mm]''
+
'' <math>RD1_{out}\!</math> =  surface runoff [mm]''
  
−
'' <math>RD2_{out}\!</math> =  Interflow [mm]''
+
'' <math>RD2_{out}\!</math> =  interflow [mm]''
  
−
'' <math>h_{perco}\!</math> =  Perkolation [mm]''
+
'' <math>h_{perco}\!</math> =  percolation [mm]''
  
−
'' <math>Beta_{NO_3}\!</math> =  Percolationskoeffizient [-]''
+
'' <math>Beta_{NO_3}\!</math> =  percolation coefficient [-]''
  
−
Der Perkolationskoeffizient stellt dabei ein Maß für die Interaktion des Oberflächenabfluss mit der Bodenmatrix des obersten Horizontes dar und Bestimmt somit den Stickstoffgehalt des Oberflächenabflusses.
+
The percolation coefficient represents a measurement for the interaction of the surface runoff and the soil matrix of the top horizon and therefore determines the surface runoff's amount of nitrogen.  
  
−
Der Stoff der mit dem Diffusionswasser den Horizont verlässt wird wie folgt berechnet. Als Diffusion wird dabei die Wasserbewegung bezeichnet die aufgrund von Potentialgradienten oberhalb der Feldkapazität stattfindet. Ein negativer Wert für das Diffusionswasser bedeutet hierbei eine absteigende Wasserbewegung während ein positiver Wert eine aufsteigende Wasserbewegung repräsentiert.
+
The material that leaves the horizon with the diffusion water can be calculated as follows: the water movement that occurs above the field capacity due to potential gradients is called diffusion. Here, a negative value for the diffusion water means a downward water movement whereas a positive value represents an upward water movement.
  
 
   
 
   
Line 533: Line 536:
 
</math>
 
</math>
  
−
und
+
and
  
 
<math>NO_3Pool[i] = NO_3Pool[i] + diffoutN \!</math>
 
<math>NO_3Pool[i] = NO_3Pool[i] + diffoutN \!</math>
  
−
und
+
and
  
 
<math>NO_3Pool[i+1] = NO_3Pool[i+1] - diffoutN \!</math>
 
<math>NO_3Pool[i+1] = NO_3Pool[i+1] - diffoutN \!</math>
  
−
mit
+
with
  
−
'' <math> concN_{mobile}\!</math> = Stickstoffkonzentration des mobilen Wassers [kgN/ha*mm]''
+
'' <math> concN_{mobile}\!</math> = nitrogen concentration of the mobile water [kgN/ha*mm]''
  
−
'' <math>diffoutN \!</math> =  Stickstoff im Diffussionswasser [kgN/ha]''
+
'' <math>diffoutN \!</math> =  nitrogen in the diffusion water [kgN/ha]''
  
−
'' <math>NO_3Pool\!</math> =  Bodennitratpool [kgN/ha]''
+
'' <math>NO_3Pool\!</math> =  soil nitrate pool [kgN/ha]''
  
−
'' <math>w_{l_{diff}}\!</math> =  Diffussionswasser [mm]''
+
'' <math>w_{l_{diff}}\!</math> =  diffusion water [mm]''
  
−
'' <math>i\!</math> =  Bodenhorizont [kgN/ha]''
+
'' <math>i\!</math> =  soil horizon [kgN/ha]''
  
  
Line 560: Line 563:
 
----
 
----
  
−
==Bodentemperaturmodul==
+
==Soil Temperature Module==
−
 
+
  
−
Für die Stoffhaushaltsmodellierung ist die Bodentemperatur eine bedeutende Steuergröße. Insbesondere mikrobiologische Prozesse wie Nitrifikation, Denitrifikation und Umsetzung von organischem Stickstoff in der Bodenzone werden stark von der vorherrschenden Temperatur beeinflusst.
 
−
Auch in dem hier erstellten Modell J2K-S spielt die Bodentemperatur bei der Berechnung der folgenden Prozesse eine Rolle (vgl. [[Bodenstickstoffmodul]]):
 
  
−
• Nitrifikation
+
The soil temperature is an important measurement for the matter regime modeling. Especially microbiological processes such as nitrification, denitrification and the transformation of organic nitrogen in the soil zone is strongly influenced by the prevailing temperature.
 +
In the here developed model J2K-S the soil temperature also plays an important role for the calculation of the following processes (see [[Soil_Nitrogen_Module_empty|Soil Nitrogen Module]]):
  
−
• Volatilation
+
• nitrification
  
−
• Umsetzung organischer Substanz
+
• volatilation
  
−
• Abbau von Pflanzenresten
+
• transformation of organic substance
  
−
• Denitrifikation
+
• decomposition of plant remains
  
 +
• denitrification
  
−
''Aufbau des Moduls''
+
''Structure of the Module''
  
−
 
+
The soil temperature is simulated according to the empirical routines of SWAT (Arnold et al. 1998) and EPIC (Williams et al. 1984). At first, a surface soil temperature is generated for bare ground on the basis of the air temperature and insolation. This surface temperature is modified by attenuation factors that describe the effect of biomass and snow. The temperature of the different soil horizons is generated as upper boundary condition between the surface soil temperature and the long lasting mean temperature as lower boundary condition. At this, the attenuation effect of the soil is defined in consideration of the soil humidity and the bulk density. The equations of the individual processes can be found in Neitsch et al. (2002).
−
Die Bodentemperatur wird in Anlehnung an die empirischen Routinen von SWAT (Arnold et al. 1998) und EPIC (Williams et al. 1984) simuliert. Zunächst wird aus der Lufttemperatur und der Einstrahlung eine Bodenoberflächentemperatur für unbewachsenen Boden ermittelt. Diese Oberflächentemperatur wird durch Dämpfungsfaktoren, die die Wirkung von Biomasse und Schnee beschreiben, modifiziert. Die Temperatur der verschiedenen Bodenhorizonte wird zwischen der Bodenoberflächentemperatur als obere Randbedingung und der langjährigen mittleren Temperatur als untere Randbedingung ermittelt. Hierbei wird die Dämpfungswirkung des Bodens unter Berücksichtigung der Bodenfeuchte und der Lagerungsdichte bestimmt. Die Gleichungen für die einzelnen Prozesse finden sich bei Neitsch et al. (2002).
+
  
  
 
[[Bild:Bodentemperaturmodul.jpg]]
 
[[Bild:Bodentemperaturmodul.jpg]]
  
−
Abbildung 1: Struktur des Bodentemperaturmoduls
+
Figure 1: Structure of the soil temperature model
  
  
 
[[Bild:Bodentemperaturtest.jpg]]
 
[[Bild:Bodentemperaturtest.jpg]]
  
−
Abbildung 2: Ergebnisse der Bodentemperaturmodellierung für die Bodenoberfläche und in 40 cm Tiefe an einem Testhang bei Zeulenroda (Thüringen).
+
Figure 2: Results of the soil temperature modeling for the surface area and at 40 cm depth at an investigated slope near Zeulenroda (Thuringia).
  
