ISOLITE: A NEW SUBSTRATE FOR HYDROPONICS

Many different substrates are used for plant support in hydroponic culture, but one of the unique requirements for research is that the media be easily separated from the roots. Peat, perlite, and vermiculite are good substrates but roots and root hairs grow into these substrates, so they are unsuitable for studies of root size and morphology. Sand can easily be removed from roots, but roots grown in sand are shorter and thicker than hydroponic roots because the sand particles are so dense. We have also found that plant growth in sand is less than in other substrates, presumably because of reduced root growth. Calcined clay (brand names: Turface, Profile, Arcillite) was the medium of choice for research hydroponics for many years because it can easily be removed from roots. Calcined clay, however, has two disadvantages: 1) It is not chemically inert. Different batches supply different amounts of available nutrients and this causes variable results. It can be repeatedly rinsed in nutrient solution to desorb undesirable nutrients, but this adds to its cost. 2) Calcined clay is not a uniform particle size, and the water holding capacity depends on particle size. Not all batches are the same.




We recently tested and began using an extruded, diatomaceous-earth product called Isolite. Isolite is mined off the coast of Japan where there is a unique diatomaceous-earth deposit mixed with 5% clay. The clay acts as a binder in the extrusion and baking of the diatomaceous-earth. Diatomaceous-earth materials were originally organisms composed primarily of silicon dioxide (SiO2). Silicon dioxide is physically and chemically inert and these characteristics make it useful for horticultural applications like putting greens and urban trees where the soil is subject to severe compaction. Isolite is available in particle sizes from 1 to 10-mm diameter. Our tests indicate that Isolite is chemically inert and has good water holding characteristics. Its disadvantage is cost at $1.22 per Liter ($.79 per pound) for small quantities, although it can be reused. We have reused it after rinsing and drying at 80 C. Isolite is made by Sumitomo

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DESIGNING HYDROPONIC SYSTEMS:

THE IMPORTANCE OF FLOW RATE Most hydroponic systems have inadequate flow rates, which results in reduced oxygen levels at root surfaces. This stresses roots and can increase the incidence of disease. Oxygen is soluble only as a micronutrient, yet its uptake rate is much faster than any other nutrient element.





The nutrient film technique was designed to improve aeration of the nutrient solution because of the thin film of solution, but the slow flow rates in NFT cause channeling of the solution and reduced flow to areas with dense roots. The root surfaces in these areas become anaerobic, which diminishes root respiration, reduces nutrient uptake, increases N losses via denitrification, and makes roots susceptible to infection. The problems with the nutrient film technique have been discussed by several authors. Bugbee and Salisbury (1989) discuss the importance of flow rate and adequate root-zone oxygen levels.

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EXPERIENCES WITH PHYTHIUM CONTROL IN HYDROPONIC SOLUTION

The phythium fungus has been the only serious disease we have encountered in our systems, and disease problems have been relatively rare, particularly when all parts of the system are kept covered to keep dust and dirt particles away from the solution. Every plant pathologist on the planet recommends sanitation as the best control procedure for phythium, yet many hydroponic systems are not as well sealed as they should be.




Last year, we discovered that Mn deficiency predisposed the plants to phythium infection. A student worker accidently used MgCl2 in place of MnCl2 for a micronutrient stock solution and we didn't discover the mistake for several months because we were doing short (25 day) studies and there was enough Mn contamination so that no visual symptoms were apparent (growth rate was reduced only about 15% and there was about 10 mg kg-1 Mn in the leaf tissue). During this time several of the systems became infected with phythium. The same systems have never been infected when Mn was adequate. Copper is well known to suppress microbial growth, but increased copper levels are toxic to plants. Manganese and zinc (divalent cations) may have a similar disease suppressive potential, but are less toxic to plants. In the interest of minimizing phythium growth, we have increased solution Mn to a level higher than that required for optimum growth. Careful studies will be required to confirm the beneficial effects of Mn on disease suppression; meanwhile, there is little disadvantage to maintaining manganese, zinc, and copper levels slightly above the minimum required for plant growth.

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WHY ADD SILICON TO NUTRIENT SOLUTION?

Although silicon has not been recognized as an essential element for higher plants, its beneficial effects have been shown in many plants. Silicon is abundant in all field grown plants, but it is not present in most hydroponic solutions. Silicon has long been recognized as particularly important to rice growth, but a recent study indicated that it may only be important during pollination in rice (Ma et al. 1989). The beneficial effects of silicon (Si) are twofold:

1. it protects against insect and disease attack (Cherif et al. 1994; Winslow, 1992; Samuels, 1991), and
2. it protects against toxicity of metals (Vlamis and Williams, 1967; Baylis et al. 1994). For these reasons, I recommend adding silicon (about 0.1 mM) to nutrient solutions for all plants unless the added cost outweighs its advantages.

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pH MONITORING AND CONTROL

Is pH control important? Most people assume pH control is essential, but there is considerable misunderstanding about the effect of pH on plant growth. Plants grow equally well between pH 4 and 7, if nutrients do not become limiting. This is because the direct effects of pH on root growth are small, the problem is reduced nutrient availability at high and low pH. The recommended pH for hydroponic culture is between 5.5 to 5.8 because overall availability of nutrients is optimized at a slightly acid pH. The availabilities of Mn, Cu, Zn and especially Fe are reduced at higher pH, and there is a small decrease in availability of P, K, Ca, Mg at lower pH. Reduced availability means reduced nutrient uptake, but not necessarily nutrient deficiency.




