Several problems that should be paid attention to in the late management of corn and their countermeasures

In 2016, the climate of Dali Prefecture was contrary to that of previous years. Rain Water was relatively abundant. Rainfall in various regions came early, frequently and violently. Corn planting in mountainous, semi-mountainous and dam areas was generally earlier, and the area was also expanded compared with the previous year. As of June 20, the planting progress of corn in the whole state was 1.7127 million mu (2015, 1.6679 million mu). At present, the growth of maize in most areas has entered the jointing and booting-heading stage, and some of them have entered the filling stage, which has generally grown well and grown healthily, which has laid the foundation for a bumper harvest of corn in the whole state this year. However, because there are too many Rain Water, there are also some unfavorable factors: first, there is basically no squatting seedlings in the dam area, and the growth is high and prosperous; second, the humidity in the field is too high, and the low-lying fields are waterlogged and waterlogged, which is easy to lead to premature senility and various diseases; third, the general lack of light during the growth of corn affects the photosynthetic efficiency; fourth, the general temperature is low, the accumulated temperature is insufficient, and the growth period of corn is lengthened accordingly. Starting from the corn core demonstration area of Dali City, Yunnan Modern Agricultural Maize Industry Technology system Dali Experimental Station, and throughout the seedling situation of the whole state, put forward the following measures or suggestions for the production management of corn in the middle and later stage for reference.

First, ploughing and cultivating soil to prevent lodging, clearing ditches and drainage to prevent waterlogging

Due to the large number of Rain Water, he skipped squatting seedlings at the seedling stage and grew fast in vegetative growth. Now, when the plant enters reproductive growth, it grows tall rapidly, and its plant height and position are significantly higher than those in previous years. According to the investigation and comparison of seven varieties of Yunrui 505, Yunrui 999 and Yunrui 407 in Wanqiao Baimu core demonstration zone of Dali corn test station, the plant height of the same variety increased by 28-68cm, 6-37cm, 16.4% and 20.7% higher than that of last year, respectively. This situation is representative, so attention should be paid to prevent the risk of continuous overcast and rain lodging in the late filling period. At present, in order to enhance the resistance of plants, we can focus on three measures: (1) for fields that are still in the jointing stage, such as varieties with high plant height or high fertilizer and water fields, spray dwarf element properly before heading, so that plant height and ear position are reduced, stalks are stout, and plant lodging resistance is enhanced. (2) ploughing and cultivating soil. In plastic film cultivation, plastic film should be removed in time, weeding, combined with ear fertilizer, focusing on deep ditches to cultivate soil, strengthen the soil at the base of the stem, assist plants to prevent toppling; (3) clear ditches and protect the ridges in the field, keep the ditches unblocked, keep the ridges intact, prevent waterlogging in the field, maintain soil permeability, ensure energy drainage and irrigation, facilitate the deep growth of roots, and prevent premature senescence of roots.

Second, remove ineffective plants, tillers and diseased plants so that healthy plants can grow fully.

When ploughing, pulling out shrinking plants, inferior plants and diseased plants in the population, most of these seedlings do not form effective panicles, even if they have spikes, and their contribution to yield is negligible. On the contrary, striving for fertilizer and glory in the field affects the growth of neighboring normal plants; some varieties will produce a large number of ineffective tillers due to their own characteristics and sufficient fertilizer and water, which will consume soil energy and plant nutrition, and should be pulled out in time to ensure the healthy growth of the main stem. In addition, the obviously seriously diseased plants should be removed and buried deeply or taken out of the field to avoid the breeding and spread of the disease.

Third, increase the application of fertilizer to ensure the supply of nutrients, promote strong stalks and large ears, and increase grain weight.

