نشریه روابط خاک و گیاه
پیاپی 35 (پاییز 1397)

In order to assess reduced nitrogen level impacts on butterhead lettuce (Lacttuca sativa L.) growth and yield, an experiment was done from May to August 2015 in research greenhouse of Shahrekord University. The experiment was conducted through randomized completed design with three replications and four treatments. The lettuce plants were grown in floating system using 60, 80, 100 and 120 mg/l nitrogen in nutrient solution. In every plot, ten plants were grown in wooden pool with 100 ×50 ×15 cm dimensions and plants were spaced 20×25 cm apart on polyester sheet. There was no significant difference among treatments in the leaf number, head weight, root fresh weight and leaf elements nitrogen, phosphor, potassium, magnesium and zinc, but significant differences were observed among treatments in leaf and root dry weight percent, stem length and diameter and leaf calcium, iron and manganese concentration. The largest fresh head mass were obtained from 60mg/l nitrogen (326 g/plant), but it had not significant difference with other treatments. The highest leaf and root dry weight percent, stem length and diameter was observed in 100 mg/l nitrogen concentration. Deceasing of nitrogen concentration until 60 ppm, did not reduce the weight of lettuce head

Silicon (Si), as a beneficial or quasi-essential element, has different effects on physiological and biochemical processes in plants. But, many greenhouse growers in Iran, especially in soilless system (hydroponic), do not use Si in their recipe and fertilization program. This experiment was conducted to assess the effects of foliar application of different Si levels (0, 50, 100 and 150 mg/L) on morpho-physiological characteristics of cucumber (Cucumis sativus L., cv. Negin) in a commercial soilless greenhouse, located at Piranshahr city, West-Azarbaijan province, Iran. Based on the results, Si foliar application significantly increased total chlorophyll, leaf relative water content (RWC), leaf calcium (Ca) and Si uptake and stability of cellular membrane, as compared to control treatment. Maximum yield and Ca uptake were observed in 100 and 150 mg/L concentrations. The highest fruit shelf life, as one of the main cucumber quality components, was observed in 150 mg/L Si foliar application, which was 29% higher than control treatment. Based on the results of Si foliar application, increasing the leaf area and total chlorophyll content and improvement of RWC increased the yield and postharvest longevity of cucumber fruit (Negin cultivar). Consequently, foliar application of Si in soilless production of cucumber is recommended

Effect of deficit irrigation on evapotranspiration, yield, water use efficiency and some growth parameters of Hamadanian pepper (Bivar) using a completely randomized design (CRD) with a full irrigation treatment (FI) and three deficit irrigation treatments (85, 70 and 55% application of water requirement; DI85, DI70, and DI55, respectively) in five replications was examined. Evapotranspiration in the FI, DI85, DI70, and DI55 treatments during the 66 days of the deficit irrigation application, were 337.8, 307.5, 281.1 and 244.2 mm and in the whole growth period were 396.2, 365.9, 339.5 and 302.6 mm, respectively. The plant’s morphological characteristics were decreased with decreasing the soil water content. However, in 79% of the cases, the difference between FI and DI85 treatments was not significant. Whereas, in all the cases, the difference between DI55 treatment and FI and DI85 treatments was significant. Applying deficit irrigation decreased the number of good-shaped fruits from 33.0/plant in the FI treatment to 15.6/plant in the DI55 treatment and similarly increased the number of bad-shaped fruits from 5.4 to 18.0 per plant. Crop yield and water use efficiency in the FI treatment were 18.98 ton/ha and 4.79 kg/m3, which did not have significant difference with the DI85 treatment (which had a yield of 17.75 ton/ha and a water use efficiency of 4.85 kg/m3). While there is not a statistically significant difference between the crop yields of FI and DI85 treatments, the DI85 treatment uses less water and gives crop yield very close to that of full irrigation treatment. Hence, the DI85 treatment can be recommended in the cultivation of Hamadanian pepper. In the severe water-scarce conditions, the DI70 treatment could be used to yield 13.48 ton/ha, which is 29% less than the FI treatment. Also, water use efficiency in the DI70 treatment was decreased by 17% compared to the FI treatment. Irrigation efficiency was 61.9, 65.3, 69.6 and 73.4% in the FI, DI85, DI70, and DI55 treatments, respectively