  
−
Die Abbildung zeigt die gemessene und modellierte Temperatur an der Bodenoberfläche (oberes Bild) sowie in 40 cm Tiefe (unteres Bild) für ein Testfeld in der nähe der Talsperre Zeulenroda. Es ist erkennbar, dass trotz gewisser Abweichungen der Temperaturverlauf gut nachvollzogen wird. Dies wird durch die hohen Bestimmtheitsmaße von rund 0.95 noch unterstrichen.
+
This figure shows the measured and modeled temperature at the surface (upper figure) as well as at 40 cm depth (lower figure) for an investigated area near the dam Zeulenroda. It can be seen that the temperature curve can be followed quite well in spite of certain deviations. This is emphasized by the high coefficient of determination of about 0.95.
  
 
----
 
----
−
==Pflanzenwachstumsmodul==
 
  
−
Die Beschreibung zur Simulation des Pflanzenwachstums ist für eine Vielzahl von hydrologischen und Stofftransport-Prozessen wichtig, wie z.B. für die Interzeption oder die Stickstoffaufnahme durch den Pflanzenbestand. Das Pflanzenwachstum wird prinzipiell über die Simulation der Blattflächenentwicklung (LAI), der Lichtinterzeption und der Transformation in Biomasse gesteuert und erfolgt in Anlehnung an SWAT (Arnold et al. 1998). Dabei wird zunächst von einem potenziellen, d.h. unter optimalen Bedingungen vorliegenden, Pflanzenwachstum ausgegangen, welches unter Einbeziehung von Stressfaktoren modifiziert wird.
+
==Plant Growth Module==
  
 +
The description for the simulation of plant growth is important for numerous hydrological mass transport processes, e.g. for the interception or the nitrogen uptake by the canopy. Plant growth is usually controlled via the simulation of the leaf area development (LAI) as well as the light interception and the transformation into biomass and is carried out according to SWAT (Arnold et al. 1998). At this, it is assumed that a potential plant growth, i.e. under optimum conditions, exists which is then modified in consideration of stress factors.
  
−
''Temperaturentwicklung und Wärmesummen''
 
  
 +
''Temperature Development and Heat Units''
  
−
Wichtigster Faktor für die Entwicklung des Pflanzenbestandes ist die Temperatur, deren Kennwerte für jede Pflanze unterschiedlich sind. Daher verfügt jede Pflanze über eine eigene Basistemperatur, die erreicht werden muss, um ein entsprechendes Wachstum auszulösen. Das Wachstum erhöht sich über die Optimumtemperatur bis es beim Überschreiten der Maximaltemperatur deutlich eingeschränkt wird.
 
−
Der pflanzenspezifische Wachstumsverlauf erfolgt über die Generierung der Wärmesummen (‚heat units = HU’). Die zugrunde liegende Hypothese hierfür beruht auf der Annahme, dass Pflanzen einen spezifischen Wärmebedarf haben, der bis zum Erreichen des Erntezustands quantifizierbar ist. Eine ‚HU’ ist als eine phänologisch wirksame Temperatureinheit definiert. Sie ergibt sich aus der täglich akkumulierten Tagesdurchschnittstemperatur, die oberhalb der pflanzenspezifischen Basistemperatur liegt. Besitzt eine Maispflanze z.B. eine Basistemperatur von 7° C und unterliegt einer Tagestemperatur von 15° C, so ergeben sich für diesen Fall 15 – 7 = 8 HU's. Auf diese Weise werden, unter Bekanntgabe der Aussaat- und Erntezeitpunkte sowie der täglichen Mittelwertstemperaturen, die individuellen Wärmesummenentwicklungen für jede Landnutzungsart simuliert. Anhand der Wärmesummenentwicklung wird der Entwicklungsverlauf des Wurzelwachstums und des Blattflächenindex gesteuert. Hierbei wird vereinfachend davon ausgegangen, dass die Pflanzen zunächst ihre Enregie in die Blattentwicklung und das Wurzelwachstum investieren. Diese Vereinfachung bedeutet auch, dass die Entwicklung von Blättern und Wurzeln unabhängig von der Wasser- und Nährstoffversorgung simuliert wird. Weiterhin wird der Reifegrad der Pflanze, der den maximalen Stickstoffgehalt in der Biomasse beeinflusst, ausschließlich über die Temperatursumme gesteuert.
 
  
 +
The most important factor that determines the canopy’s development is the temperature whose parameters are different for each plant. Therefore, each plant possesses a basis temperature that needs to be reached in order to activate a certain growth. The growth increases until the optimum temperature is reached and decreases noticeably when the maximum temperature is exceeded. The plant-specific growth development is carried out via the generating of heat units (=HU). The underlying hypothesis for this is the assumption that plants have a specific heat demand that is quantifiable until the necessary maturity state for the harvest is reached. An ‘HU’ is defined as a phenological effective temperature unit. An HU results from the daily accumulated daily average temperature that lies above the plant-specific basis temperature. Assumed that a maize plant has a basis temperature of 7° C and is exposed to a daily temperature of 15° C, its HU would be calculated as follows: 15 – 7 = 8 HUs. In this way, the individual heat unit developments are simulated for each land use type in consideration of the time of the sowing and harvest as well as the daily average temperature. The development of the root growth and the leaf area index is controlled via the heat unit development. At this, it is assumed that the plants invest their energy into the leaf development and the root growth. This simplified view also means that the development of leafs and roots is independent on water and nutrient supply. Furthermore, the plant’s degree of maturity which influences the amount of nitrogen in the biomass is exclusively controlled via the temperature sum.
  
