Cause analysis and control methods of wheat growth before overwintering

Wheat pre-winter management

The vigorous growth of wheat before winter is very harmful, first, the plant frost resistance is reduced, and it is easy to be frozen in winter and early spring; second, the occurrence of diseases and insect pests is serious; third, it is easy to lodge in the later stage; fourth, the soil nutrients are consumed too much, and it is easy to lose fertilizer and senescence prematurely. Therefore, it is necessary to earnestly strengthen the management of prosperous and long wheat fields, control prosperity and become strong, so as to achieve strong seedlings to survive the winter.

Generally speaking, the seedling age of semi-winter wheat varieties before winter is more than 7 leaves and 1 heart, spring varieties have more than 6 leaves and 1 heart, the leaves are long and large, the leaf sheaths are long and thin, the pseudostems are long and flat, the leaves are scattered, the plants are erect and high, and the total number of tillers of the population is more than 800000 per mu. The fields with closed ridges and no rows can be regarded as prosperous wheat fields. There are the following management measures for prosperous and long wheat fields, which can be selected in accordance with local conditions.

I. the reasons for the prosperity and growth of wheat

1. It's too early to sow. The soil moisture of summer corn is better after harvest, and most farmers use soil moisture sowing, focusing on sowing in the first ten days of October. Due to the high temperature after sowing, early tillering of wheat seedlings, more tillers and rapid ontogeny, the leaves are narrow and slender, the population is dense and crowded, and the more they grow, the more prosperous they become.

two。 There is a large amount of sowing. Some farmers do not have a good grasp of the characteristics of wheat varieties, do not reasonably determine the sowing amount according to the characteristics of the varieties and sowing date, and blindly increase the sowing rate under the influence of the traditional concept of "money to buy seeds but no money to buy seedlings". The average farmer sows 15-20 kilograms per mu, and some even more. After the wheat grows and tillers, the wheat seedlings are crowded and flourish.

3. Overfertilizing. Some farmers excessively apply nitrogen fertilizers such as urea or ammonium bicarbonate in wheat fields with better water and fertilizer conditions, resulting in excessive growth of wheat seedlings and serious winter prosperity.

Second, the harm of wheat prosperity.

1. Winter and early spring are vulnerable to frost damage. Because the vigorous growth can easily lead to the acceleration of the growth process of wheat, the growth of wheat seedlings is tender, the number of stems is large, and the sugar stored in tillering nodes is insufficient, especially after the young spikes differentiate into two-edge stage, the ability of frost resistance is obviously weakened, and they are extremely vulnerable to freezing injury in winter and cold in late spring. the light ones died of dead leaves and the heavy ones froze to death.

two。 It is easy to cause lodging in the middle and later stage. Prosperous seedlings have luxuriant growth, more tillers, large leaves, poor ventilation and light transmission, weak plants, long basal internodes, thin stem walls, less dry matter accumulation, poor root development, less secondary roots and shallow entry into the soil. If there are more Rain Water in spring or when there is a storm in the middle and later period, root fall and stem fall will occur at the same time, resulting in heavy losses.

3. It is prone to diseases. Under the condition of high temperature in autumn and winter, the pathogen overwintering base is large, coupled with the poor quality of prosperous seedlings and the decline of disease resistance, it is easy to cause diseases such as sheath blight, powdery mildew and root rot under suitable conditions (rainy spring, lack of light).

Third, how to determine the prosperous and long wheat field

Whether wheat is prosperous or not before overwintering can be judged by individual morphology, population status and growth index. If you look closely at the wheat seedlings, the leaves are long and large, the leaf sheaths are long and thin, the pseudostems are long and flat, the leaves are scattered, and the plants are very tall; from a distance, the wheat fields are lush, the wheat fields are ridged, and no rows are seen; the wheat fields with a total number of tillers of more than 700000 can be regarded as prosperous wheat fields.

IV. measures to control the prosperity of wheat

1. Early and middle tillage cut off part of the root system. When it is determined that the wheat seedling is growing vigorously and has the trend of vigorous growth, the wheat field should be ploughed early and deep, hoe 6-8 cm deep between the wheat rows, cut off part of the root system and reduce the absorption of nutrients, so as to control the overgrowth of the aboveground part, which is beneficial to the cultivation of strong wheat seedlings.

two。 Late watering winter water. Winter irrigation is too early, because the temperature is relatively high, can accelerate the growth of wheat seedlings, easy to form wheat growth. The winter irrigation time of wheat field is generally controlled before and after Lesser Snow, and the daily average temperature starts at 8 ℃-7 ℃ and ends at 5 ℃-4 ℃. The field standard is "freezing at night and dissipating in the day". It is necessary not only to ensure that wheat can survive the winter safely, but also to prevent wheat from flourishing.

3. Repression. It is found that the wheat fields with signs of vigorous growth can be suppressed timely according to the situation after tillering, and the wheat seedlings can be damaged by suppression, which can temporarily delay the growth of wheat leaves and leaf sheaths, control the excessive growth of tillers, and at the same time break bumpy grains, close cracks, preserve soil moisture, and promote root system development. Stone or machinery can be used to suppress it after 10:00 in the morning in fine weather and when there is no frost. The number of suppressions depends on the situation of the seedlings. Generally speaking, the wheat fields of prosperous seedlings can be suppressed 1-2 times. During the crackdown, attention should be paid to going in one direction and should not be suppressed repeatedly.

4. Chemical regulation. The effect of spraying paclobutrazol on prosperous wheat seedlings is remarkable. 40-50 grams of 15% paclobutrazol wettable powder per mu is used to explain that spraying water diluted according to the ratio can dwarf the plant, widen and thicken the leaves, enhance photosynthesis, prevent overgrowth, promote tillering and shorten the stem nodes. The concentration of pesticides must be strictly controlled according to the instructions, because this kind of growth regulators are different from pesticides and are more sensitive to concentration. Once drug damage occurs, it is difficult to take effective methods to reverse.