Soil Fertility Monitoring For Sustainable Crop Production1Ppravin Yadav
Similaire à A modelling approach to explore the impact of root distribution and citrate release on phosphorus use efficiency of crops. Zhongkui Luo (9)
A modelling approach to explore the impact of root distribution and citrate release on phosphorus use efficiency of crops. Zhongkui Luo
1. A Modelling Approach to Explore the Impact of Root
Distribution and Citrate Release on Phosphorus
Use Efficiency of Crops
Sustainable Agriculture Flagship
Enli Wang, Brad Ridoutt
Zhongkui Luo, Ulrike Bende-Michl
2. Outline of the presentation
1. APSIM and its capability to simulate crop response to soil P
2. Current understanding and available data on citrate release from
plant roots and its impact on PUE
3. New model development to enable APSIM to simulate impact of
citrate efflux on PUE
4. Simulated response of wheat growth and P uptake to citrate
effluxes
5. Summary
3. Outline of the presentation
1. APSIM and its capability to simulate crop response to soil P
2. Current understanding and available data on citrate release from
plant roots and its impact on PUE
3. New model development to enable APSIM to simulate impact of
citrate efflux on PUE
4. Simulated response of wheat growth and P uptake to citrate
effluxes
5. Summary
4. 1.1 APSIM
• APSIM: Agricultural
Production Systems
Simulator System Control
Manager
• A modular modelling Clock Report
Canopy Met
framework Wheat SoilWat
Crops E SWIM
• Simulates biophysical Maize N
G
Soil C & N
Sorghum SoilPH
I
processes in farming Legume N SoilP
E Soil
Other Crops New Module
systems Erosion
Irrigate
• Links to economic & Fertiliz Manure
Management Economics Residue
ecological outcomes of
management practices under
climate variation
5. 1.1 APSIM
APSIM is a farming systems model, able to simulate
• >20 crops, including pastures & trees
• complex rotation patterns
• water, carbon, nitrogen and phosphorus cycling
6. 1.2 Crop Modules
• Potential growth of crops
• P demand based on critical P
concentrations, biomass & new growth
• Reduction in growth due to P deficiency
7. 1.3 SoilP Module
APSIM-SoilP:
P fertilizer P fertilizer
broadcast banded • does not simulate
Placement effect
• precipitation/dissolution of
tightly bonded soil P
Dissolution Mineralization Unavailable • may not work in acidic soils
Rock P Labile P Immobilization Organic P (pH<5.5) and alkaline soils
L (pH>7.3)
Gaoss o
Desorption
Adsorption
in f av
of ai
ava lab • new development is on-going
ilab ility
ilit for P modeling in those soils
y
• original version does not
Crop P P in Soil Unavailable consider effect of root
Uptake solution Inorganic P exudation on PUE
8. Outline of the presentation
1. APSIM and its capability to simulate crop response to soil P
2. Current understanding and available data on citrate release from
plant roots and its impact on PUE
3. New model development to enable APSIM to simulate impact of
citrate efflux on PUE
4. Simulated response of wheat growth and P uptake to citrate
effluxes
5. Summary
9. 2.1 Process understanding and data availability
• Organic anions can enhance P mobilisation into soil solution
(Jones, 1998; Khademi et al, 2010)
• Release of citrate, malate & oxalate from roots increases with P
deficiency (Vance et al, 2003; Ryan et al, 2001)
Table 1 citrate efflux from plant roots
Crop Citrate Efflux References
(nmol/gFW/h)
Rice 155~360 Kirk et al (1999)
Wheat 5~185 Ryan et al (2009)
White lupin 1656~2373 Roelofs et al (2001)
Proteaceae 3600~9000 Roelofs et al (2001)
10. 2.2 Modelling
• Only one modeling study to simulate rice P uptake
in controlled laboratory experiment
• Rice (Kirk et al, 1999) –
diffusion, decomposition and P solubilisation of
citrate, only a few mm around roots, no zero
efflux treatment
• No field scale modelling studies so far
11. Outline of the presentation
1. APSIM and its capability to simulate crop response to soil P
2. Current understanding and available data on citrate release from
plant roots and its impact on PUE
3. New model development to enable APSIM to simulate impact of
citrate efflux on PUE
4. Simulated response of wheat growth and P uptake to citrate
effluxes
5. Summary
12. 3.1 APSIM enhancements
1. Original Model: crop P uptake is linked to solution P in rooted soil layers
2. Enhancement #1: need to link crop P uptake to solution P and root length density (RLD)
3. Enhancement #2: need to link crop P uptake & solution P to citrate efflux from roots (Fc)
P fertilizer P fertilizer
broadcast banded
Placement effect
Dissolution Mineralization Unavailable
Rock P Labile P Immobilization
Desorption Organic P
Adsorption
P released by citrate
Crop P P in Soil Unavailable
Uptake solution Inorganic P
13. Outline of the presentation
1. APSIM and its capability to simulate crop response to soil P
2. Current understanding and available data on citrate release from
plant roots and its impact on PUE
3. New model development to enable APSIM to simulate impact of
citrate efflux on PUE
4. Simulated response of wheat growth and P uptake to citrate
effluxes
5. Summary
14. 4.1 Biomass
1. Original Model: crop P uptake 2. Enhancement #1: need to link
is linked to solution P in rooted crop P uptake to solution P and
soil layers root length density (RLD)
7000 (a) APSIM-SoilP 7000 (b) APSIM-SoilP&RLD
Simulated wheat yield (kg/ha)
Simulated wheat yield (kg/ha)
6000 y = 1.1256x + 10.593 6000 y = 1.1742x - 259.46
R2 = 0.8891 R2 = 0.896
5000 5000
4000 4000
3000 3000
2000 2000
1000 1000
0 0
0 1000 2000 3000 4000 5000 6000 7000 0 1000 2000 3000 4000 5000 6000 7000
Observed wheat yield (kg/ha) Observed wheat yield (kg/ha)
Comparison of simulated and observed wheat grain yields under different levels of P
fertiliser inputs at one QLD site and two NSW sites.
