Changsha City is in the transitional season of cold and warm air flow in March and April, with frequent cold air activities and low temperature and rainy weather. It often causes the rotten seeds, rotten cockroaches and dead seedlings of early rice, which seriously affects the planting area of ​​double-season rice and the total grain output throughout the year, resulting in waste of seeds, rotten seeds, delayed seasons, planned failures, and passive throughout the year.
"One year's plan lies in the spring" and "six months of good", which shows that mastering the time and cultivating the strong and strong is an important part of capturing the high yield and harvest of double-season rice. To this end, the agro-meteorological conditions of the double-season early rice sowing period in Changsha City in 2012 were analyzed for reference.
I. Agro-meteorological conditions for the needs of early rice seedlings
Rice seedlings need five main conditions: sunlight, heat, moisture, oxygen and nutrients. The germination of embryos is affected by water, temperature and oxygen. After sowing, there are further requirements for light and nutrients.
1. Moisture: Water is the life of a plant. Seed germination begins with the absorption of water. The water absorption of the seed reaches more than 22% of its own weight. The enzyme starts to move, promotes the decomposition of starch and protein, and the life activity begins. Germination begins when the amount of water absorbed reaches 25% of the weight of the seed. When the water temperature is 13-15 ° C, soaking seeds for 3-4 days can germinate.
The seeds are immersed in water and germinated and then rooted. Under the moist conditions of the soil, the buds grow after the roots. Therefore, long-term deep irrigation after sowing will result in short bud roots, resulting in floating roots, inverted buds, and rotten cockroaches. If you use ventilated fields and humid irrigation, the seedlings are rooted and fastened, the root system is developed, the roots are deep and buds are short and thick, the cold resistance is improved, and the rotten sputum is less.
After the emergence of the third true leaf of the seedling, the required water is increased, and the aeration tissue of the seedling is gradually formed, and the flooding in the field does not hinder the breathing of the root system. Therefore, the frequent watering of the cover mud is beneficial to the root system to absorb nutrients to enhance photosynthesis, and at the same time reduce the heat loss in the mud, and has the function of preventing cold and heat.
2, heat (temperature): rice is a kind of warm crop, the seed needs to be higher temperature when breaking the chest, the lowest is 10-12 ° C, the most suitable is 25-30 ° C, the higher the temperature in a certain range, the speed of germination The sooner. However, the maximum temperature should not exceed 40 ° C, the high temperature time is too long, the respiration is too strong, alcohol poisoning will occur, the seed germination will be inhibited, and the burning phenomenon will occur (the soaking time of water temperature 50-54 ° C does not exceed 10 minutes).
The suitable temperature for the seedling rooting needle is 17-18 °C, the temperature can be normal growth above 15 °C, and the seedling can not be produced below 10 °C. The number of days from the sowing of rice to the emergence of seedlings is proportional to the temperature. When the daily average temperature is 10-12 °C, it takes 6-13 days for sowing to emergence; 6 days for 12.1-15 °C; 4-7 days for 15.1-19 °C; and 2-4 days for 19.1-23 °C. After the three-leaf rice, the cold resistance is the weakest, the optimum temperature is 20-25 °C, and the minimum growth temperature is 11-12 °C. In the long-term low temperature and rainy conditions, the respiration is long-term at the lowest point, the root buds almost stop growing, the photosynthesis is also very weak, and the nutrients in the endosperm have been basically consumed, the cold resistance is very weak, the roots are young, still can not Absorbed enough nutrients from the soil to supplement, so the metabolism is dysfunctional, the seedlings starve to death, resulting in rotten dead seedlings.
3. Oxygen: After the seed breaks the chest, the oxygen demand gradually increases with the elongation of the bud, and the hypoxia will cause alcohol fermentation, resulting in seed poisoning death. Generally, the oxygen content in water is 0.2-0.3%, the oxygen content in the air is 20.8%, and when the oxygen is sufficient (more than 5%), the buds grow slowly, and the roots grow fast, first rooting and then long buds. The first piece of the needle then elongates rapidly, breaking through the bud sheath. When the oxygen is insufficient (below 2%), the buds are rapidly elongated, the leaves and roots grow very slowly, and even the young shoots grow, and the young roots stop growing.
