Conclusions and Recommendations
1.2.1. Research Questions
a. Is there any relationship between tea LAI and NDVI using MODIS?
It was observed that there is linear relationship between LAI and NDVI. LAI is a key factor useful in crop growth models that may be derived from the optical remote sensing data. The LAI during the plucking stage is an important variable in tea yield modelling and can also be used in crop reflectance modelling. The relationship between tea LAI and NDVI is very important for developing yield prediction models. In this study, when field LAI and MODIS NDVI were analyzed, a variance of 0.4094 was observed between LAI and NDVI. Therefore it was found that the LAI variability could be observed using the MODIS data.
b. Is there any relationship between NDVI and tea leaf yield at critical periods?
Remote sensing measures specific wavelengths of light that are reflected from the leaves of plants in the field. In addition to light in the visible spectra, light in the near infrared spectrum (NIR, which is not visible with the naked eye and is reflected by the plant) is measured as well. The amount of NIR reflectance is related to the biomass (leaf area) of the plant and the plant’s vigor; larger plants with more leaves will reflect more NIR light than smaller plants, just as healthy vigorous plants of a given size will reflect more NIR light than diseased or stressed plants of the same size. The NIR reflectance from a plant can change over time as it encounters stress (such as disease), which can then be used to assist in the identification of a problem with the plant prior to the onset of visual symptoms. Reflectance data can be measured and used to calculate a vegetation index (such as Normalized Difference Vegetation Index; NDVI), which has been found to be correlated to plant size, vigor and yield of crops. In this study, at different critical periods the correlation between NDVI and yield was derived. Though variations could be observed between NDVI and yield, yet a positive correlation was obtained. Variations were mainly due to continuous plucking, different tea species and also due to stress such as diseases. But the study showed that a good correlation could be obtained if the above mentioned parameters could be avoided.