−
''Biomasseentwicklung''
 
  
 +
''Biomass Development ''
  
−
Die Biomasseentwicklung selbst wird zunächst als potenzielle Biomasse simuliert. Steuernde Größe für die Biomasseentwicklung ist hierbei die photosyntetisch wirksame Strahlung. So wird für jeden Tag anhand der Strahlung und der Blattfläche ein potenzieller Biomassezuwachs ermittelt (vgl. Abbildung 1).
+
 
 +
The biomass development is simulated as potential biomass at first. At this, the photosyntetic radiation is the controlling unit for the biomass development. Thus, a potential biomass increase is generated for each day with the help of the radiation and leaf area (see figure 1).  
  
  
 
[[image:Pflanzenwastumsmodul1.jpg]]  
 
[[image:Pflanzenwastumsmodul1.jpg]]  
  
−
Abbildung 1: Aufbau des Pflanzenwachstumsmoduls
+
Figure 1: Structure of the plant growth module
  
  
−
Dieser tägliche Biomassezuwachs wird anhand von Stressfaktoren auf den aktuellen Biomassezuwachs reduziert. Die Stressfaktoren sind hierbei Stickstoffversorgung, Temperatur und Wasserversorgung (vgl. Abbildung 2).
+
This daily biomass increase is reduced to the actual biomass increase with the help of stress factors, which are nitrogen supply, temperature and water supply (see figure 2).  
  
  
 
[[image:Pflanzenwastumsmodul2.jpg]]  
 
[[image:Pflanzenwastumsmodul2.jpg]]  
  
−
Abbildung 2: Aufbau des Wachstumsstresses
+
Figure 2: Structure of the growth’s stress
  
  
−
Der zu einem Punkt in Raum und Zeit am stärksten wirkende Stressfaktor bestimmt, nach dem Prinzip der limitierenden Faktoren, die aktuelle Biomasseentwicklung. Dies hat wiederum eine Rückwirkung auf den Stickstoffbedarf.
+
The stress factor that has the strongest effects at a point in space and time determines the actual biomass according to the principle of limiting factors. This, in turn, influences the nitrogen demand.  
 
----
 
----
−
==Landnutzungsmanagementmodul==
 
  
−
Die Beschreibung des Landnutzungsmanagements erfolgt in Anlehnung an die Methodik im Modell SWAT (Arnold et al. 1998). Das Landnutzungsmanagementmodul realisiert die Möglichkeit komplexe Fruchtfolgen in J2k-S darzustellen. Ausgehend von Managementoperationen wie Aussaat, Düngung und Ernte werden einzele Feldfrüchte charakterisiert. Wie in Abbildung 1 dargestellt, bezieht sich die Fruchtfolge auf eine aktuelle Pflanze, die sich wiederum aus den Pflanzenparametern und den einzelnen Managementoptionen zusammensetzt.
+
==Land Use Management Module==
 +
 
 +
The description of the land use management is carried out according to the methodology in the SWAT model (Arnold et al. 1998). The land use management module offers to represent complex crop rotations in J2k-S. The individual field crops are characterized on the basis of management operations like sowing, fertilizing and harvesting. As can be seen in figure 1, the crop rotation relates to an actual plant that in turn is build up of the plant parameters and the individual management options.  
  
  
 
[[Bild:Pflanzenmanagementmodul1.jpg]]
 
[[Bild:Pflanzenmanagementmodul1.jpg]]
  
−
Abbildung 1: Funktionsschema des Landnutzungsmanagementmoduls
+
Figure 1: Flow chart of the land use management module
  
  
  
−
Die grundlegenden Bausteine (Basisobjekte) zur Beschreibung des Landnutzungsmanagements sind Bodenbearbeitung (bisher noch ohne Funktion), Düngung, Pflanzeneigenschaften und die Fruchtfolge selbst. Während die Managementoptionen Bodenbearbeitung und Düngung mit einfachen Parametern wie Durchmischungseffizienz, Bearbeitungstiefe, Düngemenge, Ammonium- und Nitratanteil auskommen, ist das Pflanzenobjekt mit zahlreichen Parametern versehen. Die Fruchtfolge ist dann nur noch eine einfache Liste mit der Reihenfolge der einzelnen Feldfrüchte (vgl. Abbildung 2).
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The basic basis objects for the description of the land use management are cultivation (no function yet), fertilization, plant characteristics and the crop rotation. Land management and fertilization as management options have only simple parameters like mixing efficiency, machining depth, amount of fertilizer, ammonium and nitrate. However, the plant object possesses numerous parameters. Thus, the crop rotation is a simple list with the order of the individual crops (see figure 2).  
  
  
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[[Bild:Pflanzenmanagementmodul2.jpg]]
 
[[Bild:Pflanzenmanagementmodul2.jpg]]
  
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Abbildung 2: Grundlegenden Bausteine (Basisobjekte)
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Figure 2: Essential components (basic objects)
  
  
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Zur Erläuterung ist in Abbildung 3 ein Ausschnitt einer Managementparameterdatei dargestellt. In der ersten Zeile findet sich eine Bodenbearbeitungsmaßnahme. Darauf folgt die Aussaat des im Beispiel verwendeten Maises. Es finden weiterhin 3 Düngemaßnahmen mit verschiedenen Düngern statt. Weiterhin ist die Ernte mit dem geernteten Anteil der Biomasse angegeben. Der Rest verbleibt auf dem Feld und wird dem Residuen-Pool im Bodenstickstoffmodul zugeführt. Zum Abschluss findet in diesem Beispiel noch eine Bodenbearbeitung statt.
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As an explanation in figure 3 a detail of a management parameter file is shown. In the first line a cultivation type can be found. Thereupon, the sowing of the maize that was used in the example follows. Furthermore, three fertilizations with three different fertilizers are carried out. The harvest with the amount of biomass is given. The rest remains on the field and is allocated to the residue pool in the nitrogen module. Finally, cultivation is carried out in this example.  
  
