Wheat Crop Growth Monitoring using Multi-Spectral Vegetation Indices in Bhal Region, Gujarat State

Abstract

he applications of Remote Sensing techniques in the field of agriculture are wide and varied
ranging from crop discrimination, inventory, assessment and parameter retrieval and assessing long-term
changes and short-term characterization of the crop environment. The spectral crop profile development, as
monitored using Vegetations Indices derived using Multi-Spectral Remote Sensing data offers unique
advantages in crop identification and crop growth stage estimation. The analysis based on values of Normalized
Difference Vegetation Index (NDVI) at regular time interval provides useful information about various crop
growth stages and performance of crop in a season. In the present study, Multi-date Landsat-8 data for the Rabi
crop season from October-2017 to April-2018, covering Dholka and Dhandhuka Talukas in Ahmedabad
District, was downloaded from https://earthexplorer.usgs.gov/. The spectral Vegetation Indices (VIs) namely
Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI) and short-wave
infrared - Water Stress (SWIR - WSI) Index were generated using the NIR, RED and SWIR channel digital
data. Field data was collected in the selected sample locations in the study area for identification of wheat and
other competing crops grown during rabi season.
Multi-date spectral indices of wheat & cotton were generated at different growth stages. The spectral profiles of
these two crops indicate that the crops are well separated at different growth stages since their crop phenology is
quite distinct. The Water Stress Index (WSI) and Normalized Difference Vegetation Indices (NDVI) resulted the
exactly opposite profiles and their intersection points can also indicate about the spectral emergence and
physiological maturity stages of wheat crop. The study revealed that during normal crop season, the NDWI
values were positive for both the crops throughout the growing season. The positive values of NDWI were due
to higher NIR-Channel reflectance than SWIR-channel, which indicates sufficient quantities of water in the
vegetation canopy