Unfortunately, hydroponic systems are so poorly buffered that it is difficult to keep the pH between 4 and 7 without automatic pH control. Phosphorous (H2PO4 to HPO4) in solution buffers pH, but if phosphorous is maintained at levels that are adequate to stabilize pH (1 to 10 mM), it becomes toxic to plants. Plants actively absorb phosphorous from solution so a circulating solution, with about 0.05 mM P has much less buffering capacity than the fresh refill solution that is added to replace transpiration losses. Figure 2a is a titration curve of fresh refill solution compared to the recirculating solution. Six mmoles of base were required to raise the pH of fresh solution from 5.8 to 8, but only 1 mmole of base raised the pH of the circulating solution to 8. Figure 2b shows the slopes (derivatives) of the lines in Figure 2a. Figure 2b clearly shows poor buffering of the circulating solution between pH 5 to 9; small amounts of acid or base rapidly change the solution pH. The fresh refill solution is buffered by phosphorous, which has its maximum buffering capacity at pH 7.2. This point is called the pKa of the buffer and it is the point at which half of the phosphorous is in the H2PO4 form and half is in the HPO4 form. In other words, the phosphate ion absorbs and desorbs hydrogen ions to stabilize the pH. Unfortunately, phosphorous is quickly removed from the solution.

We were surprised to find that the circulating solution was better buffered below pH 5 than the fresh solution. The reasons for this are unclear, we cannot identify compounds in the refill solution that provide buffering capacity at pH 4. We are preparing to repeat these measurements and are investigating this finding.

How important is maintaining pH 5.8? We control the pH at 4 to study root respiration (to eliminate bicarbonate in solution). We compared growth at pH 4 and pH 5.8 with wheat and were not able to find a significant difference in root growth rate or root metabolism. We now routinely grow wheat crops at pH 4 during the entire life cycle. However, although there is usually a broad optimum pH, it is still best to maintain pH at about 5.8 to optimize nutrient availability. pH levels below 4 may start to reduce root growth, in one study our pH control solenoid failed just after seed germination and the pH went to 2.5 for 48 hours. The roots turned brown and died, but new roots quickly grew back and the plants appeared to make a complete recovery.

An automated pH control system. Although organic pH buffers can be used to stabilize pH (Bugbee and Salisbury, 1985), in the long run it is better and less expensive to use an automated pH control system that adds acid or base to the solution. These systems require 3 components: a pH electrode, a pH controller, and a solenoid. We have had 7 pH control systems in continuous operation at the Utah State University Crop Physiology Laboratory during the past 8 years. It is useful to pass on our experience with the system components.

pH electrodes. We have not found that expensive electrodes last any longer than cheap electrodes (about 2 years per electrode) so we use cheap electrodes. We currently use a general purpose pH electrode from Omega (model PHE-4201; $49). It appears to be important to avoid rapid flow of solution across the tip of the electrode. Rapid response time is not important and the high flow appears to greatly decrease electrode life and also causes significant calibration drift. We check the calibration of the electrode every 2 to 3 months and adjust it if necessary.

pH controller. In about 1987 a new, digital-display pH controller became available (model 3671, $225., Whatman Lab Sales, Hillsboro, OR, 1-800-942-8626). This controller has been excellent in our laboratory - we have yet to have a controller fail. Automatic temperature control is completely available with the controller for another $65. but it is unnecessary.

When the pH increases to 5.8, the controller opens a solenoid that allows nitric acid (HNO3) to flow into the bulk solution. When nitrate nitrogen is used the solution pH increases as the nitrate is absorbed so only one solenoid is necessary. The acid inlet should be in close proximity to the tip of the pH electrode so that frequent small additions of acid occur and the bulk solution pH is stable.

Acid/base solenoid. A peristaltic pump can be used to add acid or base, but a solenoid is less expensive. Proper solenoid selection is important because common solenoids quickly deteriorate from acid corrosion. We use a shielded core acid solenoid from The Automatic Switch Company (ASCO, model D8260G56V or G53V; about $76). These solenoids do not corrode, but in our experience, about 50% of the diaphragms in the valves failed in less than 2 years in continuous use. The valves are rated for a million cycles so they should last at least 10 years. We are currently working with ASCO to determine the cause of the premature failure. We previously used ASCO valve number D8260G54V, but this valve is not shielded core and corrodes in less than a year, even with 0.1 molar acid. Most plumbing suppliers sell ASCO solenoids, it pays to shop around for good price and quick delivery. Many other companies sell acid resistant valves that may be suitable, but some require a transformer for 24 volt operation.

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DEVELOPING AN APPROPRIATE REFILL SOLUTION

The objective is to develop a recipe for a refill solution that replenishes both nutrients and the water. Plants have evolved to tolerate large nutrient imbalances in the root-zone, but in recirculating hydroponic systems, imbalances in nutrient replenishment are cumulative. It is thus important to understand the principles for nutrient replacement, especially when the solution is continuously recycled over the life cycle of a crop.

Traditional nutrient solution recipes, such as Hoagland solution, can be used as refill solution if they are diluted to about 1/3 strength so that the electrical conductivity is kept constant. Hoagland solution, however, was originally developed for tomatoes and is not always appropriate as refill solution for other types of plants.