  
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Abbildung 3: Aufbau einer Managementparameterdatei
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Figure 3: Structure of a management parameter file
  
  
  
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Mit diesem Modul ist es möglich, die wesentlichen Tätigkeiten des pflanzenbaulichen Management flexibel abzubilden und Managementalternativen darzustellen.
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With the help of this tool, the essential activities of the horticultural management as well as alternatives can be represented flexibly.  
 
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==Grundwasserstickstoffmodul==
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==Ground Water Nitrogen Module==
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The description of the nitrogen’s dynamics that occurs in the ground water is carried out according to the ground water dynamics used in J2k. At this, the nitrogen load is – corresponding to the water – allocated to the two ground-water reservoirs RG1 and RG2. The water and matter proportions are generated for both ground-water reservoirs. The output is carried out analogue to the water and the generated proportions. It is possible to set up an origin nitrogen concentration.
  
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Die Beschreibung der Dynamik des Stickstoffes im Grundwasser wird in Anlehnung an die in J2k verwendete Grundwasserdynamik durchgeführt. Hierbei wird die Stofffracht entsprechend der Verteilung des Wassers auf die beiden Grundwasserspeicher RG1 und RG2 aufgeteilt. Es werden für beide Grundwasserspeicher getrennt die Wasser- und Stoffgehalte ermittelt. Die Abgabe erfolgt analog zum Wasser und den ermittelten Gehalten. Es ist möglich eine Anfangsstickstoffkonzentration vorzugeben.  
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Besides, an attenuation factor is implemented that delays the change of the nitrogen proportions in the storage. This factor used for the calibration can be set up for both ground-water reservoirs separately. It represents the mixing and diffusion effects in the aquifer.  
  
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Auserdem wurde noch ein Dämpfungsfaktor implementiert, der die Änderung der Stickstoffgehalte im Speicher verzögert. Dieser, zur Kalibration verwendbare Faktor, ist für beide Grundwasserspeicher getrennt einstellbar. Er repräsentiert Durchmischungs- und Diffusionseffekte im Grundwasserleiter.
 
  
  
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Zurück zu [[Modelle]]
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Back to [[Models]]

Latest revision as of 17:24, 30 November 2011

The water and nutrient balance model J2000-S offers a simulation of the water and nitrogen balance of meso scale catchment areas. The model is an extension to the J2000 model with which it shares most of the components for the description of the hydrologic cycle. The additional components, soil temperature, soil nitrogen balance, land use management, plant growth as well as ground water nitrogen balance, are described for the specification of the nitrogen balance. Further modules are adapted for the demands of the nitrogen balance.


Contents

Soil Nitrogen Module

The description of the soil nitrogen balance is carried out similarly to the SWAT model (Arnold et al. 1998). Within the individual soil horizons the five nitrogen pools for nitrate, ammonium, stable organic substances, active organic substance and fresh plant remains as biomass are distinguished. The fluxes and transformations between the pools and outside the soil, like nitrification, denitrification, mineralization, volatilation, plant uptake and eluviation, are calculated via the empirical relations against the soil humidity and soil temperature. The nitrogen flux is passed as well as the water transport via a routing method between the subareas to the receiving stream (see figure 1).

The nitrogen input caused by fertilization and Bestandesabfall as well as the removal through the plants is provided by the plant growth module and the land use management module. The mineral inputs are allocated to the ammonium pool or directly to the nitrate pool. The organic nitrogen is either allocated to the Bestandesabfall pool or the active organic pool. The latter is poised with the stable organic pool. The nitrate pool is the central allocation section for the discharge as eluviation, plant uptake and denitrification. The processes described in the module take place in free parameterizable soil horizons. Here, the delivery of organic substances and fertilizer as well as the removal of nitrogen with the surface runoff are limited to the top horizon.


Bild:Bodenstickstoffmodul.jpg

Figure 1: Structure of the soil nitrogen module

The here applied nitrogen module contains some simplifications. Thus, no plant uptake from the ammonium pool is offered. Furthermore, the decomposition of organic substances is directly simulated to nitrate without any detour via ammonium. The N immobilization from mineral to organic nitrogen in the soil zone is neglected completely. The water transport of nitrogen is shown very generalized. Thus, a complete mixing of nitrogen in the individual storages takes place instead of advection and dispersion. The individual processes are described in the model as follows:


Plant Uptake

At first, the plant’s demands (potential plant uptake) which shall be met by the soil nitrogen storage on the day t0 are generated:

potNup= BioNopt - BioN \! [1]

with:

potNup\! = potential plant uptake [kgN/ha]

BioNopt\! = optimal biomass [kgN/ha]

BioN\! = actual biomass [kgN/ha]

Afterwards, the proportions of the soil horizons which lie within the effective root zone are generated. At this, the horizons which lie entirely within the root zone are taken into account completely (partroot = 1). However, the horizon which lies only partly in the root zone is only considered partly:

partroot[i] = \frac {rootdepth - layerdepth[i - 1]}{layerdepth[i] - layerdepth[i - 1]} \! [2]

with:

i\! = horizon [-]

partroot\! = proportion of the horizon at the root zone [-]

layerdepth\! = lower threshold of soil horizon [-]

The allocation of the n-uptake to the individual horizons is carried out against a calibration parameter (\beta_{Ndist}\!). At this, the potential uptake for the individual horizons is calculated:

potNup_z[i] = \frac {potNup} {1 - \exp(-\beta_{Ndist})} \cdot \left(1 - \exp\left(-\beta_{Ndist} * \frac {layerdepth[i]} {rootdepth}\right)\right) - uptake[i-1] [3]

with:

i\! = horizon [-]

partroot\! = proportion of the horizon at the root zone [-]

layerdepth\! = lower threshold of the soil horizon [-]

potNup\! = potential plant uptake [kgN/ha]

potNup_z\! = potential plant uptake in the individual horizons [kgN/ha]

uptake\! = potential plant uptake which has been taken from upper horizons already [kgN/ha]

\beta_{Ndist}\! = distribution parameter of the plant uptake; default value = 1.0; possible values 1 - 15 [-]

For the calculation of the potential plant uptake which is met by upper horizons already, the following connection is applied: uptake = uptake + potNup_z[i] \! [4]

potNup_z\! = potential plant uptake in the individual horizons [kgN/ha]

uptake\! = potential plant uptake which has been taken from upper horizons already [kgN/ha]


