Cold dew hazard late rice expert support defense

According to the data of the Laibin Meteorological Bureau of Guangxi Province, the city has experienced low-temperature and rainy weather with a daily average temperature lower than 20 °C since September 30, and it lasts for a long time. Especially since October 3, the daily average temperature is less than 18 °C. Before October 7, the city still maintained low temperature and rainy weather, and the cold dew wind weather lasted for more than 8 days, and its intensity was rare for 10 years. In order to effectively reduce the damage of cold dew and ensure the safety and maturity of late rice, relevant technical measures are proposed for the reference of farmers.

Cold dew is one of the major meteorological disasters in the late growth period of southern rice. Every year before and after the autumn cold dew, it is the key period for the heading and flowering of late rice in South China. At this time, if it is caused by low temperature hazard, it will cause empty shells and glutinous grains, which will lead to production reduction.

There are three stages in the growth stage of late rice that are sensitive to low temperature: one is the panicle differentiation stage (25-30 days before heading); the other is the pollen mother cell meiosis stage (10-15 days before heading); the third is the heading flowering stage. . Among them, the chance of being damaged by cold dew in the flowering stage is relatively large, and the probability of meiosis is less affected by low temperature, but the damage is heavier after encountering, while the young panicle differentiation period is basically not affected by low temperature. In the meiosis of pollen mother cells and the initial stage of microspores, when the average daily temperature is lower than 20 °C or the daily minimum temperature is less than or equal to 17 °C, the physiological activities of rice encounter obstacles, causing grain deformities to form empty shells. The low temperature strength increases, the number of days continues to increase, and the hazard is significantly aggravated. During the rice heading and flowering period, the average daily temperature lasted for more than 3 days and was lower than 18-20 °C, and the japonica rice was damaged. The average daily temperature lasted for more than 3 days and was lower than 20-22 °C, and the japonica rice was damaged. The vast majority of late rice varieties in Laibin City are japonica rice.

The following five measures are proposed to strengthen the prevention of cold dew or to mitigate the hazards of cold dew:

The first is to increase the temperature of deep water. Before the invasion of the cold dew, the field that has not yet eared or started the ear, and the deep water protection "fetal" of 5 cm or more can increase the surface temperature of 1-3 °C. If the temperature is low, if it can be done in the night, the temperature increase effect is better.

The second is foliar topdressing. Due to the high intensity of cold dew, late rice growth is prone to premature aging. After fine weather, it is necessary to apply fertilizer in time. Generally, urea is used as 5-7.5 kg + potassium chloride 5 kg/mu, and at the same time, foliar fertilizer is applied. 100-150 grams of potassium dihydrogen, plus 45 kg of leaf spray can reduce the "cold wind" hazard and improve the seed setting rate.

The third is to properly spray the regulator. Under the influence of cold dew, the rice is slow to shoot, and it can be sprayed with about 1 gram per mu in the beginning of the earing stage, and sprayed with 45 kg of water to accelerate the heading progress. It can be used for about 3 days in the early stage, reducing the necking phenomenon and reducing Empty rate. If the head is not started before the cold dew winds, it can't be sprayed. After the temperature rises, it can be sprayed depending on the situation.

The fourth is the foliar spray to increase the humidity. The cold dew came at 9 o'clock in the morning before rice flowering and at 3 o'clock in the afternoon. After the rice was harvested, the field was artificially sprinkled, and stopped when the temperature rose. It could reduce the dryness of the leaves and prevent the pollen and stigma from drying up and promoting pollination.

The fifth is to strengthen the prevention and control of rice diseases. Special attention should be paid to the prevention and control of bacterial leaf streak and rice bacterial blight in rice. At the heading stage of rice, 20% chloroprene WP can be used in each batch of 100-125 g, or 90% bismuth is 125 g, or 10 million units of agricultural use. 10 grams of streptomycin, or 5 grams of potassium permanganate plus an appropriate amount of salt, 50 kg spray with water, have a certain effect. According to the test performance, the milk-type copper bactericide green milk copper developed and produced in recent years is a promising new pesticide variety for controlling bacterial leaf streak in rice. In the epidemic period, 100 ml of 12% green milk copper emulsifiable concentrate per acre is sprayed with 500 times of water, and once every 3-5 days, the drug is administered twice. Application of disease prevention can be combined with spraying foliar fertilizer.

(水蓉)