Recent Innovations and Challenges
The following is an excerpt from the Local Grown Salads Oxyfertigation Growing System patent.
Hydroponic Technology attempts to address many of soil-related farming's shortcomings by removing the soil from the growing method. Plants are grown in containers and the roots receive the nutrients mixed in the water. A hydroponic system may be located outside or inside. The water can be recycled or disposed of after the roots receive its nutrients. In aquaponics (a variation of hydroponics), fish are raised and their waste creates the plant nutrients that feeds the plants indirectly.
There are general problems that are consistent with all types of hydroponic systems. 1) Hydroponic systems use a large number of pipes and valves to move water around. These valves and pipes consistently fail and require maintenance. 2) Hydroponic systems are composed of water, light, and nutrients, in which algae flourish. The algae will clog, block and damage equipment, and when it dies, it creates a foul smell. 3) The nutrients that are not taken up by the plants form salts. These salts will remain and damage the equipment, and require flushing.
Hydroponic systems are designed to circulate a nutrient solution, thus the plants at the beginning of the circulation system receive the most nutrients while the plants at the end of the system receive the least amounts of nutrients. Dissolved oxygen is the most critical nutrient and its loss depends on the amount used in the system, the greater the root biomass, and the greater the absorption of dissolved oxygen.
Hydroponic-based environments typically share one nutrient reservoir. This single reservoir means that any water born disease will be spread to the environment.
The plants are rooted in some form of grow media, also called a substrate,which holds the plant steady and allows water access to the roots. The growing chamber is the container for the root zone. This area provides plant support, as well as is where the roots access the nutrient solution. It protects the roots from light, heat, and pests. The reservoir is the component of the hydroponic system that holds the nutrient solution (the plant nutrients mixed in water). The nutrient solution may be pumped from the reservoir up to the growing chamber (root zone) continuously, in cycles, or the roots can even be in the reservoir. The water/nutrient solution delivery system is plumbed so that the water/nutrient solution to the plants roots in the growing chamber and back to the reservoir.
Water is delivered to individual plants in a number of ways. A common method is drip emitters or sprayers similar to what is used in field irrigation. Plants absorb the nutrients and the water it needs, and leaves the rest of the nutrients in the growing medium. This may eventually cause a toxic buildup of mineral salts in the growing media or the reservoir. So flushing the excess nutrients from the root zone (growing media) with plain fresh water must be done regularly. Typically, the nutrient solution is recirculated and aerated in a central reservoir.
There are several variations of hydroponic systems each with unique characteristics: 1) Drip systems; 2) Ebb & Flow; 3) NFT; 4) Water Culture; 5) Aeroponics; and 6) Wick.
1) Drip systems are one of the most widely used type of hydroponic systems. Nutrients drip on the plant's roots to keep them moist. They are useful for larger plants that take a lot of root space. When using a larger amount of growing media for larger plants, more growing media retains more moisture than smaller amounts.
2) In Ebb & Flow hydroponics, the system works by periodically flooding the plant's root system with nutrient solution. The main part of the flood and drain system holds the containers the plants are growing in. A timer turns on the pump, and water (nutrient solution) is pumped through tubing from the reservoir up into the main part of the system. The nutrient solution continues to flood the unit until the media and roots are soaked at which point the water is released and drains back to the reservoir where it recirculates back through the system again.
3) Nutrient Film Technique (NFT) is typically used for plants like lettuce, herbs and baby greens. In an NFT system a thin layer of the nutrient solution is cascaded through tubing where the bare roots of the plants come in contact with the water and absorbing the nutrients from it. In NFT systems, the plants are very sensitive to interruptions in the flow of water and wilt very quickly any time the water stops flowing through the system. While the nutrient solution flowing is very shallow, the entire plants root biomass remains moist from the roots wicking moisture on the outside of the roots, as well as through humidity that's kept within the tubing.
4) A Water Culture (or Raft) system is very effective for growing plants hydroponically. Plants are suspended in baskets located in Styrofoam or other medium (the raft) floating on the nutrient solution with the roots hanging down into the nutrient solution. A variation of the water culture system includes: a) a recirculating water culture system where the growing containers (water culture reservoirs) are connected to one central reservoir; and b) the Dutch bucket method, where a plant is in a bucket filled with nutrient solution.
5) Aeroponics is the most technically challenging hydroponic system using little to no growing media. It generally uses the least amount of water. The roots get the maximum oxygen and harvesting is usually easier, especially for root crops. The plants are suspended by small baskets, or closed cell foam plugs compressed around the plants stem. These baskets fit in small holes with the roots inside the growing chamber where they get sprayed with nutrient solution with a fine mist at regular short cycles. The regular watering cycles keep the roots moist and prevent drying out while providing the nutrients the plants need to grow. The water droplet size is critical to creating a bushier root system with more surface area to absorb nutrients. Misting systems frequently clog from build-up of the dissolved mineral elements in the nutrient solution and the plants roots are vulnerable to drying out if there is any interruption in the watering cycle. The high volume of oxygen the roots receive allows the plants to grow faster than they would otherwise.
6) The Wick system has no moving parts and does not use any pumps or electricity. The wick uses a capillary action to wick up nutrient solution from the reservoir to the plant roots. Wick systems do not work well for plants that need to drink up great quantities of water. Wick systems are suited to smaller non-fruiting plants, like lettuce and herbs.
A greenhouse reduces many risks associated with the weather while leveraging natural light. It is a structure with walls and roof made of transparent material such as glass or plastic. Within the greenhouse, production is soil-based or uses hydroponic technology. Soil-based production is planted in a plot of soil or in containers with soil, or a soil substitute. As an enclosed environment, insects and diseases can be better kept out. But when an infestation occurs, it can propagate rapidly through the enclosed environment. Greenhouses become very hot in warmer temperatures and need significant ventilation. In colder temperatures, they need to be heated and are expensive to operate. Human workers and the ventilation system are the primary source for insects and diseases in a greenhouse.
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