Detailed Explanation of Key Management Techniques for Corn at the Ear Stage
The ear stage of corn refers to the period from jointing to tasseling, and is a stage in which vegetative growth and reproductive growth proceed together. During this period there is both vigorous growth of roots, stems and leaves, and the differentiation and development of the female and male ears; it is the period of the fastest development, the largest growth amount, and the greatest demand for fertilizer and water in the entire life of corn. The main goals of field management are: short, thick and plump basal internodes, and good differentiation of the female and male ears. Individual plants grow robustly, and the population develops moderately and uniformly. The main management measures are as follows:
1. Scientific topdressing. The ear stage of corn is a period when vegetative growth and reproductive growth proceed together. During this period, the speed and amount of nutrient absorption increase rapidly. In the more than 20 days of the ear stage of summer corn, nitrogen absorption accounts for 76% of the whole growth period, and the absorption of phosphorus and potassium accounts for about 63% of the whole growth period. This shows that the ear stage is an important period for topdressing corn. All plots that have not been applied with base fertilizer or have an insufficient amount of base fertilizer should be topdressed at the ear stage of corn. The best time for topdressing should be chosen at the large flare stage 10-15 days before tasseling, and if the weather is dry it can be done together with watering. Compared with topdressing at the early jointing stage, topdressing at this stage has two major advantages: (1) When the fertilizer is applied to the soil and takes effect, the basal 1-3 internodes of corn are basically fixed in length, reducing the probability of later lodging (early topdressing easily promotes excessive elongation of several basal internodes); (2) It meets the growth needs of corn in the middle and late stages, reduces the probability of fertilizer deficiency in the later stage, and lowers the degree of bare tips and missing grains on the female ear. The types of topdressing are mainly nitrogen and potassium. 30-40 jin of urea can be applied; if no potassium fertilizer was applied as base fertilizer or the amount of potassium fertilizer applied was insufficient, 20-30 jin of potassium chloride or potassium sulfate should also be added to meet the growth needs of corn and improve the lodging resistance and disease resistance of the stalks.
2. Do a good job of chemical regulation. The results of experiments in recent years show that spraying plant growth regulators at the ear stage of summer corn not only has an obvious yield-increasing effect, but also has an obvious lodging-prevention effect. When the 7th-11th leaves of corn have unfolded, foliar spraying of 30% corn Jindele or 2% Darfeng can effectively shorten the length of the basal 1-3 internodes and increase the number of aerial root layers, thereby achieving the purpose of preventing lodging and increasing yield.
3. Pay attention to the prevention and control of diseases and insect pests. The main diseases at the ear stage of summer corn are brown spot disease and stalk rot. For brown spot disease, when corn has 6-8 leaves, 20% triadimefon can be selected and added to foliar fertilizers such as potassium dihydrogen phosphate for spray control; for stalk rot, before and after tasseling, 10% Shuangxiaoling at 200 times liquid can be sprayed for prevention. The main insect pests at the ear stage are corn borer and sugarcane mealybug. Corn borer generally occurs at the small flare stage and the large flare stage. When the control threshold is reached, 2.5% phoxim granules can be scattered into the heart leaves for control, with 1-3 grams per plant, and the control effect is relatively good. In plots where sugarcane mealybug occurs, 40% phoxim emulsifiable concentrate and other agents can be selected and diluted 500-1000 times before spraying at the base of corn seedlings or drenching the roots for control.
4. Water in case of drought, drain in case of waterlogging. The large flare stage and silking stage of corn are critical periods for water demand. Once drought occurs, watering should be done in time to promote the differentiation of female and male ears and the formation and development of tassel pollen. This period coincides with the rainy season, and extreme abnormal weather such as heavy rain is very likely to occur. In case of waterlogging, accumulated water should also be drained in time to ensure the normal growth of corn.
5. Remove small and weak plants in time. Due to sowing, soil fertility, reseeding, disease and insect damage and other reasons, after corn jointing, some small and weak plants appear in the field. They usually do not bear ears or bear very small ears, not only occupying a certain amount of space, consuming fertilizer and water, and affecting the growth of healthy plants, but also easily causing shading and lodging when exposed to wind and rain. Therefore, they should be removed as early as possible to ensure the uniformity of the population.
6. Control field weeds. In plots where weed control was neglected in the early stage, resulting in lush weed growth in the field, weeds should also be removed in time. Where field weeds are relatively lush, first use a wooden rake manually to pull the weeds down, then select paraquat and wear a protective cover for spray control. The equipment selected should minimize dripping, overflowing, running and leaking, so as to avoid affecting corn.