The calculation of a demand is carried out according to the following equation:

demand = (NO_3Pool[i] \cdot partroot[i]) - potNup_z[i] \! [5]

with:

i\! = horizon [-]

partroot\!t = proportion of the horizon of the root zone [-]

demand\! = demand that can be met by the soil nitrogen pool [kgN/ha]

NO_3Pool\! = soil nitrogen pool [kgN/ha]

potNup_z\! = potential plant uptake in the individual horizons [kgN/ha]

If this demand is greater than 0, it can be met by the existing nitrogen storage with:

NO_3Pool2[i] = \begin{cases} NO_3Pool1[i] - potNup_z[i] & \mathrm{f\ddot{u}r} \; \; demand >= 0 \\ NO_3Pool1[i] - (NO_3Pool1[i] \cdot partroot[i])& \mathrm{f\ddot{u}r} \; \; demand < 0 \end{cases}

and

demand = \begin{cases} demand[i] = 0 & \mathrm{f\ddot{u}r}\; \; demand >= 0 \\ demand[i] = demand &\mathrm{f\ddot{u}r} \; \; demand < 0 \end{cases}

with

i\! = horizon [-]

demand\! = demand that can be met by the soil nitrogen pool [kgN/ha]

NO_3Pool1\! = soil nitrate pool before the time step [kgN/ha]

NO_3Pool2\! = soil nitrate pool after the time step [kgN/ha]

potNupz\! = potential plant uptake in the individual horizons [kgN/ha]

partroot\! = proportion of the horizon of the root zone [-]


Aterwards, the actual plant uptake can be calculated on the basis of the potential plant uptake and the demand that has been summed up via the horizons:

N_{uptake} = potNup + \sum^{n}_{i=1}{demand[i]} \! [10]

with

i\! = horizon [-]

n\! = number of horizons in the root zone [-]

demand\! = demand which can be met by the soil nitrogen pool [kgN/ha]

potNup\! = potential plant uptake [kgN/ha]

N_{uptake}\! = actual plant uptake [kgN/ha]

Nitrate Rising by Evaporation

Soil water from deeper layers is transported into upper horizons via the evaporation flux. This happens for each horizon according to the SWAT method:

n_{upmove} = 0.1 \cdot NO_3Pool \cdot \frac {aEvap} {act_{LPS} + act_{MPS} + sto_{FPS}} \! [1]

with

n_{upmove}\! = amount of nitrogen from the individual horizon which is transported by evaporation [kgN/ha]

NO_3Pool\! = soil nitrogen pool [kgN/ha]

aEvap\! = actual evapotranspiration of the horizon [l]

act_{LPS}\! = actual large pore storage of the horizon [l]

act_{LPS}\! = actual middle pore storage of the horizon [l]

sto_{FPS}\! = fine pore storage of the horizon [l]

Transformation Processes in the Soil

Nitrification and Ammonium Volatilation

The transformation processes of the ammonium pool in this model are the nitrification from ammonium to nitrate and the ammonium volatilation. The calculation of the total transformation of the ammonium pool is carried out for both processes together. Afterwards, the rates for both processes are separated. In order to represent the influence of the temperature, the following coefficient needs to be calculated:

\eta_{temp} = 0.41 \cdot \frac {temp_{Layer} - 5} {10}\! [1]

with

\eta_{temp}\! = soil temperature coefficient [-]

temp_{Layer}\! = temperature of the soil layer [°C]


The influence of the soil humidity on the nitrification is described via the coefficient eta_water:

for act_{LPS} + act_{MPS} < 0.25 \cdot (sto_{LPS} + sto_{MPS})\!

\eta_{water} = \frac{act_{LPS} + act_{MPS} + sto_{FPS}} {0.25 \cdot (sto_{LPS} + sto_{MPS} + sto_{FPS})} \! [2]

for act_{LPS} + act_{MPS} >= 0.25 \cdot (sto_{LPS} + sto_{MPS}) \!

\eta_{water} = 1 \! [3]

with

\eta_{water}\! = soil humidity coefficient [-]

sto_{LPS}\! = maximum large pore storage of the horizon [l]

sto_{MPS}\! = maximum middle pore storage of the horizon [l]

sto_{FPS}\! = maximum fine pore storage of the horizon [l]

act_{LPS}\! = actual large pore storage of the horizon [l]

act_{MPS}\! = actual middle pore storage of the horizon [l]


The dependency of the ammonium volatilation on the soil depth is calculated with the following equation:

\eta_{vol_z} = 1 - \frac {layerdepth} {layerdepth + \exp (4.706 - (0.305 \cdot \frac {layerdepth}{20}))}\!

\eta_{vol_z}\! = soil depth coefficient [-]

layerdepth\! = layer depth of the horizon [cm]

The Gesamtumsatz of the ammonium pool can be calculated as follows:

N_{nit + vol} = NH_4Pool * (1 - \exp(-(\eta_{water} \cdot \eta_{temp})-(\eta_{vol_z} \cdot \eta_{temp})))\!

This Gesamtumsatz is then distributed into:

frac_{nitr} = 1 - \exp(-(\eta_{water} \cdot \eta_{temp}))\!

frac_{vol} = 1 - \exp(-(\eta_{vol_z} \cdot \eta_{temp}))\!

nitri_{trans} = (frac_{nitr} /(frac_{nitr} + frac_{vol})) \cdot N_{nit + vol} \!

volati_{trans} = (frac_{vol} /(frac_{nitr} + frac_{vol})) \cdot N_{nit + vol} \!

with

\eta_{water} \! = soil humidity coefficient [-]

\eta_{temp}\! = soil temperature coefficient [-]

\eta_{vol_z}\! = soil depth coefficient [-]

NH_4Pool\! = soil humidity coefficient [kgN/ha]

N_{nit + vol}\! = Gesamtumsatz of the ammonium pool [kgN/ha]

frac_{nitr}\! = fraction nitrification [-]

frac_{vol}\! = fraction ammonium volatilation [-]

nitri_{trans}\! = amount of nitrification [kgN/ha]

volati_{trans}\! = amount of ammonium volatilation [kgN/ha]


Pre-calculation for the Influence of Environmental Conditions

In order to show the influence of the soil temperature and soil humidity in the different transformation processes, the following coefficients need to be calculated beforehand: U

