DEFICIT IRRIGATION FOR TOMATO PRODUCTION UNDER SEMI-ARID CONDITION
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Date
2018
Authors
Rathod Bipin B.
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Publisher
Mahatma Phule Krishi Vidyapeeth, Rahuri.
Abstract
The study entitled “Deficit irrigation for tomato production under semi-arid condition” was performed during rabi season of 2015-16. The experiment was conducted 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 objectives were to study of effect of moisture stress of deficit irrigation during different growth stages of tomato on its yield, to find out water use efficiency, to develop the spectral signature library for tomato crop; and to estimate the 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 60 days, fruit stage: 61 to 120 days, and maturity stage: 120 up to harvest) and three water stress levels (viz., no stress: 0 % stress, 20 % stress and 40 % stress) at each crop growth stage were laid out in Randomized Block Design (RBD) with two replications. The size of experimental field was 40 x 33 m and the treatment plot size was 4 x 4.2 m. The standard cultivation practices were followed during the crop growth period. It was found that deficit irrigation at different crop growth stages of tomato significantly affected plant height, plant branches, TSS (Total soluble solid), yield and water use efficiency. The highest tomato yield and water use efficiency of 72.53 t/ha and 0.1175 t/ha-mm were obtained when no water stress was given, followed by 66.86 t/ha and 0.1138 t/ha-mm yield when 20 % water stress was provided at maturity stage). However, at par with when no stress was induced. The tomato yield and field water use efficiency increased with increase in water stress. However the finding revealed that the stress to tomato can be planned for optimization of yield under low to sever water scarcity. The crop coefficient for tomato crop was estimated by using field water balance method. The crop coefficient varied from 0.31 to 1.34 during crop growth period. The average values of Kc was found 1.03 for vegetative stage, 1.28 for fruiting stage and 0.95 for maturity stage. However, Kc values for tomato given by FAO are 0.60 for vegetative stage (1 to 30 days), 1.15 for fruiting stage (31 to 135 days) and 0.80 for maturity stage (136 to 160 days). The Kc values estimated for semi-arid region for tomato were found higher as compared to Kc values given by FAO. The spectral reflectance of tomato crop was measured using spectroradiometer. The results indicated that tomato shows maximum reflectance at 550 nm and lower reflectance in the blue region at 450 nm and red region at 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 1300 nm). The reflectance reduces at 1400 nm because of the presence of water in leaves and strong absorption by the leaves. In general spectral signatures developed for tomato crop indicated that the spectral reflectance decreases with increase in water stress during crop growth stages. The NDVI values estimated by using spectral reflectance data and best fit of polynomial equation (5th order) varied from 0.24 to 0.77 during growth period for no stress treatment and 0.24 to 0.75 for 20 % water stress at maturity stage which is considered as the best treatment. The NDVI values varied from 0.19 to 0.69 for the maximum stress treatment (i.e. 40% water stress throughout the growth period). The linear, exponential, logarithmic, power and 2nd order polynomial type of relationships between Kc and NDVI were developed by considering growth and decline phases independently. The 2nd order polynomial type of relationships Kc = 2.1054(NDVI)2 + 4.1441(NDVI) - 0.6349 and Kc = -1.6488(NDVI)2 + 2.6556(NDVI) + 0.272 were found best suitable for estimation of Kc based on NDVI during growth and decline phase respectively for no stress treatment while exponential and 2nd order polynomial equations Kc = 0.5776e1.0557(NDVI) and Kc = 1.2007(NDVI)2 + 2.4143(NDVI) + 0.2642 were found best suitable for estimating Kc during growth and decline phases for 20 % water stress at maturity stage. This relationships can be used to find crop coefficient value and useful in irrigation water management.
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