Eight questions: How to restore vitality to the farmland after the heavy rain resumed after the disaster?

  In this flood situation in Henan, after the flood gradually receded, why did the crops in the flooded area dry up on a large scale after being soaked in the flood?

Will siltation in crop fields affect soil fertility?

Waterlogging occurs in farmland, what measures should farmers take?

The Beijing News reporter interviewed top experts in many fields such as corn, peanuts, rice, fruit cultivation, vegetable fields, soil, etc., and learned about the hazards of farmland flooding and subsequent remedies from eight aspects. These experts were directly involved in this extraordinary flood. Participated in the on-site guidance for the restoration of agricultural production in the disaster area.

  1 Flood

  How to save the soaked crops?

  In a field in Xinxiang, Henan, dry corn stalks were left after the flood receded. A villager told the Beijing News reporter that he had planted 4 mu of corn this year. In previous years, the rain was uneven. The corn field used to worry about drought resistance. I thought it was all dead after this flood.

  According to Professor Liu Tianxue of Henan Agricultural University, although the root system of corn is developed, it is not tolerant to waterlogging. Soaking in the flood for too long will cause the soil water content to be too high, the root system will be hypoxic or even rot, which will lead to the phenomenon of dead trees.

  As woody plants, fruit trees are more resistant to waterlogging than crops. However, experts in Henan’s bulk fruit industry technology system suggest that the first task for growers is to drain water. After the fruit field is flooded, the root system will have symptoms. 6 In 12 hours, fruit trees will experience mild waterlogging damage, and the capillary roots of fruit trees will begin to be damaged; 12-24 hours, fruit trees will appear moderate waterlogging damage, the capillary roots will basically die, and the yellow-brown capillary roots will begin to be damaged; 24-48 hours, that’s In severe waterlogging, a large number of fibrous roots die; more than 48 hours, extremely heavy waterlogging, when severe, the entire plant will die.

  Many watermelons grown by farmers in Henan also suffered during this flood.

According to Professor Yang Luming of Henan Agricultural University, watermelons like high temperature and dryness. Long soaking time in flood water will affect the yield of watermelon and reduce the quality of watermelon. It is easy to cause watermelon root diseases and reduce the photosynthetic efficiency of the leaves of the seedlings, thereby reducing the sugar content and making the watermelon unsweet. Rotting roots and seedlings may even occur.

  Even for rice with strong flood tolerance, if it is flooded for too long, it will still face a major risk of yield reduction.

According to Professor Li Junzhou of Henan Agricultural University, when rice is flooded, poor ventilation, blocked photosynthesis, increased respiratory consumption, physiological activities are greatly affected, and even death.

The rice seedling stage is relatively resistant to flooding. Within 3 days of flooding, as long as the water is drained in time and the restoration fertilizer is added to promote tillering, the yield will be little affected.

If it is submerged for more than 7 days, production will be severely reduced or even no harvest.

  2 Flood

  What is the impact on the soil?

  In late July, when the floods were the worst, the flooded area of ​​farmland in the disaster-stricken areas in Henan Province reached 11.32 million mu.

The agronomist pointed out that farmland floods have a huge impact on soil fertility. Under the impact of heavy rains, the fertile soil of the slope farming layer will be taken away by heavy rain, and the subsoil will be exposed, thereby destroying the good farming performance of the soil. According to calculations, the topsoil layer of the slope farming will be reduced by an average of 20 Millimeters, an average of more than 20 tons of topsoil per acre of arable land will be lost; in addition, the accumulation of quicksand brought by floods will bring micro-aggregates on the cultivated layer, causing the ground surface to clump and bark, block the soil of the cultivated layer from communicating with the atmosphere, and let the roots of the crops. Cannot absorb nutrients.

  Associate Professor Yang Mingfan of Henan Agricultural University introduced that from a microbiological point of view, precipitation is prone to soil compaction because the beneficial bacteria in the soil itself are killed by external forces such as excessive use of pesticides and excessive precipitation. Once soil compaction occurs, it will Let the cell respiration of plant roots weaken, while nitrogen and other nutrients are mostly in ionic state. The roots need to act actively to absorb these nutrients. In this process, the energy produced by cell metabolism is also consumed. If the respiration of plant roots is weakened , The energy produced by cell metabolism will be less, so the nutrient element absorption of the plant will be lower, which is ultimately not conducive to the growth and development of the plant.

  Yang Mingfan said that the impact of floods on farmland still needs to be treated in specific plots. There are many microorganisms in the soil, including bacteria that are beneficial to the growth of crops, such as nitrogen-fixing bacteria, nitrifying bacteria, and saprophytic bacteria; there are also harmful bacteria, such as denitrifying bacteria. A flood may bring more organic matter and beneficial bacteria to the soil, but it may also activate harmful bacteria that are originally "sleeping" in the soil. In other words, the harmful bacteria in the soil that are originally "sleeping" may be caused by The flood will be'resurrected'. This is also the reason for the prevention of the epidemic after the disaster."

  Many experts from Henan Agricultural University told reporters that after visiting northern Henan and southern Henan, they found that there were not many accumulations of farmland, and there was less silt accumulation.

