Substrate Properties
This section is aimed at educating the grower about the specific characteristics of
growing media. Plant roots require water, minerals, and oxygen to survive and obtain maximum growth and yields. In any particular substrate, these requirements are determined by the physical and chemical properties of the media, such as the water-holding capacity, cation exchange capacity (CEC), and pore size distribution, which determines the aeration of the media. Plant stability and oxygen availability are two physical variables that come into play when choosing a medium for growth.
Since all forms of media provide good general stability we will discuss the specific physical structure of media first. The physical structure of a substrate is made up of two major components: the solid particles and the pores between the particles, or the lattice. Of these two, the pore space between the solid particles is most important. Substrate porosity can be divided into three categories: large, small, and very small.
Large pores can be easily recognized in a substrate by saturating it and allowing it to drain. Pores that readily lose water by gravitational drainage are termed large pores and have a diameter larger than about 60 microns. These act as passages for the drainage of surplus water or nutrient, root growth, and pores for exchange of oxygen and carbon dioxide.
Small pores (0.3-60 microns) act as a reservoir for moisture that can be utilized by the plant between nutrient applications. These pores retain water and nutrients for plant growth.
Very small pores (less than 0.2 microns) retain water when plants growing in the substrate have reached the permanent wilting point. They retain water at suction levels higher than can be exerted by the plants is unavailable for plant growth. However, they do ensure capillary rise of water by conduction and therefore play a role in the spread of water through the substrate.
A good hydroponic substrate contains the right balance between large and small pores to provide sufficient moisture between nutrient applications, a high degree of aeration and capillary action to evenly spread moisture throughout the root zone, and sufficient large pore space to allow root outgrowth into the substrate. General recommendations for suitable hydroponic substrates are at least 35-50 percent water-holding capacity by volume and 25-40 percent air space after drainage.
A substrate can affect the composition of the nutrient solution and assimilation of elements by plants depending upon the size of the granules and their structural, physical, and chemical properties. Soilless media are selected based on having low levels of natural nutrients to prevent any alteration or imbalance of the nutrient solution. The ability of certain media to retain nutrients against leaching losses is related to its cation exchange capacity, or CEC. The CEC is the ability of the media to attract and hold various cations such as potassium, calcium, magnesium, and iron, for use by the plant’s roots. These positively charged ions are attracted to the negatively charged media particles and therefore aren’t leached as quickly from the media. A media with a high CEC will require less frequent applications of nutrients than a media with a low CEC. Zeolite is an example of a media with high CEC.
Coconut Fiber
Coconut fiber- also called coir- is a product made from coconut meso-carp pith, or grounded up coconut leaves. It is usually purchased for horticultural or hydroponic use in compressed blocks of dry fiber that when soaked in water expand to useable form. Some desirable qualities of coir are that it is considered “organic”, and is easy to dispose of as a soil conditioner, mulch, or compost after use. Coir fiber is a classic example of a sustainable concept. It is a byproduct of the coir industry that makes floor mats, hanging baskets and other products, so it is a renewable resource. Until it’s potential as a growing medium was realized, the residue (coir pith) from the process that extracts the useful fibers was left to waste. Waste = Food.
Perhaps the most important aspects of coir fiber as a growing medium are lack of initial nutrients and its ability to act as a pH buffer. Coir’s negligible initial nutrient composition and slightly acidic pH (pH 5.8-6.5) is ideal for plant growth and hydroponic use because it will not affect the carefully controlled nutrient and pH levels of the nutrient solution.
Coir fiber has the ability to absorb and retain large quantities of water and nutrient for plant use (typically between 80-88 percent) between irrigations. Air-filled porosity values of 23-29 percent have been measured, which is within the recommended range for a container mix but a little on the low side when compared to other free-draining media, such as expanded clay or perlite. Coir also resists decomposition, making it more desirable than other substrates, such as peat or sawdust, which have a tendency to break down and lose their free-draining structures resulting in root suffocation and rot.
Hydroponic Gardening Howto & Tips
**
Hydroponic Gardening involves growing plants with the essential elements needed for the plant to grow.