Two factors must be considered in developing a refill solution:
1. SOLUTION COMPOSITION The composition of the solution (the ratio of nutrients) should be determined by the desired concentrations of each element in the plant. A starting point for refill solution composition is the ratio of the elements in the plant leaves, which can be determined from a reference book on Plant Analysis Interpretation. I am familiar with four books that list the optimum concentrations of nutrients in plant tissue (and there are probably other books):
• Plant Analysis: An interpretation Manual. 1986. D. Reuter & J. Robinson, (eds). Inkata Press, Melbourne.
• Plant Analysis Handbook. 1991. J. Benton Jones, B. Wolf, H. Mills. Micro-Macro Publishing, Inc. Athens, GA.
• Plant Analysis. 1987. P. Martin-Prevel and J. Gagnard. Lavoisier Publishing Inc. New York.
• Diagnostic Criteria for Plants and Soils. 1966. Homer Chapman. Univ. of Calif., Riverside, CA.
Each of these books is organized differently and each has strengths and weaknesses. I recommend collecting the information from all of them for a particular crop and comparing the recommendations for the optimum range of nutrient concentrations.

Foliar analysis is based on the nutrient concentration in leaf tissue because leaves conduct the most photosynthesis and thus have the highest enzyme levels in plants. Average nutrient concentrations of whole plants are usually less than the concentrations in leaves, so a refill solution based solely on leaf tissue concentration will over supply nutrients for stems, seeds, and fruits. We have made many measurements of nutrient concentrations in different parts of wheat plants. Table 3 shows the that the concentrations of most elements are much higher in leaves than in other plant parts.

Young plants easily develop nutrient deficiencies but rarely develop nutrient toxicities so we use a relatively concentrated initial starter solution. A refill solution with adequate nutrients for early vegetative leaf growth is usually too concentrated when plants are developing stems and leaves so we alter the composition of the refill solution with the growth stage of the plant to prevent nutrient accumulation in the solution. The life cycle can be divided into 3 stages:
• Early vegetative growth, which is primarily composed of leaf tissue (starter solution).
• Late vegetative growth, during which growth is composed of about equal amounts of stem and leaf tissue (vegetative refill solution).
• Reproductive growth, during which leaf growth is minimal and nutrients are mobilized into seeds or fruits (seed refill solution).
Root growth primarily occurs during early vegetative growth and is much less significant during late vegetative growth. Root growth decreases and even stops during reproductive growth.

The rationale underlying the differences between Hoagland's solution and Utah Wheat solution are not obvious so a discussion of differences is useful.

NITROGEN: When nitric acid is used for pH control, about half of the nitrogen is supplied in the pH control solution. Nitrogen in the refill solution can thus be less than in Hoagland's solution. Ammonium nitrate (NH4NO3) can be added to the pH control solution if necessary to obtain even higher levels of N in the plants, but ammonium reduces the uptake of other cations so it should only be used if necessary.

POTASSIUM: The supply of K is more constant with a low level in the starter solution and a more concentrated refill solution.

CALCIUM: Grasses have a lower requirement for calcium than dicots.

MAGNESIUM and SULFUR (MgSO4): We have not found that 1 mM is necessary.

IRON (Fe): The use of modern chelating agents means that iron can be maintained in solution and much lower levels can be maintained.

BORON: Grasses have much a lower requirement for boron than dicots.

ZINC and COPPER: These elements are ubiquitous contaminants. Hoagland and Arnon in the 1940's and 50's probably got most of these elements from contamination of the solution. Modern plastics, especially PVC pipe, greatly reduce copper and zinc contamination.

SILICON: A beneficial element. See section on silicon in this paper.

2. Solution Concentration The concentration of ions in the refill solution is determined by the ratio of transpiration to growth. Transpiration determines the rate of water removal; growth determines the rate of nutrient removal. A good estimate of the transpiration to growth ratio for hydroponically grown crops is 300 to 400 kg (Liters) of water transpired per kg of dry mass of plant growth. The exact ratio depends on the humidity of the air; low humidity increases transpiration but does not increase growth. Elevated CO2 closes stomates and increases photosynthesis so the transpiration to growth ratio can decrease to about 200 to 1.

A knowledge of these ratios is useful in determining the approximate concentration of the refill solution. For example, 1/4 strength Hoagland's solution is about right for plants grown in ambient CO2, but 1/3 strength Hoagland's solution may be required for plants grown in elevated CO2. Total ion concentration can be maintained by controlling solution electrical conductivity. If the conductivity increases, the refill solution should be made more dilute, but the composition should be kept the same. The electrical conductivity does not change rapidly so it is usually necessary to monitor it only a few times each week. We have successfully used this approach in long-term studies (months) without discarding any solution. This procedure can eliminate the need to monitor nutrient solution concentrations in the solution.

NUTRIENT RECOVERY IN PLANT TISSUE As mentioned earlier, the mass balance approach to nutrient management assumes that all of the nutrients are either in the solution or in the plant. Surprisingly few detailed mass balance studies to test this assumption have been conducted, however, studies in our laboratory and studies by Dr. Wade Berry at UCLA clearly indicate that the recovery of several elements is less than 100%, while recovery of some micronutrients is much greater than 100%. Table 5 indicates the average recoveries of elements from solution in six replicate 23-day studies. These recoveries are typical of recirculating hydroponic systems. Because recovery of macronutrients is 50 to 85%, additional macronutrients should be added to the refill solution. Reduced amounts of some micronutrients may be warranted when the contamination is reproducible.

TABLE 5. Average recoveries of the essential nutrients in plant tissue at the end of six replicate 22 day studies with wheat. The recovery of all of the macronutrients, and iron and boron was 50 to 85% of that added to the nutrient solution (minus what was left in solution at the end of the trial). The recovery of Mn, Zn, Cu, and Mo was greater than 100% because of contamination of the hydroponic solution from elements in the plastics or the magnetic drive pumps. Many different types of plastics were used to build this system and many plastics use zinc and copper as emulsifiers in manufacturing. These recoveries are typical in recirculating hydroponic systems.