\gamma_{temp} = 0.9 \cdot \frac {temp_{Layer}} {temp_{Layer} \cdot \exp(9.93 - 0.312 \cdot temp_{Layer}} + 0.1 \! [1]

with

\gamma_{temp}\! = soil temperature coefficient [-]

temp_{Layer}\! = temperature of the soil layer [°C]


\gamma_{water} = \frac {act_{LPS} + act_{MPS} + sto_{FPS}} {sto_{LPS} + sto_{MPS} + sto_{FPS})} \! [2]

with

\gamma_{water}\! = soil humidity coefficient [-]

sto_{LPS}\! = maximum large pore storage of the horizon [l]

sto_{MPS}\! = maximum middle pore storage of the horizon [l]

sto_{FPS}\! = maximum fine pore storage of the horizon [l]

act_{LPS}\! = actual large pore storage of the horizon [l]

act_{MPS}\! = actual middle pore storage of the horizon [l]


Transfer between the Organic Pools

The transfer between the active and the stable organic pool can be calculated with the following equation:

N_{Hum_{trans}} = \beta_{trans} \cdot (N_{activ_{pool}} \cdot (\frac{1} {fr_{actN}} -1) - N_{stabel_{pool}})\!

with

N_{Hum_{trans}}\! = transfer rate between the active and stable organic pool [kgN/ha]

\beta_{trans}\! = transfer constant between the active and stable organic pool; default value= 0.00001 [-]

N_{activ_{pool}}\! = active organic pool [kgN/ha]

N_{stabel_{pool}}\! = stable organic pool [kgN/ha]

fr_{actN}\! = fraction of the organic nitrogen in the active organic pool = 0.02 [-]

The transfer rate is here subtracted from the active pool whereas it is added to the stable pool.

Mineralization of the Active Pool

The active pool is mineralized to nitrate directly without taking the nitrification into account. The rate is calculated as follows:

N_{actmin} = \beta_{min} \cdot \sqrt{\gamma_{temp} \cdot \gamma_{water}} \cdot N_{activ_{pool}}\!

with

N_{actmin}\! = transfer rate between the active organic and the nitrate pool [kgN/ha]

\beta_{min}\! = transfer constant between the active organic and the nitrate pool; default value = 0.002 [-]

N_{activ_{pool}}\! = active organic pool [kgN/ha]

\gamma_{water}\! = soil humidity coefficient [-]

\gamma_{temp}\! = soil temperature coefficient [-]

The transfer rate is subtracted from the active pool whereas it is added to the nitrate pool.


Dynamics of the Residue Pools

The dynamics of the decomposition of fresh organic substances (residue) from plant remains and organic fertilizer is carried out only in the top horizon. The residue are divided in two pools: the first one represents the biomass as a whole, the second represents the residue's amount of nitrogen. The supply to the residue pools is carried out via plant remains after the harvest and via the organic fertilization with the help of the following equation:

Residue_{pool} = Residue_{pool} + inp_{biomass} + (fertorgN_{fresh} \cdot 10)\!

N_{residue_{pool}} = N_{residue_{pool}} + inpN_{biomass} + fertorgN_{fresh}\!

with

Residue_{pool}\! = residue pool [kg/ha]

inp_{biomass}\! = inputted biomass [kg/ha]

fertorgN_{fresh}\! = inputted nitrogen via organic fertilization [kgN/ha]

N_{residue_{pool}}\! = residue pool's amount of nitrogen [kgN/ha]

The decomposition of the residue pool is carried out against the carbon-nitrogen relation (C/N-relation). The calculation of the C/N-relation is carried out according to the following equation.

\epsilon_{C/N} = \frac{Residue_{pool} \cdot 0.58} {N_{residue_{pool}} + NO_3Pool}

\gamma_{ntr} = min \begin{cases} \exp(-0.693 \cdot\frac{\epsilon_{C/N} - 25} {25})\\ 1.0 \end{cases}


with

\epsilon_{C/N}\! = C/N-relation [-]

\gamma_{ntr}\! = residue decomposition factor [-]

Residue_{pool}\! = residue pool [kg/ha]

NO_3Pool\! = nitrate pool [kgN/ha]

N_{residue_{pool}}\! = residue pool's amount of nitrogen [kgN/ha]


The decomposition constant of the residue pool is calculated with γntr, γwater, γtemp:

\delta_{ntr} = \beta_{rsd} \cdot \gamma_{ntr} \cdot \sqrt{\gamma_{water} \cdot \gamma_{temp}}\!


with

\delta_{ntr}\! = constant of the residue decomposition’s rate [-]

\gamma_{ntr}\! = residue decomposition factor [-]

\beta_{rsd}\! = residue decomposition coefficient; default value = 0.05 [-]

\gamma_{water}\! = soil humidity coefficient [-]

\gamma_{temp}\! = soil temperature coefficient [-]

The decomposition of the residue pool is carried out with the constant of the residue decomposition’s rate. At this, the nitrogen part is allocated to the active organic pool, in terms of humification, and the nitrate pool, in terms of mineralization, in a ratio of 20:80.

Residue_{pool}2 = Residue_{pool}1 - (\delta_{ntr} \cdot Residue_{pool}1)\!

N_{active_{pool}}2 = N_{active_{pool}}1 + (0.2 \cdot \delta_{ntr} \cdot N_{residue_{pool}}1)\!

NO_3Pool2 = NO_3Pool1 + (0.8 \cdot delta_ntr \cdot N_{residue_{pool}}1)\!

