As a consequence of eutrophication in lakes and coastal areas requirements for reduction of nitrogen and phosphorus from wastewater introduced in Sweden in early 1990s. To meet these requirements, many wastewater treatment plants have been upgraded for biological nitrogen and phosphorus removal. As a consequence of eutrophication in lakes and coastal areas requirements for reduction of nitrogen and phosphorus from wastewater introduced in Sweden in the early 1990s. To meet these requirements, many wastewater treatment plants have been upgraded for biological nitrogen and phosphorus removal. A small-scale HYDROPONICS system has been designed in Stockholm for domestic wastewater treatment and also removal of nitrogen and phosphorus. The treatment plant is built for research purposes and presently treats 0.6 m3 of domestic wastewater from surrounding area per day. The system uses anoxic pre-denitrification followed by aerobic tanks for nitrification and plant growth. A microalgal step further reduces phosphorus, and a final sand filter polishes the water. In this study the treatment capacity of this system was evaluated with respect to removal of organic matter, phosphorus and nitrogen. 90% COD removal was observed in the system. Nitrification and denitrification were well performed with total nitrogen reduction of 72%. Phosphorus was removed by 47% in the process. However, higher phosphorus removal values are expected, as the microalgal step will be further developed. The results show that acceptable treatment can be achieved using this kind of system. Further optimization of the system will lead to clean water as valuable plants to be harvested from the nutrient rich wastewater.

This experiment was conducted to evaluate the effect of barley green fodder produced by HYDROPONICS system on the performance of feedlot calves. In a completely block randomized experiment, 24 cross bred (Holstein×Local) male calves were assigned randomly to one of the two treatments (diets) that were either control (grain barley) or hydroponic barley green fodder (BGF) that was included to provide 22.8 percent of the total diet on dry matter basis. Seed grade barley was grown in a HYDROPONICS chamber system where the growth period was adjusted for 6 days. Body weigh gain was not significantly different between the treatments, but the animals that had received the control diet had higher (P<0.05) dry matter intake than those fed BGF diet. There was a tendency (P=0.199) toward differences in feed efficiency due to dietary treatments. From economical point of view, feed cost increased up to 24 percent when the calves were offered BGF, because of the costly production of HYDROPONICS green forage. Although the mass production of fresh fodder was about 4.5 times per kg of barley grain, this was due to water absorption during germination and growth period. Nevertheless, the dry matter obtained was less than the initial barley grain and further dry matter losses were found in the green fodder. These findings suggest that green fodder had no advantage over barley grain in feedlot calves, while it increased the cost of feed.

Introduction: Selenium is a non-metallic, rare chemical element and essential for many organisms but this element is not mentioned as an essential element for plants. Due to its presence in antioxidant defense systems and hormonal balance, selenium is known to be necessary in human and animal health Plants exhibit a variety of physiological responses to selenium. Some species accumulate large amount of selenium, while many plant species are sensitive to presence of large amounts of selenium in soil and water. The mean, the maximum and tolerance level of selenium required for humans is 45, 55 and 400 micrograms, respectively (Dietary Reference). but acute toxicity level in animals are found with a concentration of 1000 ppm. Plants absorb and storage selenium in chemical form and concentration depends on pH, salinity and calcium carbonate content. High contents of selenium reduce plant growth and plant dryness, however in some plants low selenium concentrations improved growth and increase stress resistance by maintenance of chloroplast enzymes. Positive response to the use of selenium were mentioned in lettuce, potato, mustard, crap, darnel, soybean (Glycinemax...

The development of growing cucumber in greenhouse needs to assess the accessible facilities in Iran. In different countries, various growing media are used in hydroponic systems. Hence, an experiment was conducted to find out the effect of growing media on the growth and quality of cucumber. Various growing media, perlite, vermiculite, rockwool and their mixture were used as treatments. Seeds of cucumber (Cucunis sativus cv Sultan) were planted in HYDROPONICS system and irrigated with nutrient solution. The growing period was 2.5 month and fruits were harvested at two day intervals. The results showed that the highest yield (4.5 kg per plant) was observed for perlite and vermiculite mixture treatment. Leaf number and height of the plant for perlite and vermiculite mixture treatment was 4 leaves and 40 cm higher than that of the other treatments, respectively. Nitrate concentration in the fruits was 50-67 mg/kg which is not hazardous for human health. Increasing of yield and its components were associated with apropriate conditions of the treatment having mixture of perlite and vermiculite, which is able to provide enough water and air to the plant. It can be concluded that the mixture of perlite and vermiculite could be an optimal medium for HYDROPONICS system.

Silicon (Si) has beneficial effects on the growth, yield, and tolerance of some crops against biotic and abiotic stresses. Considering the absence of Si in the nutrient solutions used in hydroponically-grown cucumber, the present study was conducted to investigate the influence of Si on the growth and yield of two cucumber genotypes (Cucumis sativus L. cvs. Dominus GRC and Super Dominus). In a hydroponic experiment, two cucumber cultivars were exposed to three Si levels (0, 100, and 200 mg L-1 Si in the form of sodium silicate). The results showed that supplement of Si in the nutrient solution increased Si concentration in cucumber root and shoot. The root and shoot dry weight, crop height, and root length of cucumber plants were significantly (P< 0.05) greater in the presence of Si in comparison with the free- Si treatments. Most of the growth parameters, did not have significant difference at the 100 and 200 mg L-1 silicate levels. According to the results of the present study, it seems that the application of 100 mg/L Si in the nutrient solution could improve the growth and yield of cucumber.

Purpose Manure extracts possess great potential as alternate inorganic fertilizers. However, limited information exists on how manure influences plant growth. This study’ s aim was to determine the impact of aerated manure extracts on romaine lettuce (Lactuca sativa var. longifolia) and Russian kale (Brassica napus var. ‘ Red Russian’ ) in hydroponic systems. Methods Chicken, cow, and turkey manure extract solutions (10, 25, and 50 g/L manure) were compared to a control (Hoagland) solution for lettuce and kale grown in an ebb and flow hydroponic system. Results The aboveground dry mass of lettuce grown in a 50 g/L turkey manure extract solution was greater than that of the control. The largest aboveground wet mass for kale occurred with the control. Nutrient analyses of all manure extract solutions showed a 29%– 79% higher concentration of NH4– N and higher total nitrogen than the control. Principal component analysis of the nutrient solutions identified six nutrients that should be monitored to maximize plant yield when using manure extracts in HYDROPONICS: NO3 − , NH4 +, Ca, Mg, Mn, and Na. Conclusions Healthy lettuce and kale plants were grown in turkey manure extract solution (50 g/L). However, reduced aboveground wet and dry mass were recorded for both plants in chicken and cow manure extract solutions compared to the control. NH4 + toxicity likely killed all plants grown in chicken extract (50 g/L). Apart from NH4 + and P, all nutrients were below suggested concentrations suggested for lettuce growth. A combined manure/mineral fertilizer may be necessary to optimize hydroponic solutions.

Borage is an important medicinal plant which must be cultivated commercially in order to meet the ever-increasing demand for pharmaceutical industry. This study was done under HYDROPONICS condition. Seeds of Borage were obtained from Neka Research Center (North of Iran). After applying Benomyl fungicide, the seeds were rinsed with distilled water and planted in vermiculite. After germination and appearance of two leaves, the plants were nourished by 0.5 Longshtein solutions. At 4-leaf stage, the plants were divided into two groups: control and salinity. Proline and soluble sugars contents were regularly studied under saline condition. While the content of proline increased, soluble sugars experienced a decrease under salinity. It was concluded that Borage was able to resist against stress due to change of contents of these compounds under salinity.

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.