A comparison between two methods to control nutrient delivery to greenhouse melons grown in recirculating nutrient solution culture

Two methods to control nutrient delivery to greenhouse melon plants grown with the nutrient film technique were compared: a conventional control system based on the adjustment of electrical conductivity (EC) of the recirculating nutrient solution, and a programmed nutrient addition, which was based simply on pre-established weekly supply of N, P and K without any attempt to maintain constant values of nutrient concentration and EC. The method to control nutrient supply did not influence significantly fruit yield or quality, but the nutrient addition reduced the crop consumption of water, N, P and K by 40–60% with respect to the EC method.     

Response of eggplants grown in recirculating nutrient solution to salinity imposed prior to the start of harvesting

Summary

The effects of exposing eggplants grown in recirculating nutrient solution to salt stress (6.1 dS m^–1) from planting until the beginning of harvesting, on plant growth, yield and macronutrient status was investigated. The salinity was imposed by adding to a basic nutrient solution either additional nutrients at two cation ratios or NaCl. The results showed that the exposure of plants to salinity prior to the beginning of harvesting reduced both vegetative growth during that time and early fruit yield, but the depression of the latter was more severe. The restriction of the early yield was a result of a reduced mean fruit weight due to a lower fruit water content. The detrimental effects of salinity on the mean fruit weight disappeared 25 d after discontinuing the salinity treatments. As a result, the total yield obtained after five months of harvesting was not influenced by exposing the plants to salinity prior to the beginning of harvesting. The salinity source had no specific effect on plant growth. Moreover, the increase of salinity up to 6.1 dS m^–1 did not cause any specific nutritional imbalance or toxicity to the plants, irrespective of the salts used to achieve it. It is suggested that the electrical conductivity of the nutrient solution may be raised to 6.1 dS m^–1 to control excessive vegetative growth in eggplants grown hydroponically. However, salt treatment should be terminated either at the first harvest, if the total yield is more important than the early yield, or three weeks earlier, if the opposite is true.     

Production and quality of greenhouse roses in recirculating nutrient systems

Greenhouse-grown rose plants were grown in either a non-recirculating (open) nutrient system, or a recirculating (closed) nutrient system with or without one of five amendments. Recirculation had no effect on harvest parameters during the first 8 weeks of the harvest period, but had a negative impact on stem length during the second 8 weeks, and on stem number and length when averaged over the entire harvest duration. Differences were not likely caused by changes in electrical conductivity or macro-nutrient concentrations of the nutrient solutions. Amendments to the recirculated solutions consisted of increased concentrations of Ca, B or Si, reduced pH, or use of an adsorbent resin to remove specific organic molecules. All amendments mitigated the negative effects of recirculation on at least two harvest parameters, but only during the second-half of the harvest period. With the exception of the intentional changes, mineral status of the nutrient solutions were similar in all recirculated treatments. Leaf chlorosis was observed in all recirculation treatments. It is likely that the reduction in rose quantity and quality in recirculation is caused by a combination of factors, some of which were ameliorated through the addition of specific amendments to the solution.     

Effects of oxygen-enriched nutrient solution on greenhouse cucumber and pepper production

A series of experiments were conducted with greenhouse cucumber and pepper plants to determine the effects of oxygen enrichment of the irrigation water on yield and fruit shelf-life. The experiments were carried out in soilless culture in research greenhouses. Depending on the experiment, treatments included sub-ambient (2 mg L⁻¹), ambient (5–6 mg L⁻¹), medium (16 mg L⁻¹) and high (30–40 mg L⁻¹) levels of oxygen in the supply tank. Cucumber plants were grown in yellow cedar sawdust and pepper plants in either sawdust or perlite. Oxygen enrichment resulted in a promotion of cucumber yield in only one experiment; in two other experiments, none of the oxygen treatments, including those at sub-ambient levels, had an effect. There were no effects of oxygen enrichment on pepper yield. However, in both cucumber and pepper, fruit shelf-life was extended in oxygen-enriched treatments. In terms of system efficacy, oxygen levels in the irrigation water were measured at the dripper and found to decrease by 20–67% of initial values compared to the supply tank values, depending on the initial oxygen concentration and on the experiment. Oxygen concentrations decreased even further to virtually ambient levels when measured in the drain water or in the substrate reservoir. Cucumber plant growth was promoted under conditions which facilitated consistently high oxygen in the root zone, achieved through heavy irrigation (1 min in two) with oxygen-enriched nutrient solution of plants grown in saturated substrate (pumice). However, those extreme irrigation rates would not be practical for commercial cucumber or pepper production. Overall, this study demonstrates that oxygen enrichment of porous substrates under typical hydroponic conditions is difficult and possibly because of this, effects on yield are infrequent. However, fruit shelf-life may be improved.     

