Document Type : Research Article
Authors
1 Ph.D graduate, Department of Horticultural Science and Landscape Architecture, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
2 Associate Professor, Department of Horticultural Science and Landscape Architecture, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
3 Crop and Horticultural Science Research Department, Southern Kerman Agricultural and Natural Resources Research and Education Center
Abstract
Introduction: the watermelon (Citrullus lanatus) is a known product with high demand and nutritional value and the capability to export all over the world, and considering that the ultimate goal of all agricultural production systems is to achieve the maximum yield of the plant, and providing the water required for the plant is most effective factor on yield, as a result, investigating of t water limitation effec seems to be an undeniable necessity. On the other hand, dificit irrigation has been introduced as a tool to increase water productivity, thus it is necessary to take into account the effects of this method of saving water consumption on plant production, which doubles the need for research and shows it more clearly, and in addition, Deficit irrigation is applied by providing a part of the plant's water needs, while regulated deficient irrigation is a type of deficient irrigation that can be implemented in several ways, including irrigation based on growth stages or, in other words, allocating of the water to stages that are more sensitive to drought. we should know that the response of plants to lack of the irrigation depends on several factors, including climatic conditions, type of plant, intensity and method of application of deficit irrigation, soil condition and management.
Materials and methods: In order to determine the effect of deficit irrigation and regulated deficit irrigation on yield and water productivity of the watermelon, an experiment in the form of randomized complete blocks with 8 treatments including three irrigation levels of 100, 70 and 50 % of the plant's water requirement (evapotranspiration estimated by the FAO-Penman-Monteith method) and 5 regulated deficit irrigation levels including 50% of the water requirement in the stages of seedling, vine, flowering, fruit expansion and fruit maturity was carried out with three repetitions under black plastic mulch, during 2020-2022, in the Research and Education Center of Agriculture and Natural Resources in the south of Kerman province. Irrigation as the main plot at three levels of 100, 70 and 50% of water requirement and mulching at three levels of crushed date palm leaf, black plastic and no mulch, as the sub-plot, were considered. Crimson B 34 watermelon seeds produced by Seminis company, were planted on January 2021, in plots with the size of 13.5 × 7 m, on furrows and ridges planting system (the width of furrows and ridges were 0.5 and 4 meters, respectively). After planting, bow-shaped wires were put on the planting rows and a transparent plastic was placed as a tunnel on them. In the first year, the total depth of the irrigation in aforesaid treatments was respectively 444, 321, 237, 413, 389, 435, 345 and 425, and in the second year 427, 303, 223, 395, 373, 416, 331 and 405 mm.
Results and Discussion: The results showed that the highest and lowest yield were observed in full irrigation and irrigation 50 % (60.1 and 16.3 t ha-1 respectively). Among the regulated deficit irrigation treatments, irrigation 50% at the seedling stage was the closest to full irrigation, and the irrigation 50 % at the fruit expansion stage had the lowest yield. the highest water productivity belonged to the irrigation 50 % in the seedling and vine stages (15.9 and 1.15 kg m-3 respectively). Irrigation 50% in fruit maturity stage despite irrigation 50% improved Qualitative characteristics such as soluble solids, vitamin C, dry matter, lycopene and fruit taste.
Conclusion: By applying of deficit irrigation with intensities used in this study, compared to full irrigation (control), a significant decrease in watermelon yield was observed. water productivity remained almost constant, there was no significant increase in the quality of the edible part, but treatments of regulated deficit irrigation including seedling stage in terms of yield without significant difference with full irrigation and irrigation 50 % of vine stage in terms of water productivity and irrigation 50% of fruit maturity stage were superior in terms of quality compared to the control. generally regulated deficit irrigation had better results than deficit irrigation due to less yield reduction, increased water productivity and fruit quality in the watermelon, which it can be noticeable in the conditions of water restriction. Finally, it is recommended that milder intensities of deficit irrigation that seem to have more favorable results in this plant should be investigated in the next studies.
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