"In some hilly farmlands, heavy rains will damage soil fertility. However, most of the farmlands in Henan are flat and concentrated, and there is not much sediment accumulation. Even if there is silt in the fields, it will not have much impact on production." An expert told reporters.

  Some experts have analyzed that the impact of flood siltation on the soil is related to the location of the farmland. The farmland near the Yellow River will play a role in soil improvement to a certain extent due to the large amount of soil nutrients carried in the Yellow River water, but also pay attention to the salinization of the land. The problem; however, the farmland in the neighboring cities will take on the industrial substances in the city, which may cause a large amount of toxic substances to accumulate in the farmland, resulting in a decline in soil farming performance. In this case, it is necessary for the growers to pay close attention to dredging the silt.

  3 Kill

  How to prevent pollution of farmland?

  Yang Mingfan believes that the traditional way to disinfect farmland is to use chemical disinfectants, but chemical disinfection always has some toxic and side effects on the land, people and animals. Farmers can also use microbial agents that are less harmful to the soil. "It can be said that microorganisms The preparation does not have any toxic and side effects, because the microbial preparation is "one thing reduces one thing", that is, through the principle of phagocytosis and inhibition of harmful bacteria by beneficial bacteria, it achieves the dual effects of disinfection and deodorization."

  "Of course, the price of microbial preparations is higher than that of chemical disinfectants. Some farmers will choose chemical disinfectants because of the price. However, from the perspective of improving the ecological environment and promoting soil protection, they use more expensive but clean and environmentally friendly microorganisms. The preparation will be better." Yang Mingfan said.

  The heat treatment technology with carbonization behavior is also a clean, efficient, and soil-improving method. According to the National Environmental Impact Assessment Engineer and Associate Professor Sang Yimin of the Beijing Institute of Petrochemical Technology, when organic pollutants such as oil flow into the farmland near the city with the flood, Will pollute the soil.

For lightly polluted soil, the self-purification of the soil can be achieved based on microbial degradation and plant absorption; for heavily polluted soil, heat treatment technology can remove organic pollutants such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and chlorobenzene, and achieve some Biochar conversion of organic pollutants.

  Fruit tree branches, agricultural straws and even peanut shells can be used as raw materials for biochar. According to reports, biochar is formed by pyrolysis and carbonization of biomass under anaerobic or anaerobic conditions. A class of highly aromatic and insoluble substances with good structure, huge specific surface area and adsorption capacity, high stability and anti-microbial corrosion ability; and there are a large number of oxygen-containing functional groups on the surface of biochar, which can increase soil cation exchange capacity and improve The soil has the ability to hold nutrients such as divalent calcium ions, potassium ions, magnesium ions and ammonium ions; it can also lock in the carbon dioxide produced by plants and improve the quality of low-fertility soils.

Therefore, biochar is commonly used as a soil amendment, which can increase soil water content, increase soil nutrients, stabilize soil pH, and enrich soil microbial communities.

  4 Drainage

  Is it enough to just dig the drain?

  Professor Yin Dongmei, a post expert on the technical system of peanut industry in Henan Province, believes that in addition to digging drainage ditches, mechanical drainage can also be used to drain the field water and the stagnant water of the cultivated layer as soon as possible to minimize the time of field water accumulation, like peanuts. Low crops require high drainage efficiency.

  For the accumulation of water in the peach orchard, multiple drainage ditches are needed. Professor Feng Jiancan of Henan Agricultural University suggested that the drainage channels and ditches between the peach orchard and the outside world should be opened first, and the accumulated water in the garden should be quickly removed; Excavate drainage ditch with a width of about 30 cm and a depth of about 50 cm. While speeding up the drainage, it improves the aeration of the soil.

Depending on the topography, the excavation of a drainage ditch perpendicular to the rows can also be considered.

  For the drainage of rice fields, corresponding measures should be taken according to the weather and plant growth. Li Junzhou suggested that the flooded fields should be drained in time to reduce the flooding time, such as rainy days, drainage should be done at one time; such as hot sun and hot weather, drainage To the shallow water layer of 3-5 cm; if the rice plants grow vigorously after flooding, and there are more floating mud on the field surface, you can also drain the field lightly to prevent lodging.

  5 ventilation

  Is it enough to just cultivate the soil to loosen the soil?

  After the flood, the soil is easy to harden, and it needs cultivating to loosen the soil to promote the growth of plant roots and nutrient absorption. For corn, once a severely lodging plot appears, it is necessary to promptly strengthen the roots and cultivate the soil to promote the growth of aerial roots.

But for the orchard, only loosening the soil is not enough. Experts suggest that we should also pay attention to the orchard to leave grass to prevent high temperature hazards. If possible, the orchard can be shaded around the orchard to prevent the fruit from being damaged by the sun.

  Sun Zhiqiang suggested that for vegetable fields that have drowned, after removing the accumulated water, the field plants and weeds need to be cleaned up in time, plowing and preparing the ground when the moisture content is suitable, and planting and planting the next vegetables in time.

For upright vegetables such as eggplants and peppers, they need to be planted and supported. If there is soil on the leaf surface, it needs to be washed clean.

