What is the impact of "late spring cold" on agricultural production?

Since the beginning of April, under the influence of strong cold air, there has been a large-scale precipitation in central and eastern China, accompanied by a sudden drop in temperature from north to south, in which there is an obvious "late spring cold" weather in some areas of the middle and lower reaches of the Yangtze River. So, what is the reason for this weather this year? What is the impact of "late spring cold" on agricultural production? How to prevent the harm caused by this kind of weather? The reporter interviewed Niu Ruoyun, a senior engineer at the research level of the National Meteorological Center, and Song Yingbo, a senior engineer at the Agricultural Meteorological Center of the National Meteorological Center.

According to experts, "late spring cold" refers to the weather phenomenon that the temperature rises rapidly in the early spring, while the temperature is low in the later stage. It is important to note, however, that this definition is only a conventional definition. Because China has a vast territory, different climates and different crops, the values of meteorological factors affecting crop growth are different. For example, Hunan has its own definition of "late spring cold", and Yunnan also has the definition of "late spring cold" in Yunnan area. the number of specific indicators depends on the specific conditions of each region.

The meteorological index of "late spring cold" commonly used in agriculture in southern China means that the daily average temperature drops below 12 ℃ and lasts for 3 to 5 days. Take this weather event as an example, if the value of meteorological elements in the middle and lower reaches of the Yangtze River reaches this target, it can be determined that there is a "late spring cold" in the corresponding area.

So, what impact will the "late spring cold" have on current agricultural production?

According to experts, under the background of rising temperature, there is a sudden "late spring cold", and the range of cooling is relatively large, which will have a certain adverse impact on the growth of crops, especially on early rice.

In this cooling process, early rice in the middle and lower reaches of the Yangtze River is in the stage of sowing and raising seedlings. If preventive measures are not taken well, the sudden "late spring cold" will cause early rice to rot. In addition to early rice, cotton at sowing time is also vulnerable, and there may be rotten seeds and dead seedlings. As last year's autumn sowing crop, rape flowering and pollination will also be affected, which will lead to a reduction in yield in the later stage.

If you want to put it in order, the one most affected by the "late spring cold" is early rice, then cotton in sowing time, and then rape.

During the "late spring cold" weather, the average temperature in South China did not drop below 12 ℃, and most of the early rice in South China had been in the period from three leaves to transplanting and returning to green, and cooling had no obvious effect on the growth of early rice. In the north, although the daily average temperature in many areas is lower than 12 ℃, because the local crops are different from those in the middle and lower reaches of the Yangtze River, the index to measure whether it is "late spring cold" is different, so the index of 12 ℃ can not be simply applied, but it can be used as a reference index. For the northwest, North China and Huang-Huai region, when the daily minimum temperature is lower than 2 ℃, there will also be "late spring cold" weather, which may lead to frost damage to winter wheat, fruit trees and vegetables. In this way, the impact of this cooling on crops in the northern region is relatively small.

Experts suggest that corresponding measures can be taken to prevent the "late spring cold" in agricultural production. The seedling raising of early rice can be covered with greenhouse film. At present, there are two main planting methods of early rice, one is to sow seeds directly in the field, the other is to raise seedlings in small fields, and then transplant the seedlings to the field. When the "late spring cold" comes, if the early rice is still in the seedling-raising period, the greenhouse film of early rice seedlings needs to be strengthened, and the conditional areas can be covered with double-film thermal insulation to protect seedlings; at the same time, phosphate fertilizer should be properly sprayed before cooling to enhance the stress resistance of rice seedlings. prevent rice seedlings from rotting and rotten seedlings caused by cold air.

Direct seeding early rice should take defensive measures according to local conditions, and those who have not yet soaked seeds should postpone sowing to avoid rotten seeds and seedlings caused by low temperature, overcast and rain; rice seeds that have not been soaked should be thinned and sown in time when the weather is improving; the rice fields that have been sowed should strengthen drainage to prevent long-term flooding from causing rotten roots and buds; and rice fields that have emerged should be properly irrigated to protect seedlings during the coming of low temperature, overcast and rain.

It is expected that from mid-April, the power of cold air affecting China will weaken, and the temperature in the central and eastern regions will rise significantly, so that the "late spring cold" weather will be improved. But this weather process has taught a practical lesson to all aspects of society, especially agricultural production. At present, in terms of the whole country, spring will continue for some time, and the relevant management departments still need to accurately understand the characteristics and hazards of the "late spring cold" weather, and prepare for the occurrence of cooling weather in spring. in order to minimize the impact of adverse weather on agricultural production.