N_{residue_{pool}}2 = N_{residue_{pool}}1 - (\delta_{ntr} \cdot N_{residue_{pool}}1)\!

with

\delta_{ntr}\! = constant of the residue decomposition’s rate [-]

Residue_{pool}1\! = residue pool before the time step [kgN/ha]

Residue_{pool}2\! = residue pool after the time step [kgN/ha]

N_{active_{pool}}1\! = active organic pool before the time step [kgN/ha]

N_{active_{pool}}2\! = active organic pool after the time step [kgN/ha]

NO_3Pool1\! = soil nitrate pool before the time step [kgN/ha]

NO_3Pool2\! = soil nitrate pool after the time step [kgN/ha]

N_{residue_{pool}}1\! = residue pool's amount of nitrogen before the time step [kgN/ha]

N_{residue_{pool}}2\! = residue pool's amount of nitrogen after the time step [kgN/ha]

Denitrification

Denitrification occurs when the soil is nearly water-saturated. The rate depends on the amount of organic carbon in the soil as well as on the soil temperature. In comparison to SWAT (0,95), the degree of water saturation is lower (0.91) when denitrification occurs. This is because SWAT - in contrast to J2000 - does not consider the soil's air capacity. Thus, the underlying pore volume for the calculation of water saturation is higher in J2000. Furthermore, it is ensured that the rate is at the most 1 kgN/ha*d since higher rates are not expected in open land.


denit_{trans} = \begin{cases} NO_3Pool \cdot (1 - \exp(-1.4 \cdot \gamma_{temp} \cdot C_{org}))& \mathrm{f\ddot{u}r} \; \; \gamma_{water} \ge \beta_{denit} \\ 0.0 & \mathrm{f\ddot{u}r}\; \; \gamma_{water} < \beta_{denit} \end{cases}

with

NO_3Pool\! = soil nitrate pool [kgN/ha]

denit_{trans}\! = denitrification rate [kgN/ha]

\gamma_{water}\! = soil humidity coefficient [-]

\gamma_{temp}\! = soil temperature coefficient [-]

\beta_{denit}\! = denitrification coefficient; default value = 0.91 [-]


Mass Transport with Water Movement in the Soil

Nitrogen Concentration of Mobile Water

For the simulation of the mass transport caused by water movement, the nitrogen concentration of the mobile water is defined. Here, it is simplified assumed that only the nitrogen of the nitrate pool is mobile and therefore is taken into account for the calculation. The amount of water is determined on the basis of the soil storages and the water streams that leave the horizon.


soil_{water} = act_{LPS} + act_{MPS} + sto_{FPS}\!

mobile_{water} = \begin{cases} (RD1_{out} * Beta_{NO_{3}}) + RD2_{out} + h_{perco} + hor_{by_{infilt}} + diff_{out} & \mathrm{f\ddot{u}r} \; \; Horizont = 1 \\ RD2_{out} + h_{perco} + hor_{by_{infilt}} + diff_{out}& \mathrm{f\ddot{u}r} \; \; i > Horizont < n\\ RD2_{out} + h_{perco} + diff_{out}& \mathrm{f\ddot{u}r} \; \; Horizont = n \end{cases}

concN_{mobile} = \frac {NO_3Pool * (1 - \exp \frac{- mobile_{water}} {(1 - \theta_{nit}) * soil_{water}})} {mobile_{water}}

with

NO_3Pool\! = soil nitrate pool [kgN/ha]

soil_{water}\! = soil water [mm]

mobile_{water}\! = amount of mobile water [mm]

\Beta_{NO_{3}}\! = percolation coefficient; default value = 0.2 [-]

RD1_{out}\! = surface runoff [mm]

RD2_{out}\! = interflow [mm]

h_{perco}\! = percolation in deeper horizons or ground water [mm]

hor_{by_{infilt}}\! = infiltration water that goes into deeper layers in a time step and therefore passes by the actual horizon [mm]

diff_{out}\! = water that leaves the horizon via diffusion [mm]

\theta_{nit}\! = fraction of the pore volume from which anions are excluded (due to positive charge preponderance of the clay mineral); default value = 0.05 [-]

concN_{mobile}\! = nitrogen concentration of the mobile water [kgN/ha*mm]

The influence of the water that expands into deeper horizons in a time step is determined with a parameter (infil_{conc_{factor}}). At this, the parameter represents to what extend the bypass water interacts with the soil matrix or bypasses the layers that are flown through in macro pores.

hor_{by_{infilt}}[i-1] = \sum^{n}_{i}{hor_{by_{infilt}}} * infil_{conc_{factor}} \!

with

hor_{by_{infilt}}\! = infiltration water that goes into deeper layers in a time step and therefore passes by the actual horizon [mm]

infil_{conc_{factor}}\! = bypass parameter [mm]

i\! = actual horizon [-]

n\! = number of horizons [-]

Nitrogen Transport in the Runoff Components

For the individual horizons the nitrogen loads for the runoff components are calculated on the basis of the mobile water's nitrogen concentration. At this, the interflow is considered in all horizons whereas the surface runoff is only considered in the top horizon. However, the percolation occurs in the deeper horizons or in the ground-water reservoir.


N_{surface} = Beta_{NO_3} \cdot RD1_{out} \cdot concN_{mobile}\!

N_{interflow} = RD2_{out} \cdot concN_{mobile}\!

N_{perco} = (hor_{by_{infilt}} + h_{perco}) \cdot concN_{mobile}\!


with

concN_{mobile}\! = nitrogen concentration of the mobile water [kgN/ha*mm]

hor_{by_{infilt}}\! = infiltration water that goes in deeper layers and thus bypasses the actual horizon in a time step [mm]

N_{surface}\! = nitrogen in the surface runoff [kgN/ha]

N_{interflow}\! = nitrogen in the interflow [kgN/ha]

N_{perco}\! = nitrogen in the percolation water [kgN/ha]

RD1_{out}\! = surface runoff [mm]

RD2_{out}\! = interflow [mm]

h_{perco}\! = percolation [mm]

Beta_{NO_3}\! = percolation coefficient [-]

The percolation coefficient represents a measurement for the interaction of the surface runoff and the soil matrix of the top horizon and therefore determines the surface runoff's amount of nitrogen.

