Source: Nongnghiep.vn
The winter-spring crop of 2020 in the North is basically in season. Photo: Pham Huong
However, also few years, joy is not complete. Even in this winter-spring crop, there are areas and rice households that have harvested a few weeks ago (in mid-May) with a loss of a few tens of kilograms of rice. Why is that?
Unusual weather
In 2020, the beginning year of a “Sixteen flower borders” with many abnormalities of the climate and weather; many old-aged “lost-cross-hybrids” exclaims that, from birth, never seen the night of 30th, the first day of the lunar new year, but it was thundered, hail and wind were shocked like that.
This year is 2 April (lunar calendar), but according to the calendar, 2020 is also a “leap year”, February has 29 days, usually 28 days; those are special duplicates of the earth and moon rotation in the “six green flower borders”; winter-spring crop, although it has been forecasted to be a warm year, the heat and warmth are also unusual, during the winter months, a few days are dressed in “Korean”, many weeks also show a short-sleeved shirt, but There has not been a year when the “she was” cold was so terrible that “put away the blanket and then take it out again”, not to the “summer” but had a hot day to 35-36 degrees Celsius and humidity below 40. %. That is the general overview of the winter-spring weather of 2019-2020.
According to the aggregated data from Lang – Hanoi meteorological stations, Thai Nguyen and Tuyen Quang stations (Provincial Hydrometeorological Center): From January to April 2020 there are 50 days of temperature from 20 degrees C or higher. down, the number of low temperature days is not large and only about 30% of the days with the average temperature below 20 degrees Celsius annually. Thus, the winter-spring crop 2019-2020 in terms of temperature is a clear warm winter-spring crop.
However, in April, when the rice was in its growing stage, the temperature fluctuations were a threat and severely affected any tea, regardless of which variety had a differentiation stage. 4-6, the mitotic stage of infection reduces the formation of pollen and pollen mother cells.
April has 11 days, average temperature is below 20 degrees Celsius, the number of days is higher than the average for many years (8-9 days).
Especially, there is a fairly long cold 5 days in a row from April 4 to 8, this is the most dangerous cold spell after many years of observation, in addition, the days 13-14 / 4 and 24-25 / 4 have the average temperature is below 20 degrees C, fortunately these cold spells are only occasional and does not affect the fertilization process with the flowering rice, flowering.
Regarding humidity, in the spring crop of 2020, the air humidity is at average level for many years, solar radiation is lower than average for many years, dry and hot westerly winds are generally not affected by pollination. fertilize the rice flowering period.
Cultivation season and the impact of extreme climate events
In the winter-spring crop of 2019-2020 in the Red River Delta and Northern Midlands and Mountains, farmers basically used short-term and temperate rice varieties.
The recommended planting time is around spring (4/2 solar calendar, corresponding to January 11); However, in some areas due to custom, people usually sow on 20-25 / 1, even earlier.
In the Red River Delta region, where summer crops are often used, early sowing is also carried out to harvest and make pear, melon, watermelon, zucchini in late April to mid-May, these areas, rice yield. Spring is a secondary crop because the income from summer crops is 3-4 times higher than the main crop.
In most of the Red River Delta provinces, the rice crop is transplanted or sowed in February and ends in February. And so the RRD is basically harvested.
Temperature requirements of rice
For rice, the period of nutritional growth (from growing to entering into differentiation) is the most suitable temperature is 27-33 degrees Celsius, the temperature range that rice plants still ensure the ability to grow is quite wide, However, at the low or high threshold, the average temperature is below or above this threshold, causing the rice to stop growing and may disturb or disrupt the biochemical and physiological activities of the plant.
The winter-spring crop in the north of 2020 is facing abnormal weather. Photo: Pham Huong
The real growth stage, especially the flower formation stage, is an extremely important stage that decides most of the factors that constitute the yield of rice, such as the number of flowers or the number of seeds / flower, the process of forming the cell. pollen mother and mitosis to accumulate substances in pollen and complete pollen generation process, deciding the number of firm grains / cotton.
According to Yoshida, the optimum temperature for the initiation of segmentation and burning is 25-31 degrees Celsius, the lower limit is 15 degrees Celsius, the upper limit is 33 degrees Celsius; in the differentiation stage, the lower limit is 20 degrees C and the upper limit is 38 degrees C, the lower flowering stage is 22 degrees C and the upper limit is 35 degrees C.
Looking back on the overall winter-spring rice crop of the North this year, basically the differentiation stage of cotton formation is from March 15 to the end of April, rising to the beginning of May of the solar calendar.
Early flowering tea about 10-15 / 4, the North Central region focuses around April 15-20, some localities in the Northern Midlands, Mountains and even the Red River Delta (the where the custom of growing summer vegetables and crops) rice also flourished at this time.
From the physiological perspective of rice, the division stage of formation of cotton is divided into 8 steps, if the temperature and light conditions are suitable, at the optimal threshold, the number of flowers (number of seeds) will be favorable, the cotton will be large, longer, more grains; Cold at this stage will also increase the rate of flower degeneration at the tip of cotton and rice sheds.
