Dirt can be transported by wind, human activity and many other factors. It was hypothesized that dirt particles collected on leaves will decrease leaf reflectance and thus make the leaf less healthy. The rationale for this is that the more dirt present on the leaf, the more inhibited photons will be in reaching leaf pigments. The leaf will therefore be less healthy as it will be less able to perform photosynthesis. To test this hypothesis, eight leaf samples with varying amounts of dirt present, were collected from the plant, Musa. A Unispec spectrophotometer was used to test the reflectance of the leaves and from the collected data the NDVI was found. A Dirt Index was created as a second form of measuring the reflectance by a leaf. A Leaf Area Meter was used to measure the area of each of the eight samples. The data was then normalized taking into the account the amount of dirt on each sample and the area of each sample. The data coincided with the hypothesis. The dirt index and NDVI were both correlated with the amount of dirt on the leaf yet the NDVI had better accounted variance. The T-tests of both the DI and NDVI verified the hypothesis that leaves with greater amounts of dirt had lower reflectance.
Knight, Lorelle; Carrington, Alexis; French, Angela; and Barker, Roxanne, "The effect of dirt on inhibition of light absorption in Musa leaves" (2012). Pepperdine University, Featured Research. Paper 48.