AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Winter 2000, No. 5
Collecting is the first step. Strategically-placed rain gauges are probably the most important initially. Temperature, solar radiation, relative humidity, and other parameters do not vary as much over a small region, so data from a local public weather station may be adequate. Of course, on-site data are preferred. Depending on the detail and accuracy you desire, you can start with inexpensive rain collection tubes that are read manually, or you can select from a range of automated systems. If your area of interest covers a large geography, just reading the rain gauges may be time consuming. Of course, there is the side benefit of providing an excuse to visit the various fields regularly. The ideal system is to have recording rain gauges, along with temperature, humidity, and solar radiation sensors….and sensors for other data that may be of interest. These can be stored in a data logger on site and collected periodically, or systems are available that use telemetry to transfer the data to your office computer.
The advantage of automatic recording stations on the farm is that the data are already in digital format and can be readily used to prepare summaries and graphics. A simple graph of temperature, rainfall, and other weather parameters is a useful diagnostic and analysis tool. With a little more effort, computed values such as growing degree-days or water stress indices can be derived. These can help predict crop growth, insect life cycles, and onset of disease problems. On-farm weather stations are also becoming important as a means of documenting conditions when pesticides are applied. This information is helpful if there is a problem with herbicide activity, such as a complaint about spray drift, for example, or merely as a reference for future decisions.
Data from on-farm weather stations can also be used to run a wide range of simulation models that are becoming available to help predict crop growth, pest problems, and yield. These models are much more complex than simple growing degree models. The more sophisticated the model, the more important the local, detailed data set. Some models trigger warning systems that alert the farmer by sending an automatic computer message or telephone call warning that a potential problem is developing. High-speed wireless internet communications systems are coming to many rural communities, offering potential to communicate with your data loggers from anywhere in the world. They could dramatically change the way we manage crops, make marketing decisions, and interact with suppliers, landowners, and potential customers.
While soil variability is one of the most important data sets to evaluate spatial variability in the field, weather data are critical to evaluating changes from one growing season to the next (temporal variability). The combination of spatial and temporal data sets with growth and development models can become a powerful management tool once enough years of data are available. Value increases as more years of data become available and comparisons are made among growing seasons. So, even farmers who currently do not use prediction models should begin collecting weather data for use in future comparisons of growing seasons.