It is cultivated in pure water solution, and the roots of plants are suspended in liquid culture medium (nutrient solution).
There are many methods of hydroponics. Simple methods can be cans, plastic cups, plastic plates (or cans) and other containers. The plastic cover of a can or a plastic cup. Punch two holes in the cover plate, one large and one small. The macropore is a planting hole for planting plants, and the plants are fixed in the hole with wax-soaked absorbent cotton or foam plastic; The small hole is an exhaust hole, which can be inserted into the exhaust pipe and pumped in by a small air pump to raise goldfish. A certain amount of nutrient solution should not be filled in the container, so that there is a space of several centimeters between the liquid level and the cover plate. The roots and necks of plants should not be immersed in the nutrient solution, but should be left in this space (Figure 13-3).
Figure 13-3 plastic tray with plastic cup method can be planted with two trays of the same width, one deep and one shallow. There are many holes at the bottom of the shallow tray, and there are drainage holes at the bottom of the deep tray, which are connected with rubber tubes and transparent glass tubes to control the liquid level of the lower tray. The shallow plate is placed on the deep plate, which is filled with sand, slag, peat or vermiculite as the supporting plate for plants. Plants are planted on the substrate, and the lower tray is filled with nutrient solution. Pouring water or nutrient solution from the tray to keep the substrate moist is beneficial to the germination and rooting of plants. For the nutrient solution in the lower plate, the distance between the initial liquid level and the bottom of the upper plate should be 0.5- 1 cm, which is beneficial to guide the roots of plants to enter the nutrient solution below through the holes in the bottom of the plate. When the plants grow up and the roots are completely immersed in the nutrient solution, the liquid level should be gradually reduced to a distance of 2.5-5 cm from the bottom of the upper plate. Replace the nutrient solution every 10- 15 days (Figure 13-4).
Figure 13-4 Plastic Plate Method Section
If the planting method of plastic tray is expanded, it will become a larger planting trough. You can also build a larger tank with cement, separate the solid matrix with plastic net, and have inspection holes, which is convenient for checking the change of liquid level. You can also install a water pump to make the nutrient solution flow periodically.
Nowadays, most hydroponics methods used in commercial production adopt nutrient membrane technology (NFT for short), which was invented by Douglas. He published a paper at the third international soilless culture conference in sassari in 1973. He made a tank out of plastic or other materials, planted plants in it, and the nutrient solution circulated in the tank with a very shallow water flow (Figure 13-5).
Figure 13-5 Douglas nutrient film
After continuous improvement, various forms of nutrient membrane technology have emerged, and it is also useful to use plastic plates as permanent culture tanks. Multi-layer planting is adopted, and each layer is equipped with fluorescent lamps to supplement light. The plants planted by this method grow well and have developed roots, forming a dense layer of roots in the trough. This method is often used for large-scale planting. Because it has simple equipment, easy operation and less investment; Easy to manage and replace crop stubble; Nutrient solution circulation is shallow, and the root system is easy to absorb fresh oxygen; Save water; When the light conditions change, it is easy to adjust the nutritional formula to control the plant growth; Internal insecticides and fungicides can be used in nutrient solution to control the occurrence of pests and diseases; The nutrient solution can also be heated to maintain the most suitable temperature of plant roots, so that the temperature in the greenhouse is lower than normal temperature, so as to save energy. So it is very popular with the vast number of soilless cultivators. Medicinal plants suitable for hydroponics can try whole grass and whole leaf medicinal plants, such as foxglove, andrographis paniculata, patchouli, perilla, belladonna and mint.
Air culture is also a kind of hydroponics. The roots of plants are hung in a closed dark room, and nutrient solution is sprayed on the roots of plants regularly with a nozzle, and the relative humidity in the room is kept at 1000%, so that the roots are soaked in the nutrient solution fog.
To make hydroponics successful, we must pay attention to the following three points:
1. Let the roots get enough air.
Growing roots need oxygen to breathe. The content of oxygen in static aqueous solution is limited, which can not meet the needs of root respiration continuously. Without oxygen radicals, it will suffocate and rot, and then the whole plant will die. Therefore, the oxygen content in nutrient solution is an important factor affecting plant growth. To ensure that the oxygen in nutrient solution can continuously meet the needs of root respiration, it is necessary to ventilate frequently. Ventilation method: one is forced ventilation, that is, a porous tube is placed in the planting bed or at the bottom of the container, and air is blown into the nutrient solution through the tube. The other is to circulate the nutrient solution with a pump, leaving a certain gap when the nutrient solution flows into the planting ditch and flows back to the nutrient solution tank, and dissolving fresh air into the nutrient solution when the nutrient solution flows or drops. In addition, the root neck and some roots can be exposed to humid air environment to directly absorb oxygen in the air.
