Soilless Culture System Research Articles

緩速砂ろ過の除菌率測定方法の検討およびＮＦＴシステムにおけるトマト青枯病拡散抑制効果

Slow sand filtration (SSF) is one method for disinfecting nutrient solutions in a closed soilless culture system. Microbe removal efficiency of such filtration was evaluated by determining the definite inoculant microbe density of influents and filtrates. The well water was inoculated with a suspension culture of tomato bacterial wilt pathogen (Pseudomonas solanacearum) to a density of 1.2×103 cfu·ml-1 as an influent. When the inflow of this water to the sand filters kept at 30°C lasted for 32 hr, the bacterial density of filtrate began to increase 16 hr after the inflow started (HAS) and reached the maximum value of 2.2×102 cfu·ml-1 at 32 HAS. The time course of the density of filtrate was observed to have a plateau between 24 and 36 HAS. The mean value of 1.7×102 cfu·ml-1 during the period was employed as the definite density of filtrate. The filtrate/influent ratios revealed that the removal efficiency was 86% whereas it was 99% when the temperature of the sand filter was uncontrolled. The performance of SSF against the spread of tomato bacterial wilt was investigated in a NFT tomato growing system. When the system did not include SSF, the disease spread from two previously inoculated tomato plants to the rest of the 18 plants in the same bed within 25 days. The pathogen density of the nutrient solution kept increasing up to 107 cfu·ml-1 by the end of the culture. When SSF was installed into the NFT system, no wilting damage was observed unless plants were located downstream of the previously inoculated ones. The pathogen density of the solution, which passed through the rhizosphere of infected plants, increased up to 104 cfu·ml-1 and did not decrease throughout the experiment, although no pathogen was detected in the filtrates.

DISEASE SUPPRESSIVE SOILLESS CULTURE SYSTEMS; CHARACTERISATION OF ITS MICROFLORA

The trend in glasshouse horticulture has always been to start culture systems as aseptic as possible. However, several root diseases still cause problems under these conditions. The present paper shows the importance of the microflora to suppress Pythium aphanidermatum, a fungal root pathogen which is a serious threat in cucumber. Introduced single antagonists as well as the indigenous microflora suppressed pythium root and crown rot. Pseudomonas fluorescens, Streptomyces griseoviridis, Pythium oligandrum, and 2 isolates of Trichoderma harzianum reduced the disease occurrence by 60 ␘r more in several, but not all, of the experiments. The indigenous microflora showed a very constant disease suppression of 50 to 100 EThis was tested in experiments where P. aphanidermatum was added to sterilised and non-sterilised rockwool, and to sterilised rockwool that had been recolonised with the original microflora. Suppressiveness correlated with the number of filamentous actinomycetes present in the nutrient solution in the rockwool slabs. If a beneficial microflora is present in the cropping system, it should not be disturbed or eradicated by treatments such as disinfection of the recirculated nutrient solution. Therefore, the effects of different disinfection procedures on the composition of the microflora were compared. Numbers of filamentous actinomycetes in the nutrient solution in the tank after the disinfection treatment were highest without disinfection, intermediate after slow filtration, and lowest after UV treatment. Numbers of actinomycetes in the slabs, i.e. around the roots, were not distinctly different between the treatments. The implication of potential shifts in the microbial populations due to certain treatments for the disease development is not known. Increased knowledge on the beneficial microflora and the treatments that influence the composition of such a microflora, will stimulate the exploitation of microbially balanced and optimised soilless culture systems.

MOLECULAR FINGERPRINTING OF MICROBIAL POPULATIONS IN SOILLESS CULTURE SYSTEMS

The molecular fingerprinting technique (PCR-DGGE) of microbial populations was successfully adopted for soilless culture systems. Relatively low concentrations of micro-organisms in the nutrient solutions could be assessed. PCR-DGGE was applied in several experiments to compare the composition and diversity of the bacterial populations in different treatments, as well as at different locations and ages of the crop. Although numbers of culturable aerobic bacteria were similar in different rockwool treatments, the PCR-DGGE patterns showed that the bacterial composition and diversity differed. The bacterial composition in treatments which were suppressive to Pythium aphanidermatum (i.e. previously used rockwool and used rockwool that was recolonised after autoclaving) differed from that in autoclaved used rockwool with a high disease incidence. Additionally, a shift in the bacterial populations during plant growth was seen. Samples of the nutrient solution from different locations in a closed soilless culture system, i.e. drain, effluent, and solution in the rockwool slabs, showed different banding patterns. The results summarised in this paper showed that PCR-DGGE is a powerful tool to study the microflora under different conditions.

