Precision Agriculture

Precision agriculture is a catch-all term for techniques, technologies, and management strategies aimed at addressing the variability of parameters that affect crop growth.  These parameters may include soil type, pH, soil organic matter, plant nutrient levels, topography, water availability, weed pressure, insect pressure, etc.  The purpose of implementing a precision agriculture management plan is to address this variability and thereby improve the efficiency and profitability of the farm operation.

We have been involved in precision agriculture projects for more than 15 years.  Our latest work is on variable rate application of agrochemicals on cotton, using RTK-based GPS guidance for planting and inverting peanuts, promoting the use of yield maps, and precision irrigation.  You can find more information on precision irrigation under the Smart Irrigation page.  For the other topics, please see information below.

Variable Rate Application of Agrochemicals for Cotton

During the 2008 – 2012 growing seasons, we conducted research to evaluate the feasibility of variably applying defoliants, plant growth regulators (PGRs), and side-dress N on cotton.  We used the GreenSeeker® sensing system as the basis for measuring the status of the cotton crop.  The GreenSeeker measures light reflectance from plants in the red and near infra-red wave bands and uses this information to calculate vegetation indices (VIs).  VIs are mathematical ratios of reflectance data.  The most commonly used VI is the NDVI (Normalized Difference Vegetation Index).  Under most circumstances, NDVI is highly correlated with plant biomass.  Although our results with the variable rate application (VRA) of PGRs are mixed, our research team feels very comfortable in recommending the VRA of defoliants and side-dress N on cotton.

This project was funded by the Georgia Cotton Commission and by Cotton Incorporated.

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Using RTK-Based GPS Guidance for Planting and Inverting Peanuts

GPS guidance of farm machinery has been adopted by increasingly larger segments of the farming community over the past decade because of the inherent gains in efficiency that it provides.  We conducted a study for two consecutive years (2010 and 2011) on a working farm in Georgia to quantify the yield benefit of using RTK-based automated steering (auto-steer) to plant and invert peanuts under a variety of terrain conditions.  Auto-steer outperformed conventional (manual driving) by 516 lb/ac (579 kg/ha) in 2010 and 402 lb/ac (451 kg/ha) in 2011.  If we apply the yield gain resulting from auto-steer to the average area planted to peanuts each year by the cooperating farmer (180 ac, 73 ha), the farmer would have realized an economic gain of $27,851 in 2010 and $34,350 in 2011.  The large difference in economic return between 2010 and 2011 is caused by the large difference in peanut prices between the two years.  In 2010, the farmer sold his peanuts for $600/ton while in 2011 he sold his crop for $950/ton.  Considering that installation of an RTK-based auto-steer system on a tractor costs between $22,000 and $25,000 (depending on the manufacturer) and requires an annual RTK correction subscription of between $800 to $1000, investing in an auto-steer system is a good economic decision as the system can easily pay for itself in short order.

Funding for this project was provided by National Peanut Board’s Southeastern Peanut Research Initiative Committee through the Georgia Agricultural Commodity Commission for Peanuts.


Vellidis, G., B. Ortiz, J. Beasley, R. Hill, H. Henry, and H. Brannen. 2013. Using RTK-based GPS guidance for planting and inverting peanuts. In: J.V. Stafford (Ed.), Precision Agriculture 2013 – Proceedings of the 9th European Conference on Precision Agriculture (9ECPA), Lleida, Spain. Download PDF


Auto-steer Driving Peanut Grower Profits – from the Southeast Farm Press website

Yield Maps and Profit Maps for Cotton

Yield maps provide a visual image which shows the variability of yield across a field and can be used to identify high or low yielding areas.  Yield maps can be viewed as both the entrance and the final exam for precision agriculture: as an entrance exam because they can be used to determine if there is enough variability to justify the use of precision agriculture; as a final exam because they can subsequently be used to determine if the investment in precision agriculture was worthwhile.  By incorporating production costs, yield maps can be converted to profit maps which provide a vivid image of the least and most profitable areas in the field.  Managing these areas individually will typically result in higher overall profitability.  Yield maps are created from data collected by a yield monitor – a sensor – or group of sensors –  installed on harvesting equipment that dynamically measure spatial yield variability.

Graphic of 3 yield maps

Yield map (left) of a 64 acre field in southern Georgia created with an Ag Leader yield monitor mounted on a 4-row John Deere 9965 cotton picker. The center and right figures are profit maps of the field created from the yield data using the 2011 Georgia estimates for the average price of lint and irrigated production costs ($1.00/lb and $528/ac, respectively) (center) and the 2012 Georgia estimates for the averages of $0.75/lb for price of lint and $577/ac for irrigated production costs (right). In the center map, 9.7% of field resulted in a net loss to the producer. In the right map, 29.9% of field resulted in a net loss to the producer because of lower cotton prices and higher production costs.

All commercially available cotton yield monitors are mounted on or behind the ducts of a cotton picker and measure the cotton passing through the ducts during harvest.  Depending on the model of yield monitor, sensors may be installed on 2, 4 or 6 ducts.  Cables from the sensors on the ducts lead to the cab of the picker where a user interface console is installed. The console receives and processes data from the sensors, displays yield information and yield maps in real time, and stores the data for later use.  Yield data are typically stored in pounds of seed cotton harvested per acre although the user can choose to display yield data in many forms including bales per acre.  Each yield data point is associated with a unique location (latitude and longitude) provided by a GPS receiver.  At the end of the harvest, the yield data can be downloaded to a personal computer and used to create and print yield maps.

We have developed two user-friendly publications to assist cotton producers with the selection of cotton yield monitors and to assist them in understanding how yield maps can be used to improve the efficiency and profitability of the farm operation.

Download PDF:  Why Yield Maps?

Download PDF:  Cotton Yield Monitors: The Entrance Exam &Final Exam for Precision Agriculture

This project was funded by Cotton Incorporated.

Additional information can be found on Cotton Inc.’s Precision Crop Management for Cotton website.

Cotton Yield Maps: Tools for Increasing Efficiency and Profitability – Cotton Incorporated and Plant Management Network ‘Focus on Cotton’ webcast.


Yield Maps Considered Entrance and Final Exam for Precision Agriculture – from the Southeast Farm Press website