Journal of Soil and Plant Interactions

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To study the effects of adding a superabsorbent (bentonite) to different substrates on the vegetative growth and yield of snap beans, two randomized complete block design experiments with 4 replications were conducted at Greenhouse of Isfahan University of Technology. In the first experiment, 9 treatments including rice hull, saw dust, sand and their combinations, with 10 and 20% superabsorbent (v/v) were used. The results showed that the highest stem length, number of nodes and leaves, shoot fresh weight and pod number were observed using rice hull (90%)+superabsorbent (10%). The lowest vegetative growth was related to treatments containing sand and superabsorbent. Increasing superabsorbent from 10 to 20% reduced vegetative growth parameters in most cases. Based on the results of the first experiment, sand treatment was deleted and in the second experiment rice hull, saw dust, perlite and their combinations with 5 and 10% superabsorbent were used. The results showed that the highest plant height, number of nodes and leaves, plant dry weight, branch number and yield were obtained in perlite (95%)+superabsorbent (5%) and pure perlite. Adding 5 and 10% superabsorbent to rice hull and saw dust caused a significant increase in the vegetative growth. This increase was higher for 10% superabsorbent compared to 5% superabsorbent. Finally, the results showed that adding 10% superabsorbent to rice hull and saw dust increased vegetative growth and yield, while it decreased the loss of nutrient solution.

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Despite of increasing request for greenhouse vegetables, there is quite limited information on their nutritional quality. This study was carried out to investigate nutritional status of macronutrients (Ca, Mg, P and K) and micronutrients (Fe, Mn, Cu and Zn) in greenhouse cucumber and bell pepper in Isfahan province. After selecting 25 greenhouses, the concentration of macronutrients and micronutrients was measured in soil and edible parts of cucumbers and bell peppers. The results showed that mean concentration of P and K in the soils was much higher than their critical deficiency level. Mean concentration of DTPA-extractable Fe, Zn, Cu and Mn of the soils was 12.0, 4.9, 1.9, and 14.5 mg kg-1. Mean fruit Mg, P and K concentrations in the cucumber and bell pepper were greater than their sufficiency level, while more than 75% of the greenhouse cucumbers were Ca deficient. Also more than half of the greenhouse cucumbers and about 20% of greenhouse bell peppers had Mn deficiency. Also more than 60% of greenhouse cucumbers were Fe and Zn deficient. According to the results, high concentration of some macronutrients such as P and K, and widespread deficiency of Ca and micronutrients in greenhouse production, is probably due to nutritional mismanagement, unbalanced fertilizer application, unstable greenhouse conditions and environmental pollution risks.

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One of the problems for unequal distribution of salts in the root media is toxicity of sodium (Na) and reduced uptake of some nutrients, particularly calcium (Ca) and potassium (K), by the roots growing in the saline section. There is a hypothesis that addition of Ca and K to these systems might alleviate salt-induced damages to plants. This study was carried out to evaluate the effect of Ca and K application on fruit yield, water use and crop per drop (CPD) of tomato (Lycopersicon esculentum var. Falcato F1) plants grown in a hydroponic system with unequal distribution of salts in the root media. Tomato roots were divided into two equal splits and one half was immersed in the full Johnson nutrient solution. In the other root half, 40 mM NaCl solution, alone or in combination with KCl (6 mM), CaCl2 (4 mM), K+Ca (3+2 mM) or half-strength Johnson nutrient solution, was applied. A control treatment was also used in which both root splits were immersed in the Johnson nutrient solution (C). The root splits were exchanged every 7 days. Results showed that addition of 40 mM NaCl in one side of the root media resulted in reduction of fresh and dry weight of root and shoot, stem diameter, shoot height, number of leaves and fruit yield of tomato in comparison with the control treatment. Addition of Ca, K+Ca and half-strength Johnson nutrient solution to the saline part of the root media increased significantly the root and shoot growth and fruit yield of tomato compared with the sole application of saline solution. In contrast, addition of K could not alleviate the adverse effects of salinity and even reduced the fruit yield. Application of 40 mM NaCl in one side of the root media reduced significantly the plant water use. Addition of Ca, K+Ca and half-strength Johnson nutrient solution to the saline part of the root media resulted in significant increase in CPD. Addition of Ca, K+Ca and half-strength Johnson nutrient solution caused replacement of 48, 43 and 43% of nutrient solution with saline water, respectively. According to the results of this study, in case of dynamic and non-uniform distribution of salts in the root media, by addition of Ca to the saline solution, it would be possible to replace about half of the crop water demand with saline water, with no significant fruit yield reduction.

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Silicon (Si) is a beneficial nutrient for growth of crops such as cucumber. It seems that Si improves antioxidant capacity of plants and reduces damages induced by environmental stresses and metal toxicity. This research aimed to investigate the interaction of Si and cadmium (Cd) on growth, dry matter yield and catalase (CAT) activity, as an antioxidant enzyme, in cucumber. This hydroponic experiment was carried out at the greenhouse of Soilless Culture Research Centre, Isfahan University of Technology, Isfahan, Iran, and was set up in a completely randomized factorial design in triplicates. Treatments consisted of two Cd levels (0 and 5 µM), two Si levels (0 and 1 mM) and two cucumber cultivars (greenhouse cultivar called Negin and field cultivar called Super Dominus). Cadmium had no significant effect on the fresh and dry weight of shoots in both studied cucumber cultivars, while significantly decreased the root fresh and dry weights. Effect of Si on shoot dry weight differed in cultivars. Si nutrition significantly increased shoot dry weight of Super Dominus cultivar, but was not effective on shoot dry weight of Negin cultivar. Catalase activity was affected by the presence of Si and Cd, such that Cd reduced the activity of CAT in both cucumber cultivars. In contrast, CAT activity in Negin cultivar was increased by addition of Si to the nutrient solution. It seems that addition of Si to cucumber growth media can improve antioxidant capacity of plant under Cd toxicity, although this effect is cultivar-dependent.