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DIFFERENTIAL NUTRIENT REMOVAL FROM SOLUTION

The essential nutrients can be put into 3 categories based on how quickly they are removed from solution. Group 1 elements are actively absorbed by roots and can be removed from solution in a few hours. Group 2 elements have intermediate uptake rates and are usually removed from solution slightly faster than water is removed. Group 3 elements are passively absorbed from solution and often accumulate in solution.

Approximate uptake rates of the essential plant nutrients.

GROUP 1 Active uptake, fast removal NO3, NH4, P, K, Mn
GROUP 2 Intermediate uptake Mg, S, Fe, Zn, Cu, Mo, C
GROUP 3 Passive uptake, slow removal Ca, B

One of the problems with individual ion monitoring and control is that the concentration of the group 1 elements (N, P, K, Mn) must be kept low to prevent their toxic accumulation in plant tissue. Low concentrations are difficult to monitor and control. Table 2 shows typical measurement errors associated with the use of ICP emission spectrophotometry for analysis of hydroponic solutions. Nitrogen cannot be measured by ICP-ES. Accuracy for the macronutrients is good, but solution levels of B, Cu, and Mo cannot be accurately measured by ICP-ES. The calculations in this table are for a typical refill solution, not for the low concentrations that should be maintained in the circulating solution. The measurement errors for K, P, and Mn can be 10 times higher because the solution levels are lower.


The total amount of nutrients in solution can easily and accurately be determined by measuring the electrical conductivity of the solution. However, because of the differential rate of nutrient uptake, conductivity measurements mostly measure the calcium, magnesium and sulfate remaining in solution. The micronutrients contribute less than 0.1% to electrical conductivity.

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Nutrient Management in Recirculating Hydroponic Culture

By Bruce Bugbee

INTRODUCTION

In preparation for writing this paper, I read the related papers from previous HSA proceedings. I am impressed by the amount of useful information. The annual meeting and proceedings of HSA have become an important source of technical information on the hydroponic culture of plants. This information is not necessarily available at the annual meetings of related professional societies such as The American Society for Horticultural Science, or The American Society of Agronomy.

It was necessary for me to read other papers because many of them discuss nutrient management in recirculating hydroponic systems. Authors at every meeting in the past 5 years have stressed the need to recirculate and reuse nutrient solutions to reduce environmental and economic costs. Dr. Pieter Schippers (1991 HSA proceedings) reviewed nutrient management and clearly indicated the need for data when he said, "One of the weakest points in hydroponics...is the lack of information on managing the nutrient solution." I was moderately surprised to find that previous authors recommended measuring the concentrations of individual nutrients in solution as a key to nutrient control and maintenance. Monitoring ions in solution is unnecessary. Even worse, the rapid depletion of some nutrients often causes people to add toxic amounts of nutrients to the solution. Monitoring solutions is interesting, but it is not the key to effective maintenance.




MANAGING NUTRIENTS BY MASS BALANCE

During the past 12 years, we have managed nutrients in closed hydroponic systems according to the principle of "mass balance," which means that the mass of nutrients is either in solution or in the plants. We add nutrients to the solution depending on what we want the plant to take up.

Plants quickly remove their daily supply of some nutrients while other nutrients accumulate. This means that the concentrations of nitrogen, phosphorous, and potassium can be at low levels in the solution (0.1 mM or a few ppm) because these nutrients are in the plant, where we want them. Maintaining a high concentrations of nutrients in the solution can result in excessive uptake that can lead to nutrient imbalances.

For example, the water removed from solution through transpiration must be replaced and it is necessary to have about 0.5 mM phosphorous in the refill solution. If the refill solution was added once each day, the phosphorous would be absorbed by the plant in a few hours and the solution phosphorous concentration would be close to zero. This does not indicate a deficiency, rather it indicates a healthy plant with rapid nutrient uptake. If the phosphorous level is maintained at 0.5 mM in the recirculating solution, the phosphorous concentration in the plant can increase to 1% of the dry mass, which is 3 times higher than the optimum in most plants. This high phosphorous level can induce iron and zinc deficiency (Chaney and Coulombe, 1982).

Feeding plants in this way is like the daily feeding of a pet dog, some dogs would be far overweight if their food bowls were kept continuously full.

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Hydroponic Strawberries Avoid Soil Pests

The first recorded use of hydroponics is in one of the seven wonders of the ancient world: the Hanging Gardens of Babylon where, historians say, plants were grown in a steady stream of water. Centuries later, U.S. troops stationed on infertile Pacific Islands during World War II ate fresh fruits and vegetables produced by hydroponics.

Hydroponics from the Greek words hydro (water) and ponos (labor) is the science of growing plants without soil. Nutrients that plants usually get from soil are added to water.





Scientists with USDA's Agricultural Research Service successfully using this time-honored way of producing crops at the Appalachian Fruit Research Station in Kearneysville, West Virginia.
There, they are using hydroponics to grow strawberries without soil and even more, without pesticides.

But why hydroponics?

"Strawberry growers worldwide fumigate the soil with methyl bromide before planting to control soilborne insect pests, diseases, and weeds," says Fumiomi Takeda, an ARS horticulturist at Kearneysville. "This fumigation is essential to get high yields and high-qualify fruit.

"But with the fast-approaching ban on use of this chemical, growers are anxiously looking for alternatives. It is estimated that banning methyl bromide will cut in half the annual production of field-grown strawberries in California and Florida, our major producing states."