The modified model performed slightly better than the original one!
15. 4.2 Scenario analysis
• Study site: Kingaroy, QLD (1957-2009)
• Cropping system: Continuous wheat, rainfed condition
• Citrate efficiency = 0.4
• Five levels of soil P sorption capacity:
• Low 50, 100
• Medium 200
• High 500
• Very high 1000
• Seven levels of citrate efflux (nmol/gFW/h): 0, 50, 100, 200,
500, 1000, 2000
• 11 levels of P application rates (kg P/ha): 0~200 kg P/ha with
increase of 20 kg P/ha.
20. Outline of the presentation
1. APSIM and its capability to simulate crop response to soil P
2. Current understanding and available data on citrate release from
plant roots and its impact on PUE
3. New model development to enable APSIM to simulate impact of
citrate efflux on PUE
4. Simulated response of wheat growth and P uptake to citrate
effluxes
5. Summary
21. 5. Summary
Long-term effect is different from short-term
effect, due to residual effect of applied P.
Major impact is to increase PUE of applied P
fertilisers, because soil P reserve can be depleted
in a relatively short time period.
P rate required to achieve maximum crop yield
decreases with increasing citrate efflux from the
roots.
The impact increases with soil P sorption
capacity, decreases with P application rate.
For the start year (single year 1957), the results show that: 1) biomass increased with citrate efflux levels at all P application rates, 2) the biomass increase is the highest at medium level of soil P sorption capacity (a=200), and 3) the biomass increase becomes smaller with increased P application rates. If no P fertiliser was applied, a citrate efflux of 200 nmol/gFW/h (similar to the level of Carazinho Wheat) lead to a biomass increase by 78-116% on soils with sorption capacity between 50-200, and by 16 and 31% on soil with sorption capacity of 500 and 1000, respectively (Fig 6a). For long-term (1957-2009) averaged biomass, the difference in biomass responses to P application rates under different citrate effluxes and soil sorption capacities are much smaller than that in a single year (Fig 5). The reduced difference in the response curves at lower rates of P applications is due to the depletion of soil P reserve in the first 15-20 years (Fig 7b, 7d), leading to near zero biomass production thereafter. The reduced difference in the response curves at high rates of P applications is due to the accumulation of P in the soil to reach a point where P supply could meet crop P demand on soils with any sorption capacity. As a result, the potential increase in biomass production at long term increases with citrate efflux levels and becomes increasingly higher on soils with higher sorption capacity (Fig 6b). If no P fertiliser was applied, a citrate efflux of 200 nmol/gFW/h (similar to the level of Carazinho Wheat) lead to a biomass increase by 30%,81%, 216%, 210% on soils with sorption capacity of 50, 100, 200 and 500, respectively (Fig 6b). Fig 7b, 7d show the simulated time courses of biomass, grain yield, and the total inorganic P in the top 30cm layers on a soil with sorption capacity of 200.
The reduced difference in the response curves at lower rates of P applications is due to the depletion of soil P reserve in the first 15-20 years (Fig 7b, 7d), leading to near zero biomass production thereafter. The reduced difference in the response curves at high rates of P applications is due to the accumulation of P in the soil to reach a point where P supply could meet crop P demand on soils with any sorption capacity. As a result, the potential increase in biomass production at long term increases with citrate efflux levels and becomes increasingly higher on soils with higher sorption capacity (Fig 6b). If no P fertiliser was applied, a citrate efflux of 200 nmol/gFW/h (similar to the level of Carazinho Wheat) lead to a biomass increase by 30%,81%, 216%, 210% on soils with sorption capacity of 50, 100, 200 and 500, respectively (Fig 6b). Fig 7b, 7d show the simulated time courses of biomass, grain yield, and the total inorganic P in the top 30cm layers on a soil with sorption capacity of 200.
P application rates required to achieve 90% of the potential biomass under different levels of citrate effluxes on a given soil (Fig 9). With increased level of citrate efflux from the roots, the P application rates required to achieve 90% of the potential biomass is significantly decreased, particularly on soils with high P sorption capacity. Fig 8 shows the simulated impact of citrate efflux on average P recovery (calculated as crop P uptake divided by P application rate) on different soils at three P application rates. The results show that: 1) P recovery increases with citrate efflux till certain efflux rate is reached, 2) the increase in P recovery is more significant on higher sorption soils, and 3) the increase in P recovery becomes much smaller with increased P application rates.
P application rates required to achieve 90% of the potential biomass under different levels of citrate effluxes on a given soil (Fig 9). With increased level of citrate efflux from the roots, the P application rates required to achieve 90% of the potential biomass is significantly decreased, particularly on soils with high P sorption capacity. Fig 8 shows the simulated impact of citrate efflux on average P recovery (calculated as crop P uptake divided by P application rate) on different soils at three P application rates. The results show that: 1) P recovery increases with citrate efflux till certain efflux rate is reached, 2) the increase in P recovery is more significant on higher sorption soils, and 3) the increase in P recovery becomes much smaller with increased P application rates.