High returns from the grid-pool fish-lotus polyculture model

The grid-pool fish-lotus polyculture technique involves partitioning a hardened lotus pool with roof tiles, hard boards and the like into small grids of 2-4 sq m each, planting lotus within the grids, yielding an average of 0.5 wan kg of lotus and 400-450 kg of fish per mu of water surface, with a net return of over 10,000 yuan per mu. This technique can make use of waste pits, wasteland, river beach land and scattered corner plots to build grid-pool fish-lotus polyculture systems; it features small investment, low cost, quick returns and high benefits, is suitable for vigorous development by countless rural households, and has very broad prospects for extension.

Economic and prospect analysis

This project requires an investment of about 4,000 yuan per mu, and once the pool is built it can be used for a long time. The average yield is 5,000 kg of lotus per mu; calculated at 2.0 yuan per kg, the income per mu can reach 10,000 yuan. In terms of market conditions, lotus root is a popular food with large market demand, can be supplied at any time to fill market gaps, and is a pollution-free food; as people's awareness of green food increases, the public's demand for lotus root will rise substantially. In addition, ecological agriculture requires large amounts of organic fertilizer, which can drive the development of animal husbandry such as @#@230@#@ and @#@227@#@, organically combining crop farming with livestock and fish farming so that they promote and develop together; for developing tourism and sightseeing agriculture, regulating the climate and improving the ecological environment, it has very important social and ecological benefits, and therefore has very broad development prospects.

Lotus pool conditions and infrastructure

1. Selection of the lotus pool: wasteland, waterlogged low-lying land, abandoned kiln pits and old lotus pools both inside and outside the village can all be used. As far as possible, choose a site with convenient transport, good water source conditions, unpolluted water quality, convenient irrigation and drainage, and no tall buildings or shade-casting objects around it for building the lotus pool.

2. Lotus pool construction: Lotus pool construction can be divided into several types: single-brick running-wall isolation type; lime-concrete structure with roof-tile isolation type; plastic film bottom-lining with roof-tile isolation type; and plastic sheet or cement board isolation type. Whichever type is used, the surface must be plastered with cement. Generally the lotus pool area is 1-3 mu, with 1-1.5 mu being best, and the pool depth should be 0.8-1.2 m. After the pool is built, backfill 35-40 cm of fertile soil as the living layer for the lotus, and apply base fertilizer, then partition it with roof tiles, cement boards, plastic boards, gypsum asbestos tiles or other hard boards into small grids of 2-4 sq m; the partition boards should be buried 40 cm into the soil and stand 20 cm above the ground, with a board height of 60-70 cm; set water inlet and outlet openings crossing the lotus pool, install fish-blocking nets, and set up "-" or "+" shaped fish trenches in the pool, 1.0 m wide and 0.5-1.0 m deep, occupying about 15% of the pool area. Practice has proved that large grids give low lotus yields; although small grids require a relatively large one-time investment, the yield is very high.

3. Apply sufficient base fertilizer: Lotus likes heavy fertilization; abundant backfilled soil and manure are the key to obtaining high pool-lotus yields. Fertilization should be based mainly on base fertilizer with supplementary topdressing, and mainly on organic fertilizer with supplementary chemical fertilizer. Use about 2,000 kg of fully fermented organic fertilizer per mu, ammonium sulfate 10-15 kg/mu, urea 5-10 kg/mu, potassium nitrate 3-7 kg/mu, and superphosphate 5-10 kg/mu. Chemical fertilizers should be mixed with water and sprinkled, avoiding direct scattering into the fish trenches so as not to harm the fish. After applying base fertilizer, use 50 kg of quicklime per mu, slaked into a slurry and sprinkled evenly over the whole pool, to improve the soil, increase the calcium fertilizer content and adjust the pH of the pool mud, while also killing pathogens and preventing and treating disease.

