The Granular Crop Model FAQ
What is the Granular Crop Model?
The Granular Crop Model (GCM) is a daily time-step mechanistic crop growth computer program that simulates both the growth of a corn plant and the soil processes given inputs of weather, soil, management and crop genetics. The Granular Crop Model simulates plant growth, plant uptake, water availability, nitrogen and organic matter transformations and more on a daily basis. Granular Crop Model was developed by Corteva in 2018 and has been used in Encirca Nitrogen 2.0 and is currently being used in Granular Agronomy Nitrogen. Corteva holds two patents in environmental management zone modeling and analysis, enveloped in Granular Agronomy Nitrogen and the Granular Crop Model.
Why is there an update to the model?
The Granular Crop Model, as it was released in 2018, was a major step forward. However, newly available research from internal and external efforts helped us to determine that updates could be made to improve the accuracy of certain sub-model functions. Additionally, as the Granular Crop Model was applied on customers farms, new features were requested based on their needs. A team of crop modelers, field and data scientists and software engineers was formed in 2019 and tasked with addressing these areas of the model for improvement.
What improvements were made to the model?
Improvements focused primarily on the below-ground portion of the model, specifically soil moisture and temperature. These sub-simulations are foundational for them properly modeling nitrogen movement and transformation (nitrification, denitrification, leaching and plant uptake). At the same time, efforts were made to properly simulate over-wintering conditions, such as snow cover (and it’s insulative effect), frozen soil water and the cessation of mineralization, nitrification, and leaching while the soil is frozen.
The team addressed and improved urea volatilization simulation and the effectiveness of stabilizer usage This is crucial for in-season top dressing applications. Additional functionality to allow fertilizer blends to be used enables users to create their own fertilizer blends containing non-standard ratios of nitrogen forms.
While working in these areas, the team also reconfigured the model’s inputs and outputs to be ready for future enhancements, such as cover crops, biological nitrogen fixation products, new nitrogen stabilizers, tillage, and more. Many of these features are intended for future releases of Granular Nitrogen. Overall, the team made 52 revisions to the initial Granular Crop Model version from early 2019.
What research was used to make these changes?
The improvements to the Granular Crop Model were made based on a diverse set of research studies and literature review.
Primarily, the Pioneer Regional Nitrogen Trials (PRNT), a collaboration between Pioneer and eight Midwestern universities, aligned trial and measurement methodology, conducted in 2014 to 2016, was extensively utilized for model tuning and validation.
Additionally, Corteva Nitrogen Trials from 2018 to 2020, conducted at various Pioneer research sites in the Midwest, were used for crucial soil and plant measurements.
Finally, on-farm nitrogen response trials, conducted with the assistance of Granular Certified Service Agents and their farmers in 2020, provided a diverse data set that spanned from Ontario, Canada to the Mississippi Delta. Extensive literature review of existing research papers was made to incorporate and validate new model adjustments and features.
Research continued in the 2021 crop season with the Corteva Nitrogen Trials and CSA-Farmer N Response Trials, along with newly established university collaborations with University of Nebraska, University of Minnesota, Purdue University, University of Guelph, University of Delaware, University of Maryland, and Penn State University.
These efforts and collaborations will ensure that the Granular Crop Model will benefit from the latest in nitrogen management research for years to come.
How do these changes improve nitrogen monitoring and nitrogen recommendation generation compared to the current version?
With these improvements, the Granular Crop Model is more dynamic and responsive to weather, soil and management inputs. This provides users with greater ability to make management decisions when weather conditions take a turn for the better or worse.
As part of the new Granular Crop Model version, the soil nitrogen target at VT/R1 growth stage, used to determine if enough nitrogen is available to carry the crop through grain fill, has been adjusted based on updated measurements from research. The updated calculation results in lower, more accurate target values than the prior calculation; based on extensive research, we find this target provides nitrogen recommendation at similar or better accuracy than the older model.
Based on the improvements in soil temperature and moisture estimation, the new model version will simulate wetter conditions over the winter than the older version. In turn, leaching (downward flow of nitrogen) is simulated at higher levels than previously. This change corresponds to actual field observations and measurements and provides better simulations of nitrogen losses in the spring generally found in the Midwest US, helping users make more timely management decisions.
Granular and Corteva are committed to delivering the best science in nitrogen management to you. This update to the Granular Crop Model, central to nitrogen management efforts at Granular, will ensure greater accuracy and responsiveness and enable future enhancements that deliver value to farmers.