Type of growing medium affects growth of the hydroponic crops. In order to select a suitable medium for hydroponic lemon balm, two greenhouse experiments were carried out on growing media containing different particle sizes of perlite and peat moss mixed with perlite. In the first experiment, growing media treatments were very fine perlite (<0.5 mm), fine perlite (0.5-1 mm), medium perlite (1-1.5 mm), course perlite (1.5-2 mm) and very course perlite (>2 mm) as 100% by volume. Treatments of the second experiment were mixed grades of perlite with 50% peat moss and peat moss (100% V/V). The experiments were arranged in a randomized complete blocks design with three replications. Results showed that significant differences were observed in the measured parameters in inorganic substrates (perlite with different sizes), organic substrates (peat moss) and mixture of organic and inorganic substrates. The highest fresh weight (98 g), dry weight (29.5 g), and essential oil yield (0.13 g/pot) were obtained in the treatment with perlite size of 0.5-1 mm. In the mixture of perlite and peat moss media, the highest fresh weight (189 g) and dry weight (62.4 g) was obtained in the perlite size of 1-1.5 mm. The highest essential oil yield (0.28 g/pot) was observed in pure peat moss treatment. In general, it could be concluded that although addition of peat moss to perlite substrates increased growth parameters and yield of lemon balm, but the size of perlite should be considered in the preparation of growth medium

Plants often accumulate cadmium (Cd) in their edible parts that causes a decrease in crop yield and quality. In order to evaluate the effect of different concentrations of potassium (100, 200 and 300 mg/L) in tomatoes under Cd stress (0, 2 and 4 mg/L) and its efficiency in reducing stress effects, a factorial experiment was carried out based on completely randomized design with 3 replications. Results showed that application of Cd significantly increased Cd concentration in fruits. Existence of Cd in nutrient solution significantly decreased fresh and dry weight of fruit, firmness, titratable acidity, and finally yield. Also, the negative effect of Cd stress on fruit titratable acidity and firmness was neutralized by increasing the potassium (K) level. Potassium caused an increase in total soluble solids and color by affecting a* color parameter and fruits had more red color and ripeness. The treatments had no significant effect on fruit pH and pericarp thickness

Due to the beneficial effects of silicon (Si) on ornamental plants, the aim of this study was to investigate the effect of different sources and concentrations of Si on some characteristics of Rose (Rosa hybrida cv. Beverly Watson). This research was conducted in 2015 in one of the greenhouses of Parks and Landscape Organization of Urmia and in Research Laboratories of Horticultural Science Department, Faculty of Agriculture, Urmia University. A factorial experiment, based on completely randomized design, was conducted with 2 factors of Si source (calcium silicate, potassium silicate and sodium silicate) and Si concentration (0, 50, 100, 150 and 200 mg/L) with 3 replications. Treatments were applied weekly via foliar spray for 10 weeks. Results showed that Si treatment increased leaf number and thickness, leaf fresh and dry weight, leaf chlorophyll content, soluble sugar content and protein content. Because of these beneficial effects of Si on leaf number and chlorophyll content, it can improve the photosynthesis. Potassium silicate spray caused the highest content of chlorophyll a and the highest content of chlorophyll b and carotenoid was resulted from the application of calcium silicate. The highest content of fresh and dry weight of leaf, chlorophyll a, b and total chlorophyll and carotenoid was achieved in 200 mg/L silicate application. Due to the positive effects of Si on growth characteristics and photosynthetic pigments, these materials can be used to improve the rose quality.

Cotton aphid, Aphis gossypii Glover (Hem.: Aphididae) is one of the most important pests in greenhouses and farms that decreases the quantity and quality of the product. Besides several plant viruses transmit by this pest such as cucumber mosaic virus and watermelon mosaic virus. The aim of this study was to evaluate the effect of cotton aphid feeding on some physiological parameters that are involved in plant resistance in four varieties of cucumber plants (Delta, Super Domino, 2201 and hybrid Luna). This experiment was done as factorial biased on completely randomize design with three replication. The results revealed that the amount of phenol, soluble sugar and sucrose were increased as plants were exposed to cotton aphid and Delta had the greatest amount of increase among cultivars tested. Also, the amount of photosynthetic pigments, starch, soluble proteins and concentrations of iron, copper, zinc and manganese were significantly decreased by feeding of aphid. According to the results of this research it can be concluded that different cultivars have different reactions to the damage of cotton aphid and phenol, proline, soluble sugars and sucrose content of plants were increased in response to the cotton aphid damage. From this results, it can be concluded that among the tested cultivars, Delta may have more potential to show resistance than other cultivars tested against cotton aphid damage