Kadam, S.A.Mandre Nileshkumar Prakash2018-12-272018-12-272018http://krishikosh.egranth.ac.in/handle/1/5810086477The study entitled “Crop coefficient and yield response factor for rabi potato” was conducted during rabi season of 2015-16 and 2016-2017 at the Instructional Farm of Department of Irrigation and Drainage Engineering, Dr. Annasaheb Shinde College of Agricultural Engineering and Technology, Mahatma Phule Krishi Vidyapeeth, Rahuri. The study was conducted with the objectives to study effect of moisture stress of different quantity during different growth stages of potato on its yield, to develop crop coefficient (Kc) for potato crop, to develop yield response factor (Ky) for potato crop, to develop the spectral signature library for potato crop and values of Normalized Difference Vegetation Index (NDVI) over crop growth period and to develop the relationship between Kc and NDVI. Twenty seven treatment combinations that included three crop growth stages (viz. vegetative stage: 0 to 30 days, tuber development stage: 31 to 60 days, and maturity stage: 61 to 100 days) and three water stress levels (viz. No stress: 0 % stress, 20 % stress and 40 % stress) at each crop growth stage were laid out with two replications in randomized block design. The total area of layout size was 40 x 28.8 m with net plot size of one treatment was 4 x 3.6 m. The standard cultivation practices were followed during the crop growth period. It was found that deficit irrigation at different crop growth stages of potato significantly affected plant height, plant branches, plant leaves and yield. The highest potato yield of 31.20 t/ha were obtained with no water stress treatment (T1) followed by 29.80 t/ha yield in treatment T2 (20 % water stress at maturity stage) which is at par with treatment T1. The potato yield is found higher with less water stress and reduced with increase in water stress. The crop coefficient for potato crop was estimated using field water balance method. The crop coefficient varied from 0.39 to 1.28 during crop growth period. The average values of Kc for potato found 0.63 for vegetative stage, 1.12 for tuber development stage and 1.10 for maturity stage. However, Kc values for potato given by FAO were 0.50 for vegetative stage (1 to 20 days), 1.15 for tuber development stage (21 to 80 days) and 0.75 for maturity stage (81 to 100 days). The Kc values estimated for semi-arid region for potato were found higher for vegetative stage (26 %), maturity stage (46.66 %), respectively and found (2.60 %) lower at tuber development stage as compared to Kc values given by FAO. Crop yield response factor (Ky) indicates a linear relationship between the decrease in relative water consumption and the decrease in relative yield. It shows the response of yield with respect to the decrease in water consumption. In other words, it explains the decrease in yield caused by the per unit decrease in water consumption. The seasonal yield response factor (Ky) for potato crop was found as 1.44. The stage wise yield response factors were determined for dated water production function given by Stewart et al.,(1976) equation. The value of stage wise crop reduction factor (Ky) were obtained as, for vegetative stage, Ky is 0.534, for tuber development stage, Ky is 0.581 and for maturity stage, Ky is 0.331. The spectral reflectance of potato crop was measured using spectroradiometer. Potato crop shows maximum reflectance at 550 nm and lower reflectance in the blue region at 450 nm and red region 650 nm. Beyond the visible region (> 700 nm) the spectral signatures shows strong rise in the reflectance. The high reflectance is evidence of the NIR region (750 to 1300nm). The reflectance reduces at 1400 nm because of strong absorption by the leaves due to presence of water in it. In general spectral signatures developed for potato crop indicated that the spectral reflectance decreases with increase in water stress during crop growth stages. The NDVI values estimated using spectral reflectance data and best fit polynomial equation (5th order) varied from 0.21 to 0.77 for potato crop during growth period for no stress treatment and 0.23 to 0.81 for 20 % water stress at maturity stage treatment which is considered as best treatment.ennullThesis