**A hydroponic gardening system can be outdoor or indoor.
**The essential elements are: nutrients, water, light, habitat.
**The rate of growth of a hydroponic plant can be up to 50% faster than a soil plant grown under the same conditions.
**The reason for this is that the plants get their nutrition fed directly into their roots from nutrient rich water. Since this water is so high in nutrient content, the plant does not need large roots to search for nutrition. And since the plant expends less energy in growing roots it has more energy available to be productive above the rootline! Hydroponically grown vegetables are healthy, vigorous, and consistently reliable. This form of gardening is clean and extremely easy, and it requires very little effort.
**Hydroponic systems are normally categorized as passive or active. An active hydroponic system moves the nutrient solution with a pump. A passive hydroponic system relies on the capillary action of the growing medium or a wick.
In a passive system the nutrient rich solution is absorbed by the medium or the wick and passed along to the plant's roots. But a downside with this method is that they are usually too wet and do not supply enough oxygen to the root system for the best growth rates.
Hydroponic systems are also characterized as recovery or non-recovery. In recovery systems, the nutrient solution is re-circulated for reuse. In a non-recovery system however, the nutrient solution is not recovered.
You may be unsure of whether to buy or build a hydroponic system. If you have an 'engineering mind' and want to build one, consider buying one first just to get familiar with the inner workings. Buy a system which does not cost a lot of money. It will give you a better understanding of how hydroponics works and the hands-on experience can be worth the cost of the system as you will be able to reuse the parts when you decide to build one.
**Hydroponic Gardening allows you to grow approximately two to ten times the normal growing yield in less than half the space and half the time, making it very popular among Indoor Gardeners.
**Of all soilless methods, water culture, by definition, is true hydroponics. It is also the simplest active hydroponics system to set up on a small scale. In this system the plant roots are totally immersed in a nutrient solution. In a water culture system the roots grow directly into the reservoir as opposed to having a remote reservoir. The actual design of the system is limited only by the imagination of the builder. The system must provide means to (1) support the plant above the solution, (2) aerate the solution, and (3) prevent light from reaching the solution (to prevent the growth of algae).
**Wick systems are passive systems, meaning it has no moving parts and the nutrient solution remains in one place. Plants are fed through capillary action from a wick drawing nutrient solution into the growing medium from the reservoir. The biggest draw back of this system is that plants that are large or use large amounts of water and nutrient may use up the nutrient solution faster than the wick(s) can supply it. In this case additional wicks may be used as a supplement, or another technique can be utilized.
**Drip systems are probably the most widely used type of hydroponic system in the world. They are similar to drip irrigation systems popular with commercial farmers for their ability to conserve water through direct feeding. Operation is simple; a timer controls a submersed pump, which turns the pump on and off. Nutrient solution is dripped onto the base of each plant by a small drip line. In a recirculating drip system the excess nutrient solution that runs off is collected back in the reservoir for re-distribution.
**The Ebb and Flow (or flood and drain) system works by temporarily flooding the grow tray with nutrient solution and then letting the solution drain back into the reservoir. This action is normally done with a submerged pump that is connected to a timer. The timer is set to come on several times a day, depending on the size and type of plants, temperature and humidity and the type of growing medium used. The drain cycle improves the oxygen contact with the plants roots. Using the right medium will ensure that moisture will be available for the roots so that they do not dry out between cycles. One of the main attractions of an Ebb and Flow system is the ability to containerize your plants and physically move them around. This aids in continuous production scenarios and enhances the control of a grower utilizing a veg (blue) and bloom (red) room scenario. The main disadvantage of this type of system is that unless your medium ensures moisture retention there is a vulnerability to power outages, since the only way for your plants to access food is through the action of the pump.
**The Nutrient Film Technique (NFT) is a water-cultural technique in which plants are grown with their root systems contained in a plastic trough through which nutrient solution is continuously circulated. Work on NFT cropping was pioneered by Allen Cooper at the Glasshouse Crops research Institute in Littlehampton, England, in 1965. The term nutrient film technique was coined to stress that the depth of liquid flowing past the roots of the plants should be very shallow in order to ensure that sufficient oxygen would be supplied to the plant roots.
**Feel free to experiment by building your own hydroponic system. As long as you have oxygenated nutrified water at the proper pH it doesn’t matter how you feed them. The possibilities are endless! Be sure to enclose your reservoir so as to prevent evaporation and control feeding times via timers in the case of a top-drip or ebb and flow setup.
