Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2012
Publication Date: 7/9/2012
Citation: Kornecki, T.S., Arriaga, F.J., Price, A.J. 2012. Evaluation of methods to assess termination rates of cover crops using visual and non-visible light active sensors. Transactions of the ASABE. 55(3):733-741.
Interpretive Summary: Visual assessments of cover crop termination stage have been the only method utilized in cover crop kill rate evaluation. This method, however, is a subjective in nature and is dependent on individual skills of the evaluator and the perception how a human eye can detect the color differences. The problem is that even similarly trained evaluators can assess termination rates of cover crop differently due to differences in the ability of the human eye to detect color changes in plant. This experiment allowed developing the relationship between visual evaluation of cover crop termination rates and two sensors data: Greenseeker and chlorophyll meter. The strong linear relationship between the linear models and visual observations warranted to utilize this linear model to calculate the cover crop termination rates and use relatively unskilled workers in this task. To determine the accuracy of the model prediction, these models were validated using visual termination rates from different locations. The results indicate that both Greenseeker and chlorophyll meter sensors can be effectively utilized for assessing future rye and crimson clover cover crop termination rates in place of the visual evaluation method.
Technical Abstract: Determination of cover crop termination rate has been based exclusively on visual evaluation of color by a trained evaluator to describe the life state of the plant. However, visual color-based assessment is a subjective method and can vary from one evaluator to another. Differences are associated with how the human eye responds to color assessment in different ambient light conditions. If several skilled individuals are involved in the plant evaluation process in the same field, most likely a deviation associated with the cover crop evaluation will occur due to differences in eye response to colors. To remedy this problem, two experiments over three growing seasons were conducted in Alabama to evaluate cover crop termination rates utilizing three different evaluation methods;1) the visual method and manual data generation; 2) a chlorophyll meter, and 3) an active light sensor (Greenseeker meter) with built-in data loggers. A linear correlation procedure was employed to develop a relationship between observed termination rates and data collected with the instruments. The goal was to establish a relationship between visual determination and instrument readouts, and to utilize these results for developing a procedure for future cover crop senescence assessment (termination rate in % of the cover crop). The instruments have the advantage of performing these evaluations quickly and effectively, and assessments can be performed by relatively unskilled personnel in the field. Two cover crops were evaluated: cereal rye (Secale cereale, L.) and crimson clover (Trifolium incarnatum, L.). Results from three years of data between 2009 and 2011 from two sites showed that there was a strong linear relationship between visual observation and data obtained from the instruments. Because of this strong relationship with R-Squared values from 0.713 to 0.945, models were developed to predict termination rates for the two cover crops. This work developed equations to assess cover crop termination rates using Greenseeker and chlorophyll meters, which are being utilized in agricultural research for different plant evaluation purposes.