Spectral Characteristics of K Deficiencies in Multiple Cotton Cultivars At the Canopy Scale

An effective, efficient method to determine N status in-season independent of K status would give a producer the opportunity to correct yield-reducing N deficiencies without making unnecessary fertilizer applications.  The objective of this research was to describe the spectral characteristics of K deficiencies in multiple cotton cultivars at the canopy scale.  Field trials were conducted in 2012 at the University of Arkansas Experiment Station in Marianna, AR.  Canopy reflectance was measured by a Crop Circle ACS-470 unit (Holland Scientific, Inc., Lincoln, NE) within three hours of solar noon.  The most recently matured, fully expanded main-stem leaf and petiole four to five nodes from the apical meristem and uppermost white flower were harvested at the time of reflectance.  Tissue sampling and reflectance was measured weekly from early flower to peak flower.  Tissue samples were dried, ground, and sent to the Plant Diagnostic Laboratory for nutrient analysis.  Results are expected to show heightened sensitivity of the flower to K deficiency as compared to leaves or petioles and a strong correlation between flower K concentration and spectral response of K deficiencies.