**A hydroponic gardening system can be outdoor or indoor.
**The essential elements are: nutrients, water, light, habitat.
**The rate of growth of a hydroponic plant can be up to 50% faster than a soil plant grown under the same conditions.
**The reason for this is that the plants get their nutrition fed directly into their roots from nutrient rich water. Since this water is so high in nutrient content, the plant does not need large roots to search for nutrition. And since the plant expends less energy in growing roots it has more energy available to be productive above the rootline! Hydroponically grown vegetables are healthy, vigorous, and consistently reliable. This form of gardening is clean and extremely easy, and it requires very little effort.
**Hydroponic systems are normally categorized as passive or active. An active hydroponic system moves the nutrient solution with a pump. A passive hydroponic system relies on the capillary action of the growing medium or a wick.
In a passive system the nutrient rich solution is absorbed by the medium or the wick and passed along to the plant's roots. But a downside with this method is that they are usually too wet and do not supply enough oxygen to the root system for the best growth rates.
Hydroponic systems are also characterized as recovery or non-recovery. In recovery systems, the nutrient solution is re-circulated for reuse. In a non-recovery system however, the nutrient solution is not recovered.
You may be unsure of whether to buy or build a hydroponic system. If you have an 'engineering mind' and want to build one, consider buying one first just to get familiar with the inner workings. Buy a system which does not cost a lot of money. It will give you a better understanding of how hydroponics works and the hands-on experience can be worth the cost of the system as you will be able to reuse the parts when you decide to build one.
**Hydroponic Gardening allows you to grow approximately two to ten times the normal growing yield in less than half the space and half the time, making it very popular among Indoor Gardeners.
**Of all soilless methods, water culture, by definition, is true hydroponics. It is also the simplest active hydroponics system to set up on a small scale. In this system the plant roots are totally immersed in a nutrient solution. In a water culture system the roots grow directly into the reservoir as opposed to having a remote reservoir. The actual design of the system is limited only by the imagination of the builder. The system must provide means to (1) support the plant above the solution, (2) aerate the solution, and (3) prevent light from reaching the solution (to prevent the growth of algae).
**Wick systems are passive systems, meaning it has no moving parts and the nutrient solution remains in one place. Plants are fed through capillary action from a wick drawing nutrient solution into the growing medium from the reservoir. The biggest draw back of this system is that plants that are large or use large amounts of water and nutrient may use up the nutrient solution faster than the wick(s) can supply it. In this case additional wicks may be used as a supplement, or another technique can be utilized.
**Drip systems are probably the most widely used type of hydroponic system in the world. They are similar to drip irrigation systems popular with commercial farmers for their ability to conserve water through direct feeding. Operation is simple; a timer controls a submersed pump, which turns the pump on and off. Nutrient solution is dripped onto the base of each plant by a small drip line. In a recirculating drip system the excess nutrient solution that runs off is collected back in the reservoir for re-distribution.
**The Ebb and Flow (or flood and drain) system works by temporarily flooding the grow tray with nutrient solution and then letting the solution drain back into the reservoir. This action is normally done with a submerged pump that is connected to a timer. The timer is set to come on several times a day, depending on the size and type of plants, temperature and humidity and the type of growing medium used. The drain cycle improves the oxygen contact with the plants roots. Using the right medium will ensure that moisture will be available for the roots so that they do not dry out between cycles. One of the main attractions of an Ebb and Flow system is the ability to containerize your plants and physically move them around. This aids in continuous production scenarios and enhances the control of a grower utilizing a veg (blue) and bloom (red) room scenario. The main disadvantage of this type of system is that unless your medium ensures moisture retention there is a vulnerability to power outages, since the only way for your plants to access food is through the action of the pump.
**The Nutrient Film Technique (NFT) is a water-cultural technique in which plants are grown with their root systems contained in a plastic trough through which nutrient solution is continuously circulated. Work on NFT cropping was pioneered by Allen Cooper at the Glasshouse Crops research Institute in Littlehampton, England, in 1965. The term nutrient film technique was coined to stress that the depth of liquid flowing past the roots of the plants should be very shallow in order to ensure that sufficient oxygen would be supplied to the plant roots.
**Feel free to experiment by building your own hydroponic system. As long as you have oxygenated nutrified water at the proper pH it doesn’t matter how you feed them. The possibilities are endless! Be sure to enclose your reservoir so as to prevent evaporation and control feeding times via timers in the case of a top-drip or ebb and flow setup.
Tuesday, July 5, 2011
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