Evaluation the effects of deficit irrigation and grafting on yield, yield components and water use efficiency in watermelon

After potato, watermelon is the most important vegetable that cultivated in Iran. Irrigation is necessary for watermelon cultivation due to its high growth rate, short growth period and high fruit water content (90-92%). In addition high evaporation during growth and development stages and low rainfall in arid and semi-arid area caused that cultivation of watermelon need a lot of water. To minimize drought stress effect on yield of agricultural crop in arid and semi-arid areas, cultivation of drought tolerant cultivars, deficit irrigation practice and grafting of high yielding cultivars onto tolerant rootstocks are recommended. No paper has been published about grafting and deficit irrigation for watermelon cultivation in Khuzestan province yet, therefore present research was conducted to study the effects of these factors on yield, yield components and water use efficiency of grafted watermelon (B32 cultivar) onto pumpkin ‘Cubalt and Ferro’ (Cucurbita maxima × Cucurbita moschata.) and deficit irrigation in nongrafted watermelon.

This study was carried out at Behbehan Agriculture Research Station from 2020 to 2021. The experiment was done as strip plot in randomized complete block design with nine treatments and three replications. Three irrigation regimes, full irrigation, 80% and 60% of full irrigation were considered as vertical strips. Horizontal strips included B32 cultivar grafted onto pumpkin ‘Cobult and Ferro’ rootstocks (Cucurbita maxima × Cucurbita moschata.) and nongrafted B32. Watermelon and pumpkin seeds were planted in greenhouse in 5 and 10 January respectively and watermelon seedlings were grafted onto pumpk in 4 February. Seedlings were transplanted in 24 Feb. and fruits harvested from early to mid-June. Results were analyzed by MSTATC statistical software and comparison of meanes were done using Duncan,s Multiple Range Test at 1% probability level.

Yield, mean fruit weight and water use efficiency in grafted plants were significantly higher than nongrafted plants. Yield and mean fruit weight decreased significantly due to deficit irrigation. The most yield in grafted and nongrafted plants were obtained in full irrigation. The decrease of yield in nongrafted plants applied 80% of full irrigation as compared with full irrigation was not significant. In full irrigation regime the mean yield of grafted plants were significantly higher (50%) than nongrafted plants. The yield of grafted plants applied 80% of full irrigation were higher than nongrafted plants applied full irrigation , however this difference was not significant. Water use efficiency of grafted plants was significantly higher as compared with nongrafted plants. The differences of water use efficiency in grafted plants onto Cobult and Ferro rootstocks applied full irrigation, 80 % and 60% of full irrigation were not significant. In nongrafted plants the most water use efficiency belong to applied 80% of full irrigation. The decrease of water use efficiency in plants applied full irrigation was not significant as compared with this treatment. However the decrease of water use efficiency in plants applied 60% of full irrigation was significant in comparison to plants applied 80% of full irrigation.

grafting of B32 cultivar onto Cobult and Ferro rootstocks and applied full irrigation and 80% of full irrigation were recommended in no water restriction and water shortage conditions respectively for the maximum watermelon production in Khuzestan province.