2. Hide the roots in the dark.
Illumination of nutrient solution will promote the growth of algae, not only compete with plants for nutrients, make nutrient solution stink and deteriorate, but also consume oxygen in nutrient solution and hinder the growth of plants. Therefore, opaque materials should be used as planting ditches, beds or covering containers. At the same time, roots need to grow well in a dark environment.
3. Appropriate nutrient solution is also important.
The salt species, nutrient ratio, nutrient solution concentration and pH value suitable for the growth of this plant were explored. So as to prepare a nutrient solution which is most suitable for plant growth.
(2) Substrate cultivation method
Substrate cultivation means that a certain container is filled with a certain substrate to grow plants, and nutrient solution is supplied regularly and quantitatively. There are many substrates that can be used for soilless culture, such as sand, gravel, peat, slag, vermiculite, perlite, sawdust, pumice, foam plastic, chaff, rock wool and so on. Using these substrates to cultivate plants can be called sand culture, gravel culture, peat culture, slag culture, vermiculite culture and so on. These substrates can also be mixed with each other, and the thickness can be matched. The combination of good water absorption and poor water absorption can make up for the shortage of using a certain substrate alone. The purpose of mixing is to make the water, fertilizer and gas in the matrix coordinate with each other and create an environment more conducive to root growth.
The substrate for soilless culture must provide an excellent place for the growth of plant roots, just like soil; Can support the growth of roots; After adding nutrient solution, it can keep the balance of air, water and nutrients and meet the needs of plants for the three; Has no adverse effect on plant growth. Several substrate cultivation methods are introduced below.
1. Sand-based culture
It is a cultivation method with sand as the culture medium. It is the most widely used method, simple to operate and easy to master. Sand particles should not be too fine or too coarse, too fine is easy to retain water, too coarse is easy to drain too fast and dry. The diameter of sand is not less than 0.6mm and not more than 3mm, and the mixed thickness is the best. Fine sand can be used for cutting seedling, which has a long history in China and is still widely used today.
There are also many forms of sand culture. The planting bed can be made of cement, a ditch can be dug in the ground and lined with plastic cloth, or it can be made of stone or brick. The watertight planting bed made of cement and lined with plastic sheets should have a certain small slope at the bottom, generally 1: 100-200, and be equipped with drainage pipes or holes, and the opening should be padded with gravel with a thickness of about 10cm to prevent sand from flowing out. A simple planting bed made of stone or brick can be paved with a layer of gravel about 5cm thick at the bottom of the bed, and then filled with coarse sand with a thickness of 15-20 cm. The width of the groove should not be too narrow or too wide, generally it is 1- 1.2m, which is suitable for easy operation.
Fertilization: it can be made into mixed fertilizer for dry application, or it can be made into nutrient solution for spraying. Dry application 10 once a day, once every 7 days in rainy season, and the dosage of each application 10-30g/ m2, depending on plant species and growth period; The concentration of nutrient solution is 0. 1-0.2%, 2-3 times a week, and watering is subject to a small amount of water flowing from the bottom drainage hole, and it can be watered less often in rainy season.
Irrigation: According to the age, development period and climate of medicinal plants, determine the watering times. The weather is dry and hot, just water it 2-3 times a day, generally 1 time. The amount of water should not be too much, and it should be watered thoroughly. From half a month to 1 month, the concentration of soluble salt in the water discharged from the planting bed should be measured (if possible, the utilization of salt by plants should be tested). If the total content of soluble salt exceeds 2000ppm, it should be washed with clean water to remove salt. According to the determination results of salt, the fertilization scheme can also be changed. There are many medicinal plants suitable for sand culture. Such as ginseng, American ginseng, rehmannia root, coptis root, digitalis, mint, Gynostemma pentaphyllum and the like.
Conditional units can also use bottom irrigation to keep the surface sand dry and prevent algae from breeding and spreading.
2. Gravel culture
It is a soilless culture method with cobblestones as culture medium. Granite gravel is the best, the diameter of small particles is not less than 1.6mm, and the diameter of large particles is not more than 2cm, accounting for half of the total volume, and the diameter should be1.3cm. Gravel cultivation method has large particles, good drainage performance and poor water retention performance, and is suitable for continuous circulating running water irrigation with nutrient solution. Suitable for planting tall medicinal plants.