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One of the main factors of an aggregate hydroponic system is to use a suitable plant media with local origin. Thus the objective of this research was to study the possibility of replacement of cocopeat as an imported material with local materials and the effects of such media on the growth and flowering characteristics of Rosa hybrida cv. Maroussia. A randomized complete blocks design experiment with four replications was conducted. The treatments were nine growing media: cocopeat (100%), perlite (100%), leca (100%), cocopeat (75%) + zeolite (25%), perlite (75%) + zeolite (25%), leca (75%) + zeolite (25%), cocopeat (50%) + perlite (50%), cocopeat (50%) + leca (50%) and perlite (50%) + leca (50%). Results indicated that plants grown in cocopeat and cocopeat + zeolite showed high vegetative and reproductive growth. The highest number of flowers per plant was observed in in cocopeat (8.31) and cocopeat + perlite (7.81) substrates, which had no significant difference with cocopeat + zeolite medium (6.87). Adding zeolite to cocopeat, perlite and leca improved length of flower bud and number of flowers per plant over their pure medium. Also, adding cocopeat to perlite increased fresh and dry weight of cut flowers and number of flowers per plant. Based on the results and availability of zeolite in Iran, mixture of cocopeat (75%) + zeolite (25%) is recommended.

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In order to investigate the effect of some substrates on uptake and concentration of nutrients in cherry tomato (Lycopersicon esculentum Mill. cv. Cerasiforne), this non-recycling soilless culture experiment was carried out as a completely randomized blocks design with 9 treatments and four replicates, with two plants in each pot. Treatments included perlite-vermiculite 50:50 %v, perlit-zeolite 50:50 %, perlite 100%, rice husk 100%, rice husk-vermiculite 50:50 %, rice husk-zeolite 50:50 %, perlite-rice husk-vermiculite 37.5: 37.5: 25 %, perlite-rice husk-zeolite 37.5: 37.5: 25 %, and cocopeat 100%. Results of the analysis of nutrients in the substrates showed that cocopeat and zeolite had the greatest concentration of potassium (K). The highest concentration of calcium (Ca) was found in zeolite medium, magnesium (Mg) in cocopeat, manganese (Mn) in rice husk, copper (Cu) in vermiculite, zinc (Zn) in cocopeat and iron (Fe) in vermiculite. The highest concentration of K and Mg in shoots of tomato plants was found in cocopeat, while plants in the vermiculite medium had the highest Ca concentration in their shoots. No significant relationship was found between concentrations of measured nutrients, except for K, in the substrates and their uptake by plants. In general, the highest nutrients uptake by cherry tomato plants was found in the medium containing a mixture of perlite and vermiculite, which is probably due to optimum root growth conditions, particularly high porosity and high ability for retention of water and nutrients.

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For comparing the effects of two planting substrates on vegetative growth, flowering rate, fruit appearance and qualities, yield of four bell pepper (Capsicum annum L.) cultivars, a greenhouse 4×2 factorial experiment was done by using a completely randomized design with 4 replications. First factor was 80% cocopeat + 20% perlite and 80% mosspeat + 20% perlite and the second one was four bell pepper cultivars consisted of green Traviata, red Inspratian, orange Aracia, and yellow Taranto. The results showed that mosspeat caused better effects on vegetative growth consist of length and diameter of stem, relative chlorophyll, fresh and dry weight of root and stem and reproductive factors consist of flowering rate, fruit length and diameter, fruit shape index, rigidity and pericarp thickness and it increased fruit number and fresh and dry weight of fruits in each plant in comparison to cocopeat. Amongthe cultivars red cultivar was the superior one for important factors vincluding relative chlorophyll, fresh and dry plant weight, fruit shape index and pericarp thickness. There was significant interaction between cultivar and bed indicating that the response of bell pepper cultivars was varied in different beds

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Soilless culture in greenhouse is being developed in Iran, as in many countries of the world. This study was conducted to evaluate the possibility of applying sawdust as well as the effect of adding bentonite and pumice on vegetative growth of bell pepper cv. Inspratian. The experiment was conducted as a completely randomized blocks design with 8 treatments and 4 replications, in greenhouse of College of Agriculture, Isfahan University of Technology. The planting media consisted of different v/v ratios [100% sawdust, sawdust+ pumice at the ratios of 5, 10 and 15%, sawdust+ bentonite at the ratios of 5, 10 and 15%, and a common planting medium (85% peat+ 15% perlite) as control]. Results showed that after peat, in most cases, plants grown in sawdust+ pumice showed better vegetative growth as compared to those of pure sawdust or sawdust+ bentonite. For example, the highest fresh and dry weight of shoots and dry weight of roots were in 85% sawdust+15% pumice treatment. The results also showed that after peat, the highest chlorophyll content was determined in 95% sawdust+ 5% pumice and 90% sawdust+ 10% bentonite media. The lowest chlorophyll content was related to 100% sawdust medium. After peat treatment, the earliest flowering, fruiting and color establishment was observed in 85% sawdust+ 15% pumice, which was not significantly different from 95% sawdust+ 5% and 90% sawdust+ 10% pumice.