An Economic Analysis of Soilless Culture in Gerbera Production

The financial effectiveness of the soilless culture system (SCS) of gerbera (Gerbera jamesonii Bol. ex Adlam.) production was compared with that of the soil culture system in heated greenhouses in northern Greece. Evaluation was based on budgeting procedures that assumed a project life of 9 years. The decision to accept or to reject the investment was based on the following criteria: 1) net present value analysis (U.S. $18,414), 2) benefit/cost ratio, and 3) risk exposure ratio. The soilless culture system, particularly the plastic bag system using perlite media, was more profitable. Application of sensitivity analysis illustrated the significance of product price and discount rate in determining the accrued benefits.

Automated Composition Control of Nutrient Solution in Closed Soilless Culture Systems

A computer algorithm was developed to perform replenishment and reuse of the drain nutrient solution in close hydroponic systems on the basis of dispensing as many nutrients and water in it as were needed to maintain a target electrical conductivity in the irrigation solution. To achieve this in each watering application, dilution ratios of the concentrated fertilizer solutions are automatically adjusted through a computer program based on this algorithm, in relation to the volume and the electrical conductivity of the drain solution. It was proved that the returning nutrient solution could be corrected and reused efficiently through this method. However, the concentration of P, Mn and Zn in the irrigation nutrient solution was extremely low in samples taken after continual reuse of the drain solution for a fortnight. Since the analysed irrigation solution was prepared using a large quantity of drain solution, it seems likely that reduced P, Zn and Mn concentrations in the former were due to the high pH of the latter, and this may have caused immobilization of these elements.

Nitrogen Demand of Cut Chrysanthemums in Relation to Shoot Height and Planting Date

Refined nutrient delivery systems are important for environmentally friendly production of cut flowers in both soil and hydroponic culture. They have to be closely orientated at the actual nutrient demand. To solve current problems, express analysis and nutrient uptake models have been developed in horticulture. However, the necessity of relatively laborious analysis or estimation of model input parameters have prevented their commercial use up to now. For this reason, we studied relationships between easily determinable parameters of plant biomass structure as shoot height, plant density and dry matter production as well as amount of nitrogen removal of hydroponically grown year-round cut chrysanthemums. In four experiments (planting dates 5.11.91; 25.3.92; 4.1.93; 1.7.93) with cultivar `Puma white' and a fixed plant density of 64 m2, shoots were harvested every 14 days from planting until flowering, with dry matter, internal N concentration and shoot height being measured. For each planting date, N uptake (y) was closely (r2 = 0.94; 0.93; 0.84; 0.93, respectively) related to shoot height (x) at the time of cutting and could be characterized by the equation y = a * × b. In the soilless cultivation system, dry matter concentrations of N remained constant over the whole growing period, indicating non-limiting nitrogen supply. In agreement with constant internal N concentrations, N uptake was linearly related (r2 = 0.94 to 0.99) to dry matter accumulation. It is concluded that shoot height is a useful parameter to include in a simple model of N uptake. However, in consideration of fluctuating greenhouse climate conditions needs more sophisticated approaches including processes such as water uptake and photosynthetically active radiation.

Protected Culture Systems for Strawberry Production

Strawberry plants (cvs. Camarosa, Chandler, Sweet Charlie, Primetime, Jewel, and Tribute) were grown in soilless culture systems in a greenhouse from October to May. Fresh-dug and runner-tip Aplug® plants were transplanted into two systems: vertically stacked pots (24 plants/m2) containing perlite and horizontal nutrient film technique troughs (13 plants/m2). Plants were fertigated continuously with recirculating nutrient solution. In a 7-month production cycle, the plug plants bloomed earlier and produced more fruit during the first month of harvest (December) than the fresh-dug plants. Higher yields from plug plants were a result of more fruit numbers and not larger fruit size. Fruit production averaged 6.0 and 3.5 kg/m2 in the trough and pot systems, respectively. The vertical growing system allows greater plant densities, but light intensity reaching the plants in the lower sections of the tower can be less than 20% of levels measured at the top. Establishment costs of protected culture systems are higher, but production is earlier and labor costs are typically reduced. Greenhouse hydroponic culture systems could extend the winter strawberry production to more northern locations.

Influence of nutrient solution pH on N2O and N2 emissions from a soilless culture system

The influence of nutrient solution pH on the emission of N2O and N2 was investigated during cultivation of cucumbers in a closed-loop rockwool system. Between pH 4 and 7 these gaseous nitrogen losses increased from 1.6 to 21.1% of the N fertilizer input. This was equivalent to average flux rates of 0.06 and 0.85 kg nitrogen per hectare greenhouse area and day, respectively. The N2O/N2 ratio was inversely related to the total gaseous nitrogen losses. At neutral pH dinitrogen was the main emission product, whereas more acidic conditions favoured the emission of nitrous oxide. The pH effects were probably not indirectly affected by root respiration or exudation as much as by a direct inhibition of the activity of denitrifying microorganisms due to high H+ concentrations since similar results were obtained in unplanted nutrient solution systems with the addition of glucose as carbon source. Despite the low microbial denitrification activity under acidic conditions, nitrogen balance deficits of up to one-fifth of the N input still occurred. It is suggested these losses were predominantly caused by chemodenitrification.

