نشریه روابط خاک و گیاه
پیاپی 3 (پاییز 1389)

Given the increasing growth of the population, soil and water limitations and the decrease of the foodstuff, plantation in greenhouses could be one of the solutions for efficient use of natural resources. As for the 10 times increase of the outcome compared with the plantation in open air, the agricultural experts believe that greenhouse plantation is appropriate for maintaining the nutrition security. Nevertheless, people with entrepreneurship motivations are required for developing the greenhouse plantation units because entrepreneurship is to convert a new idea to a new product or new services. This entails such privileges as facilitating products marketing, job creation, rising productivity, economic self-reliance, and growth in agricultural products. The present research studied the impact of entrepreneurship on the greenhouse products of West Azerbaijan via time series data of 241 greenhouses. The Cronbach alpha coefficient was calculated as 0.85, which shows the appropriate reliability of the research tools. The content validity of the questionnaire was confirmed through the experts and the teachers dealing with the subject. The results showed that the entrepreneurship has a negative impact on the quantity of consumable elements. In other words, the entrepreneurship decreases the quantity of consumable elements. It must be noted that the risk-avoidance affects the consumable elements negatively.

Salinity plays an important role in the reduction of tomato growth, especially in arid and semi-arid regions. Nitrogen (N) may increase tomato tolerance to salt stress by increasing plant growth. In order to investigate the interaction effect of salinity and nitrogen on tomato growth, fruit quality, and micronutrient concentration in tomato plants, a hydroponic experiment was conducted in a completely randomized design with three replications. Treatments included 3 salinity levels (0, 30 and 60 mM), and 3 nitrogen rates (0, 1.5, and 3 mM). Results indicated that salinity decreased tomato height, shoot and fruit fresh weight, and increased citric acid in tomato fruit and consequently caused blossom-end rot in tomato fruit. However, salinity improved fruit quality (flavor). The use of N increased plant height, shoot, and fruit fresh weight compared to control. By application of N to saline nutrient solution, plant height increased. Salinity increased concentration of iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in roots, as`well as Fe and Cu in fruit. Increasing N rates in nutrient solution increased micronutrients concentration in tomato roots. Interaction of 60 mM salinity and N decreased micronutrients concentration in root, compared to control. Our tentative conclusion shows that the addition of N to the nutrient solution may decrease detrimental effect of salinity on the growth of tomato plants.

The effect of salinity and nitrogen on yield, vitamin C, citric acid and nutrient distribution of tomato in hydroponics culture was investigated. Tomato seeds were first let germinate in yonolit pots with wet coco peat and then their seedlings were transferred to plastic tanks containing 5 liters nutrient solution. Treatments were three levels of salinity (0, 30 and 60 mM as NaCl and CaCl2) and three levels of nitrogen (0, 1.5 and 3% as NH4Cl and NH4H2PO4 and 2:1 w/w). The results showed that nitrogen application increased wet and dry weights but salinity decreased them. Furthermore, salinity application had no effect on vitamin C, but 60 mM salinity increased citric acid compared to that of control. Nutrients distribution varied in different parts of then plants. Salinity increased iron and manganese uptake, but it had no effect on uptake of other nutrients. Salinity and nitrogen application reduced this inappropriate effect.

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.

To investigate the effects of different methods of seed bed preparation on yield of greenhouse cucumber, a two-year long experiment was conducted as a randomized complete block design with four replications in Jiroft from 2004. Different methods of seed bed preparation were as follows: 1) ridge with 20 cm height and 50 cm width and 2 plant rows with 40 cm distance, 2) furrow with 20 cm depth and 50 cm width and 2 plant rows inside, with 40 cm distance, and 3) planting on flat area with 40 cm distance. The results showed that the effect of planting bed on yield of greenhouse cucumber was significant. Furrow and flat area increased yield significantly, compared to the ridge treatment. Analysis of yield components such as plant height, number of pickling fruits, number of leaves, photosynthetic area and number of flowers showed that they are all correlated with fruit yield. The number of pickling fruits was significantly more in furrow and flat area than in ridge treatment. The height of cucumber plants on flat bed was significantly higher than that of the other treatments. The number of leaves and photosynthetic area of plants on flat bed were significantly greater than those in the other treatments. The least dead plants due to fungi disease were observed in ridge treatment. In view of yield and its components under the condition of this experiment, it can be concluded that flat area and furrow treatments are better than ridge treatment.

Aquaponic is a combination of fish and plant cultivated in recirculating systems. Fish culture in closed recirculating systems causes organic waste accumulation in the system. If these metabolites are used for plant nutrition, they are not mere waste, but have economical value and however benefit the fish production systems. Most aquaponic systems are designed as perlite-filled media, thin layer of nutrient solution, or Raft system. Photosynthesis parameters and water relations are good indexes for recognition of healthy plants and are used as tools for studying physiological conditions of plants. In this experiment, mint plants were cultivated in Raft aquaponic system and perlite medium. In Raft system, plant roots were suspending in water and absorbed water from pot bottom. Whereas in perlite system, roots were in the perlite medium and irrigation water was applied from top of the pots. The plants grown in Raft system showed mineral elements’ deficiency as leaf chlorosis. Photosynthesis and water parameters analysis showed that photosynthesis rate, stomatal conductance, transpiration, mezophyll efficiency, water use efficiency and photosynthesis active radiation were higher in the plants grown in perlite than in raft aquaponic system. On the other hand, stomatal conductance, leaf temperature and sub-stomatal CO2 were higher in the raft aquaponic system than perlite medium. Thus, due to better physiological conditions of mint plants, perlite medium might yield better results compared to raft aquaponic system.

Arbuscular mycorrhizal fungi (AMF) can affect their host plants growth through nutrient uptake enhancement. Determination of chelators (siderophores and phytosiderophores) in root leachates is of importance in order to account for the effects of AMF on nutrient uptake by plants. In this study, tomato plants were inoculated with either Glomus intraradices or Glomus etunicatum or left un-inoculated as non-mycorrhizal control, in pots containing sterile and acid washed perlite. Rorison’s nutrient solution harbouring three levels of Fe, Mn, Zn and Cu (full strength, half strength and without micronutrients) was applied to the pots during three month- growth period. Root leachates were collected and total chelator concentration was quantified by titration with DTPA. Plant roots showed lower mycorrhizal colonization in this condition. The amounts of chelators produced by roots were significantly different in AMF species. In plants inoculated with G. intraradices, the highest chelator production occurred in the absence of micronutrients and in its half strength as well, but the micronutrient levels had no significant effect on chelator production in plants inoculated with G. etunicatum. In the absence of micronutrients, chelator production was higher in G.intraradices inoculated plants compared to the G. etunicatum ones.