Pimpale, Dr. A. R.AKKARA, MONCY S.2024-01-112024-01-112022-11-28AKKARA, MONCY S. (2022). Estimation of evapotranspiration of chickpea using vegetation indices based crop coefficients. Department of Irrigation and Drainage Engineering, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola. M. Tech. 2022. Print. xiv, 113p. (Unpublished).https://krishikosh.egranth.ac.in/handle/1/5810206155Ever growing water demand of world along with the severe reduction in water availability- quantitatively and qualitatively, necessitates monitoring and management of existing water resources in the best possible way. Agriculture being major shareholder of fresh water consumption calls for an immediate action to adopt proper irrigation methods and develop technology to make judicious use of water. Better estimation of irrigation water requirements is essential for water conservation aspects as well as better yield and economic aspects. Evapotranspiration being the major consumptive use of irrigation water, crop evapotranspiration represents crop water requirement and is calculated by FAO-56 procedures based on literature derived crop coefficients. Irrigation scheduling based on literature derived crop coefficients often leads to over irrigation due to the non optimal actual field conditions and spatial and temporal variations in Kc. Remotely sensed multispectral vegetation indices (VIs) have similar pattern as that of crop coefficients (Kc). Hence, Kc can be modelled using VIs. The Kc derived from VI responds to actual field conditions and captures spatial variability. Thus, VI based approach can be used for crop identification, acreage estimation and precision irrigation management. Furthermore, yield and quality of moisture sensitive chickpea crop can be considerably increased by applying precise irrigation in critical stages though it is a rabi crop. The present investigation entitled ‘Estimation of Evapotranspiration of Chickpea using Vegetation Indices Based Crop Coefficients’ was undertaken with major objective of identifying the most appropriate VI having highest correlation with crop coefficients of rabi chickpea crop in order to estimate the water demand. The study was conducted in Akola district located in Maharashtra. Multidate Sentinel 2 A (MSI sensor) satellite images were used to extract most commonly used vegetation indices RVI, NDVI, NDWI and SAVI. The spectral behaviour of the chickpea crop suggested that the VIs follow a similar pattern to crop coefficients. The two stage hybrid classification technique of remote sensing was employed to compute the crop acreage. The results showed an overestimation of 3.12% than the crop statistics published by the Department of Agriculture, Government of Maharashtra. The values of multi-date vegetation indices RVI, NDVI, NDWI and SAVI were distributed according to the age of the crop on each day of satellite data acquisition. Simple linear regression analysis was applied to derive the relationship between the mean weekly VI values and the week-wise crop coefficients (Kc) recommended by MPKV Rahuri and the relationships were established in the form of prediction models. All the vegetation indices exhibited good correlation with crop coefficients (Kc) with high R² values. However, NDWI-Kc model outperformed all other regression models. NDWI-Kc model showed highest R² and D values of 0.9550 and 0.9884 respectively with lowest values of SE, RMSE and PD of 0.0743, 0.0698 and 4.1016 respectively. Hence, NDWI was identified as the most superior remote sensing indicator for estimation of chickpea crop coefficients. The weekly crop coefficients were derived from the best performing NDWI-Kc model and the crop water requirement was estimated as 248.23 mm for chickpea crop. Crop water demand of rabi chickpea in Akola district was determined as 213.4138 Mm3. The outcomes of this study show the potential of multispectral vegetation indices for estimating spatial crop coefficients, leading to the determination of site-specific crop water demand and thus ultimately helping in precise irrigation water management, by providing irrigation with high water use efficiency and saving significant amount of water.EnglishThesis