Impact of Waterlogging on Corn and Technical Recommendations for Post-Disaster Management

According to information released by the provincial meteorological observatory, from 08:00 on July 18 to 14:00 on July 20, most areas of our province experienced rainfall weather processes. The average rainfall in the rainfall area was 114 mm, and rainfall in most areas of Baoding, Langfang and areas south of them was generally above 100 mm (torrential rain), among which 1,170 townships received rainfall exceeding 100 mm (heavy torrential rain), and in particular, in southwestern Baoding, western Shijiazhuang, western Xingtai, and central and western Handan, 289 townships received rainfall exceeding 250 mm (extraordinary torrential rain). Among them, in Ci County, Jingxing, Zanhuang, Yuanshi, and Pingshan, a total of 9 stations recorded rainfall exceeding 600 mm. Because the intensity of this precipitation process was relatively high and it was accompanied by strong winds, waterlogging or wet injury occurred in corn fields in some areas, and lodging of varying degrees occurred in some fields.

I. Harm of waterlogging and wet injury to corn

In plots where waterlogging occurs, because corn plants are soaked in water, root poisoning can be caused in a short period, leading to rot of some roots, and prolonged soaking leads to root asphyxiation and death. In plots where wet injury occurs, root vigor is generally reduced, the ability of plants to absorb water and nutrients is weakened, and plant growth and development are slowed. When waterlogging disasters occur, because the soil is saturated with water and the soil is soft, if strong winds occur at the same time, lodging is extremely likely to occur. The resistance of corn to waterlogging and wet injury is related to the growth stage; generally, the larger the plant, the stronger its resistance to waterlogging and wet injury. At present, most spring-sown corn in our province has entered the tasseling and pollen-shedding stage, and its resistance to waterlogging and wet injury is relatively strong; however, summer-sown corn is currently at the small funnel stage, and its resistance to waterlogging and wet injury is relatively weak.

II. Field management techniques after waterlogging disasters

1. Drain accumulated water from the field. For plots with obvious accumulated water in the field, every possible method should be used to drain the accumulated water from the field and reduce the time during which corn plants are soaked. Ditches, field-edge drainage ditches, and other facilities should be fully used, or drainage ditches can be dug manually; where conditions permit, machinery and pumps and other facilities can be used for drainage. If there is a large amount of mud on the plant leaves, it should be washed off promptly during drainage to increase the leaf area receiving light and promote the restoration of normal photosynthetic capacity.

2. Intertillage to reduce soil moisture. For plots where accumulated water in the field has already been drained, or plots that have only suffered wet injury, intertillage and hoeing can be carried out promptly when the field can be entered. This is not only conducive to reducing soil moisture, improving the rhizosphere environment, and promoting the recovery of root growth, but also breaks up possible soil compaction caused after rain. During intertillage, be careful not to damage newly grown aerial roots. For plants that are tilted or lodged, the plants can be righted as appropriate and soil can be gathered around the base and compacted, which can both prevent secondary lodging and promote the development of corn aerial roots.

3. Supplementary application of quick-acting fertilizer. Corn harmed by waterlogging and wet injury generally shows yellowing leaves and slowed growth and development. After the disaster, quick-acting fertilizer should be applied as soon as possible to promote the recovery of corn plant growth. In view of the fact that summer corn in our province will enter the large funnel stage, it is recommended to combine topdressing at the large funnel stage with post-disaster fertilizer management. For plots that have not yet been topdressed with ear fertilizer, 20-25 kg of urea can be applied per mu; for plots that have already been topdressed with ear fertilizer, an additional 5-10 kg of urea can be applied per mu. When topdressing, be sure to open furrows and apply deeply, or apply in combination with intertillage, and avoid broadcast application. Where conditions permit, promptly use a foliar topdressing solution of 0.5% urea + 0.2% potassium dihydrogen phosphate when the weather clears after rain; when spraying, be sure to ensure that the urea and potassium dihydrogen phosphate are completely dissolved and mixed evenly, so as to avoid leaf scorch caused by excessively high local concentration and aggravation of the disaster; generally it can be sprayed twice consecutively at an interval of about 7 days.

4. Do a good job in post-disaster disease and pest prevention and control. After being affected by the disaster, plant growth and development are poor, and the ability to resist diseases and pests is reduced; in addition, after waterlogging disasters, because field humidity is high and temperature is high, outbreaks of diseases and pests are extremely likely to be induced. For summer corn, special attention should be paid to the prevention and control of diseases such as brown spot, root rot, and top rot; relatively high field humidity after rain is conducive to the hatching of corn borers, and corn borers are the key targets for pest control after disasters. For spring corn, special attention should be paid to strengthening the prevention and control of diseases such as northern leaf blight and pests such as corn borers. In summer sowing areas, spring corn sown in early spring should be monitored for the occurrence of bacterial wilt when the weather clears suddenly after rain. In addition, under conditions of excessive rainwater and excessively high soil moisture, weeds are likely to grow in the field, and weed control in the field should also be strengthened after waterlogging disasters.

III. Management techniques for lodged field plots

For plots in waterlogged disaster areas where lodging also occurred, corresponding field management measures can be taken according to the specific circumstances of the lodging.

1. For spring-sown corn or plots that have already entered the tasseling and pollen-shedding stage, lodged plants have basically lost the ability to restore upright growth on their own, so after lodging they need to be lifted manually and fixed with soil.

2. Summer corn is currently at the small funnel stage, and after lodging generally no special management measures are needed; it will slowly restore upright growth on its own after rain.

3. For summer-sown plots that were knocked down by floods, part of the plant leaves are often buried by silt, making it difficult for the plants to restore upright growth on their own. In such plots, after the disaster, the mud on the leaves should be removed as soon as possible, or the leaf portions buried by silt should be cut off with a sickle to help the plants restore upright growth as soon as possible.

4. For summer-sown corn in which some sediment has entered the whorl after lodging, this often makes it difficult for subsequent leaves in the whorl to emerge. In such plots, after the disaster, the portion of the whorl leaves containing sediment can be cut off with a sickle to help subsequent leaves emerge. However, the fewer leaves cut off, the better, and try not to damage the plant's apical growing point.