Assessing the Economic Efficiency of a Soilless Culture System for Off-season Strawberry Production

The financial effectiveness of a soilless vertical bag system of hydroponics culture was evaluated for off-season strawberry (Fragaria ×ananassa Duch) production in heated greenhouses in northern Greece. Financial analysis revealed that the implementation of this soilless culture system instead of the traditional production system under plastic tunnels would not be profitable for Greek farmers due to its high initial investment and high fuel consumption. Sensitivity analysis indicated the importance of product price in affecting the magnitude of benefits, confirming the interest of farmers to produce off-season strawberries to market them when prices are likely to be higher. In addition, yield increase will have a positive effect upon farmers' income.

Effect of increased cobalt treatments on cobalt concentration and growth of tomato plants

An experiment developed in soilless culture was used to study the effect of several levels of Co2+ (0, 5, 15, and 30 mg L‐1 ) on the growth of tomato plants (Lycopersicon esculentum M. cv. Ramy). Absorption, transport, and accumulation of this metal in roots, stems, leaves, and fruits were also studied. Uptake was increased by application of this metal concentration in the nutrient solution, efficiency of root uptake of cobalt decreased with increased Co2+ treatment in the soilless culture system. The translocation of Co2+ from roots to aerial vegetative parts was increased with the time of experiment and Co2+ concentration in the nutrient solution. The presence of this metal in nutrient solution reduced tomato leaf production and elongation, specially at higher treatments.

A Multilayer Soilless System for Greenhouse Tomato Production Pioneered in Shandong Province, People's Republic of China

A new multilayer soilless culture system for greenhouse tomato production is described. Experiments over two spring seasons and one winter season demonstrated faster plant growth rate, higher dry matter productivity, higher fruit yield, and better fruit quality with the multilayer soilless culture system compared to the traditional soil-based culture system. The multilayer soilless culture system is suggested as a replacement of the soil-based production system to achieve significant yield improvement in greenhouse tomato production.

Evaluation of the acetylene inhibition method for measuring denitrification in soilless plant culture systems

Evaluation of the acetylene inhibition method for measuring denitrification in soilless plant culture systems

Influence of nitrogen concentration and form in the nutrient solution N20 and N2 emissions from a soilless culture system

AbstractThe influence of nitrogen concentration and form in the nutrient solution on the N2O and N2 emissions from a closed rockwool system with cucumber crops was investigated. At optimum, nitrate‐accented nitrogen supply of plants (120 mg N l−1) on average 0.59 kg N per hectare greenhouse area and day was released. Comparable emission rates occurred with moderate sub‐ and supraoptimum nitrogen fertilization. Thus, in this range the N supply was non‐limiting for the gaseous nitrogen losses. Only in the case of severe suboptimum N supply (40 mg N l−1) the N2O N2 emissions were clearly lower, probably as a result of diminished plant growth and therefore reduced root respiration and exudation of organic carbon sources for microorganisms. The proportion of nitrous oxide in the gaseous nitrogen losses increased on average from 5 to 13% with increasing N supply, possibly because of an impaired N2O reduction in denitrification due to high nitrate concentrations.Short‐term shifting with optimum nitrogen supply from nitrate‐ accented composition to pure nitrate did not affect the gaseous nitrogen emissions, whereas an exclusive ammonium supply resulted in a considerable decrease. The results indicated that the N2O emission and the total nitrogen losses from the soilless culture system were predominantly caused by denitrification.

Effects of varying sulphate concentrations on growth, physiology and yield of the greenhouse tomato

In soilless culture systems, recycling the nutrient solution causes an accumulation of sulphate ions, which can generate nutrient imbalances affecting crop yield. This study determined the effects of four sulphate concentrations in the nutrient solution on growth, foliar mineral composition, physiology and yield of greenhouse tomatoes. Ten days after transplanting, young tomato plants ( Lycopersicon esculentum Mill, cultivar ‘Trust’) grown in rockwool were subjected to four sulphate concentrations (S 0 = 0, S 1 = 5.2 (control), S 2 = 10.4 and S 4 = 20.8 mmol L −1) in the nutrient solution. The S 0 reduced plant dry weight, photosynthetic rate, chlorophyll content, and the total number of fruits. The S 0 treatment was associated with high concentrations of P, Ca and Mg, but low levels of S in the leaves. The highest concentration of sulphates in the nutrient solution did not reduce shoot dry weight, photosynthesis, crop yield and fruit quality, although it decreased Mg, Ca and P content in the leaves. Consequently, tomato plants appeared prone to sulphate deficiency but tolerated sulphate concentrations up to 20.8 mmol l −1 in the nutrient solution with no apparent detrimental effects on yield and fruit quality over a short cropping period.