But growing strawberries hydroponically eliminates the need for methyl bromide on this crop.
As for foliage pests, Takeda says, "Two-spotted spider mites, thrips, and powdery mildew were the major problems we encountered in our greenhouse production of strawberries. We used beneficial predatory mites to control the thrips and two-spotted mites. The mildew problem can be resolved by moderating the humidity level in the greenhouse and by growing varieties that resist mildew infection," he says.

In the Kearneysville greenhouse, Takeda grew strawberries in round pots, vertically stacked square pots, and horizontal troughs similar to rain gutters.

He used both established plants and runner tips from greenhouse-grown Chandler and Camarosa, strawberry varieties developed in California; Sweet Charlie, developed in Florida; and Tribute and Primetime, developed by ARS in Beltsville, Maryland. He also included freshly dug Canadian nursery plants of Chandler, Camarosa, and Sweet Charlie.

"We controlled temperatures at 68oF during the day and 57oF at night, and we preconditioned transplants for 150 degree-hours of chilling at or below 45oF. Combining this with the natural photoperiod and supplemental lights during overcast days produced plants that yielded lots of good-sized fruit," Takeda says.

Camarosa proved to be the most productive variety. "We picked over 2 pounds of marketable strawberries from each Camarosa plant," Takeda reports. In soil fumigated with methyl bromide, Camarosa and Chandler will each yield over 2 pounds of high-quality fruit.

In late August 1997, Takeda set runner tips in bedding plant containers with peat mixture to produce "plug" plants. He misted the plants intermittently until they had well-developed roots. On October 1, plug plants and fresh-dug plants shipped from Canada were placed in the hydroponic growing systems.

Takeda subjected plants in troughs to a continuous flow of recirculating nutrient solution. He fed the plants in pots intermittently with a nutrient solution and also transplanted plug plants to pots stacked to form towers.

"We harvested ripe fruit twice a week from December to May, the period when shipments of California strawberries slow down. Fruit quality and taste were excellent," he says.

Transplants or plug plants produced more fruit than field-nursery plants. According to Takeda, the root system of both types of plants remained healthy throughout the 7- to 8-month growing period, with no appearance of root diseases. However, in the stacked-pot towers, the top sections got more light and therefore bore healthier plants and more fruit.

Light intensity greatly affects strawberry growth and development. Since light levels reaching the plants at the lower section of the towers were only 20 percent of levels measured at the top, fruit production was reduced.

"Slightly taller pots spaced farther apart on the towers would reduce this problem," says Takeda.

Bruce Pape, an organic grower of herbs and ornamentals on Maryland's Eastern Shore, has been experimenting with pot-grown strawberries as ornamental plants. "We have some specialty market outlets that would probably be able to sell ornamental strawberry plants quite well," he says. "Consumers would not only get a beautiful ornamental hanging basket, but a way to grow a few strawberries in the winter months as well." Pape and his wife Carmen have experimented with several strawberry varieties.

Hydroponic systems reduce space requirements and growing time needed to produce a crop. Since there is no soil involved, no tillage is necessary and there are no weeds to contend with. The amount of chemicals needed is reduced, since biocontrol measures work better in the controlled environment of a greenhouse and there are fewer pests.

Environmental factors aren't a problem in greenhouses since lighting, temperature, humidity, and irrigation can be controlled. Nutrients used for plant growth are recyclable, to be used again and again.

Using hydroponics also reduces the cost and increases the efficiency of labor. Field-harvesting strawberries involves back-breaking labor, since laborers must stoop to pick the crop. Hydroponically grown berries can be harvested from a standing position.

"Although initial set-up costs for hydroponic farming are high, growers may recoup that cost by producing a higher value product, increasing yields, and spending less money to control pests and diseases," says Takeda. "Our research demonstrated that two California strawberry varieties can be grown by soilless means. However, we need more research to measure the performance of other strawberry varieties and to investigate the influence of plant type--plug, fresh-dug, dormant, or single or multiple crown as well as planting dates."--By Doris Stanley, Agricultural Research Service Information Staff.

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The Aerogarden Hydroponics System - An Indoor Gardener's Dream

Looking for a different gift for your gardener in your life? Or something to give to your favorite cook? Once in a while something new shows up in the world of gardening, and that describes the Aerogrow Aerogarden Indoors Hydroponics System. It uses technology that didn't even exist ten years ago. It's so different that it was actually featured in Time magazine in 2005.






The Aerogrow hydroponic system is a completely self contained hydroponics system. Hydroponics is a system of growing plants without soil, where the plant's root system actually grow in enriched or fertilized water. Because the Aerogarden is a soil-less system, it eliminates many problems associated with indoor container gardens. You eliminate many soil-borne diseases and pests when using a hydroponics growing system.

The Aerogrow Aerogarden kit comes complete not only with the hydroponics system, and it includes with a computer controlled pump, and it has a built in grow light too. With this automation, you can set the system up and won't need to attend to it for about two weeks. The Aerogarden includes seed sets for many different types of plants. You can grow herbs to to lettuce and other salad fixings to small vegetables. There are seed kits for many different types of vegetables. With the computer control you simply set it for the type of seeds you have selected.

Since this is an indoor hydroponic unit, the Aerogrow Garden can be used year round. Harvesting herbs and vegetables in the middle of winter is great, and it can be used indoors in the summertime to keep a supply of vegetables that would normally wilt in the heat.

How well does the the Aerogarden system work? We have a complete Aregrow Aerogarden Hydroponic System Review along with time lapse videos of the unit in operation at http://howtogardenguide.com/

By John Ruppel

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Growing Hybrid Grapes

By Jim Bruce

Growing hybrid grapes is becoming more popular for wine and eating. This popularity comes from the fact that hybrid grapes can be grown in areas where the traditional European grapes cannot survive. It also comes about because more and more people are growing grapes in their backyard to produce their own vintage wine.