The material that leaves the horizon with the diffusion water can be calculated as follows: the water movement that occurs above the field capacity due to potential gradients is called diffusion. Here, a negative value for the diffusion water means a downward water movement whereas a positive value represents an upward water movement.


diffoutN = \begin{cases} w_{l_{diff}}[i] * ConcN_{mobile}[i] & \mathrm{f\ddot{u}r} \; \; w_{l_{diff}} < 0 \\ w_{l_{diff}}[i] * ConcN_{mobile}[i+1] & \mathrm{f\ddot{u}r} \; \; w_{l_{diff}} < 0 \end{cases}

and

NO_3Pool[i] = NO_3Pool[i] + diffoutN \!

and

NO_3Pool[i+1] = NO_3Pool[i+1] - diffoutN \!

with

concN_{mobile}\! = nitrogen concentration of the mobile water [kgN/ha*mm]

diffoutN \! = nitrogen in the diffusion water [kgN/ha]

NO_3Pool\! = soil nitrate pool [kgN/ha]

w_{l_{diff}}\! = diffusion water [mm]

i\! = soil horizon [kgN/ha]




Soil Temperature Module

The soil temperature is an important measurement for the matter regime modeling. Especially microbiological processes such as nitrification, denitrification and the transformation of organic nitrogen in the soil zone is strongly influenced by the prevailing temperature. In the here developed model J2K-S the soil temperature also plays an important role for the calculation of the following processes (see Soil Nitrogen Module):

• nitrification

• volatilation

• transformation of organic substance

• decomposition of plant remains

• denitrification

Structure of the Module

The soil temperature is simulated according to the empirical routines of SWAT (Arnold et al. 1998) and EPIC (Williams et al. 1984). At first, a surface soil temperature is generated for bare ground on the basis of the air temperature and insolation. This surface temperature is modified by attenuation factors that describe the effect of biomass and snow. The temperature of the different soil horizons is generated as upper boundary condition between the surface soil temperature and the long lasting mean temperature as lower boundary condition. At this, the attenuation effect of the soil is defined in consideration of the soil humidity and the bulk density. The equations of the individual processes can be found in Neitsch et al. (2002).


Bild:Bodentemperaturmodul.jpg

Figure 1: Structure of the soil temperature model


Bild:Bodentemperaturtest.jpg

Figure 2: Results of the soil temperature modeling for the surface area and at 40 cm depth at an investigated slope near Zeulenroda (Thuringia).


This figure shows the measured and modeled temperature at the surface (upper figure) as well as at 40 cm depth (lower figure) for an investigated area near the dam Zeulenroda. It can be seen that the temperature curve can be followed quite well in spite of certain deviations. This is emphasized by the high coefficient of determination of about 0.95.

Plant Growth Module

The description for the simulation of plant growth is important for numerous hydrological mass transport processes, e.g. for the interception or the nitrogen uptake by the canopy. Plant growth is usually controlled via the simulation of the leaf area development (LAI) as well as the light interception and the transformation into biomass and is carried out according to SWAT (Arnold et al. 1998). At this, it is assumed that a potential plant growth, i.e. under optimum conditions, exists which is then modified in consideration of stress factors.


Temperature Development and Heat Units


The most important factor that determines the canopy’s development is the temperature whose parameters are different for each plant. Therefore, each plant possesses a basis temperature that needs to be reached in order to activate a certain growth. The growth increases until the optimum temperature is reached and decreases noticeably when the maximum temperature is exceeded. The plant-specific growth development is carried out via the generating of heat units (=HU). The underlying hypothesis for this is the assumption that plants have a specific heat demand that is quantifiable until the necessary maturity state for the harvest is reached. An ‘HU’ is defined as a phenological effective temperature unit. An HU results from the daily accumulated daily average temperature that lies above the plant-specific basis temperature. Assumed that a maize plant has a basis temperature of 7° C and is exposed to a daily temperature of 15° C, its HU would be calculated as follows: 15 – 7 = 8 HUs. In this way, the individual heat unit developments are simulated for each land use type in consideration of the time of the sowing and harvest as well as the daily average temperature. The development of the root growth and the leaf area index is controlled via the heat unit development. At this, it is assumed that the plants invest their energy into the leaf development and the root growth. This simplified view also means that the development of leafs and roots is independent on water and nutrient supply. Furthermore, the plant’s degree of maturity which influences the amount of nitrogen in the biomass is exclusively controlled via the temperature sum.


Biomass Development


The biomass development is simulated as potential biomass at first. At this, the photosyntetic radiation is the controlling unit for the biomass development. Thus, a potential biomass increase is generated for each day with the help of the radiation and leaf area (see figure 1).


Pflanzenwastumsmodul1.jpg

Figure 1: Structure of the plant growth module


This daily biomass increase is reduced to the actual biomass increase with the help of stress factors, which are nitrogen supply, temperature and water supply (see figure 2).


Pflanzenwastumsmodul2.jpg

Figure 2: Structure of the growth’s stress


The stress factor that has the strongest effects at a point in space and time determines the actual biomass according to the principle of limiting factors. This, in turn, influences the nitrogen demand.

Land Use Management Module

The description of the land use management is carried out according to the methodology in the SWAT model (Arnold et al. 1998). The land use management module offers to represent complex crop rotations in J2k-S. The individual field crops are characterized on the basis of management operations like sowing, fertilizing and harvesting. As can be seen in figure 1, the crop rotation relates to an actual plant that in turn is build up of the plant parameters and the individual management options.


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Figure 1: Flow chart of the land use management module


The basic basis objects for the description of the land use management are cultivation (no function yet), fertilization, plant characteristics and the crop rotation. Land management and fertilization as management options have only simple parameters like mixing efficiency, machining depth, amount of fertilizer, ammonium and nitrate. However, the plant object possesses numerous parameters. Thus, the crop rotation is a simple list with the order of the individual crops (see figure 2).


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Figure 2: Essential components (basic objects)


As an explanation in figure 3 a detail of a management parameter file is shown. In the first line a cultivation type can be found. Thereupon, the sowing of the maize that was used in the example follows. Furthermore, three fertilizations with three different fertilizers are carried out. The harvest with the amount of biomass is given. The rest remains on the field and is allocated to the residue pool in the nitrogen module. Finally, cultivation is carried out in this example.


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Figure 3: Structure of a management parameter file


With the help of this tool, the essential activities of the horticultural management as well as alternatives can be represented flexibly.

Ground Water Nitrogen Module

The description of the nitrogen’s dynamics that occurs in the ground water is carried out according to the ground water dynamics used in J2k. At this, the nitrogen load is – corresponding to the water – allocated to the two ground-water reservoirs RG1 and RG2. The water and matter proportions are generated for both ground-water reservoirs. The output is carried out analogue to the water and the generated proportions. It is possible to set up an origin nitrogen concentration.

Besides, an attenuation factor is implemented that delays the change of the nitrogen proportions in the storage. This factor used for the calibration can be set up for both ground-water reservoirs separately. It represents the mixing and diffusion effects in the aquifer.


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