High-Yield Cultivation Techniques and Precautions for Konjac, an Alkaline Food
Konjac grows under sparse forests and is a beneficial alkaline food. For people who eat too much animal-based acidic food, eating konjac alongside it can achieve acid-base balance in the diet. In addition, konjac also has multiple functions such as lowering blood sugar, lowering blood lipids, lowering blood pressure, dispersing toxins, beautifying the skin, promoting circulation, aiding weight loss, relieving constipation, and stimulating appetite.
The entire konjac plant is toxic, with the tuber being the most toxic. It cannot be eaten raw and must be processed before consumption. After poisoning, the tongue and throat become burning hot, itchy, painful, and swollen. In folk practice, a small amount of vinegar with ginger juice is taken orally or used as a gargle to provide relief.
High-yield konjac cultivation techniques are as follows:
1. Soil selection. Konjac likes fertility and fears barrenness, likes moisture and fears drought, likes shade and fears sun, and likes coolness and fears heat. It is best planted in sandy loam at an altitude of 900-2000m with deep, fertile soil and good permeability, with mountain valleys and sloping land being most suitable. The optimal temperature for growth is 25°C, and the soil pH should be above 6.0.
2. Variety selection and pre-planting treatment
1. Variety selection: mainly flower konjac and white konjac. White konjac has the best quality, but flower konjac has higher yield than white konjac and broader adaptability. Generally, disease-free, undamaged, round or oblong small corms or rhizomes with short and sturdy terminal buds (less than 3cm), smaller leaf stalk scars, and shallower bud depressions are selected as seed corms. For rhizomes, 2-year-old plants are generally better.
2. Pre-planting treatment: before planting, sun-dry the seed corms for 1-2d,
3. Cultivation methods
1. Crop rotation: crop rotation is the best method for cutting off disease transmission in konjac cultivation, with 1 rotation every 3 years being better. The key is to avoid crops of the cruciferous family, ginger, and other crops prone to soft rot, southern blight, and root rot. Generally, rotation with gramineous crops is safer.
2. Intercropping or relay intercropping. Because the leaves and leaf stalks of konjac form a “T” or “Y” shape, light penetration is poor, the leaf area index is small, and light utilization is low, so it is better to choose crops taller than konjac for intercropping or relay intercropping, such as grain crops like sorghum and corn and economic crops like eucommia and castor. This allows tall-stemmed plants to receive sufficient sunlight in the upper layer while konjac receives appropriate shade in the lower layer.
4. Land preparation and fertilization
1. Land preparation: deeply plow the land before winter, then deeply plow and finely prepare the soil after spring, and open beds and drainage ditches.
2. Applying base fertilizer: the roots of konjac are fibrous roots, relatively shallow, with weak absorption capacity, so the soil must be enriched and fertilization must be scientific. Konjac has a very large demand for organic fertilizer, generally using 24,000 kg/hm2 of decomposed compost, or 22,000 kg/hm2 of biogas residue as base fertilizer. Where conditions permit, the amount of pure nitrogen, phosphorus, and potassium to be applied should be calculated according to konjac's demand for nitrogen, phosphorus, and potassium fertilizers, soil supply, and utilization rate. Throughout the entire growth process of konjac, generally 260.9 kg/hm2 of nitrogen fertilizer, 930 kg/hm2 of phosphorus fertilizer, and 280 kg/hm2 of potassium fertilizer (potassium sulfate) are applied. During fertilization, nitrogen fertilizer must not be applied in a biased manner. The proportion of base fertilizer should account for 70-80% of the total fertilization amount, and for special plots more than 80% should be used as base fertilizer, with slow-release fertilizers as the main type. When fertilizing, apply the base fertilizer in the ditch or dig a separate fertilization ditch beside the ditch, or apply it to the soil surface from late May to early June when a few sprouts emerge from the ground, and then earth up.
Base fertilizer is generally applied 10-15d before planting. Dig a fertilization ditch between two planting rows, mix the base fertilizer evenly and apply it in the ditch, or first dig a planting ditch 12-15cm deep, apply compost or biogas fertilizer at the bottom of the ditch, place the seed corms diagonally on top, then apply about 3cm of base fertilizer on top, and then cover with soil. The base fertilizer should be applied in a concentrated manner, close to the seed corms but not directly touching them, so as to maximize fertilizer utilization efficiency without damaging the seed corms.
5. Planting treatment
1. Sowing period: konjac must be sown only after the physiological dormancy period of the seed corm is broken and the average temperature rises back to 12 to 14°C, with the minimum temperature around 10°C. Generally, planting is done from early March to early April. The planting time also varies with different varieties. Generally, the temperature required for flower konjac to sprout is slightly lower than that for white konjac, so flower konjac can be planted slightly earlier in the same area.
2. Density and seed quantity: konjac planting density is generally relatively sparse. When corms expand well, more rhizomes are produced, and the yield per plant is higher. However, if the density is too sparse, the yield per unit area decreases, the leaf area coefficient is too small, and sunlight directly shines through to the ground surface, raising the soil temperature above 35°C, which adversely affects the roots. Varieties with “Y”-shaped leaves are more suitable for dense planting than varieties with “T”-shaped leaves. Konjac planting density is related to the size of the seed corms; the larger the seed corms, the sparser the density. Generally, for flower konjac seeds of about 100g, the planting spacing is 25cm between plants and 60cm between rows, and about 10g of seeds per mu is 80—100 kg.