What are hybrid grapes? To answer this question, we must look back in history about 100 years to when the European vineyards were being decimated by the phylloxera louse that had been brought from North America. The European grape species, Vitis vinifera, is extremely susceptible to this louse. Vineyard after vineyard was succumbing to this imported pest as well as to grape diseases that had also come from America.




But Native American species of grapes had evolved with the pest and were resistant to its attacks on the vine's roots. In an effort to save the wine industry in France, some individuals began to cross breed the European and American species to obtain new varieties that had the wine characteristics of the European grapes and the resistance to the phylloxera louse and other diseases that the American grape species possessed.

It is from these breeding programs that the original hybrid grapes were grown. At first, the grape varieties produced were no better than their American parents. But as time has gone on, more complex hybrids have been made and the quality of the grapes has increased. Today, wines made from some hybrid grape varieties even rival the wines made in California and other traditional wine producing areas.

The way you grow hybrid grapes depends upon the varieties you choose. Some varieties' growth habit resemble their American parents while others grow like their European parents. And then there are those that are in-between in their growth habit. The growth habit of the variety will dictate what type of trellising system you will use to grow them. It also will dictate how the vines are pruned.

European varieties and hybrids that take after them tend to grow upright. These varieties will need a vertical shoot positioning trellis system that allows you to tie up the shoots as they grow upward. American varieties and hybrids that resemble them have a growth habit that droops. These vines are usually trained to a high wire about six feet off the ground and the shoots are allowed to grow downward over the growing season.

You can find a hybrid variety that will grow in almost anywhere in the United States. Alaska is about the only state you won't find one adapted to. The right hybrid grape variety for your location is dependent upon the percentage of native species found in the cross. Varieties adapted to northern locations tend to have a high percentage of the native Vitis riparia that lives in areas where the winters can go as low as -35F. Southern varieties generally have Vitis aestivalis in their background if from the southeast or other native species if found in areas like Texas.

Grape hybrids often are known by only the breeder's number. They may be called S.V 5-276 or S. 7053. Only the best of hybrids have a true name, such as Foch or Seyval. These named varieties have shown their worth over many years and are usually being used to make wines commercially where a name is important on the label.

Growing hybrid grapes may mean having to deviate from the traditional grape growing methods. Some grape hybrids produce way too much fruit because of hybrid vigor. You will have to remove some of the fruit early in the growing season to prevent them from over-bearing and succumbing to premature death. Each variety will behave slightly different. You will have to get to know the grape varieties you grow and adjust accordingly.

The big question is which varieties to grow? The answer to this depends on where you live. You must buy varieties that are adapted to your region. Some hybrid grape varieties mature their fruit in 135-140 days while others need 170 days or more to get ripe. The goal is to have ripe fruit so be sure that you're not growing a long season variety in a short season.

Hybrid grapes also vary in how winter hardy they are. Make sure that you get a very hardy variety if you live where the winters are cold. Or a southern adapted variety if you live where there's hot humid summers and long growing seasons. Winter hardiness is not the concern under those conditions.

What you are going to use the fruit for is also a concern when picking the right variety. Most hybrids have been developed to make wine. But there are varieties for eating too. Most of the grape varieties that you buy locally at a greenhouse or nursery are eating varieties. You will need to go online to find wine varieties for sale.

If you're passion is to grow grape vines in your backyard either for wine or eating, I suggest that you look into hybrid grapes. These have been bred to get the best of the tastes of the European grapes combined with the resistances and winter hardiness of the native grape species. Whatever your growing conditions are, you'll find a hybrid grape variety that is adapted to your area and needs.

Jim Bruce has been growing grapes since 1974. He is currently conducting grape research at his Rist Canyon Vineyards. Jim has just written a Tips for Growing Grapes eBook that can be found at: http://www.grapegrowingbook.com/

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Conversion from conventional culture to passive hydroponics

Medium is rinsed and soaked overnight. The plant is removed from the old pot and old medium is thoroughly removed from the roots. Rotten roots are cut away and overlong roots are trimmed. All the roots are thoroughly washed in lukewarm water. Some new medium is arranged at the bottom of the new container. The plant is accommodated and more new medium is put around, the pot is gently shaken, more media is put in, more shaking and so on. The pot is flushed with tepid water. The Orchid is placed in the shade with no fertilizer for the following month.





Which orchids can be grown?

Most popular orchids will more or less thrive in hydroponic culture: Paphiopedilums, Phragmipediums, Masdevallias, Phalaenopsis, Cattleyas, Cymbidiums, Oncidiums, Dendrobiums, Epidendrums, Miltoniopsis, Pleurothallids and Zygopetalums.
Exceptions would be very big or "thirsty" plants or those whose roots must dry sometimes completely and even those that require dry rest like Dendrobium nobile.

Advantages of Passive Hydroponics

Its simplicity and effectiveness. No guessing about watering and fertilizing, no media decomposition, practically no root rot, healthy plants, fine blooming, no moving parts, low cost, reusable media. In hot and dry environments, passive hydroponics may help, since the roots stay in a high humidity chamber with some air flow.

Disadvantages

The main disadvantage can sometimes be the need of more frequent watering, especially when plants begin to fill their pots, are big or otherwise demand lots of water. Obviously, a bigger water pot/reservoir may help (or side holes higher up on the pot). If the sides of the translucent containers receive enough light exposure then algae will grow on the outer layer of the potting media. This is mainly an aesthetic concern and not a big problem indoors. If the medium consists of small expanded clay pebbles and the plant is newly established then tipping it over may cause the spilling of said medium and plant. Build up of salts (fertilizer) which are not easily removed from clay substrates and "reservoir" (lower section below drainage holes). If chemicals are used for pest and/or disease control excess is retained.