Growth,gas exchange,and nutrient status in pepper (Capsicum annuum L.) grown in recirculating nutrient solution as affected by salinity imposed to half of the root system

Pepper plants grown in recirculating nutrient solution were exposed to NaCl-salinity (60 mM NaCl, 8 dS m⁻¹) imposed either to the entire or to half of the root system and compared to plants supplied with a standard nutrient solution (1.9 dS m⁻¹). The saline solution was obtained by adding NaCl to the standard nutrient solution. In the split-root treatment, the root compartment not exposed to salinity was supplied with raw water (0.38 dS m⁻¹). Both the stem and the root dry weights were markedly restricted by salinity, irrespective of salinizing half or the entire root system. In the split-root treatment, the dry weight of the root compartment receiving raw water did not differ significantly from that exposed to salinity. The net photosynthesis and the leaf chlorophyll content were restricted by both salinity treatments, but the decrease was more marked when the entire root system was exposed to salinity. In contrast, the stomatal conductance and the transpiration rate were equally reduced, regardless of salinizing the entire or part of the root system. The leaf Na and Cl concentrations were raised by the NaCl-salinity, but only in one sampling date the increase was significantly higher when the entire root zone was exposed to salinity, as compared with salinization of half of the root system. Salinity reduced significantly the leaf K, Ca, and Mg uptake but not to levels that could cause nutrient deficiencies. These results indicate that pepper is susceptible to high salinity, predominantly due to reduced stomatal conductance. However, after long-term exposure to salinity the growth may be suppressed due also to inhibition of photosynthesis at chloroplast level. The adverse effects of high NaCl-salinity are hardly mitigated when only a part of the root system is salinized, which indicates that the response is governed by root exposure to high NaCl concentrations and not by inefficiency of the roots to take up water.     

Closed cycle subirrigation with low concentration nutrient solution can be used for soilless tomato production in saline conditions

Closed cycle soilless techniques can be adopted to minimize water and fertilizer losses in greenhouse cultivation. There is a general lack of information regarding the soilless cultivation of vegetables with closed cycle subirrigation techniques, specifically when using saline water. In this study, a trough bench subirrigation system (SUB), with two fertilizer concentrations (“100%”, containing 9.8 mol m⁻³ N-NO₃, 1.6 mol m⁻³ P-H₂PO₄, 8.7 mol m⁻³ K⁺, 2.8 mol m⁻³ Ca⁺, 1.8 mol m⁻³ Mg⁺, 4 mol m⁻³ S-SO₄, and “70%”, containing 70% of the macronutrient concentration) in the nutrient solution (NS), was compared with open cycle drip-irrigation (DRIP with “100%” NS). For all the three treatments, NS was prepared using rain water (0.05 dS m⁻¹) and adding NaCl (1 g L⁻¹), in order to simulate moderate saline irrigation water. The effect of the treatments on tomato (Solanum lycopersicum L.) plant growth, yield, fruit quality, water use efficiency (WUE) and fertilizer consumption was evaluated. Substrate and recirculating NS composition were also studied. Subirrigation, regardless of NS concentration, reduced plant height (by 30 cm), leaf area (by 1411 cm²), total fresh and dry weight (by 429 and 48.5 g plant⁻¹, respectively) but not dry matter percentage of the whole plant, with respect to DRIP. Yield was reduced when plants were subirrigated with the higher concentrated NS, but no differences with open cycle DRIP were recorded when the lower NS concentration was used in SUB. Fruit quality was not affected by irrigation system or NS concentration. The higher WUE was obtained with subirrigation. NaCl accumulated similarly over the crop cycle in recirculating NS of both SUB treatments and in growing substrates of all the three treatments. Higher salt concentration was found in subirrigated substrates, in particular in the upper part of the substrate profile. Fertilizers accumulated in the subirrigated substrates when the higher NS concentration was used, but not when the NS concentration was reduced by 30%. The results of this study indicate that tomato can be grown successfully in a closed cycle subirrigation system, using saline water, by reducing the fertilizer NS concentration normally used with traditional open cycle systems.     

