Canopy Characteristics and their Ability to Predict Peanut Maturity

Abstract

AbstractTo ensure maximum economic return, a peanut producer must accurately predict harvest time, delaying as long as possible to reach optimal crop maturity without risking losses through mechanical damage due to deteriorating peg attachments. Currently utilized methods for predicting peanut maturity are based on hull color determination and are labor-intensive and subject to the observer's ability to finely discriminate color classes. This study sought to test and evaluate canopy traits that may be correlated with crop maturity. Specifically, the objective of this study was to determine if plant canopy characteristics could be used successfully to predict peanut maturity, through the correlation of solute concentrations, chlorophyll content, nutrient analysis, and reflectance with crop maturity. Using sequential harvest dates in 2003 and 2004 at two sites (Sasser and Dawson, GA), canopy characteristics including: Brix, osmolality, chlorophyll content, macro- and micro-nutrients, and spectral indices were correlated with the maturity of the crop represented by Maturity Index 1 (the percentage of brown and black pods). Stepwise regression of these canopy characteristics with Maturity Index 1 indicated seven leaf characteristics were important in predicting the maturity of the crop: nitrogen, phosphorus, potassium, magnesium, calcium, manganese, and iron. By calculating and summing the relative change of these leaf nutrients from the first to the last harvest, it was determined this Change Index showed a quadratic relationship across harvests. Therefore, it appears that crop maturity in the southeastern U.S. can be accurately and objectively predicted through the use of late season canopy nutrient analysis. Canopy reflectance in the 830 and 850 nm region also showed strong correlation with crop maturity indicating that the use of remotely sensed spectral indices should be further developed as a crop maturity predictor in this region.