Building a model based on APSIM that simulates smallholder crop-livestock systems. David Parsons
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Building a model based on APSIM that simulates smallholder crop-livestock systems. David Parsons

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A presentation made at the WCCA 2011 event in Brisbane, Australia.

A presentation made at the WCCA 2011 event in Brisbane, Australia.

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Building a model based on APSIM that simulates smallholder crop-livestock systems. David Parsons Building a model based on APSIM that simulates smallholder crop-livestock systems. David Parsons Presentation Transcript

  • David Parsons Building a model based onChuck Nicholson APSIM that simulatesBob Blake smallholder crop-livestockQuirine KetteringsLuis Ramirez systemsDanny FoxLuis TedeschiJerry Cherney TIAR – research • development • extension • education • training
  • Yucatan MexicoMilpa – shifting cultivation TIAR – research • development • extension • education • training
  • Hair sheep in YucatanTIAR – research • development • extension • education • training
  • The role for modelling mixed systems in developing countries• There is a general lack of knowledge of what actually goes on in these complex smallholder mixed systems.• “Modelling realistically offers the only way of identifying and quantifying the subtle but highly significant interactions that occur between the various components of smallholders’ systems” (Thornton & Herrero, 2001).• Modelling is a method for integrating information in a rational way. TIAR – research • development • extension • education • training
  • Challenges for crop-livestock models• Often sufficient in one discipline (soils, crops, livestock, economics) but not the others• May not be dynamic between components• Modelling can be very time consuming• Construction of a model for a specific application is costly, therefore a generic modelling framework is preferable. TIAR – research • development • extension • education • training
  • Objectives• Develop a crop-livestock model to assess the biophysical and economic consequences of management decisions/farming practices evident in Yucatan mixed systems.• Dynamically link all components of the model• Be descriptive of the system, predictive in relation to outcomes (given specific farmer decisions), but not prescriptive (suggesting what farmers should be doing). TIAR – research • development • extension • education • training
  • Movement of nutrients through sheep and fodder Forest Home garden Cut & carry Within village Graze Tree purchase & Sheep pens Forage purchase Cultivated forage Field Crops Graze residues Graze Tree harvest Cut & carry residues Cut & carry Grain Cultivated forage Cut & carry GrazeMovement of fodder Outside villageMovement of sheep By-product purchase Grain purchase Supplement purchase Buy and sell sheep TIAR – research • development • extension • education • training
  • Components of the integrated model• APSIM (Agricultural production simulator) – Simulate crop production (soils, crops, weather)• Vensim – Icon-based modeling software – ‘System dynamics’ software• SRNS (Small Ruminant Nutrition System) – Based on CNCPS-S (Cornell Net Carbohydrate and Protein System for Sheep) TIAR – research • development • extension • education • training
  • The Integrated model APSIM Vensim™ Climate Flock dynamics Soil organic matter, Livestock feeding nutrient ,and water Venlink Nutrient allocations dynamics interface Management Surface organic matter variables Labor Plant growth Economics Crop Grass Corral SRNS data Intake Weight gain Manure quantity Manure quality TIAR – research • development • extension • education • training
  • Venlink interface variables Crop Grass CorralAPSIM Grain harvested Grass leaf and stem Manure in pile Grain protein available Manure N in pile to Stover harvested Grass leaf and stem Refusals in pileVensim protein Stover protein Refusal N in pileVensim Manure to milpa Manure to grass Manure to corral to Manure C:N Manure C:N Manure C:N Refusals to milpa Refusals to grass Refusals to corralAPSIM Refusals C:N Refusals C:N Refusals C:N Milpa cultivation Urea to grass Empty manure cycle pile signal Urea to milpa Fraction of stover harvested TIAR – research • development • extension • education • training
  • Example - manure APSIM Vensim™ Crop Manure Manure allocation allocation, C:N calculations Effects of applied and use info manure Manure C:N calculations Grass Define manure use Effects of applied Quantity and manure C:N of stored manure Corral Manure quantity Manure quality Breakdown of stored manure SRNS data Manure quantity Manure quality TIAR – research • development • extension • education • training
  • Example Vensim screen TIAR – research • development • extension • education • training
  • Some model limitations• Not all modules in APSIM are P responsive.• SRNS also does not track P (yet).• Wider range of tropical crop modules needed in APSIM, particularly forage crops.• Simulation time TIAR – research • development • extension • education • training
  • Possible model improvements• More choices of soils and crops.• Lack of knowledge of the underlying processes of manure decomposition: – Manure decomposition in soil is ok – Manure on surface and in piles not as well understood – Technologies that improve manure management• Secondary feed quality data is needed to generate SRNS runs, i.e. data that is not generated by the APSIM model section.• A dynamic SRNS would offer numerous benefits. TIAR – research • development • extension • education • training
  • Why not code it all in APSIM?• APSIM has great flexibility to write ‘manager’ code• Visual nature of Vensim is a great help• Partial model testing• Accessing text/excel data using Vensim• Sensitivity analysis, optimization TIAR – research • development • extension • education • training
  • Types of scenario analyses• What are the biophysical and household outcomes from differing: – Types of farms (livestock vs. crop vs. livestock & crop) – Manure management and use practices – Livestock feeding practices – etc. TIAR – research • development • extension • education • training
  • Example Implications of model outputs 1. Logical for smallholders to make use of the natural resources available. Focus on using common land 2. Cut and carry systems can be more labor efficient than common land grazing systems (where continuous supervision is needed). 3. Investment in increased integration through the use of crop by-products may not be a favorable option while common land is available. 4. Investment in infrastructure to grow improved forages may lead to decreased returns to labor and net income. TIAR – research • development • extension • education • training
  • Review of this modeling approach• Crop-livestock systems, particularly those in developing countries, are variable and complex, making it difficult for a particular modeling package to be applicable to every situation.• Our model builds on a foundation of well a established soil- crop-climate model (APSIM) and sheep model (SRNS)• Links with Vensim allow flexibility to develop model structure to simulate individual systems and address particular research questions TIAR – research • development • extension • education • training