3. Planting method: generally adopt high beds and narrow frames, with 2 ditches opened per frame; wide beds with shallow ditches can increase the number of planting ditches. For rhizomes, the seed corms can be placed horizontally in the ditch in the same direction; for small corms, place 1 every 15-20cm according to their size; for seed corms of 50-100g or more, pit planting or ditch planting can be adopted, with ditch depth of 10-15cm according to seed corm size. Seed corms are generally planted diagonally at 45° on flat land; if the land is sloping, the terminal bud should be planted upward along the slope, because if not placed diagonally, the seed corms may rot due to water accumulation in the bud depression at the top of the corm. The depth of soil covering should be determined according to the soil thickness of the plot, generally covering with .6-9cm of soil.
6. Field management
1. Weed control: konjac roots are mostly distributed parallel in the upper soil layer, and roots are easily damaged during intertillage and weeding, so generally after spring plowing and land preparation, herbicides are used to thoroughly remove weeds. After konjac leaves unfold, only manual pulling of weeds can be done to prevent damage to roots and leaves.
2. Mulching: this is an indispensable management task in konjac cultivation. When planting, cover with 6-9cm of soil,
and then cover with a layer of 5-10cm thick straw or grass, generally covering more than 22,500 kg/hm2 of straw or grass, with it being preferable that no soil is visible after covering with straw. This can not only keep the soil loose and moist, avoid soil erosion, and improve soil fertility, but also increase the early-stage ground temperature and lower the mid-stage ground temperature, which is beneficial to konjac growth and development.
3. Earthing up and topdressing: (1) Intertillage and earthing up. When konjac begins to sprout and emerge 30-40d after planting, shallow intertillage can be carried out before the root system has spread throughout the soil layer to improve soil permeability, or earthing up can be combined with applying base fertilizer at the same time, generally earthing up 7-9cm. (2) Topdressing. Topdressing is divided into 3 times: the 1st time from the end of May to early June to promote the upper growth of konjac; the 2nd time from late June to early July, mainly to promote the underground development of konjac; the 3rd time in late August, using 75 kg/hm2 of potassium dihydrogen phosphate mixed with about 1000 kg/hm2 of water for root irrigation.
4. Pest and disease control: the main diseases of konjac are southern blight and soft rot. Once disease occurs, the damage to konjac is extremely great. In prevention and control work, strict disinfection of seed corms must be carried out. When disease occurs in the middle and late growth stages, pesticides should be used for control at the early stage of disease occurrence. For southern blight, use 1500g/hm2 of jinggangmycin mixed with 900kg/hm2 of water, or 3000g/hm2 of carbendazim mixed with 900kg/hm2 of water, spraying the base of the konjac plants once every 10d for 3 consecutive sprays. Soft rot: (1) immediately pull out diseased plants to reduce bacteria left in the soil; (2) use 10 million IU agricultural streptomycin at 600-700 times dilution, or 70% dexon at 500-600 times dilution to pour on the base of the plants; pour once every 10d for 3 consecutive pours. Insect pests are mainly aphids, mites, and leafhoppers, which can be controlled with general insecticides and acaricides.
5. Timely harvesting: harvesting too early will reduce yield, while harvesting too late will reduce both yield and quality. The best time for harvesting is about 10d after the konjac plants fall over.
Storage methods
1. Open-field overwintering storage: this refers to not digging and harvesting konjac that year but leaving it in the field to overwinter naturally. It can be used in konjac production areas where winters are not too cold. The specific method is: after the konjac plants naturally fall over, immediately cover with materials such as rice straw, thatch, and leaves, and the layer must not be thinner than 17cm, otherwise it will be difficult to provide cold protection. At the same time, deeply open surrounding ditches and bed ditches and make the ditches connect with each other to facilitate drainage and waterlogging removal. After spring begins the following year, carefully dig out the konjac before sowing, dry off the moisture, and then sow. This method is relatively primitive and greatly affected by natural conditions. In case of severe cold, low-temperature chilling injury and rot are likely to occur.
2. Heap storage: choose an indoor location with good ventilation and a dry floor, or an outdoor location with good drainage, ventilation, and sunlight. Surround it with bamboo poles, wooden strips, etc., and carefully place dried and wound-healed pretreated konjac corms in net bags,
into rows in the enclosure, leaving a certain ventilation section for each row. If outdoors, a rainproof canopy can be built above. This method is generally suitable for short-term storage of konjac awaiting processing at processing plants.
3. Rack storage: this method is mainly used for storing seed corms. The advantage is that the seed corms are spread on the rack layers, allowing full ventilation and exposure to scattered light, thereby effectively controlling the spread of corm diseases and preventing seed rot, which is especially important for seed corms in fields where diseases were severe during the growing period. The specific method is to first make multi-layer shelves with a layer spacing of 45?50cm and a width of 1?1.2m. The number and length of shelf layers can be determined according to specific circumstances. On each shelf layer, 3?4 layers of seed corms can be placed (farmers with flue-curing barns or houses with a second floor can also refer to this method). The disadvantage of this storage method is that the corms lose too much water, so appropriate covering should be carried out in the middle and late stages.