  6 Top dressing

  Is the more the better?

  For peach trees, long-term flooding will cause the tree to become weak. Feng Jiancan suggested that due to the high soil moisture and the difficulty of topdressing, spray 0.4% urea + 0.5% potassium dihydrogen phosphate on the leaves. The time and frequency can be based on the fertility of the peach orchard. Determine with the tree vigor; after the tree vigor is restored, add nitrogen fertilizer, phosphorus potassium fertilizer, calcium fertilizer, etc.

  For peanuts, the effect of applying compound fertilizer in combination with intertillage and topdressing will be better. Yin Dongmei introduced that extra-root topdressing is carried out during intertillage.

Every 7-10 days, spray a full-nutrient foliar fertilizer on the foliage.

  Rice needs to be supplemented with restoring fertilizer. Li Junzhou introduced that after being flooded, a lot of nutrients are needed to restore growth. In addition, there is a lot of loss of fertilizer in the rice field. Restoring fertilizer should be applied after 3-5 days of drainage.

Top dressing should be based on quick-acting fertilizer, generally 5 kg of urea per mu or spraying of potassium dihydrogen phosphate foliar fertilizer 1-2 times to improve plant disease resistance and promote rice plants to resume growth as soon as possible.

  Corn must be supplemented with nutrition. Liu Tianxue said that it should be topdressing with intertillage and topdressing with about 20 kg of quick-acting nitrogen fertilizer per mu; if the field is too wet and temporarily unable to enter the field, you can use drones to spray 1% urea+ on the foliage. A 0.2% potassium dihydrogen phosphate aqueous solution is used to supplement nutrients and promote the restoration of normal plant growth.

  7 pests

  Do I just need to fight medicine?

  After the flooding, the humidity in the field is high, and a variety of pests and diseases are prone to occur. For peanuts, corn, melons and vegetables, farmers should investigate and prevent them in time to control the occurrence and spread of diseases.

  But for fruit trees, a multi-pronged approach such as reasonable pruning, fruit bagging, and application of medicines is needed to effectively prevent the invasion of pathogens.

According to reports, storms can cause a large number of wounds to the tree, and pathogens can easily invade through the wounds. After cutting the wounded branches, medicine should be applied to the wound and the cut mouth in time to promote healing and prevent the invasion of pathogens.

  Immature fruit trees should be properly thinned out according to the tree species, tree age, degree of flooding, etc., according to the method of "thinning and retaining the best" to reduce the load of the tree body; many trees will also appear deciduous after flooding. The fruit is directly exposed to the scorching sun, and the fruit surface is prone to sunburn. The fruit bag can be filled to improve the appearance and quality of the fruit, reduce losses, and prevent the spread of pests and diseases.

  For Taoyuan, Feng Jiancan suggested that preventive spraying of fungicides can be used to prevent the occurrence of diseases. You can choose chlorothalonil 800 times solution or carbendazim 600 times solution or thiophanate methyl 1000 times solution, or add a certain amount Of pesticides, such as pyrethroid and so on.

  After the rice is flooded, what kind of medicine is needed?

Li Junzhou suggested that leaf damage, reduced plant disease resistance, and high temperature and high humidity will increase the spread of pests and diseases. Rice blast, sheath blight, rice planthopper, stem borer and other pests are prone to occur in large areas, and pests should be monitored and controlled.

For the prevention and control of rice blast, drugs such as tricyclazole, rice blasting, and kasugamycin can be used.

For the prevention and treatment of sheath blight, hexaconazole, jinggangmycin, benzproconazole and other agents can be used.

For the control of rice planthoppers, buprofezin, imidacloprid, fipronil and other agents can be used.

  8 Replant

  Is it too late?

  Liu Tianxue suggested that for plots that are severely affected and difficult to produce yields, land preparation should be promptly eradicated, and crops with shorter growth periods should be replaced. On the one hand, the soil base fertilizer will be lost with the flood, but it has a limited impact on the soil structure. As long as the farmland water is removed in time and a reasonable topdressing, the next crop will not be affected."

  According to Sun Zhiqiang, in most areas of Henan Province, greenhouse tomatoes, eggplants and peppers can be planted in early August, and cucumbers can be planted in mid-August; autumn and winter fruits and vegetables in solar greenhouses can be planted in late August to late September.

These need to grow seedlings in advance, usually 25-35 days for solanaceous seedlings, and 20-25 days for cucumber and zucchini seedlings.

  For open-field vegetables, it is still too late to plant carrots in early August in southern Henan, and potatoes can also be planted in early and mid-August.

Celery is transplanted in early August and can be harvested in early November.

Other fast-growing leafy vegetables such as lettuce and Chinese cabbage can be sown at any time, generally within 40-50 days to harvest.

  Cabbage, cauliflower, and broccoli can be planted in mid-August, and seedlings must be cultivated 20 days in advance.

For hardy leafy vegetables, coriander can be sown in mid-August, spinach can be sown in mid-to-late August, and garlic seedlings can be planted in mid-to-late August.

  New Beijing News trainee reporter Zhao Lixin