平菇营养液配方的研究

本试验是通过平板试验，在培养基中添加VB1，复合肥(N、P、K)、NPP、乙烯利，通过四因素三水平的正交试验，旨在选择一种最佳组合。试验结果表明VB1(0.002%)，N.P.K(0.05%)、NAA(5×10-6)、乙烯利(500×10-6)，此种配比最适合平菇菌丝的生长。     

无土栽培循环营养液的灭菌

与传统的土壤栽培方式相比,无土栽培的优点在于既可以生产廉价的无公害、绿色食品以满足人们的生活需要,又可向高精尖的方向发展,提高农产品的种植密度以提高产量,甚至可以满足航天、极地条件下的农作物生产的需要,所以无土栽培的发展前景不可估量.近年来,我国的无土栽培面积迅速增加,2000年达到500 hm2(公顷),2002年达到了856 hm2(公顷).     

黄瓜椰糠栽培营养液的适宜浓度探索

为了探索黄瓜椰糠栽培中适宜的流出液EC值指标,根据流出液EC值的高低来调节灌溉液浓度,实现肥料的合理施用。试验设置了1.8、2.2和2.6 mS·cm^-1三个流出液EC值指标,灌溉液浓度的“增减量(/g·L^-1)=(EC值设定值-EC值测定值)×流出率/%”。此模型不仅考虑了EC值设定值与测定值的差异,而且考虑了流出率因素。通过“配液浓度=在用浓度+增减量”,对灌溉液浓度进行连续调控。结果显示,伴随灌溉液浓度的升高与降低,流出液EC值围绕设定值上下波动,基本实现了稳定。流出液中氮、磷、钾、钙、镁元素的含量与EC值设定值正相关,反映了肥料供应水平的高低。当流出液EC值设定在2.2和2.6 mS·cm^-1时,黄瓜的产量差异不显著,却又都比EC值在1.8 mS·cm^-1设定值时显著增加。所以,2.2~2.6 mS·cm^-1可作为黄瓜椰糠栽培适宜的流出液EC值控制区间。     

The influence of irrigation system and nutrient solution concentration on potted geranium production under various conditions of radiation and temperature

Zonal geranium (Pelargonium × hortorum ‘Real Mintaka’) were grown in closed soilless systems to evaluate the effects of irrigation system (drip and subirrigation) and nutrient solution concentration (half and full) under various conditions of radiation and temperature (winter and summer) in terms of substrate electrical conductivity (EC_s), growth, quality, crop evapotranspiration (ET_c) and growth index water use efficiency (WUE_GI) and nutrient uptake. At he end of the cultural cycle the highest EC_s in the upper and lower layers were recorded in the spring season on plants grown in subirrigation using a full nutrient solution concentration. The highest shoot biomass, leaf area, plant growth index, and quality index were recorded in the winter season on plants grown in both drip-irrigation and subirrigation using half and full nutrient solution concentration, whereas the lowest value was observed in the spring season on plants grown with subirrigation using the full nutrient solution concentration. The highest maximum air temperature recorded during the first 20 days after transplanting in the spring growing season was presumably responsible for the reduction in shoot biomass production, growth and quality index, and in time of geranium flowering compared to the plants grown in the winter season. The ET_c was 44% higher in spring than in winter season treatment, while the effect of the irrigation system was less pronounced with an increase in 11% in the subirrigation treatment compared with the drip-irrigation system. WUE_GI was not stable and showed a seasonal variability. Solar radiaton (R_s), air temperature (T_a) and vapour pressure deficit (VPD) were greatly higher in the spring season, which influenced WUE_GI negatively. The WUE_GI improved especially when R_s, T_a and VPD were below 12 MJ m², 20 °C and 0.6 kPa, respectively. The highest N, and Mg uptake were recorded in the winter season, especially on plants grown with subirrigation at 2 dS m⁻¹. The highest P, K, and Ca uptake values were measured during winter season using subirrigation system, and on plants grown under full strength nutrient solution. The variation of the nitrate concentration and EC in the nutrient solution during the spring growing cycle was less pronounced in the subirrigation than with a drip-irrigation system which represents an important aspect for the simplification of the closed loop management of the nutrient solution.     

