A Novel Foliar Color Model for Nitrogen Deficiency Diagnosis of Rubber Trees

The foliar color pattern under the stress of nitrogen deficiency varies usually in a uniformly distributed way, so it seems reasonable to fabricate a detection index directly using the averaged value or any of the relative form of its color components. However, these color components are linearly correlated with each other, and the mineral contents don’t have a precise metric description themselves, which makes the color modeling a very tough task. In this paper, a novel foliar color model of rubber trees is proposed to approach the detection index by combining the relative components with the absolute ones, taking full considerations of vagueness of nutritious description, for which a slope angle as a metric to evaluate the fitness of the color model is proposed. Our experimental results have substantiated this supposition.