Rice seedlings generally grow in two ways, cell division and cell elongation. Cell division is a cell division into two, the protein is multiplied, requires a large amount of sufficient oxygen, provides nutrients and energy through aerobic respiration; cell elongation is the expansion of individual cell volume, protein increase is not much, in the mode of hypoxia It can also be done. The coleoptile is an established organ, and its growth mode is mainly carried out by means of cell elongation. The young shoots and young roots are new organs, mainly by cell division.
Irrigation caused the soil to form an oxygen-deficient environment, inhibited the growth of root buds, and the buds grew rapidly, resulting in a phenomenon of falling feet. In the warm and sunny weather after the cold weather and cold weather, the temperature rises, and the anaerobic respiration of the seedlings is rapidly strengthened. The anaerobic microorganisms in the soil also rapidly multiply, producing reducing substances such as hydrogen sulfide (H2S) and cotton rot, which cause a large area of ​​rotten sputum.
4, light: the bud sheath has a strong phototaxis, after the buds are muddy, if the water is flooded, the sunlight is blocked, the buds are rapidly elongated, rushing out of the water surface, fighting for the sun, the deeper the irrigation, the longer the bud sheath extends, the root growth The slower, the phenomenon that the buds are long and short.
After the seedlings grow out of the true leaves, they need sufficient sunlight for photosynthesis. The shallow water is covered with muddy water. The water surface can refract sunlight and increase the area of ​​photosynthesis. It is greener than the non-irrigated seedlings and grows faster. Light also has the effect of suppressing the length of the child and making the seedlings strong. Therefore, it is impossible to sow too densely to prevent the contact of the seedlings with light, and it is too crowded to form a fine silk thread.
The length of the light wave also affects the seedlings. For example, 315 micron light waves (ultraviolet rays) are harmful to all plants, 280 micron light waves can kill plants; and 400-500 micron light waves (blue) can activate the movement of plant chloroplasts. Conducive to plant growth; 600-700 micron light wave (red) can enhance the ability of chlorophyll to absorb photosynthesis, but also facilitate plant growth; 500-600 micron light wave (green) can reduce photosynthesis and reduce growth. The colored blue film can absorb a large amount of light of 600 micron wavelength through a large amount of light of 400-500 micron wavelength, so that the seedling grows short, the photosynthetic ability is strong, and the accumulated dry matter is large; the red film can pass through a large amount of 600 micron or more. Light, a large amount of light that absorbs wavelengths below 600 microns, can be bred into short stunted seedlings, especially roots that grow well; green films can transmit light waves of 500-600 microns.
5, nutrition: the seed germinated to the first true leaf, mainly relying on the endosperm to supply nutrients, rice grains are still hard, the embryo consumption is very small. After the emergence of the second true leaf, the endosperm supplies half of the nutrients, about half of the nutrients are absorbed from the roots and foliar photosynthesis, and the rice grains have softened. After the emergence of the third true leaf, nutrients are mainly produced by root absorption and foliar photosynthesis, and only a small amount of endosperm is supplied. After the emergence of the fourth true leaf, the endosperm nutrients have all been consumed, and the seedlings have entered a completely independent life. Therefore, after the three-leaf stage, the amount of fertilizer absorbed by the seedlings increased significantly. The fertilizer in the field was short-lived, and the seedlings turned yellow. The cold resistance was weakened. In cold weather, cold weather often caused dead seedlings. The fourth leaf requires more fertilizer.