In the stage of differentiation step 4-6, the formation of pollen mother cells and the completion of pollen formation process, the appropriate conditions, the pollen will be more, the good vitality, the ability to fertilize high fertilization, the rate of the kernels will be low; On the contrary, unfavorable, when the temperature below the minimum threshold lasts, the pollen will die or the number of pollen is small – the result is very clear when we check by the technique of dyeing and dyeing pollen.
When rice steps into segmentation, which is also the stage of burning formation, shaping into the rice root will see the hard and no longer flat base. The heat is not suitable, difficult to reach, the height of rice of this tea is only 80-85% of its average height.
Observe the tea, rice varieties early flowering in this season the final height is also lower than the height in favorable seasons. The phenomenon of non-draining cotton neck is very pronounced in the flowering varieties in mid-April, the cotton is also shorter and of course the number of firm grains on the cotton is also low.
Reduce local productivity
At the Institute of Food Crops and Food Crops, a 20-hectare model with 415, glutinous, short-term, early-planting varieties with the aim of early harvest for high new sticky rice prices, this year is really black. enough rice, differentiated rice, especially the formation of pollen and pollen mother cells on the occasion of 5 consecutive days of freezing below 20 degrees Celsius, instead of 160-180 kg / sao in previous years, this crop has only a few dozen kg.
This situation is also observed in some communes of Kinh Mon – Hai Duong, Tam Duong – Vinh Phuc … Some localities in the northern mountains such as Thai Nguyen, Tuyen Quang and even some scattered delta areas. Hồng and Thanh Hóa.
Looking back on warm winter-spring crops and seasonal lessons
In the actual production of the winter-spring crop in the Northern provinces, we have witnessed this situation many times in previous years, especially the production period is popularized by the long-term cold group.
The victory of the winter-spring crop of 2020 has drawn many valuable lessons for the following years. Photo: Pham Huong
In the winter-spring crop of 1987, a crop in which many Northern provinces lost their crops, we planted it popularly with long- and medium-day varieties such as X21, VN10, M2, C70, C71 …
The planting season is also earlier than the current calendar, sowing at the end of November and early December of the solar calendar, and almost transplanted before the Lunar New Year and compact in January.
That year was a very warm year in the winter, when transplanting 6-7 leaves and transplanting down was still warm, the rice went up rumbling, after Tet, the firefighters finished because the fields were differentiated and at the time of planting. cotton has been cold for 4 consecutive days with the threshold of 18-20 degrees Celsius.
That year Thai Binh, an intensive province with a rice yield of over 60 quintals / ha in the previous spring crop, had an average of 19 quintals / ha. The following years were in irregular cycle but the warm spring crop happened in 1990-1991, 1996-1997 and 2012-2013.
In these crops, rice productivity has decreased, even susceptible varieties have been lost on an area of thousands of hectares. Specialized ministries and provinces had to set up a “steering committee” to combat warmth in the winter-spring crop.
Later, when the results of the research and investigation evaluated and confirmed the safety frequency for rice field differentiation and flowering, it was concluded for the regions: North Central Coast 25 / 4-5 / 5 and Dong by the Red River and the Northern Midland and Mountain in the beginning of May to 20/5 of the solar calendar; The short-term cold rice variety, which is fully in the spring crop (not over winter), has been strongly affirmed and recommended for decades to bring stability to the spring rice crop in the North.
Based on this crop, farmers who do short-term transplants, adhere to the science of seasonal calendar and take the main rice production, belong to the Red River Delta and the Northern Midlands if harvested from late May to 15 / 6, productivity increases with the direction of time.
Need scientific assessment
Spring 2020 rice harvest in Thanh Tri – Hanoi. Photo: Tung Dinh
There is still the phrase “crop failure is caused by natural disasters”, but now, the single crop pattern is often attributed to the same. It also seems to be somewhat unjust, because the same thing, transplant elsewhere in the region, if deviated a bit, later than 5-7 days, which means that the most sensitive stage of it is flower fragmentation and formation. pollen grains, avoiding the cold, “she bung”, are “carefree”, high productivity is no less than normal years.
Rice production in particular and agriculture in general are highly risky. In poor seasons, farmers suffered misery, six months of looking at trees did not equal one day to look for fruits, their livelihoods and livelihoods were seriously affected, and grassroots cadres also suffered because they had to rush to run, have to consider and assess. The reason for this is that the seed supply business is also struggling due to this consequence. Granted, there are more sensitive reaction varieties, but the result is “first and foremost” – The timing of planting, the time of differentiation and flowering is extremely important.
Evidence is that many varieties of rice were “stuck” in this net but when transferred, trained and instructed in detail to the people, knowing what varieties are, what is strong, what is weak, where should they be sowed? how to take care of it, which crop is the main … and it is still well received by the farmer and to the farmer, effective: productivity, high quality, good taste, good price not to mention many cultivation issues .
