Greenhouse production is based on either soil or soilless culture. In soil culture, vegetables are produced in the native soil or in a loamy soil brought inside the greenhouse. Soilless culture, the production of plants in a soilless medium, can be done via hydroponics or with an organic (or artificial) substrate.
The two broad categories of soilless culture are illustrated in the diagram below, with examples of media used in each.
The two broad categories of soilless culture are illustrated in the diagram below, with examples of media used in each.
In soil culture, also known as ground culture, vegetables are raised on level ground as well as in mounded beds. Soil culture is more popular with organic growers than hydroponic methods. One of the reasons organic growers prefer soil culture to hydroponics is that soil-building practices are an already familiar concept based on decades of research and experience.
Production techniques used in ground culture are similar to intensive market gardening methods used in the field. Rear-tine tillers or mechanical spaders are used in soil preparation, and specialized wheel hoes and hand tools are used for cultivation and weed control. Organic fertilizers and soil amendments are extensively used to feed the soil.
Production techniques used in ground culture are similar to intensive market gardening methods used in the field. Rear-tine tillers or mechanical spaders are used in soil preparation, and specialized wheel hoes and hand tools are used for cultivation and weed control. Organic fertilizers and soil amendments are extensively used to feed the soil.
Soilless culture methods usually have higher yields than ground culture systems. Another advantage of a soilless system is easier control of disease problems. In the soilless techniques described below, the media can be disposed of after one crop has been grown, or it can be pasteurized relatively easily.
Bag Culture - In bag culture, plants are grown in a soilless medium contained in lay-flat or upright polyethylene bags (2-5 gallons in size) and fed with liquid fertilizers through drip irrigation lines. Media can be peat/vermiculite, sawdust, rockwool, rice hulls, pine bark, peanut hulls, or mixes of any of those. Bag culture is adaptable to both aggregate hydroponics fed with liquid fertilizers as well as standard soilless culture, in which the bulk of fertility is supplied via compost-based potting mixes.
Bag Culture - In bag culture, plants are grown in a soilless medium contained in lay-flat or upright polyethylene bags (2-5 gallons in size) and fed with liquid fertilizers through drip irrigation lines. Media can be peat/vermiculite, sawdust, rockwool, rice hulls, pine bark, peanut hulls, or mixes of any of those. Bag culture is adaptable to both aggregate hydroponics fed with liquid fertilizers as well as standard soilless culture, in which the bulk of fertility is supplied via compost-based potting mixes.
Vertical Towers - A form of bag culture is the vertical tower. Long bags full of media are hung from support wires or beams, and plants are placed in slits or holes made on the sides of the bag. The appeal of this system is the very efficient use of greenhouse space; since the plants are using vertical space, very little floor space is needed.The most popular vertical tower is a patented system called Verti-Gro. Verti-Gro uses square, styrofoam pots, which are stacked 8-10 pots high and can be re-used for 5-10 years. Tim Carpenter, who owns the company, recommends using perlite and coir (coconut fiber) for media. Fertilizer is supplied by a drip irrigation system, in which solution flows from the topmost to the bottom box and into a gravel support base, where it can be captured and re-used. Crops that have been grown with this system include lettuces, strawberries, herbs, tomatoes, greens, spinach, nasturtium, and cut flowers.
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