Updated: Mar 13, 2020
Do you ever stop and wonder if there are other microgreens growing mediums out there? Most likely not, right? Who would! What if you began to notice that you've been missing the right information about microgreens production without a solid rooting medium?
Definition Of The Nutrient Film Technique
Nutrient film technique microgreens production (commonly known as NFT microgreens production) is a method of growing in which the microgreens have their roots in shallow stream of recirculating water, which consist of all dissolved elements required. There is no soil rooting medium.
A root mat develops which is partly in shallow stream of recirculating water and partly above it. The stream is very shallow and the upper surface of the root mat which develops above the water, although it is moist, is in the air.
So around the roots which are in the air, there is a film of nutrient solution hence the name nutrient film technique. It is extremely important to maintain this basic principle of a nutrient film because it confers an important advantage. In conventional agriculture, if an abundance of water is provided there is inadequate air at the root surface. As the soil dries out, air penetrates.
When there is an abundance of oxygen there in inadequate water. In conventional agriculture, either with planned irrigation or with unplanned dependence on local rainfall, the balance between the supply of water and oxygen at the root is continually changing and, usually, one or the other is limiting. In an NFT crop there is a permanent abundance of both air and water at the root provided the nutrient film principle is maintained.
The Basic Layout Of An NFT System
NFT channels are to used, these are then laid in position on the slope so that they will discharge directly into the trench. A polytene supply pipe is then connected to the circulating pump so that water from the trench is delivered to the inlet ends of the NFT channels. A small bore polytene tube delivers the water from the supply pipe into each channel. These delivery tubes are prepared by tapering the end of the tube that is to be inserted in the supply pipe.
If the tubes have not been prepared by the manufacturer, they can easily be tapered using a pencil sharpener. A hole is then drilled in the supply pipe which has a smaller diameter than the external diameter of the delivery tube. When the tapered end of the delivery tube is pushed into the upper sized hole, a very tight fit is ensured. Before inserting the delivery tube, an oblique cut is made across the tapered end. This ensures that when the delivery tube is inserted into the supply, the end of the tube cannot be sealed off by resting on the internal face of the supply pipe.
The water flows by gravity as a very shallow stream down the channels, each channel discharging directly into the trench. If it is desired not to have a trench but merely a small tank at the lowest corner of the rectangle of land, then the NFT channels will have to discharge into a catchment pipe which, in its turn, will discharge into the small tank.
Method Of Supporting microgreens
When an NFT channel is laid on a prepared surface, or when a universal NFT channel with an integral rigid base is positioned, it is very difficult, no matter how careful the preparation or the positioning, to ensure that there is not a slight fall across the width of channel. The avoidance of a cross fall means that the bubble in a spirit level must remain central when the spirit level is laid across the width of the channel.
If the bubble is not central then, when the recirculating nutrient solution flows down the channel it, like the bubble, will not remain central but will flow down one side of the channel, leaving the majority of the width of the channel dry. Microgreens placed in the channel could wilt and die because lack of water. Even if it were possible, with great care, to ensure that the solution flowed near the centre of the flat base, it would meander as a narrow rivulet because of the surface tension between the liquid and the plastic. This would result in some of the plants dying for lack of water. Once the roots of the plants grow across the width of the channel, they act as tiny dams which are sufficient to spread the recirculating solution across the width of the channel.
Until this happens, however, some other method of spreading the liquid must be employed. The method first used was to roll out inside the channel, and covering the full width of the channel, a thin absorbent material, rather like unrolling a roll of toilet paper along the length of the channel. It is essential that the material used should not be phytotoxic, it should not have any adverse effect on the growth of the plants. It must be capable of spreading the liquid across the full width of the channel. If there is only a slight cross fall, a transverse filament acting as a tiny dam would be sufficient. If there is greater cross fall, an absorbent material with sufficient capillary action to wick the liquid across the width of the channel is required. The material used is irrelevant, provided it is not phytotoxic and it will do the job, it could range from cellulose to man made fibers.
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