1. Heavy application of jointing and booting fertilizer. The booting stage of maize (jointing-male loose powder) is the period of both vegetative growth and reproductive growth of maize plant, the peak period of fertilizer demand, and the key stage to determine the ear size and grain number. Through the application of fertilizer, many important goals can be achieved, such as large root thickness, strong stem, broad and thick leaves, thick green color, large ear, many grains and so on. This period can be judged according to the number of leaves: 8-9 leaves of early-maturing species and 10-11 leaves of middle-mature species. During this period, management should emphasize timely re-application of panicle fertilizer, according to the principle of more application of thin field, less application of field fertilizer, more application of weak plants and less application of strong plants, mainly N fertilizer and K fertilizer, generally topdressing urea 25-35 kg per mu + potash fertilizer 10-15kg, or high efficiency compound fertilizer 35kg-45kg to ensure adequate plant nutrient supply.

2. Supplementary application of flower and grain fertilizer. For the fields that have entered the pollination period, a certain amount of flower and grain fertilizer should be applied according to the growth of seedlings. Generally, urea 10-25 kg + potassium fertilizer 10kg per mu was applied to prolong the functional period of upper panicle leaves and grain filling rate, reduce bald tip and increase grain weight.

Fourth, strengthen the investigation of diseases and insect pests in the field and control them in time.

The main diseases in the middle and later stages of corn production in our state are: corn gray leaf spot, large leaf spot, small leaf spot, rust, ear rot, insect pests, corn borer, aphids and so on. The climate of this year is objectively conducive to the occurrence of all kinds of diseases, especially gray spot, rust, and ear rot, and all localities should pay attention to it. They should often conduct in-depth field investigations, grasp the changes in the disease and insect situation, and take universal control measures in a timely manner to control diseases and insect pests at an early stage. Specific prevention and control measures are as follows:

1. Corn gray leaf spot: the disease has a long incubation period and should be prevented and treated in advance. In the early stage of gray spot infection (in the stage of big trumpet mouth to early filling), 25% propiconazole is used, or difenoconazole, 50% carbendazim wet powder, methyl carbendazim, mancozeb and so on are used in the early stage of gray spot infection (in the stage of big trumpet mouth-filling), once every 10 days, for 2 consecutive times.

2. Corn leaf spot and small leaf spot: at the initial stage of the disease, 50% carbendazim wettable powder, or 70% thiophanate, mancozeb, 80% Xinwansheng, paracetamol, Shigao and other sprays were used for 1-3 times, and the second control was made at an interval of 5 colors for 7 days.

3. Corn rust: at the initial stage of the disease, 20% triadimefon EC, or 50% powder rust clear, 12.5% diniconazole, 25% powder rust Ling wettable agent, continuous prevention and control 2-3 times, once every 10 days.

4. Corn ear rot: during the male silking stage, spray the female ear and lower stems and leaves with 25% enemy demulsified oil, or 50% carbendazim wettable powder, 70% methyl topiramate wettable powder.

5. Corn borer: big trumpet stage, using 10% cis-cypermethrin emulsion and 12% methylvitamin. Fipronil emulsion is sprayed in the heart leaves.

6. Corn aphids: from jointing and booting stage to male silking stage, 40% dimethoate EC, 50% aldicarb wettable powder and 10% imidacloprid wettable powder can be sprayed for 1-3 times.

5. harvest at the right time, drying and threshing in time to ensure the increase of production and income

The bracts of corn begin to turn yellow, indicating that they have entered the mature stage. After maturity, if the weather is good, the varieties are resistant to ear rot and under the condition of no effect on cropping, the harvest can be appropriately prolonged for 5-7 days, so that the grains can be completely finished, which is beneficial to increase the 1000-grain weight. After harvest, timely ventilation, drying, threshing, in order to prevent mildew and insect erosion caused by yield loss, to ensure production and income increase.

Finally, the management measures in the middle and later period are summarized into six sentences:

Control high soil to resist lodging, clear ditches and protect ridges to prevent waterlogging

Except for tiller disease and inferior plant, healthy plant can grow freely.

Heavy application of panicle fertilizer to replenish flower fertilizer for sufficient nourishment and distribution to promote spike and grain

The investigation of diseases and insect pests should be carried out deeply, and the cost should be saved, the effect should be improved and the prevention should be popularized as soon as possible.

In the right time to harvest and dry frequently, pay attention to reducing the loss of molds and insects.

Agricultural management is diligent, and scientific and technological measures ensure the "three increases".