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Uninvited Houseguests

By Jack DeAngelis

Many gardeners move potted plants from outdoors to indoors in the fall to protect them from winter weather. For example you may have a potted jade plant that does fine on the deck from April to September but would die if exposed to even moderately cold fall weather. In fact, potted houseplants often do better if given this yearly exposure to outside sun and air. Be aware, however, that you may introduce some uninvited houseguests indoors by this practice. Slugs, root weevils and spiders are notorious for hitching a ride on these plants. As the plants warm up the critters become active and will often move off the plants. These houseguests (unlike some!) pose no threat whatsoever unless, of course, the spider happens to be one of the very few poisonous species in your area. So, if you find slugs or root weevils wandering across the floor this winter they probably came off the potted plant that you moved indoors from the deck in fall.





One solution is to give the plants a "bath" before moving them indoors. On a warm day in early fall hose the plants off with water then spray with insecticidal soap, wait 30 minutes then rinse with water. Allow the plants to dry completely. This procedure will also remove any dirt, aphids and spider mites that you also don't want to take indoors.

Small greenhouses are another ideal solution for protecting non-hardy plants during winter. Even if the greenhouse is unheated the enclosure will protect many plants from the harsher winter extremes. This, of course, depends on the climate, and plants involved, and will require some experimentation.

Other "uninvited houseguests", not associated wth moving potted plants around, include cluster flies, boxelder bugs and Harmonia lady beetles.

See http://www.livingwithbugs.com/ for related and additional information about all these uninvited houseguests.

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Orchids Hydroponics

Popular media
LECA (Lightweight Expanded Clay Aggregate) - expanded/fired clay pellets or clay pebbles , perlite, vermiculite, gravel, charcoal, rockwool, coconut husk chips and their combinations.Diatomite is expanded silicaseous earth, good as a component and beautiful too.






Water
Medium is flushed with tepid water solution when reservoir is nearly empty. Translucent pot may help to see when it is.

Fertilizer
Orchids are fertilized with 1/2 or 1/4 of recommended strength of balanced inorganic fertilizer with every watering. Container is flushed with plain water every month to prevent harmful salt build up.

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Hydroponics for orchid cultivation

Passive hydroponics is a method of growing plants without soil. Instead a practically inert wicking medium transports water and fertilizer to the roots by capillary action. Medium contains a multitude of free air spaces and thus delivers oxygen to the roots. This has been applied to orchid growing where, as well as its commonly-cited advantages, the sterility and the humidity associated with the technique are of particular benefit.



Passive hydroponics culture. Development of roots in clay pebbles.

Planting
Orchids can be planted in any container (not glass) with no drainage holes at the bottom but a few extra holes 3-5 cm up at the sides of the pot. The idea is to provide a water reservoir at the bottom of the container from which the medium wicks moisture to the roots.

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6 Fashion Tips for Gardeners

By Linda Gray

Clothes and skin cream are far removed from potting out your begonias, or digging a trench for a line of potatoes. But the clothes you wear are important for your protection in the garden. Here are six simple but effective solutions to various gardening hazards...

1. Starting from the top, you need to protect your head. Body heat escapes through the head and in the cold weather a warm hat should be worn. Knit yourself a 'gardening crazy' hat or buy a simple woollen hat on the high street.
   And in the summer, even more attention should be paid to the head. The sun's rays are not only hot but they actually burn you. We all know this but how easy it is to forget when you want to soak up the sun after months of grey or cold weather. Invest in a cool sunhat. Not only will it help protect you from sunstroke, it will also protect against the drying out of your hair and skin.
2. Keep one old comfortable jacket or short coat, preferably with fairly large pockets, especially for the garden. When you're working, you won't need to worry about dirty marks. Leave them there, it's all part of the gardener's designer uniform!
3. Suitable trousers.. again keep a couple of old pairs especially for gardening. Wear heavy duty jeans for heavy duty work. A good waterproof pair are handy in damp climates. In fact, in damp climates, a whole waterproof gardening suit is invaluable. There is always planting to do in the rain, and a waterproof hat, jacket and trousers tucked in a pair of boots will keep you nice and dry!
4. Protect your hands. For light work, potting on or pinching out tomato plants, a disposable plastic pair of gloves or a pair of kitchen rubber gloves will be enough. For heavier work - pruning roses, weeding thistles and nettles, wear heavy duty gardening gloves, or your hands will suffer.
5. Watch those toes! Invest in a pair of steel toe capped boots and wear them! If you're pottering in the greenhouse or doing a little weeding, a simple pair of wellington boots will do, or even sandals if the weather allows. But as soon as you pick up a large tool, your steel toe-caps should be worn. If you're not used to them, these boots can feel heavy and cumbersome at first, but stick with it. If you're doing heavy work, you need heavy boots.
6. And last but certainly not least, you must protect your skin. Moisturise all exposed body parts whenever you are woking in the garden, rain or shine. Working outside will give you a nice healthy glow, but the wind and sun will dry your skin given half a chance.