Grid pool construction technique

Building the lotus pool well is the key to lotus production; generally a site with sufficient water source, convenient irrigation and drainage, and no tall shade-casting objects should be chosen for planting. We should proceed according to our own actual circumstances; as long as water can be supplied, the lotus pool can be built as a semi-underground type as far as possible, in order to reduce earthwork labor. The operation process is as follows.

1. Making cement boards: Taking the construction of a 500 sq m lotus pool as an example, it is best to use a 25 m x 20 m layout, requiring 240 cement boards of 0.5 m x 0.8 m x 0.04 m. Each board requires 10 jin of cement, 30 jin of gravel and 20 jin of sand.

2. Building the surrounding pool walls: According to the chosen location, mark lines around the pool to determine its size, dig down 40 cm from the ground, then compact layer by layer with an electric tamper, building the wall to 40-45 cm above the ground (80 cm in total); take soil from inside the pool, and after tamping, according to the angle required for building the pool (the slope forms a 60-degree angle with the horizontal plane), shape the slope and then attach the cement boards. The slope should be smooth and firm.

3. Laying the bottom and attaching cement boards to the four walls of the pool: For the bottom laying, earthwork labor should be minimized; block-by-block bottom laying can be used. Suppose the lotus pool is 50 m x 10 m; it can be laid in two blocks. On one side of the pool, measure out a 5 m wide area, dig down 40 cm, turn the soil to both sides, keep the pool bottom basically level, mix 12 jin/sq m of white lime evenly with the soil to a thickness of about 10 cm, and compact it with an electric tamper. Then attach the wall cement boards and fill the gaps well. If the pool bottom is too dry, first sprinkle a layer of water and let it moisten, then plaster the bottom with a ratio of 100 jin of cement mixed with 500 jin of sand, 2.5 cm thick; trowel the mortar surface smooth, and after it has basically set, complete the other half of the pool in the same way. Be careful to handle the joints well to prevent water leakage; cover the overlaps with woven bags or film. After that is done, remove them and plaster the cement surface to prevent soil intrusion. (This method does not involve digging fish trenches; if fish are to be polycultured @#@233@#@ then fish trenches need to be dug.)

4. Fill with water and build the grids: After the pool bottom is hardened, level the soil in the pool, apply all the various organic and inorganic fertilizers needed for lotus growth into the pool and mix them evenly with the soil to a thickness controlled at 35 cm, then fill with water so that the water surface is 2-3 cm above the ground inside the pool, then a person can tread back and forth several times in the pool to prevent leakage from the pool bottom, then insert large tiles into the soil to form 2 m x 2 m grids. Then fill with water and wait for sowing.

5. Materials and cost for building the pool: cement boards: 0.5 m x 0.8 m x 0.04 m, 240 pieces (2 yuan/piece); cement: 4 tonnes (reference price 190 yuan/tonne); lime: 3 tonnes (reference price 90 yuan/tonne); sand: 14 cubic meters (reference price 10 yuan/cubic meter); large grid-making tiles: 1,800 pieces (reference price 0.1 yuan/piece); total: 1,830.00 yuan.

Pool lotus cultivation

1. Selection of seed lotus: It is advisable to choose fresh, robust, vigorous-budded, fine-noded, disease-free and injury-free high-quality white lotus root as seed; each seed lotus plant should preferably have a complete three-node lotus body and carry 1-2 daughter lotus roots. Daughter lotus roots can also be used as seed, but they must be robust, with at least more than 2 fully mature lotus body nodes and intact terminal buds. The lotus seed can be soaked in 20 mg/kg naphthalene acetic acid for 40 minutes, propagated by plastic-film seedling raising, and planted out after 15 days, which can bring pool lotus to market earlier and increase yield by more than 15%.

2. Planting time: Plant when the air temperature rises above 12-15 degrees C. If too early, the soil temperature is low and the seed lotus tends to rot; if too late, the buds grow long and are easily broken. In Shandong Province, planting around Qingming is generally suitable.