Second, the relationship between early rice breeding and weather
Rice is a thermophilic crop. The resistance of seedlings to low temperature is weakened with increasing leaf age. The biological minimum temperature from emergence to trifoliate is 10-12 °C. When the temperature drops below the biological minimum temperature of rice, It will destroy the normal physiological mechanism of rice, make the seedling oxidation system dysfunctional, and stop growth and development. According to many years of research, the agricultural meteorological indicators of early rice rotten are: daily average temperature is lower than 8 °C (indica) -11 °C (indica), minimum temperature is lower than 5 °C (indica) -8 °C (indica), low temperature and no sunshine For more than 3 days, the cold wave invades the bad weather with strong winds or hail, night frost, late snow, etc. In the case of poor management in the field, rotten can occur. The longer the rainy and low temperature weather, the longer the rot. According to the statistical analysis of agricultural meteorological data over the years, the weather conditions for early rice rotten are summarized into four types:
1. Low temperature and rainy weather type: The spring cold wave intrusion causes the average daily temperature below 11 °C. The low temperature and low temperature of the rainy weather lasts for more than 3 days. Because of the low temperature and no sunlight, the root system can not grow, the photosynthesis is weak, the nutrient consumption is not supplemented, and the nutrient imbalance occurs. And die. "Smashing a needle" occurs under such weather conditions. For example, during the early rice growing period in 1996, Changsha experienced 20 days of low-temperature and rainy weather; in 2002, it appeared 16 days; in 2003, there was cloudy and low temperature for 17 days during early rice growing; in 2009, the rain was low for 9 days. The average temperature fluctuates below 12 ° C or around 10-12 ° C, and the seedlings cannot grow. Caused serious bad rotten, rotten sputum, dead seedling rate of more than 40%.
2. Temperature sudden change weather type: Before and after the three-leaf stage of seedlings, the nutrients of the seed endosperm have been almost consumed, the new leaves have just formed, the root system is still young, the photosynthesis is weak, and the resistance to stress is very weak. After a period of low temperature and rainy weather, the weather suddenly turned fine. During the day, the strong temperature of the sun rises to above 25-30 °C, and the temperature difference between night and daytime is above 15 °C, which often causes physiological dehydration during the day, resulting in withering, dead seedlings and rotten cockroaches.
3, cold and snow, night frost weather type: the seedlings grow out of the real leaves after encountering severe cold and night frost, snow and ice weather, often causing a large number of seedlings to die.
4, hail, wind, heavy rain type: Qingming to Guyu Festival, local convection is strong, often in some parts of the city to form hail, wind and heavy rain. The seedlings are thrown into the mud, drowning and dying; or being overwhelmed by heavy rain, flash floods, and silt, the wind blows down the seedlings, the water is transpiration too much, and the water loses and the plants die, causing serious damage. seedling. For example, the live seedlings around April 10, 2010 suffered from the cold damage of April 13-16, and suffered from the heavy rain of 25.2mm on the 16th, causing the early rice rotten and the rotten rate of more than 40%.
In summary, understand the relationship between the growth and development of early rice seedlings and the weather, correct and reasonable understanding, master the changes of sunlight, water, temperature, oxygen and nutrients, etc., to prevent the early rice rotten, cultivate strong and good, and plow the spring The key to producing the first flaw.
The rainwater festival has passed, and the spring has returned to the earth. The temperature has risen above 5 °C, reminding farmers that they should pay close attention to the preparation of fine varieties and farmland ploughing, and the preparation of spring ploughing materials such as fertilizers and pesticides, and strive to achieve a good harvest of early rice in the Year of the Dragon.
ABS Plastic Steel Tape Measure
ABS Plastic Steel Tape Measure
Shell made of ABS material, black rubber, can protect it from falling damage, durable, buckle and sling design, easy to carry, handheld and portable. Just pull the tape to lock the size in place. Perfect for daily use, travel, camping, etc.
It is suitable for kitchens, garages, manufacturing factories, steel factories, hardware stores, etc. it can be used to measure the length and width of measuring tools or casting aircraft, machines, furniture, etc., and it can be used to measure the accurate large tape.
Abs Plastic Steel Tape Measure,Abs Steel Measure Tape,Abs Rubber Tape Measure,Steel Tape Meter Stick Measure
Shangqiu Yuan Xiang Measure Tools Co., Ltd. , https://www.yuanxiangtool.com