So there we have it, not a fashion designer's dream, but these 6 garden fashion tips will make life a lot more comfortable, and safer, for the average home gardener. Happy gardening!
Linda Gray is a freelance writer and has spent more than ten years creating an organic family garden from an acre of neglected land. Linda shares her experience and expertise at http://www.flower-and-garden-tips.com

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Greenhouse Accessories

By Garry John

Accessorizing your greenhouse isn't quite the same as accessorizing any other 'room' in your home. Greenhouse accessories aren't a fashion statement - they're functional things like shelves, misters, irrigation systems, covers and heaters that increase the functionality of your greenhouse. What greenhouse accessories should you consider if you're building a new (or refurbishing an old) greenhouse? It depends a great deal on how you use your greenhouse and where it is.

Among the greenhouse accessories you might consider are thermometers and humidity gauges, automatic plant misting systems, plant lighting options, soil sterilization and treatment kits, potting benches, specialty shelving systems that can create mini-greenhouses within the greenhouse, shades and shelters and venting and roof openers.





Potting benches

Potting benches are one of the most useful greenhouse accessories you'll invest in. Generally, a potting bench has one or two shelves to hold potting supplies like pots, dirt and fertilizer, and a slatted top with a tray to make it easy for you to clean. By keeping all your potting supplies on one easy to move potting bench, you save yourself all sorts of steps and labor and keep everything you need close at hand.

Greenhouse shelving

There are a number of different styles of specialty shelving for greenhouses that can be counted as greenhouse accessories. Grow shelves are aluminum frames into which you can fit seedling trays. Grow shelves often come with UV stabilized plastic covers to create greenhouse conditions within the greenhouse for starting new plants or isolating specialty plants that need different conditions than standard.

Misting Propagation Systems

One of the most important factors for healthy growth and propagation of plants is the moisture in the air. Automatic misters can maintain the high humidity needed by rooting plants. They're available with timers that you can set to mist the entire greenhouse at specified intervals, or with moisture sensors that will send out a cooling mist whenever the moisture content of the air falls below a specific density. A misting propagation system can be one of the important greenhouse accessories in a greenhouse that grows tropical plants, or in which you intend to often start plants from leaf cuttings. There are many choices that can be both affordable and useful.

Rainwater Systems

For the eco-conscious gardener with a greenhouse, rainwater systems allow you to collect rainwater via gutters and downspouts and reuse it for irrigation and watering of your plants. Remember the old-fashioned rain barrel? Welcome to the modern version, which will automatically recycle rainwater for use in your greenhouse.

Lighting Greenhouse Accessories

Grow lights are one way to increase the amount of available full-spectrum light for your plants, particularly during northern winters when days are short. They come in full kits that include wiring, or as individual lights that can be set up for specific purposes.

Whatever the needs for your greenhouse, you'll find greenhouse accessories that are specially designed to fit the needs and help you grow lush, beautiful plants with a minimum of effort.

Garry John contributes to many http://www.home-improvement.web.com home improvement and garden sites such as http://www.greenhouses.gb.com greenhouses and http://www.uk-conservatories-online.co.uk conservatories.

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Bloggerwave for Blogger

Dear Gardener and Readers,

Bloggerwave is a sponsor site for blogger who offer the opportunity just write and post some story about advertiser who want to promote the product on the powerful online market in the world. Blogger's money earned from paid posting can help bloggers to pay for anything such as advertise online, I think Bloggerwave pay highest from the other sponsor site.
For Advertiser who wants to promote your products to target customer such as seeds, garden equipment, greenhouse. You can promote by relevant blogs write and posting the story about your product or service with Bloggerwave.

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Greenhouse Gardening as a Hobby

By Brigitte Smith

For people who would like to do more gardening but live in a short growing season area, a hobby greenhouse is the answer. A hobby greenhouse is not large enough to produce vegetables or flowers on a commercial basis. It will, however, give you a place for a tomato plant or two and some fresh greens even if you live in the northern regions.



Greenhouse enthusiasts even have their own association, called the Hobby Greenhouse Association, which publishes a quarterly magazine. The organization also sponsers events and helps individuals connect to get help with the aspect of gardening that they are interested in, whether it's growing cacti or saving seeds.

If you are in the market for a hobby greenhouse, there are several types on the market. The smallest type is not large enough to walk into and must be accessed from the outside. It resembles an old-fashioned phone booth made all of glass and outfitted with shelves. This type is designed to fit as many plants as possible in as small a place as possible. The shelves are made of glass to allow as much light as possible to reach plants on the lower shelves. Another inexpensive version of this sort of hobby greenhouse is shelving covered with a zippered tent of clear plastic. This sort of arrangement is great for the small-scale hobby gardener wanting a place to keep her flowers or houseplant starts.

There are a variety of designs of hobby greenhouse that are large enough to walk into but made entirely of clear glass or plastic. They are often about the same size as a small storage building. Some independent builders have started making these to sell locally. Among national brands, one of the nicest is called the "Solar Prism." It is called this because of it's unique construction. This hobby greenhouse is made of a single piece of durable clear plastic which is designed to work like tiny prisms side by side. They trap the rays of the sun and shoot them back into the greenhouse at all angles. For this reason, these little greenhouses are said to glow when the weather is cloudy.

Better hobby greenhouses are equipped with automatic sensors that open vents which allow ventilation and keep the interior temperatures from getting too high. These are a great labor saver, but can get expensive. Another benefit sometimes found in nicer greenhouses is a built in irrigation or misting system. Members of the Hobby Greenhouse Association, or HGA, have invented many interesting designs of greenhouses.

If gardening is your hobby, greenhouse growing will interest you. With a greenhouse, you can have the earliest tomatoes and salad greens all year. You can also start seedlings for the main garden early in the spring when outdoor temperatures would kill them. A hobby greenhouse can be a good investment.

Find out more about hobbies of all types at the Learn How Guides - where you can learn how to do just about anything!

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