نشریه روابط خاک و گیاه
پیاپی 11 (پاییز 1391)

In a greenhouse research، the effects of soil water conditions، sewage sludge and chemical fertilizers on growth characteristics and water use efficiency of rice (Oryza sativa L. cv. Ali Kazemi) were studied in a loamy sand alkaline non-calcareous soil. The study was performed as a factorial experiment in a randomized complete blocks design including soil water conditions in three levels (continuous submergence، alternate submergence and alternate saturation) and source and amount of organic and chemical fertilizers in 10 levels [control، 100% chemical fertilizers (434. 8 mg urea، 66. 1 mg KH2PO4، 40 mg KCl، 50 mg FeSO4. 7H2O، 38. 5 mg FeSO4. 7H2O، 21. 3 mg ZnSO4. 7H2O and 7. 9 mg CuSO4. 5H2O per kg of soil)، 20 g sewage sludge per kg of soil with and without 50% of chemical fertilizers، 40 g sewage sludge per kg of soil with and without 50% of chemical fertilizers، 20 g poultry manure per kg of soil with and without 50% of chemical fertilizers and 40 g poultry manure per kg of soil with and without 50% of chemical fertilizers] with three replications. At the end of growth period، tiller and leaf number per plant، length and diameter of stem، length and volume of roots، and shoot and root dry matter were measured and water use efficiency (WUE) was calculated. The results showed that application of 20 and 40 g poultry manure per kg of soil prevented the growth of rice due to increase of soil salinity. Application of 20 and 40 g sewage sludge per kg of soil increased significantly tiller and leaf number per plant، length and diameter of stem، length and volume of roots، shoot and root dry matter and WUE compared to control and 100% chemical fertilizers treatments. Addition of 50% chemical fertilizers to 40 g sewage sludge per kg of soil did not significantly affect tiller and leaf number per plant، stem length، volume of roots، shoot dry matter and WUE of rice. The highest tiller number per plant، stem diameter، root length and the ratio of shoot dry matter to that of root were observed in continuous submergence treatment. The highest WUE of rice plant was in alternate saturation treatment. The effect of soil water conditions on plant height، leaf number per plant and shoot dry matter was not significant. In general، alternate saturation with application of 40 g sewage sludge per kg of soil could be recommended to achieve optimum growth of rice plant and increase of WUE.

This research was performed in 2011 at University of Mohaghegh Ardabili، Iran، to evaluate osmotic-stress tolerance، at seedling stage، of rapeseed (Brassica napus L.)، as a split plot experiment based on randomized complete blocks design with four replications. Levels of osmotic stress were considered as main factor and twelve rapeseed cultivars were sub-factor، that were evaluated under aquaculture conditions، based on length، volume، area and dry weight of roots، shoot dry weight and biological yield. The results showed that stress levels had signification effect on studied traits (P≤0. 01). Significant differences were observed between rapeseed cultivars. Effect of osmotic stress on length، volume، area and dry weight of roots، shoot dry weight and biological yield of different cultivars was not the same. The greatest amount of reduction in the studied traits under osmotic-stress conditions was observed in shoot dry weight and biological yield; root length was reduced the least. Based on cluster analysis، at all three levels of drought stress، canola cultivars were placed in three groups. The Licord cultivar، at all three conditions، was located in the group that its traits were higher than other groups. The Okapi، Quantum، Tallaye and Hyola308 cultivars showed lower tolerance to osmotic stress. The Licord cultivar had higher tolerance to osmotic stress as compared to other cultivars.