3. Peat culture
Peat consists of semi-decomposed aquatic, swamp or bryophyte. Different peat has different characteristics. There are three kinds of peat: sphagnum, reed, Carex and peat humus. Sphagnum is not easy to decompose, and is formed by Sphagnum or other mosses, with high water holding capacity (10 times its dry weight) and high acidity (pH 3.8-4.5). It contains a small amount of nitrogen (about 1%), but contains no phosphorus or potassium. It is often mixed with other substrates or made into peat blocks for cultivation. Peat produced by other mosses decomposes much faster than sphagnum moss, so it is not ideal as a culture medium. Peat formed by marsh plants such as Carex and Phragmites australis also decomposes quickly and is not suitable for use.
4. Vermiculite culture
Vermiculite is a mica mineral. After heating and calcining to 1000℃, it expands, water turns into steam, and the mineral layer explodes, forming small and porous sponge particles. It is hydrated magnesium aluminum ferric silicate [[〔3MgO (Fe, Al) 2O 3 3sio2]], which is very light and weighs 96- 160kg per cubic meter. Neutral, good buffering, insoluble in water, and can absorb 500-650 1 per cubic meter. It has a high cation exchange capacity, so it can maintain nutrition and release nutrition. And contains magnesium and potassium which can be utilized by plants.
There are four grades of vermiculite for gardening: No.65438 +0 particles with a diameter of 5-8 mm; No.2 particle is 2-3 mm in diameter, which is most commonly used; No.3 is1-2mm; No.4 is 0.75- 1 mm, which is the most commonly used substrate for seed germination and seedling raising. Expanded vermiculite should not be extruded after absorbing water, so as not to destroy the good porous structure.
Vermiculite can cultivate a variety of medicinal plants. Vermiculite has strong water and fertilizer conservation, and the bottom of the container should be porous to facilitate drainage. Generally, surface watering is adopted, and the frequency of watering and nutrient solution should not be too much. Vermiculite can be mixed with sand according to the volume of 1: 1-3, and a planting trough with a height of 20-25cm, a width of 1m and a length of 10m or more can be built with bricks, and gravel with a thickness of about 5cm can be paved under it. Planting ginseng or American ginseng. According to our experiments for many years, the seedling emergence rate and seedling preservation rate are high, reaching about 90%, saving seeds, growing well and not easy to root rot. Can be combined with commercial production, and one or two-year-old seedlings can be transplanted. If planted with 6×6cm row spacing, annual seedlings can be planted alternately, and biennial seedlings can be planted alternately. If the plants are too dense, they can also be planted properly, which should be carried out after returning to seedlings in autumn. Because of the loose culture medium, the seedlings are easy to damage the roots and the roots of commercial seedlings left nearby, and the transplanting survival rate is high. After the mixture of foxglove and perlite, the plant grows rapidly, the root system is developed and the yield is increased by more than 90%.
In addition, using vermiculite or its mixture with sand and perlite to cut medicinal plants such as Catharanthus roseus, Lonicera japonica, Gynostemma pentaphyllum, etc., cuttings take root quickly, the root system is developed, and the survival rate can reach almost 65,438+000%, and seedlings are easy to sprout, the root system is not easy to be damaged, and the transplanting survival rate is high.
5. Perlite culture
It is a kind of silicon substance, which is a mineral formed by lava flow. After the coarse ore is dug out and screened, it is heated to 760℃ in the furnace, and a small amount of water in the particles becomes steam, which makes the particles loose and forms light spongy particles, weighing 80- 130 kg per cubic meter. Particles with a diameter of 1.5-3 mm are often used in gardening. They can keep water 3-4 times heavier than themselves, and are basically neutral, with a pH of 6.0-8.0, but they have no buffering effect. Unlike vermiculite, they have no cation exchange performance and no mineral nutrition. It can ventilate the mixture best, because it is stable in structure and will not decompose, but it will break into small particles when it collides. Fine particles can be used for seed seedling, coarse particles can be mixed with peat in equal amount for cutting seedling, or mixed with peat and sand to plant a variety of medicinal plants.
There are many kinds and forms of substrate cultivation. Here is a simple and interesting method called vertical cultivation. The simplest method is long bag cultivation. A long bag with a diameter of 15cm and a length of 2m is made of black plastic cloth with a thickness of 0. 15mm, and is filled with a mixture of light wood chips, shavings, peat or vermiculite. The bottom end is tied to prevent the substrate from falling, and the upper end is tied and hung in the greenhouse, just like a column, which makes full use of the three-dimensional space. There are 2.5-5cm wide holes around the bag at regular intervals for planting plants. Nutrient solution flows in from the top of the bag, leaks downward through the whole bag, and flows to the drainage hole below (Figure 13-6).
Figure 13-6 Schematic Diagram of Bagging Cultivation