TY - BOOK AU - Jayalakshmi T AU - Aswini A (Guide) TI - Standardisation of fertigation and evaluation of chitosan as a bio stimulant on the biochemical and morphological traits of seedless watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] U1 - 635.6 PY - 2023/// CY - Vellanikkara PB - Department of Vegetable Science, College of Agriculture KW - Vegetable science KW - Watermelon KW - Citrullus lanatus (thunb.) matsum and nakai KW - Fertigation and evaluation of chitosan N1 - MSc N2 - Watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] is a popular dessert vegetable of the Cucurbitaceae family. Even though the demand for fruit is very high, watermelon production confines to a limited area of 100 hectares with a production of 840 metric tonnes in Kerala. Precision farming is gaining importance in vegetable production and fertigation is an integral part of it. Watermelon responds well to fertigation in terms of growth and yield enhancement at different stages of crop like establishment phase, vegetative phase, flower initiation and at the time of harvesting. Erratic rainfall is the main limiting factor for watermelon cultivation in southern Kerala. Chitosan as a bio stimulant has a potential role in improving yield, quality, biotic and abiotic stress resistance of agricultural crops which can be exploited in the production of watermelon also. Researchers reported that bio stimulant effect of chitosan on plants was not much clear and it might be due to the increased photosynthetic rate by its application. Hence the present study was undertaken with an objective to standardise fertigation and to evaluate the effect of chitosan on biochemical and morphological characters of triploid seedless watermelon hybrid, Shonima from December 2021 to March 2022 at the Department of Vegetable Science. The experiment was conducted in split plot design with four levels of fertigation (50 % RDF, 75 % RDF, 100 % RDF and 125 % RDF) in main plots and three chitosan concentrations as foliar application (0.1 %, 0.2 % and 0.3 %) in subplots. Control was maintained with a level of fertilizer application @ 70: 25: 25 kg NPK/ha (KAU POP) and without any foliar application of chitosan. Fertigation was scheduled at three days interval and foliar application of chitosan was done at the pre flowering and fruit setting stages. Weather parameters like maximum temperature, minimum temperature, relative humidity and rainfall were recorded. As the crop duration during the summer season was shortened from 120 days to 90 days, only 25 splits of fertigation (6, 12, 7 during establishment, vegetative and fruiting stages respectively) were completed out of 40 (6, 12, 22 during establishment, vegetative and fruiting stages respectively). Fertigation doses given were 21.87: 15.62: 37.5 kg NPK/ha (50% RDF), 32.81: 23.44: 56.25 kg NPK/ha (75 % RDF), 43.75: 31.25: 75 kg NPK/ha (100% RDF) and 54.68: 39.06: 93.75 kg NPK/ha (125 % RDF). Fertigation levels significantly influenced vegetative and floral characters of watermelon. Longest vine length (3.87m) was recorded by 125% RDF. Male flower anthesis (24.39 days) was found to be early in 50 % RDF. Fruit and yield characters along with quality parameters were significantly influenced by fertigation doses. 100% RDF recorded maximum equatorial diameter (16.90 cm), polar diameter (17.55 cm), fruits/plant (4.52), average fruit weight (1.61 kg), yield/plant (5.97 kg/plant) and lycopene content (5.76 mg/100g). Maximum TSS (8.64°Brix) was recorded in 75 % RDF and maximum total sugar (5.38%) in 50 % RDF which was on par with 75 % and 100 % RDF. Chitosan concentrations influenced fruit, yield and quality parameters of watermelon. Foliar application of 0.1 % chitosan recorded maximum fruit equatorial diameter (16.76 cm), polar diameter (17.43 cm), fruits/plant (4.25), average fruit weight (1.94 kg), yield/plant (6.23 kg/plant), TSS (8.87 °Brix), lycopene content (4.96 mg/100g), reducing sugar (3.54 %) and total sugar content (5.38 %). 50% RDF recorded lowest rind thickness (1.17 cm). Interaction effect of fertigation doses and chitosan concentrations on fruit and yield characters and quality parameters was found to be significant. Treatment combination of 100 % RDF + 0.1 % chitosan spray recorded maximum equatorial diameter (18.08 cm), polar diameter (18.87 cm), average fruit weight (2.38 kg), yield/plant (8.06 kg/plant) and lycopene content (6.72 mg/100g). Maximum TSS (9.46 °Brix) and reducing sugar (3.98 %) was recorded by 75 % RDF + 0.1 % chitosan spray. Maximum total sugar content (5.67 %) was observed by 50 % RDF + 0.1 % chitosan spray. BC ratio (2.01) was found to be maximum with 100 % RDF + 0.1 % chitosan. Soil nutrient status was increased after the crop duration. Vulnerability index of watermelon bud necrosis virus, percentage disease index (PDI) of fusarium wilt and gummy stem blight reduced after foliar application of chitosan. The crop duration was reduced during the summer season hence, the recommended dose of fertigation for Shonima (90 days duration) was 43.75: 31.25: 75 kg NPK/ha. The recommended chitosan concentration was 0.1 % and treatment combination 100 % RDF + 0.1 % chitosan was found to the best for yield and quality parameters of watermelon. Fertigation enhanced the nutrient uptake thereby improved the growth, yield and quality of watermelon. Chitosan having potential role in biotic stress tolerance by regulating the jasmonic acid responsible for this by generating hydrogen peroxide. Enhanced yield and quality of fruits with foliar application of chitosan could be studied further with reference to physiological aspects like photosynthetic rate, stomatal conductance, transpiration rate etc. Biochemical and morphological traits of seedless watermelon was improved with influence of fertigation and foliar application of chitosan compared to conventional method of fertilizer application without any foliar spray of chitosan ER -