Effect of nutrient sources on cucumber production in different substrates

The research was conducted in two successive seasons to compare the effect of nutrient sources, organic manure and inorganic conventional nutrient solution, in cucumber production performed with different local substrates. In fall, the experiment was designed to test three factors, namely cultivar [(a) Armada, (b) Gordion], nutrient source [(a) inorganic nutrient solution, (b) solid organic manure] and substrate [(a) 3 + 1 perlite + clinoptilolite, (b) 1 + 1 perlite + clinoptilolite, (c) 3 + 1 tuff + clinoptilolite, (d) 1 + 1 tuff + clinoptilolite, v/v]. Results showed that organic manuring decrease the total yield by 22.4% in comparison to inorganic nutrient solution. In organic manure treatment, vigorous variety (Armada) gave higher yield than less vigorous variety (Gordion). In the spring season, the tested factors were decreased to two and tested as nutrient source [(a) inorganic nutrient solution, (b) solid organic manure, (c) organic nutrient solution] and substrate. Armada was the only cultivar. Compared to that of the inorganic nutrient solution, total yield was reduced by 10.9% in the organic nutrient solution system and 31.3% in solid organic manure treatment.     

Differential tolerance to iron deficiency of citrus rootstocks grown in nutrient solution

We studied the effects of Fe deficiency on physiological parameters of citrus rootstocks grown in nutrient solution. Three 4-week old rootstocks (‘Troyer’ citrange – Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf., Citrus taiwanica Tan. and Shim., and ‘Swingle’ citrumelo – Poncirus trifoliata (L.) Raf. × Citrus paradisi Macf.) were grown in nutrient solutions with 0, 5, 10, 15 and 20 μmol Fe dm⁻³. Calcium carbonate (1 g dm⁻³) was added to all solutions to mimic the natural conditions in calcareous soils. For each rootstock, shoot length, number of leaves, and root and shoot dry weights were measured at the end of experiment. Chlorophyll concentration was estimated using a portable SPAD-502 meter calibrated for each rootstock. The amount of nutrients (P, K, Mg, Ca, Fe, Zn, Mn, and Cu) was determined in shoots. Chlorophyll fluorescence parameters (F₀: basal fluorescence; F_m: maximum fluorescence; F_v = F_m − F₀: variable fluorescence) were measured with a portable fluorimeter. ‘Troyer’ citrange rootstock was the most tolerant to Fe deficiency. These plants grew more and accumulated more chlorophyll and nutrients than the others in the presence of low levels of Fe (10 μmol Fe dm⁻³). ‘Swingle’ citrumelo plants needed 20 μmol Fe dm⁻³ in the nutrient solution to secure adequate growth. ‘Taiwanica’ orange rootstock had an intermediate behaviour, but could be distinguished from ‘Troyer’ citrange based on fluorescence parameters, since there was a variation in the basal fluorescence in the former, whereas in ‘Troyer’ citrange the basal fluorescence was not affected by the supply of Fe.     

不同营养液配方对阳台水培黄瓜的影响

以‘戴多星’黄瓜为试材,系统研究了7种不同营养液配方T1~T7对阳台水培黄瓜生长的影响,通过测定黄瓜的株高、茎粗、SPAD值、产量、可溶性固形物含量和维生素C等指标,初步筛选和评价出适合阳台水培黄瓜的最佳营养液配方。结果表明:使用T7营养液配方水培黄瓜可以显著提高叶面积,达到429.25 cm2;SPAD值增至47.08;结瓜数14个、单瓜质量65.08 g和单株产量889.34 g、维生素C含量145.68 mg·kg-1和可溶性固形物含量4.24%。与其他配方相比,T7增幅差异显著,可作为阳台上水培黄瓜的最佳营养液配方。     

