Variable Rate Technology on:
[Wikipedia]
[Google]
[Amazon]
In 
Variable rate application can be either map based or sensor based.
* ''Map based VRA'' is pre-planned, and applications are based on VRA prescription maps that an
precision agriculture
Precision agriculture (PA) is a farming management strategy based on observing, measuring and responding to temporal and spatial variability to improve agricultural production sustainability. It is used in both crop and livestock production. ...
, Variable Rate Application (VRA) refers to the application of a material, such that the rate of application is based on the precise location, or qualities of the area that the material is being applied to.Grisso, Robert & Alley, Marcus & Thomason, Wade & Holshouser, D & Roberson, O.T.. (2011). Precision farming tools: Variable-rate application. Precision, Geospatial, & Sensor Technologies. 442-505. This is different from uniform application, and can be used to save money (using less product), and lessen the environmental impact.Sawyer, J. E. 1994. Concepts of Variable Rate Technology with Considerations for Fertilizer Application. J. Prod. Agric. 7:195-201.
Variable rate application can be either map based or sensor based.
* ''Map based VRA'' is pre-planned, and applications are based on VRA prescription maps that an Agronomist
An agriculturist, agriculturalist, agrologist, or agronomist (abbreviated as agr.), is a professional in the science, practice, and management of agriculture and agribusiness. It is a regulated profession in Canada, India, the Philippines, the U ...
or Advisor prepares based on data sources. Prescription maps can be created using electromagnetic induction
Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field.
Michael Faraday is generally credited with the discovery of induction in 1831, and James Cle ...
, which is considered to be cost-effective, and non-destructive.
* ''Sensor based VRA'' is calculated realtime, based on sensors that are local to the variable rate applicator.
Applications of VRA
In precision agriculture, VRA is known to be used in the following areas.Variable Rate Seeding
Planters and drills can be made into VRA sensors, by attaching a motor or gear box. With this, you can vary the rate of the seeds. The seeding rates can also be connected to match the application of agrochemicals.Variable Rate Weed Control
For variable rate weed control you need both a task computer and a system to physically change the flow rate of theagrochemicals
An agrochemical or agrichemical, a contraction of ''agricultural chemical'', is a chemical product used in industrial agriculture. Agrichemical refers to biocides (pesticides including insecticides, herbicides, fungicides and nematicides) an ...
.
Variable Rate Fertilizer
Crops do not always require a uniform application, as some areas will have different nutrient requirements due to their location (soil properties, sunlight). Variable rate fertilizer spreaders can be used to increase or decrease fertilizer application rate, using a global positioning system (GPS). They can also use "on-the-go" sensors, or a combination of the two.Saleem, Shoaib Rashid, and Dalhousie University. Department of Agricultural Engineering. ''Variable Rate Fertilization in Wild Blueberry Fields to Improve Crop Productivity and Reduce Environmental Impacts / : By Shoaib Rashid Saleem.'' (2012).References