Variable rate application (VRA) in precision agriculture is an area of technology that focuses on the automated application of materials to a given landscape. The way in which the materials are applied is based on data that is collected by sensors, maps, and GPS. These materials include things like fertilizers, chemicals, and seeds, and they all help optimize one’s crop production.

There are many forms of technology that are used in variable rate application for precision agriculture. They include everything from drones and satellites to artificial intelligence (AI) and hyperspectral imaging. Regardless of which variable rate application technology is used, it is important to understand the general way in which this technology is applied.

Variable Rate Application Technology and Fertilization

Applying fertilizer is a common agricultural activity that can be completely automated with the correct implementation of variable rate application technology (VRT). Here is a step-by-step guide on how you would go about utilizing VRT for spraying fertilizer.

1. Zoning/Management Zones – Management zones are separate parts of a field where different materials should be applied. When using variable rate application for precision agriculture, it is important to dictate which zones the machines should apply specific materials to, otherwise you may be setting yourself up for a problem.

Due to its importance, the first step when applying fertilizer with variable rate application technology is to set proper the management zones. It is also crucial to make sure this information is properly inputted into the VRA system itself.

2. Map-Based vs. Sensor-Based VRA – Variable rate application in precision agriculture can be map-based or sensor-based. The second step is to figure out which form is more viable for the problem that you are facing. This can also be influenced by the limitations of the variable rate application technology that is being used.

Map-based VRT is when a map is generated of the landscape and inputted into the system before the system goes about its activities. Sensor-based is when the variable rate application technology integrates sensors that can automatically detect the data that will help it decide which fertilizer should be applied. For example, it could sense the crop health and make a decision based on that.

3. What Data/Imagery Should Be Used – After selecting map-based or sensor-based, the next step is to determine what type of data the sensors should be collecting, or what sort of imagery should be used in the mapping. Many VRA technologies utilize drones or other imaging systems to detect information about the landscape. Others include sensors on the application hardware itself. The most popular machinery-based sensors are N-sensor from Yara, Isaria from Fritzmeier and GreenSeeker from Trimble.

Some of the information that is relevant for applying fertilizer would be things like soil quality and materials, type of crop, climate information, and the speed at which the vehicle is traveling while applying the fertilizer. All of this information and more is made available through the variable rate application technologies that are being used.

Other Applications and Benefits

Variable rate application in precision agriculture focuses on many other areas than just fertilization. Some of the other uses of VRA technology are for the application of herbicides, lime, and other chemicals, seeding, and the detection of weeds and diseased crops.

Overall, VRA technology is primarily used to both detect information about a given landscape and to have a system make decisions based on that information. The decisions that are made by the variable rate application technology systems determine which materials should be applied to the land.

The benefits of having a VRA system is that it can help automate this part of the agricultural process. The more automation and precision that a company introduces to their operations, the more money they can save through higher production and efficiency. Multiple sources present various economic benefits of VRA highlighted below

1. Savings on fertilizers and chemicals. Based on a study at the University of Illinois, the farmers can save about 5 USD per acre due to a VRA technology for nitrogen fertilization.

2. Potential yield increase due to more efficient fertilization and spraying based on actual crop needs and variability of fields.

3. Environmental protection from excess fertilization or spraying of chemicals.

A comprehensive study of the economic benefits of variable-rate application is here.