Gaseous nitrogen losses from a soilless culture system in the greenhouse

Gaseous nitrogen losses from a closed-loop rockwool system were investigated during the vegetative growth and the stem fruit stage of cucumbers. On average 12.4% of the N input were released in form of N2O and N2. This was equivalent to a mean emission rate of 0.62 kg nitrogen per hectare greenhouse area and day. The highest emission rates occurred during the stem fruit development as an increased root decay and an intensive substrate respiration came on. The proportion of N2O in the gaseous nitrogen losses decreased with increasing N2O+N2 evolution. On average it amounted to 9.6%. A comparison of different cucumber crops during the season showed that the gaseous nitrogen losses were nearly twice as high in the summer as in the autumn. Thus it proceeded almost parallel to the plant growth which also doubled. Furthermore, an effect of the substrate temperature is conceivable, since it was 3–4°C higher in the radiation-rich summer-time. With increasing root density in the substrate gaseous nitrogen losses increased while the N2O/N2 ratio declined. Possible reasons for this were a greater rhizodeposition of easily decomposable organic substances, an accelerated oxygen consumption by root respiration and a high density of microorganisms in close vicinity to the roots. The growth of green algae on the substrate surface stimulated the production of N2O.

Restriction analysis of amplified ribosomal DNA of Pythium spp. isolated from soilless culture systems

Fifteen isolates of Pythium in the filamentous non-inflated sporangia (F) group of Plaäts-Niterink were studied using polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis (RFLP), in comparison with eight Pythium species. Two different sizes of the DNA regions coding for the nuclear rDNA of internal transcribed spacers (ITS) including the 5·8 S gene were observed. The amplified ITS region for Pythium with filamentous sporangia was about 870 base pair (bp) long, and the ITS for P. ultimum was about 910 bp long. Each length variant showed distinct banding patterns after digestion with enzymes Alu I, Hinf I and Hae III. The 15 undetermined isolates of Pythium F showed similar banding patterns after digestion. These banding patterns were identical to those of P. aquatile and P. coloratum . The digestion of the amplified ITS region with the three enzymes could differentiate the species or groups of Pythium most frequently obtained from soilless cultures of tomato or cucumber.

Production of medicinal plants by soilless culture system. I. Studies of morphological characteristics and saikosaponins content in Bupleurum falcatum cultivated by Ebb & Flood system

We studied that the morphological and histological characteristics, and the content (%DW) of saikosaponins on the root of Bupleurum falcatum cultivated in an Ebb & Flood system (E & F), a kind of soilless culture system, by both the direct sowing and the transplanting methods, and that effects of pinching on the root growth and the content (%DW) of saikosaponins in each part of root. Yield of root and content (%DW) of saikosaponins in each part of root, 8-months-old, cultivated in E & F by both methods were at the same level as that cultivated for the same period in soil condition by generally standard procedures. Morphological characteristics of the root cultivated by the direct sowing method were the same appearance as that by soil condition, but by the transplanting method main root branched off in all direction and the lateral root were more developed than by the direct sowing method. By pinching lignification in xylem on the main root were inhibited, but the dried weight of total root part and content (%DW) of saikosaponins in each part of the root were not shown to be significantly changed.

Evaluation f four tomato varieties growing under a soilless culture system base don pinching and high densities

In order to determin if greenhouse tomatoes growing under a soilless culture system based on pinching of plants to leave just one or two inflorescences per plant and using high population densities (9, 16, 20 or 24 plants.m²) yield more and have better quality than the conventional system without pinching and normal population density (3 to 6 plants.m²) a trial with four tomato varieties (Hayslip, Florida, Floradade and Río Grande) was carried out at the University Chapingo in the State of Mexico. The evaluated variables were fruit number and yields per m², by plant and by fruit cluster. There were no significant differences in yield m² between pinching to leave one or two fruit clusters, but there were significant differences when compared against the control without pinching showed the lowest yield. At higher densities of population yield.m² was higher; densities of 24 and 20 plants.m² yielded more than densities of 9 and 6 plants.m². Hayslip and Floradade yielded statistically better than Florida and Río Grande per m² and per plant.

A novel procedure for raising rice seedlings and its potential application for mass-screening of rice strains for salt tolerance

A soilless culture system is described whereby all the necessary steps of raising rice seedlings, including seeding, surface-sterilization, germination and growing of seedlings, can be conveniently achieved within a small plastic container. The system is especially suited for experiments with massive number of entries and can e.g. be used for screening of rice genotypes for salt tolerance.