How can corn planting be adapted to local conditions? The ecological conditions in the Southwest region are complex
Editor's note: The ecological conditions in China's Southwest region vary greatly, which also causes large variations in the growth period of corn. The Southwest corn region includes Sichuan, Yunnan, Guizhou, Chongqing, southern Shaanxi, Guangxi, the western hilly areas of Hunan and Hubei, and a small part of Gansu Province. It is the third largest corn-producing region in China. The climate, topography and ecological conditions of this region are very complex. More than 90% of the land is hilly, mountainous and plateau, while river valley plains and intermountain flatlands account for only 5%. The planting patterns are complex and diverse. Corn is mainly spring-sown and summer-sown, with autumn sowing and winter sowing as well. The planting areas range from river valleys at an altitude of a few dozen meters to high mountains at 3,200 meters. The temperature and accumulated temperature differ noticeably among different regions, showing an overall trend of gradually increasing from northwest to southeast. At present, some areas have completed sowing, while some areas are preparing to sow. In response to this situation, how should service work be carried out well? Experts from Sichuan, Yunnan, Guizhou and Chongqing have all made plans. Experts including Liu Yonghong, a scientist in the Modern Agricultural Corn Industry Technology System, Ren Hong, head of the Guiyang Comprehensive Experimental Station, Huang Jimei, head of the Yunnan Qujing Comprehensive Experimental Station, and Yang Hua, head of the Chongqing Comprehensive Experimental Station, answered reporters' questions on how local farmers should carry out spring plowing and production.
Sichuan Slow seedling growth, pay attention to pest control
Reporter: Spring corn sowing in Sichuan Province has basically ended, and corn in most areas is at the emergence to seedling stage. Since March, because rainfall has been low in most corn-producing areas and the daily maximum temperature has been higher than in previous years, drought has appeared in some local areas. How should local farmers respond?
Corn industry system expert: Affected by earlier drought and various other factors, the main problems currently existing in corn production include: weak seedling vigor, slow seedling growth, fertilizer deficiency in some fields, overgrown weeds in the fields, and relatively serious occurrence of underground pests. In response to the above problems, the following technical suggestions are proposed:
Comprehensive control of underground pests. The corn seedling stage is the main period when underground pests occur. Underground pests such as cutworms, white grubs and mole crickets cause relatively great damage. Generally, chemical spraying or spraying the roots and stems is used to control underground pests, mainly to eliminate larvae before the 3rd instar. The selection of chemicals should mainly focus on pyrethroid insecticides and organophosphorus insecticides. A 2.5% deltamethrin emulsifiable concentrate at 2,000 times dilution or a 20% fenvalerate emulsifiable concentrate at 2,000-3,000 times dilution can be used; 2.5% trichlorfon powder can also be used at 1.5-2 kg per mu for dusting, directly sprayed on corn seedlings; or 48% chlorpyrifos emulsifiable concentrate or 50% phoxim emulsifiable concentrate at 1,000 times dilution can be directly sprayed on the root and stem parts of corn seedlings, with the pesticide liquid preferably seeping into the soil, and the water amount per mu is preferably 50-60 kg. In addition, underground pests can also be comprehensively controlled by spreading poisoned soil, manually catching larvae, poisoning bait to trap and kill them, and timely clearing weeds at field edges and corners.
Check seedlings and fill gaps in time. After corn emerges, the emergence status should be checked in time. When missing seedlings or broken rows are found, reseeding or replanting should be done in time. For missing seedlings before the 2-leaf stage, plump seeds can be soaked to promote germination and then watered for reseeding; for missing seedlings after the 2-leaf stage, the soil-bearing transplanting method can be used to fill the gaps, carried out on rainy days or in the evening, watered after planting, and covered with soil to preserve moisture. In addition, two plants can also be left near the missing seedling position to ensure the basic density.
Thin and finalize seedlings at the appropriate time. For fields using manual direct seeding, seedlings should be thinned and finalized at the appropriate time. Thinning is generally carried out at the 3-4 leaf stage, removing weak, white, yellow, diseased, inferior and mixed seedlings; finalizing is generally carried out at the 5-6 leaf stage, retaining strong seedlings according to the planned density, and removing excess seedlings in time to prevent competition for water and fertilizer.
Strengthen chemical weed control. For chemical weed control at the seedling stage, the types of herbicides should be strictly selected, the optimal application period should be grasped, and the dosage should be accurately controlled. After corn sowing and before emergence, pre-emergence herbicides such as acetochlor can be used, with 70 grams of active ingredient per mu mixed with 40-50 kg of water, or 40% acetochlor-atrazine mixture, 200 ml per mu mixed with 50 kg of water, evenly sprayed on the soil surface, which can effectively control annual grassy weeds; when corn seedlings are at the 5-6 leaf stage, corn-specific herbicides can be selected for directed inter-row spraying.
Apply seedling-promoting fertilizer as topdressing. Topdressing at the seedling stage has the effect of promoting roots, strengthening seedlings, promoting leaves and strengthening stalks. When corn seedlings have 5 expanded leaves, 4-6 kg of urea and 5 kg of potassium chloride per mu can be applied as seedling-promoting fertilizer. When topdressing, distinctions should be made, applying fertilizer with water, with heavier application to small and weak seedlings, and attention should be paid to side deep application, promoting “small seedlings catching up with large seedlings and weak seedlings catching up with strong seedlings”, so as to achieve balanced growth of corn at the seedling stage.
Cultivate at the appropriate time. Timely cultivation at the corn seedling stage can play the role of “controlling the aboveground and promoting the underground”. Cultivation should be “shallow beside the seedlings, deep in the middle”, both removing weeds and not pressing down the seedlings, with a depth generally of 3-5 cm.
Chongqing Cultivation in shallow hilly areas, rush sowing in high mountain areas
Reporter: The ecological differences among Chongqing's corn production areas are great. Sowing has been fully completed in shallow hilly and flat-basin areas, and corn growth is at the seedling stage or has entered the jointing stage. It is understood that due to earlier drought and little rain, seedlings in most areas are relatively weak. However, sowing has not yet been carried out in mountain areas above 800 meters. How should farmers carry out production?
Yang Hua, head of the Chongqing Comprehensive Experimental Station: Corn sowing and seedling-stage management in Chongqing are both in intense progress. At present, the following production measures should be taken:
Because corn seedlings in shallow hilly and flat-basin areas are affected by drought and grow weakly, cultivation and weeding should be carried out in time, or corn-field-specific herbicides should be used for weed control, and clear manure water should be applied to promote seedlings. Generally, 5 kg of urea per mu mixed with 750 kg of pig manure water is used to drench the planting holes. At the jointing stage, cultivation, hilling and fertilization for jointing and booting should be done well. Fertilizer should be applied into the holes about 15 cm away from the corn plants, generally about 10 kg of urea, and then covered by cultivation and hilling, thickening the soil layer around the roots of the corn plants to form high ridges of about 10-20 cm, so as to prevent corn lodging caused by wind and rain and to use the rainy period for drainage.
In high mountain areas where corn sowing has not been completed, sowing should be sped up; at the emergence stage, control of underground pests should be strengthened. If underground pests occur, insecticides such as Decis at 800 times dilution can be sprayed on the base of seedlings to control underground pests at the seedling stage, and seedlings should be checked and replanted in time to ensure the density for increasing yield.