Illinois
Fertilizer Conference Proceedings
January 24-26, 2005
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H. F. Reetz, JR., R. C. Schroeder, AND R. K. Stewart
1
This project is an education module development project which is adapting nutrient management system model into a training package that will be used to help teach agricultural service providers some of the basics of potassium nutrition, with emphasis on the interactions with various soil and crop factors. It applies the basic principles and interactions to whole field and site-specific management and provides both agronomic and economic analyses. The product will be useful in training for Certified Crop Advisers, Extension staff, students, and others desiring an understanding of the concepts of potassium nutrition. This will lay the groundwork for a more in-depth training package including on potassium, as well as nitrogen, phosphorus, and other nutrients.
A Focus Group of stakeholders (Selected examples of various potential end users) met in late summer of 2004 to review the model and plans for the training kit. Their comments and recommendations helped guide the refinement of the model and the final design of the training kit. The next phase of the project will include some pilot programs to use the materials in training and get further evaluation and suggestions.
We are working to accomplish this by further developing educational "tools" that have been generated under a recent FAR project funded by the USDA-CSREES Initiative for Future Agriculture and Food Systems (IFAFS) program. The existing "tools", developed in cooperation with CENTREC Agricultural Consulting, LLC, consist of simulation models, illustrative case studies, and related teaching aids designed to:
Why this work is needed
Site-Specific Management (SSM) systems have the potential to offer many benefits to the Midwestern crop producer, the environment, and society as a whole. A significant component of that benefit can come from the more effective management of plant nutrients.
Understanding nutrient management concepts requires the ability to understand systems that are both dynamic and complex. These systems are dynamic in the sense that they are in a constant state of change over time. They are complex in that there are many forces coming together and interacting with each other—chemical, biological, climactic, economic, and social.
The introduction of SSM practices increases the complexity of the system exponentially. On the surface, it seems that SSM is simply a matter of replicating WFM fertility management techniques on a smaller scale. However, it is not sufficient to apply traditional WFM logic to manage SSM systems.
Educational tools are needed to help producers, agronomic consultants, and researchers to create a shared understanding of important management issues and provide a foundation for framing relevant research questions. FAR and CENTREC recently completed a project under the IFAFS program that was focused on understanding the conceptual differences between WFM and SSM systems. A key deliverable that came out of this project was a simulation model designed to illustrate the impact of different strategies for managing potassium in corn and soybean production.
The Potassium Training Kit is built around a simple conceptual model of potassium (K) in the soil-crop system, managed under whole-field management. Using standard system dynamics design, the model uses "stocks" representing available K, soil test level, and crop yield, and "flows" representing build-up and maintenance nutrient applications, and crop nutrient removal. Various factors affecting each of these "flows" are adjusted as management decisions in running the model. See Figure 1.
Multiple replicates of the model run are used to apply the decisions on a site-specific basis, which can represent either grid-based or zone-based nutrient management. See Figure 2.
Multiple replicates of the model run are used to apply the decisions on a site-specific basis, which can represent either grid-based or zone-based nutrient management.
The Potassium Training Kit allows the user (teacher or individual user) to compare several options simultaneously, such as the examples in Figure 3.
The package also allows the user to compute an economic analysis of the different scenarios and compare the results among options over multiple years in the cropping system, as in Figure 4.
A combination of graphical and tabular results provides a quick visual overview of results and specific numeric analysis that can be used in conjunction with other decision tools. The economic analysis includes adjustment for the time value of money invested in the nutrient management options being compared. See Figure 5
The complete Potassium (K) Model is built within a Microsoft Excel spreadsheet. Figure 6 is a screen capture of the user interface, where the user can, as the model is running, watch the soil test levels and K application rates change in map format, line graph, and 3-dimensional surface projections. This is just an example of the output options available.
These presentations can show visually, as well as numerically, how the K status changes over time, and its impact on yield and economic return. Such visualization is helpful in making management decisions and is a useful way to present the information to landowners, lenders, and others who have influence on decisions on the farm.
Projected yields for each grid cell or management zone are mapped, and tabular and graphical representations of selected parameters are presented (Figure 7). Annual and 5-year average yields and overall economic reviews are also produced.
The user has control over the designation of potential yield levels for each crop, for each grid cell/management zone (Figure 8). Deviations from expected yield for each year of the model run are computed.
Tabular and graphic representations of economic analysis are presented (Figure 9) to provide statistical and visual comparisons of the options being studied. This series of tools provides much more complete analysis of "What if...?" scenarios that a farmer and his advisers needs to make better-informed nutrient management decisions.
The user has complete control over a wide range of input parameters (Figure 10) upon which the model generates the reports.
Rates of inputs, soil test goals, fertilizer and crop prices, charges for services, and field layout, and other controls are selected by the user and entered as model input values. Cropping sequence can also be varied as desired. Each of these values can be adjusted for successive model runs to develop comparisons of different management decision options.
This project is in its first year, so the work is ongoing. The model will be demonstrated in the oral presentation and will be posted on the FAR websites: www.ppi-far.org and www.farmresearch.com , with updates as the project continues. For questions about the model or the Potassium Training Kit, contact Dr. Harold Reetz by e-mail at hreetz@ppi-far.org or by phone at 217-762-2074.
Figure 1. General concept of the K Model
Figure 2. For Site-Specific scenarios, multiple runs of the basic model are made.
Figure 4. Projected crop yield results for one of the scenarios.
Figure 5. Economic analysis of scenario comparison.
Figure 6. Example output screen for K Model.
Figure 7. Example output report from the K Model.
Figure 8. Yield comparisons for grid or zone analysis.
Figure 9. Annual summary of yield and economic analysis from the K Model.
1 H. F. Reetz, Jr. is President, Foundation for Agronomic Research, Monticello, Illinois. R. C. Schroeder and R. K. Stewart are with CENTREC Consulting Group, LLC, Savoy, Illinois.
