A Modelling Approach to Explore the Impact of RootDistribution and Citrate Release on PhosphorusUse Efficiency of CropsSus...
Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and ava...
Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and ava...
1.1 APSIM• APSIM: Agricultural  Production Systems  Simulator                                                      System ...
1.1 APSIM APSIM is a farming systems model, able to simulate • >20 crops, including pastures & trees • complex rotation pa...
1.2 Crop Modules  • Potential growth of crops  • P demand based on critical P    concentrations, biomass & new growth  • R...
1.3 SoilP Module                                                                                  APSIM-SoilP:            ...
Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and ava...
2.1 Process understanding and data availability• Organic anions can enhance P mobilisation into soil solution  (Jones, 199...
2.2 Modelling• Only one modeling study to simulate rice P uptake  in controlled laboratory experiment   • Rice (Kirk et al...
Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and ava...
3.1 APSIM enhancements1.   Original Model: crop P uptake is linked to solution P in rooted soil layers2.   Enhancement #1:...
Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and ava...
4.1 Biomass                       1. Original Model: crop P uptake                                 2. Enhancement #1: need...
4.2 Scenario analysis•   Study site: Kingaroy, QLD (1957-2009)•   Cropping system: Continuous wheat, rainfed condition•   ...
4.3 Biomass responses: short-term vs long-term                                  First year 1957                           ...
4.4 Biomass, yield and inorganic soil P                                                (a) Citrate Efflux = 0             ...
4.5 P rate required for 90% max biomass     P rate required for 90% max biomass (kg/ha)   160                             ...
4.6 P recovery                       (a) P Rate = 20 kg/ha               (b) P Rate = 40 kg/ha               (c) P Rate = ...
Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and ava...
5. Summary     Long-term effect is different from short-term      effect, due to residual effect of applied P.     Major...
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A modelling approach to explore the impact of root distribution and citrate release on phosphorus use efficiency of crops. Zhongkui Luo

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A presentation at the WCCA 2011 event in Brisbane.

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  • 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.
  • A modelling approach to explore the impact of root distribution and citrate release on phosphorus use efficiency of crops. Zhongkui Luo

    1. 1. A Modelling Approach to Explore the Impact of RootDistribution and Citrate Release on PhosphorusUse Efficiency of CropsSustainable Agriculture Flagship Enli Wang, Brad Ridoutt Zhongkui Luo, Ulrike Bende-Michl
    2. 2. Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and available data on citrate release from plant roots and its impact on PUE3. New model development to enable APSIM to simulate impact of citrate efflux on PUE4. Simulated response of wheat growth and P uptake to citrate effluxes5. Summary
    3. 3. Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and available data on citrate release from plant roots and its impact on PUE3. New model development to enable APSIM to simulate impact of citrate efflux on PUE4. Simulated response of wheat growth and P uptake to citrate effluxes5. Summary
    4. 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. 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. 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. 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. 8. Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and available data on citrate release from plant roots and its impact on PUE3. New model development to enable APSIM to simulate impact of citrate efflux on PUE4. Simulated response of wheat growth and P uptake to citrate effluxes5. Summary
    9. 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. 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. 11. Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and available data on citrate release from plant roots and its impact on PUE3. New model development to enable APSIM to simulate impact of citrate efflux on PUE4. Simulated response of wheat growth and P uptake to citrate effluxes5. Summary
    12. 12. 3.1 APSIM enhancements1. Original Model: crop P uptake is linked to solution P in rooted soil layers2. 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. 13. Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and available data on citrate release from plant roots and its impact on PUE3. New model development to enable APSIM to simulate impact of citrate efflux on PUE4. Simulated response of wheat growth and P uptake to citrate effluxes5. Summary
    14. 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. 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.
    16. 16. 4.3 Biomass responses: short-term vs long-term First year 1957 Average 1957~2009 (a) Citrate efflux = 0 nmol/gFW/h (b) Citrate efflux = 200 nmol/gFW/h (a) Citrate efflux = 0 nmol/gFW/h (b) Citrate efflux = 200 nmol/gFW/h 20 20 20 20 Biomass (ton/ha) Biomass (ton/ha) Biomass (ton/ha) Biomass (kg/ha) 16 16 16 16 12 12 12 Sorption: 12 Sorption: 50 50 8 8 8 100 8 100 200 200 4 4 4 500 4 500 1000 1000 0 0 0 0 0 40 80 120 160 200 0 40 80 120 160 200 0 40 80 120 160 200 0 40 80 120 160 200 P Rate (kg/ha) P Rate (kg/ha) P Rate (kg/ha) P Rate (kg/ha)(c) Citrate efflux = 1000 nmol/gFW/h (d) Citrate efflux = 2000 nmol/gFW/h (c) Citrate efflux = 1000 nmol/gFW/h (d) Citrate efflux = 2000 nmol/gFW/h 20 20 20 20 Biomass (ton/ha) Biomass (ton/ha) Biomass (ton/ha) Biomass (ton/ha) 16 16 16 16 12 12 12 Sorption: 12 Sorption: Sorption: 50 50 8 8 50 8 100 8 100 100 200 200 4 200 4 500 4 500 4 500 1000 1000 1000 0 0 0 0 0 40 80 120 160 200 0 40 80 120 160 200 0 40 80 120 160 200 0 40 80 120 160 200 P Rate (kg/ha) P Rate (kg/ha) P Rate (kg/ha) P Rate (kg/ha)
    17. 17. 4.4 Biomass, yield and inorganic soil P (a) Citrate Efflux = 0 (b) Citrate Efflux = 200 25 25 Biomass or grain yield (ton/ha) Biomass or grain yield (ton/ha) nmol/gFW/h nmol/gFW/h Biomass Biomass 20 Yield 20 Yield 15 15 10 10 5 5 0 0 1950 1960 1970 1980 1990 2000 2010 1950 1960 1970 1980 1990 2000 2010 Year Year (c) Citrate Efflux = 0 (d) Citrate Efflux = 200 200 200 Total inorganic soil P (kg/ha) Total inorganic soil P (kg/ha) Layer 1 Layer 1 Layer 2 Layer 2 150 Layer 3 150 Layer 3 100 100 50 50 0 0 1950 1960 1970 1980 1990 2000 2010 1950 1960 1970 1980 1990 2000 2010 Year Year
    18. 18. 4.5 P rate required for 90% max biomass P rate required for 90% max biomass (kg/ha) 160 SP50 140 SP100 SP200 120 SP500 SP1000 100 80 60 40 20 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Citrate efflux (nmol/gFW/h)
    19. 19. 4.6 P recovery (a) P Rate = 20 kg/ha (b) P Rate = 40 kg/ha (c) P Rate = 60 kg/ha 180 180 180 Sorption = 50 160 160 160 Sorption = 200 Sorption = 500 140 140 140 Sorption = 1000P recovery (%) 120 120 120 100 100 100 80 80 80 60 60 60 40 40 40 20 20 20 0 0 0 0 500 1000 1500 2000 0 500 1000 1500 2000 0 500 1000 1500 2000 Citrate efflux (nm/g/h) Citrate efflux (nm/g/h) Citrate efflux (nm/g/h)
    20. 20. Outline of the presentation1. APSIM and its capability to simulate crop response to soil P2. Current understanding and available data on citrate release from plant roots and its impact on PUE3. New model development to enable APSIM to simulate impact of citrate efflux on PUE4. Simulated response of wheat growth and P uptake to citrate effluxes5. Summary
    21. 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.
    22. 22. Thank you

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