Sewage sludge (SS) as a source of macro- and micro nutrients has been utilized in many countries for crop and vegetable production. To compare the influence of SS with chemical fertilizer on macro- and micro nutrients bioavailability in three textural classes of a calcareous soil after harvesting spinach (Spinacia oleracea L.)، a factorial experiment was carried out in a completely randomized design with two factors and three replications under glasshouse conditions. The first factor was SS levels (0، 10، 20، 40، and 80 mg per kg soil) and the second factor was soil textural classes (sandy، sandy loam، and clay loam). A chemical fertilizer treatment was used for comparison with the applied SS treatments. Results indicated that total nitrogen (N) and available phosphorus (P) was significantly higher in SS amended soils compared to fertilizer treatment. Effect of increasing soil potassium (K) due to addition of SS was less than P and N، which is probably due to low content of K in SS. Soil DTPA extractable iron، zinc، copper، and manganese were significantly increased in SS treatments in all soil textures and were higher than fertilizer treatment. Based on nutrients’ bioavailability in soil after harvesting spinach، especially at high rates of SS، addition of most nutrients is not necessary for the next crop. Concentration of DTPA extractable cadmium (Cd) and lead (Pb) was not detectable in all treatments. Therefore، because of low contents of Cd and Pb in the utilized SS، reaching to a toxic level of these elements in soil is unexpected. However، if high levels of SS are applied frequently، soil test is recommended for monitoring heavy metals concentration in amended soils. Prior to any SS recommendation، the results of this research need to be verified under field conditions.

Application of salicylic acid (SA) as a phytohormone has been increased due to resistance to stresses such as salt stress. To evaluate the effects of SA on growth and ornamental characteristics of Persian petunia under salt stress، a factorial experiment، based on completely randomized design، was conducted with 3 levels of SA (0، 1 and 2 mM) and 3 levels of NaCl (0، 150 and 300 mM) with 4 replications under controlled greenhouse conditions. Salicylic acid was applied via foliar spray once every two weeks. NaCl was also applied as drench (200 ml per pot) at flowering stage in 3-day intervals. The results showed that salinity of 300 mM NaCl decreased plant height، biomass، number of flowers and chlorophyll index by 52، 59، 100 and 61 percent as compared to control، respectively. Under non-saline conditions، foliar application of SA (2 mM) increased number of flowers، flower diameter، plant height and chlorophyll index by 100، 35، 40 and 39 percent as compared to control، respectively. Plants treated with 1. 0 mM SA had the highest leaf area، shoot and root dry weight and biomass at 150 mM salinity. Based on the results of this experiment، foliar application of SA improved growth and ornamental characteristics of Persian petunia under saline and non-saline conditions.

Due to alkalinity of most soil and water resources in Iran and consequently bicarbonate-induced high pH of plants’ growing medium and different effects of ammonium and nitrate on pH of plant growing medium، research about deleterious effects of factors like alkalinity and interactive effect of nitrogen with bicarbonate on chemical and ecophysiological characteristics of plants seems to be necessary. Thus، an experiment was carried out on snap bean as a factorial trial with completely randomized design and two factors of sodium bicarbonate (0، 1، 5 and 15 mM) and nitrogen form (ammonium and nitrate). The results of this experiment showed that bicarbonate decreased SPAD index and plant pigments in leaves. Proline concentration in ammonium treated plants increased with bicarbonate linearly; whereas in nitrate treatment and at 1 mM bicarbonate، it decreased slightly but increased again markedly with elevating of bicarbonate content. In ammonium treatment، the photosynthesis rate، mesophyll efficiency and water use efficiency decreased with bicarbonate، whereas in nitrate treatment، they increased with low and medium concentrations of bicarbonate. It is concluded that in ammonium treatment، bicarbonate decreased photosynthesis efficiency and water utilization in snap bean at all concentrations، whereas، in nitrate-fed plants، bicarbonate at low concentration (1 mM) was suitable، probably due to providing some CO2 or carbon skeleton for nitrogen assimilation in plants.

Application of grafting technique could be an approach for increasing salinity resistance of tomato cultivars. To assess the impact of grafting on resistance of tomato to salinity، two varieties of conventional tomato called Hamra and Kevin were grafted on a salt-resistant base، called AR-9704، using chisel grafting method، and were grown in the greenhouse، using a hydroponic system، under three levels of salinity (EC of 2. 3، 5. 3 and 8. 3 dS/m). The results showed that 8. 3 dS/m treatment significantly reduced yield per plant. The main reason for this reduction was lower number and weight of the fruits. Interaction of salinity and cultivar was also statistically significant (P<0. 01). The use of grafted cultivars of Hamra and Kevin increased yield per plant at different salinity levels. However، this increase was significant at 2. 3 dS/m salinity level. At low salinity level (2. 3 dS/m)، the lycopene content in grafted Hamra and β-carotene content in both grafted Hamra and Kevin cultivars had significant advantage over other treatments. The amount of ascorbic acid and lycopene at moderate and high salinity levels (5. 3 and 8. 3 dS/m، respectively)، and fruit’s soluble solids concentration at salinity level of 8. 3 dS/m in grafted cultivars were significantly higher than non-grafted cultivars.

