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United States Department of Agriculture

Agricultural Research Service

Research Project: NEW AND IMPROVED CULTURAL PRACTICES FOR SUSTAINABLE SUGARCANE PRODUCTION AND ENVIRONMENTAL PROTECTION

Location: Sugarcane Research Unit

Title: Prediction of sugarcane sucrose content with high resolution, hyperspectral leaf reflectance measurements

Authors
item Johnson, Richard
item Richard Jr, Edward

Submitted to: International Sugar Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 27, 2010
Publication Date: January 20, 2011
Citation: Johnson, R.M., Richard Jr, E.P. 2011. Prediction of sugarcane sucrose content with high resolution, hyperspectral leaf reflectance measurements. International Sugar Journal. 113:48-55.

Interpretive Summary: Remote sensing for crop maturity parameters may offer sugarcane producers a method to develop harvest schedules that maximize sucrose production. Several tests were initiated to determine if leaf reflectance measurements could be used to predict theoretically recoverable sugar (TRS) levels (crop maturity) prior to harvest. Leaf samples were collected from multi-variety first-ratoon (FR) sugarcane maturity studies in 2005 at three sample dates and from the plant-cane (PC) and first-ratoon (FR) sugarcane maturity studies throughout the 2006 September through December harvest season. Results from the 2005 FR maturity studies showed that leaf reflectance was effective at predicting TRS in 36 to 79% of the cases if varieties were combined and in 65 to 100% of the cases if the varieties were considered separately. Results from regression analyses between leaf reflectance and TRS values indicated that simple models could be developed to more effectively predict sucrose levels before harvest. Regression analyses also identified several spectral regions that appeared to be important in describing stalk sucrose levels, including: ultraviolet, blue, green and yellow, orange and red, and the near-infrared wavelengths. These combined results indicate that it may be possible to utilize remote sensing techniques to estimate sugarcane maturity (TRS) of the various varieties grown in Louisiana prior to harvest. This would allow growers and mills to more effectively manage field and varietal harvest schedules to insure maximum sucrose yields.

Technical Abstract: Remote sensing for crop maturity parameters may offer sugarcane producers a method to develop harvest schedules that maximize sucrose production. Several tests were conducted to determine if leaf reflectance measurements could be used to predict theoretically recoverable sugar (TRS) levels (crop maturity) prior to harvest. Leaf samples were collected from multi-variety first-ratoon (FR) sugarcane maturity studies in 2005 at three sample dates and from the plant-cane (PC) and first-ratoon (FR) sugarcane maturity studies throughout the 2006 September through December harvest season. Sugarcane juice was extracted from a fifteen-stalk sample and analyzed for its Brix, sucrose, and fiber contents to predict TRS. Leaf reflectance measurements were taken from four locations on each leaf, using a dual input, fiber optic spectrometer. Results were analyzed using multivariate methods and stepwise regression analysis. Results from discriminant analysis of the 2005 FR maturity studies showed that leaf reflectance was effective at predicting TRS in 79% and 54% of the cases if varieties were combined using resubstitution and cross validation techniques, respectively. If the varieties were considered separately then 100% of the cases could be correctly classified using both resubstitution and cross validation. In the 2006 FR and PC maturity studies leaf reflectance was effective at predicting TRS levels in 59 and 76% of the cases using resubstitution and 37 and 36% using cross validation. When varieties were considered separately reflectance predicted TRS in 100% of the cases in both PC and FR tests using re-substitution techniques. Cross validation studies showed that when varieties were considered separately TRS could be predicted correctly in 65-92% of the cases for FR and in 60-93% of the cases in PC. Results from regression analyses between leaf reflectance values and TRS indicated that simple models could be developed that described much of the variability present in stalk sucrose levels. Results were better when varieties were considered separately than when they were combined. Regression analyses also identified several regions that appeared to be important in describing stalk sucrose levels, including; the ultraviolet (250-330 nm), blue, green and yellow (450-590 nm), orange and red (590-650 nm), and the near-infrared (740-850 nm). These combined results indicate that it may be possible to utilize remote sensing techniques to estimate sugarcane maturity (TRS) prior to harvest. This would allow growers and mills to more effectively manage field and varietal harvest schedules to insure maximum sucrose yields.

Last Modified: 4/20/2014
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