a model of soil nitrogen reserves in an irish grass sward c. paillette 1, 2, d. hennessy 1, l....
TRANSCRIPT
A model of soil nitrogen reserves in an Irish grass sward C. Paillette1, 2, D. Hennessy1, L. Delaby3,
D. O Connor2 and L. Shalloo1
1Animal & Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork;
2Cork Institute of Technology, Bishopstown, Cork; 3INRA, AgroCampus Ouest, UMR 1348, PEGASE, F-35590
Saint-Gilles, France
Introduction:
Grass growth highly variable within and between years
Factor influencing grass growth Soil type Climatic conditions Management Soil reserves of nutrients
Nitrogen Water
Models as management tools Soil reserves influenced by
Environmental factors Sward management
Objectives
Develop a dynamic model to predict Organic nitrogen reserves Mineral nitrogen reserves Water reserves
Depending on Weather Management of the farm
Stocking density and timing of grazing Timing and quantity of fertilizer
Weather data Precipitation Temperatures Solar radiation
Inputs
Weather data Precipitation Temperatures Solar radiation
Soil type Composition Water Holding Capacity
Inputs
Weather data Precipitation Temperatures Solar radiation
Soil type Composition Water Holding Capacity
Management data Dates of grazing and stocking rate Timing and quantity of fertilization
Inputs
Weather data Precipitation Temperatures Solar radiation
Soil type Composition Water Holding Capacity
Management data Dates of grazing and stocking rate Timing and quantity of fertilization
Grass quantity
Inputs
Model development:
Relationships are derived from the existing literature
Two sub models Soil N reserves
Organic N Mineral N
Water reserves
Organic N Stock
Mineral N Stock
Soil N model (1)
General Mineral N stock
General Mineral N stock
General Mineral N stock
General mineral N stock
Urine affectedMineral N stock for first grazing
Urine N deposition
General Mineral N stock
Urine affectedMineral N stock for first grazing
Urine N deposition
Day of rotation
Proportion of surface affected
Urine affected mineral pool
General mineral
pool
0 0 1
1
Number of animals*number of urine
patches*2m²
=0.01
0.99
2 0.02 0.98
3 0.03 0.97
4 0.04 0.96
General Mineral N
stock
General Mineral N
stock
Urine affected Mineral N stock for
1st grazing
…0…000…0…00…
…0…000…0…00second grazing
…0.03…0.030.020.01…0…00first grazing
…0.96…0.970.980.99…1…11general pool
Proportion of surface
…x+2x+1x…21day of simulation
General Mineral N
stock
Urine affectedMineral Nstock for
1st grazing
Urine affectedMineral Nstock for
2nd grazing
day of simulation 1 2 … x x+1 x+2 … y y+1 y+2 …
Proportion of surface
general pool 1 1 …1… 0.99 0.98 0.97 …0.96… 0.952 0.944 0.936 …
first grazing 0 0 …0… 0.01 0.02 0.03 …0.03… 0.03 0.03 0.03 …
second grazing 0 0 …0… 0 0 0 …0… 0.008 0.016 0.024 …
… 0 0 …0… 0 0 0 …0… 0 0 0 …
Urine affectedMineral Nstock for
2nd grazing
Urine affectedMineral Nstock for
1st grazing
General Mineral N
stock
…
day of simulation 1 2 … x x+1 x+2 … y y+1 y+2 …
Proportion of surface
general pool 1 1 …1… 0.99 0.98 0.97 …0.96… 0.952 0.944 0.936 …
first grazing 0 0 …0… 0.01 0.02 0.03 …0.03… 0.03 0.03 0.03 …
second grazing 0 0 …0… 0 0 0 …0… 0.008 0.016 0.024 …
… 0 0 …0… 0 0 0 …0… 0 0 0 …
Organic N Stock
Mineral N Stock
Vegetation
Grass GrowthAbscission
Loss to the atmosphere
Leaching
Fertilization Fertilization
Soil N model (2)
Water Reserve
Leaching
RainEvapotranspiration
Soil Water Model:
Outputs
Daily Organic nitrogen reserve Mineral nitrogen reserve Nitrogen leached
Conclusion: This work shows that reserves of nutrients in the soil can be
modelled
This model Uses equations extracted from different models that have
proven accurate for Irish conditions Combines them to get a comprehensive model.
Future work will be to link to a grass growth model to Take into account the effect of nitrogen availability on
grass growth Modulate the grass uptake of nitrogen.
Thank you