Introduction: Cucumber (Cucumis sativus L.) belonging to the family Cucurbitaceae is a warm-season vegetable, grown throughout the world under tropical and subtropical conditions. Extensive production of this plant is done not only in the outdoor, but also in the greenhouse, so to achieve maximum yield, especially in greenhouse crops, in addition to creating a favorable environment for plant growth, it is necessary to use appropriate farming techniques. The protected vegetable cultivation technology can be utilized for the year-round production of high-value quality vegetable crops, with high yields. Increased harvesting efficiency and greater yields, improved pest management, straighter fruits and, more number of plants per unit due to closer rows are major advantages of adequate spacing; it is of vital importance for healthy and luxuriant growth of crop plants. Plant spacing is one of the agronomic techniques in achieving optimum yield. A recommended number of plants per unit area contributes to adequate utilization of the available planting space, thus ensuring an even distribution of water, nutrient, light, and air. However, an unregulated plant spacing may result in a relatively lower yield and poorfruit quality. Planting spacing depend on the cultivar and growth method. Although greenhouse cucumber has been produced using various cultivars for more than three decades, producers still do not have accurate information about greenhouse cucumber cultivars. Therefore, the present study was performed to evaluate the effect of plant spacing in the rows on the growth and yield of cucumber cultivars.
Material and Methods: A greenhouse study was conducted as a factorial experiment baesd on a randomized complete block design with three replications in 2018 and 2019 in Pakdasht city, Tehran province, Iran. The experimental treatments included plant spacing (37, 42 and 47 cm) and five cultivars of greenhouse cucumber (Viola, Yazan, Kadir, Saturn, and Yekta). The Viola and Yazan are multiple-flowers cultivars, Kadir is medium-flowers cultivar (more than four flowers per node), Yekta is few-flowers cultivar (between two to three flowers per node) and Saturn is single-flower cultivar. During the plant growth period, sampling of the midline of each plot was performed according to the margins and between competing plants. In this study, the measured traits included plant height, number of stem nodes, number of flowers per node, leaf weight, fruit number, mean of fruit weight, firmness of fruit, total wet and dry biomass and root dry weight. In addition, fruit yield was measured from middle rows of each experiment plot with 1 m² area. Experimental data were analyzed statistically using SAS software version 9.2. Means comparison was done using the least significant difference (LSD) adjustment at P = 0.05.
Results and Discussion: The results of variance analysis of data showed that all traits except firmness of fruit and number of stem nodes were affected by cultivar× plant distance interaction. Comparison of means showed that by reducing the distance between plants from 47 to 37 cm, although the mean of fruit weight increased by 11.4-34.8% and the total biomass weight per m² increased in all of the cultivars, but their single plant biomass decreased. In both years, the highest number of fruits was obtained in Saturn cultivar from a distance of 47 cm and in other cultivars from a distance of 42 cm. Also, the maximum yield of Saturn cultivar was obtained from 47 cm (217.38 t ha^-1) and in other cultivars at a distance of 42 cm was produced (the average yield of Viola, Kadir, Yekta and Yazan cultivars was 270.03, 252.31, 238.83 and 216.03 t ha^-1, respectively). Therefore, multi-flowered cultivars at a distance of 42 cm and single-flowered cultivar at a distance of 47 cm showed the highest yield. Saturn cultivar dropped by 37 cm. However, in the case of flowering cultivars, this trend was different and the highest yield was observed at a distance of 42 cm, and with a decrease or increase from a distance of 42 cm, the yield decreased, which could be due to high intra-plant competition between fruits at a distance of 47 cm Between plants to absorb light and nutrients at a distance of 37 cm.
Conculation: Based on the obtained results, the distance on the row is 47 cm for single-flowered cultivars such as Saturn and the distance on the row 42 cm is recommended for multi-flowered cultivars to achieve the highest cucumber yield in the greenhouse. For future studies, similar to the present study, it is suggested that in addition to plant density, different planting arrangements, measuring the concentration of some elements in the leaves and light dissipation coefficient to measure the penetration of light into the lower part of the plant canopy.