From OMAFRA Crop Talk, June 2015
http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2015/ct-0615a2.htm
By Ian McDonald - Applied Research Co-ordinator/OMAFRA
Precision agriculture has great potential to enhance both economic returns and reduce the environmental impacts of agriculture. A large site specific management project, sponsored by the Grain Farmers of Ontario through Growing Forward 2, is moving ahead with help from OMAFRA, Niagara College and other partners. The goal is to create simple systems for developing management zones within fields.
Creating management zones is not well understood. Management zone creation and site specific input management will enable farmers to target inputs for optimum economic returns. Under current management systems of blanket application rates, some areas are getting too much input, while others might not be getting enough. This reduces input use efficiency, increases costs of production, and leaves more inputs in the environment that are not contributing to production. Low productive areas of a field are the most problematic with blanket field management. In order to meet the needs of the medium and high responsive areas, these low productive areas are getting too much input.
Developing Management Zones
Management zones are created using one or more site specific "layers" of data. Management zones bring together what you see, measure and achieve to provide data layers that are identified by time and location (Figure 1).
- "What you See" is the topography, with its knolls, depressions, slopes and curvatures that impact crop yields. This includes RTK elevation data, satellite and other imagery.
- "What you Measure" are the soil chemistry and biology characteristics measured by nutrients, organic matter, texture, CEC, electrical conductivity, etc. Soil sampling, soil and plant sensors, and lab analysis are used.
- "What you Achieve" is the crop yield. This requires the combine to be RTK equipped.
The layered data is fed through commercially available or research integrated processing tools to produce management zone maps. A challenge is determining what layers are needed and what do you do if you don't have key layers, such as multiyear yield maps?
Figure 1. Logic Model of the development of management zones (adapted from Aspinall and Sweeny, OMAFRA, 2014)
Research Project
For the 3 year project, data layers will be collected for yield, topography, soil texture, soil chemistry, imagery, CEC, and electrical conductivity across 30 fields. The various data layers will be run through the processing system and then tested for accuracy and stability of the management zones produced. This will determine what variables work best for defining management zones and whether the chosen variables are consistent across sites or vary depending on site specific conditions (Figure 2).
Figure 2. An example of various data layers that are overlapped in the generation of management zones. Top to bottom - yield, water, soil type, soil chemistry.
Variable Rate Application Outcomes
Extensive research by Dr. Raj Khosla (Colorado State University) has found that the site specific management response can vary significantly. Figure 3 identifies possible outcomes from implementing variable rate applications (VRA) of nitrogen. The first bars of the graph illustrate a blanket input application at a field scale where that level of input achieves a given level of yield. From left to right, various results can occur when VRA is implemented.
VRA could end up with exactly the same response as a blanket application.
Inputs may stay the same and yield increases.
Inputs may be lower and yields stay the same.
Both inputs and yields may be greater.
Input levels declines and yield increases. This is the best scenario.
Inputs and yield both decline. Occurring about 10% of the time, you are no further ahead than with blanket field applications. This is the worst case scenario.
The response to site specific management and VRA generally fit into senarios 2-5.
Figure 3. Responses with a site specific management variable rate application (SS-VRA) system. (Adapted from Raj Khosla, Colorado State U, SW Ag Conferene, 2015)
Learn More The Grain Farmer magazine is publishing a series of OMAFRA prepared precision ag articles, beginning with the February issue. ( http://www.gfo.ca/Research/PrecisionAg.aspx ). While precision ag and site specific management have been around for 10-20 years, the technology is rapidly evolving so that the average person can become engaged. If you have a keen interest in precision ag, attend or review InfoAg Conference presentations held in southern Illinois each summer.
Source: OMAFRA