3. Method and amount: First plow and harrow the soil and manure in the lotus pool evenly and finely to a thickness controlled at 35-40 cm, then fill with water; after filling, tread back and forth several times in the pool to prevent leakage from the pool bottom, then insert roof tiles or other partition boards into the soil to form 2-4 sq m grids (2 x 2 sq m is preferable), and plant the lotus. For lotus planting in the pool, use 1 seed lotus or 2 daughter lotus roots per 2 sq m, generally using 320-380 kg of seed per mu. When planting the seed lotus, the bud end should be slightly lower and the rear part slightly raised, at a 20-30 degree tilt, 5-8 cm from the ground level, which is exactly the depth of the first water filling.

Fish stocking

1. Stocking time: Generally fish can be stocked when the water temperature stabilizes at 8-10 degrees C; when stocking Clarias leather carp (Clarias gariepinus) fingerlings, wait until the water temperature stabilizes above 15 degrees C before stocking.

2. Stocked species: Generally speaking, all fish that can be farmed in ponds can be farmed in lotus fields, mainly including grass carp, silver carp, bighead carp, common carp, crucian carp and bream; in addition, faster-growing fish such as Clarias gariepinus and Pengze crucian carp are good species for lotus field farming. Because the light on the water surface of lotus fields is poor, the temperature is lower, and there is less plankton in the water, the main fish should not be filter-feeding silver carp or bighead carp; it should be mainly feeding fish with filter-feeding fish as a supplement.

3. Stocking density: This should be decided according to the fish species, stocking size, water quality and water source conditions and management level. Generally stock 200-300 large-size fingerlings per mu, or 600-800 Clarias gariepinus fingerlings per mu.

4. Mixing ratio: The general fingerling stocking ratio is grass carp 70%, common carp 15%, silver carp and bighead carp 5%, and others 10%; or common carp 70%, grass carp 15%, silver carp 10%, and bighead carp 5%. Clarias gariepinus, Pengze crucian carp and the like should be stocked alone. It is worth noting that before the lotus grows two standing leaves, large-size grass carp fingerlings must not be stocked, so that the grass carp do not eat the lotus leaves.

Management techniques

1. Water level regulation: In spring, to raise the water temperature and ground temperature, the water level should be shallower, kept at about 10 cm; afterward, as the water temperature rises, gradually deepen the water level. The deepest water level in the fish trenches can reach 0.8-1.0 m. When adding water, use the method of small amounts and many times, to maintain good water quality.

2. Rational topdressing: When the lotus leaves have spread over the whole ground, apply 10-15 kg of ammonium sulfate per mu, or 5-10 kg of urea. When the terminal leaves appear, apply 5-10 kg of urea per mu, 10 kg of superphosphate or 20 kg of potash fertilizer.

3. Weeding and leaf removal: During the growth of lotus, especially in the early growth stage, there are many weeds, which need to be removed in time. In the mid-management period, it is also necessary to regularly thin the leaves and break off excess flower buds so that sunlight can penetrate into the water.

4. Feed feeding: To make the fish grow quickly and obtain higher yields, artificial compound feed must be fed rationally; when farming Clarias gariepinus, animal offal such as chicken intestines should be fed, ensuring that the fish can promptly eat fresh, high-quality and sufficient feed.

5. Disease and pest control: The main lotus diseases are rot disease, leaf blight and brown spot disease. Rot disease: applying an appropriate amount of quicklime into the pool before cultivation can have a preventive effect, and a 600-800 times solution of 80% zineb wettable powder can also be sprayed directly; leaf blight: in the early stage of the disease, spray with an 800 times solution of 50% thiophanate, continuously 2-3 times; brown spot disease: control is the same as for leaf blight; pests and diseases: mainly aphids, cutworms and root maggots; for aphids, a 1500-2000 times solution of 40% dimethoate emulsion can be sprayed; for cutworms, a 1000 times solution of 90% trichlorfon crystals can be sprayed at night; for root maggots, 3 kg of 3% carbofuran per mu mixed with 30 kg of fine soil can be evenly broadcast.