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October 16, 2019 - Don't let the monitor fool you! Capitalize on varietal performance by understanding the cotton yield monitor.

As we try to figure out which of our cotton varieties performed best for us, we may jump to conclusions with giving a variety a chance, or over estimating something because of poor calibration.

It was an optimistic end to the week, as reports of exceptional yields from PhytoGen® brand cottonseed are starting to trickle in with harvest kicking off in East Georgia. Just as exciting, December cotton prices jumped nearly 3 points at closing Friday, with even more optimism coming from recent US and China trade discussions. USDA Crop Progress Report estimated nearly 30% of Georgia cotton acres to have been harvested, nearly doubling the average pace over the last 5 years. With perfect weather conditions for finishing a cotton crop setting in, cotton harvest should go by quickly.

As bolls reach the basket and cotton prices slowly rise, the temptation is to trust yield monitor estimations to get a jump on crop marketing. But I encourage you to evaluate and interpret cotton yield monitor results. Currently, there are two types of yield monitoring technologies deployed on the farm that measure cotton mass flow, 1) microwave (John Deere) and 2) optical (Ag Leader/Case IH). While both sensor technologies provide unique advantages to precision crop management, it is imperative to calibrate the systems often, as accuracy is heavily influenced by parameters within the monitors that determine formula as mass flow is converted to volume.

Optical sensors from Ag Leader, and found in Case IH cotton pickers, contain sensors opposite one another within the ducts, emitting light which is modulated into electrical signal as seed cotton flows through to the basket, determining the mass. As seed cotton breaks one of the five infrared light emitters within each sensor, the amount of light reduced by the cotton bolls is recorded and calculated to determine total mass of harvested seed cotton. Microwave sensors, exclusive to John Deere cotton pickers, work similarly, however within these systems, microwaves are emitted and bounce off the cotton seed in attempt to “see” the number of seed passing through the ducts. Based upon estimated number of seeds, total cotton mass is calculated as it enters the basket. To determine flow rate in both systems, a sensor is also installed on the blower fan, providing speed of the cotton traveling through the ducts. The final portion of the yield monitor is the GPS, in which each volumetric batch estimation is georeferenced to the area of the field in which it was harvested.

Understanding the differences that genetic and environmental interaction make on cotton lint yield and quality, one may question the accuracy of cotton yield monitors. While yield monitors can provide accurate relative differences in an area with the same variety and management, substantial changes will quickly skew estimations. When following along in the user manual on calibration procedures, it is highly recommended to recalibrate when variety, moisture, management, defoliation, or environment change to achieve acceptable levels of accuracy. In previous personal discussions with Dr. John Wilkerson, agricultural engineer at the University of Tennessee who developed the original optical cotton yield sensor, he stated variances in fiber parameters and seed size would be the primary limitation to determining varietal differences with on-board yield monitoring alone without calibration between each variety, unlike unbiased impact sensors used to monitor grain in a combine.

Due to the major differences in seed size, fiber length, moisture, leaf trash, gin turnout, and overall fluffiness amongst varieties, flaws in both optical and microwave sensors cause poor estimations when attempting to make comparisons. To overcome these challenges, many research studies have been developed to determine the cause of estimation error amongst varieties, with graduate studies even completing thesis projects in reviewing and further testing to improve calibration formulae (cited links below).

For a few reasons this is an issue. The first being with increased effort to maximize profits by precisely placing the right variety on the right acre, we lose the benefit of yield interpretation when looking at lint yield maps with different varieties in the same field. Additionally, while we look to compare varieties on our acres using our management strategies, we may gain a misconception of some varieties when struggling to keep from peeking over to the right at the screen.

As we look to capitalize on program and early order benefits, we want to understand which variety is performing best so we can make plans for the next growing season. While instantaneous yield information may not be provided without repetitive recalibration, an improved method of developing true yield and fiber quality differences may soon be possible using RFID technology through Granular Agronomy. Tags within each round bale module will log a georeferenced point from which it was harvested allowing both true lint yield and fiber quality to be traced back to respective site-specific areas within the field for improved precision cotton management.

One PhytoGen variety that is continuously being talked about through its strong yield performance is PhytoGen 350 W3FE (pictured below in Appling County, GA). While it continues to perform, it also may be one that is most severely impacted by negative yield differences without recalibrating your yield monitor. While typically demonstrating strong gin turnout, it easily is the largest seed planted in the Southeast, conversely having a lower number of seed per boll. As earlier mentioned, less seed “seen” by John Deere yield monitors will quickly negatively impact yield estimations. Moral of the story is to not be fooled by the screen while you pick and thrive with PhytoGen brand cotton. 

http://trace.tennessee.edu/cgi/viewcontent.cgi?article=1565&context=utk_gradthes

https://ispag.org/proceedings/?action=download&item=5138

https://www.cottoninc.com/wp-content/uploads/2017/03/cottonyieldmonitors.pdf

https://vellidis.uga.edu/wp-content/uploads/2018/12/Simultaneous-Assessment-Cotton-Yield-Monitors.pdf


For more information about cotton production practices in your area, contact your state Extension cotton specialist. As always, your PhytoGen cotton development specialist also is available to discuss agronomic options.

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