Mapping Agewise Discrimination of Arecanut Crop Water Requirement Using Hyperspectral Remote Sensing

Abstract

Arecanut is one of the major plantation crops in India. The crop is grown extensively in many regions of the country due to its high commercial value. A part of Channageri taluk of Davanagere district, Karnataka, known as “the land of arecanut” is chosen for the study. The majority of the study area consists of arecanut plantations of various age groups. Growth stage is one of the major factors that govern the crop water requirement (CWR), which in turn influences irrigation planning and scheduling. Accurate estimation of crop area, area under different age groups and area under stress are extremely important to estimate CWR. Traditional methods of area estimation are costly and time consuming. With the advancement in hyperspectral remote sensing, within crop variations can be discriminated with enhanced reliability and accuracy. Using ASD FieldSpec Pro® handheld spectroradiometer spectral signatures of different age groups and stressed arecanut crops are collected to build spectral library. Using the spectral library and Hyperion imagery, arecanut crops of various age groups and under stress (crown choke disease) are mapped by Spectral Angle Mapper (SAM) algorithm with 73.68% accuracy. NDVI based approach is adopted to determine crop coefficients, and Hargreaves & Samani equation to compute reference crop evapotranspiration to assess CWR. In the study area 784.80 hectares of land is under arecanut crop cultivation with daily irrigation requirement estimated to be 28056.09 m3. From the analysis, the average CWR is observed to vary from 19 to 23 litres/day for juvenile to adult arecanut crop. Another interesting observation is that though 16.9% of the existing crop area is stressed due to crown choke disease, the water consumption of it is equivalent to that of healthy crops. Immediate response to address this issue will lead to enhanced plant life and thereby yield.