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Cotton yield maps

How cotton yield monitors work?

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.



The yield map in the Figure 1 is of a 64 acre field in Georgia and is detailed enough to see the tracks of the center pivot irrigation system in the lower portion of the map (arcs). The map also exhibits a high level of yield variability which is typical of many fields. In this field, the variability is attributed to many factors. The lower end of the field is not irrigated and consistently yields less than most irrIgated areas. The low wet area at the center right of the field generally produces lower yields in wet years because it receives nutrient-rich runoff from the surrounding slopes which results in rank growth rather than high yields. Conversely, this area produces high yields during dry years.  The top center and top right areas of the field are eroded and generally have poor stands and consequently low yields. The top left area of the field was recently brought into duction after being in pasture for decades. High soil organic matter and good soil structure resulted in excellent yields. With a yield map, a producer can compare the yields between highly productive and less productive areas and make appropriate management decisions and answer questions such as: Is intervention a good investment?


Figure 2 presents profit maps created from the yield map shown in Figure 1. The profit maps were created by multiplying the yield data by the market price of cotton lint and then subtracting the production costs. The result is a map of net revenue in terms of dollar per acre commonly referred to as a profit map. The profit map on the left uses the 2011 Georgia estimates for the price of lint and irrigated production costs – $1.00/lb and $528/ac, respectively. With these figures, 9.7% of the area resulted in a net loss of income, 21.9% of the field provided a net return of between $0 and $250 per acre, 41.1% provided a net return of between $250 and $500 per acre, 27.4% provided a net return of greater than $500 per
acre. When nearly 10% of a field results in net loss of income even under relatively high cotton prices, it provides the opportunity for management changes that should lead to increased profitability. The profit map on the right uses the 2012 Georgia estimates for the price of lint and irncreased profitability. The profit map on the right uses the 2012 Georgia estimates for the price of lint and irrigated production costs – $0.75/lb and $577/ac, respectively. With these figures, the profit map is dramatically different and 29.9% of the field results in net loss of income. When yield patterns don’t vary much from year to year within a given field, it is relatively simple to evaluate scenarios with different levels of yield, price, and production cost and identify areas of the field which are chronically unprofitable.


Figure 3 shows how a yield map can have an immediate management benefit. This 53 acre field is irrigated by a center pivot. The two dark green circles of higher yield were caused by leaks in the center pivot. As a result, the cotton immediately under the leak received more water than was applied to rest of the field. In addition to pointing out that the leaks should be repaired, the yield map clearly indicates that there is opportunity to increase yields by irrigating more.

(Source  – http://www.cottoninc.com/fiber/AgriculturalDisciplines/Engineering/Precision-Crop-Management-for-Cotton/Cotton-Yield-Maps/Cotton-Yield-Maps-PDF.pdf)


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