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Ways to Apply Using Variable Rates

What’s available for lime, fertilizer, weed control and seed to us Variable Rate Application (VRA)? There’s a variety both with and without GPS! Most VRAs fit into one of two categories: sensor-based or map-based.

The VRA technology that is map-based uses a “prescription” map that is stored electronically to apply the materials at different rates.

On the other hand, VRA that is sensor-based doesn’t need a GPS system or a map. Sensors judge the earth and plants and then send the info to a computer that controls what should be input and where, based on the sensor. Both have pros and cons, so there are now SSCM technologies that attempt to have the best of both worlds.

VRA that uses Maps

Since these VRAs use maps that have been measured and made at a previous time, application can be done in a variety of ways. Farmers and consultants came up with different ways for different kinds of inputs. These are based on soil (type, color and texture), topography, yield, data from visual surveillance, and images from remote sensors in addition to other information about the crops or area. Some approaches count on just one source of info and others use multiple sources of information. It doesn’t really matter where the information comes. In the end, the applicator must analyze the map of information, know its own location, and apply appropriately.

To develop such an electronic map, you might have to:

  • sample the soil systematically.

  • create maps of the soils nutrition and other characteristics

  • have an algorithm that determines the need of each area of the field

  • take the map of this information and have a fertilizer applicator use it

A GPS unit would be needed during sampling and applying so that the farmer is sure that the VRA system is being applied to the needy areas.

VRA that uses Sensors

Using sensors makes it possible to judge the needs of an area without a map or collecting info on an area. The sensors can measure soil nutrition or characteristics in real time, mid run. The real-time data is then used to judge what needs to be applied immediately. VRA with sensors don’t need to have a GPS unit, and don’t necessitate in-depth research into what’s needed. Yet, recording the sensor’s data with GPS data is helpful for planning for crops in the future and making a “prescription” map for other future plans. It also helps to see what work has been done and how it succeeded. 

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