When is rice harvested in the south and north? Why is there a difference?

When is rice harvested in the south and north? As we all know, only by accurately grasping the rice harvest time, sowing at the right time and harvesting at the right time can we increase the yield. Let's take a look at the rice harvest time in the north and south.

In the north and north of China, there is single cropping rice. One-season rice must be sown before the Qingming Festival and transplant at the end of April and the beginning of May (if conditions permit, it can also be transplanted in Grain Rain). The northern and northeastern regions are early-maturing single-cropping rice. The sowing time is around April. The growing period of northern double cropping rice is 104 days for the first cropping rice and 87 days for the second cropping rice. They are generally precocious varieties. Avoid winter. Extra-early-maturing varieties must be cultivated for double-cropping rice in the north.

In the first season of southern China, rice seedlings were raised in the middle of April in the Gregorian calendar and can be harvested at the beginning of August, about 104 days. In the second season, rice is generally planted while harvesting. It was harvested before it reached the freezing ground. In the south, taking the plain of the middle and lower reaches of the Yangtze River as an example, early rice was sown in mid-April, planted in early May, harvested in late July, followed by immediate transplanting of late rice (known as double grabbing), which usually ended before the Beginning of Autumn, and late rice harvested from late October to November.

For nearly half a century, the Neolithic rice sites in the Yangtze River basin and its south are 4,000 to 10,000 years ago, while the Neolithic rice sites in the Yellow River basin are only four or five thousand years ago. it shows that the rice from the north was introduced into the Yellow River basin from the south in the late Neolithic period. In the late Neolithic period, the average annual temperature in the north was about 2C0 higher than it is now, and there were more Rain Water and lakes than today, so rice quickly took root in the north where there was plenty of water. After entering Tibet, the general trend of the climate in the north is to develop in the direction of drought, the rainfall gradually decreases, lakes and rivers gradually shrink, and the area of rice naturally shrinks. Although rice is still cultivated in the north, it is characterized by the fact that it has not been planted on a large scale. The current distribution is that Xinjiang, Gansu Hexi Corridor, Inner Mongolia River set, Ningxia Yellow River diversion Irrigation area is one; parts of Shaanxi, Shanxi and Hebei are one; parts of northeast Liaoning, Jilin and Heilongjiang are the same. Most of them are planted with japonica rice.

Indica rice is mainly distributed in the vast areas of South China, but no longer go northward in the Yangtze River basin, while japonica rice is mainly distributed in the Yellow River basin and its north. What is the reason for this? Judging from the process of rice domestication, indica rice is the first to be domesticated, which is easy to understand because wild rice is distributed to the south of the Yangtze River. Indica rice inherits the characteristics of wild rice and is naturally warm rather than cold-tolerant. Let's try to compare the relationship between the climate difference between South China and North China and the growth and development of rice, which can deepen our understanding of the problem of indica and japonica.

The climate of South China is characterized by the highest temperature, the richest heat, the most abundant Rain Water and the longest rice farming time. The annual average monthly temperature in South China is more than 10 ℃, and the average annual rainfall is more than 1500-2000 mm. During the period of rice cultivation, the average temperature is 22: 26 ℃, and the temperature difference between day and night is only 5: 8 ℃. Two crops of rice can be planted in one year. The climatic characteristics of North China, such as Beijing and Tianjin, are that the average temperature during rice cultivation is 1921 ℃, the temperature difference between day and night is as high as 12 to 15 ℃, and the monthly average temperature is 10 ℃.

The above period is only more than six months, with an average annual rainfall of more than 500 mm, and the time allowed for rice growth is only about five months (even shorter in the northeast rice region), so early rice can only be grown once a year.