Diurnal variations in the oxygen content and acid requirement of recirculating nutrient solutions and in the uptake of water and potassium by cucumber and tomato plants

The oxygen content of recirculating nutrient solutions was measured in July and August, together with the amounts of acid required to maintain a constant pH in the solution and the rates of uptake of water and potassium. The oxygen content of the solutions declined to a minimum during the brightest part of the day. The oxygen deficit was highly correlated with both the temperature and the amount of acid required to maintain the pH of the nutrient solution. Under similar environmental conditions, the oxygen content of the solution was reduced to lower concentrations by cucumber (2.7 mg l^?1; 34% saturation) than by tomato plants (6.7 mg l^?1; 84% saturation), reflecting the thicker root mat formed by cucumber.     

营养液不同配方对草莓苗N、P、K含量的研究

配制不同比例的营养液,测定花果初期草莓苗的地上部分和地下部分的氮磷含量。研究营养液中氮磷钾元素的配比,对草莓氮磷含量的影响,为草莓营养液的配比提供理论基础。结果表明：在N、P、K配比1.369：0.288：1.443下,花果初期草莓苗氮磷含量最高。因此,营养液中的氮磷钾的相对含量会对花果初期草莓的氮磷钾含量造成影响。     

The effects of nutrient solution sterilization on the growth and yield of hydroponically grown lettuce

Two methods of removing bacteria from hydroponic nutrient solution [ultraviolet (UV) radiation and submicronic filter] were evaluated for efficiency and for their effects on lettuce (Lactuca sativa L.) production. Both methods were effective in removing bacteria; but, at high intensity, the ultraviolet sterilizer significantly inhibited the production of plants grown in the treated solution. Bacterial removal by lower intensity UV or a submicronic filter seemed to promote plant growth slightly, but showed no consistent, statistically significant effect.     

Effects of night-time humidity and nutrient solution concentration on the calcium content of tomato fruit

Calcium intake into tomato fruits was greater when nights were humid rather than dry and nutrient solutions dilute rather than concentrated.The concentration of calcium in the wall tissue of the distal segment of fruits damaged by blossom-end rot was 0.03% of dry matter, but was 2- to 3-fold greater in the most favourable conditions of humidity and solution concentration, when fruits were undamaged.Adding extra calcium to the nutrient solution increased the calcium concentration in the proximal, but not in the middle or distal, segments of the fruit.The results support the hypothesis that a positive root pressure at night promotes transport of calcium into tissues and organs that have restricted transpiration.     

The effect of intermittent irrigation with cold nutrient solution on the growth of tomato seedlings propagated in rockwool

Seedlings of tomato, cv. Counter, propagated in rockwool blocks were irrigated five times every 24 h with nutrient solution at 10°C or 18°C for up to three weeks. The mean block temperature was lowered by 3.5-4.0 degrees C by irrigation at 10°C. One week of irrigation at the lower temperature caused the seedlings to develop a characteristic dark purplish colour. This treatment reduced fresh weight and leaf area but not dry weight which suggests that water uptake was also reduced. Dry weight was reduced following two or more weeks of irrigation at 10°C. When seedlings which had been irrigated at 10°C were returned to irrigation at 18°C, the purple colour slowly disappeared and the percent dry matter decreased. When plants were grown on, the total yield of fruit was unaffected by these seedling treatments.     

Effects of different nutrient solution formulations on morphological and biochemical characteristics of nursery fig trees grown in substrate culture

This research was carried out to determine the effects of different nutrient solution formulations on the growth of nursery fig trees in substrate culture, which is one of the soil-less culture techniques. The hardwood cuttings of Ficus carica L. cv. “Sar?lop” (Calimyrna) were planted into pots filled with 13 L of perlite. Five different nutrient solution formulations were tested on the quality and growth progress of nursery fig trees. The trials were conducted in two different growing conditions, namely, high-tunnel and open-field conditions in substrate culture. To observe the effect of different nutrient solution formulations on nursery fig trees, some morphological and biochemical characteristics were determined. It was concluded that the use of Hewitt's and Hoagland's nutrient solution formulations led to increased growth of nursery fig trees in high-tunnel and open-field conditions, respectively.