In order to investigate the effects of plant density and pruning on yield characteristics and growth of two bell pepper cultivars، a 2×3×2 factorial experiment was conducted in a complete randomized block design with three replications and three factors of plant density (2. 5، 3 and 3. 5 plants per m2)، shoot pruning at two levels (without pruning and training plants with 3 main stems) and two bell pepper cultivars (Tomson and Maratos)، in greenhouse of Ferdowsi University of Mashhad، Iran. The results showed that the effect of shoot pruning on yield per m2، yield per plant، fruit weight، number of fruits per plant and plant weight was significant (P<0. 01). The effect of cultivar on plant height، shoot diameter and plant weight was significant (P<0. 01)، and also the amount of these parameters for Tomson cultivar was higher than Maratos cultivar. Plant density had a significant effect on total yield، average fruit weight، plant height، shoot diameter and plant weight. Plant density of 3. 5 plants per m2 produced the highest yield (10. 80 kg/m2) and 2. 5 plants per m2 showed the lowest yield (6. 95 kg/m2). Average fruit weight decreased with increasing plant density، such that 2. 5 plants per m2 produced the highest fruit weight (109. 8 g). Plant weight and shoot diameter decreased with increasing plant density، while plant height increased with higher plant density. Pruning decreased total yield، yield per plant، plant weight and number of fruits per plant، but it increased fruit weight. The results of this experiment showed that pruning of bell pepper plants caused an increase in fruit weight and improved fruit quality.

This experiment was performed to investigate the effect of some Trichoderma spp. isolates as growth promoters of cucumber (Cucumis sativus L.) seedlings under greenhouse conditions. Inoculai of 19 Thrichoderma spp. isolates were prepared from disinfected wheat grain. The upper half of the soil in pots (containing field soil and sand) was mixed with these inoculai at 3% ratio and the pots were irrigated with tap water for 28 days. After four weeks, the seedlings were sampled for growth comparison on stem length, root length and total fresh weight. The results showed that some isolates improved significantly the cucumber seedlings’ growth and others had inhibitory effect. Application of Trichoderma spp. 17 and T. longibraciatum increased stem length more than 74% as compared to control. Also, these isolates increased significantly)P<0.05) the total fresh weight about 40% and 25%, respectively, as compared to control. Furthermore, Trichoderma sp. 19 decreased significantly the stem length, root length and total fresh weight as compared to control. These results show the ability of Persian Trichoderma spp. isolates in promoting cucumber growth and its potential for other plants.

Various species of serpentine leaf miner are serious pests of vegetable crops، especially on cucumber and tomato، in greenhouse and open fields. Reduction of chemical insecticides’ use in order to minimize pesticide residues on these crops is one of the most important aspects of food safety. Yellow sticky cards have been used successfully for many pests and can be used for leaf miners too. Therefore، this investigation was performed to find out how to use these cards، including their height and spacing. To find the most proper height in the first step، three different heights (50، 120 and 170 cm from ground level) were considered، based on randomized complete blocks design with five replications، at the beginning of the growing season (plants with 5-6 leaves and less than 50 cm height). Results showed that traps on 50 cm height captured most of the insects، were in the same statistical group with 120 cm high traps، and had significant difference with 170 cm high treatment. In the second step، at which the experiment was replicated in the peak of adult population، when the plants were in their full height (160 cm)، the 170 cm high traps adsorbed most of the adult leaf miners in three days. To find out the best trap spacing، the 170 cm high traps were placed at three different spacing of 1، 2 and 3 m and were compared to control (no trap). Results revealed that 1 m spacing treatment had the best efficiency، was in the same group with 2 m spacing treatment، and had significant difference with other treatments.

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.