What kinds of rice are there?

Rice varieties, in the earlier written records of Guanzi Yuan Di, the names of 10 rice varieties and their suitable soil conditions were recorded. Later generations of agricultural books and even some poems often describe rice varieties.

In the process of rice cultivation, the ancient working people in China have accumulated rich experience in rice field types, cultivation time, sowing and seedling raising, irrigation, fertilization, pest control and harvest.

Wang Zhen, an agronomist in Yuan Dynasty, divided farmland into nine categories in his agricultural books: mine field, district field, paddy field, enclosure field, cabinet field, shelf field, terraced field, painted field and Shatian. There are six categories related to rice planting: enclosure field, cabinet field, shelf field, terraced field, coated field and Shatian.

Reclamation in Taihu Lake area originated in the Spring and Autumn Period, gradually developed from Warring States to Qin Dynasty, and further expanded in Han Dynasty. At the beginning of reclamation, due to the large water surface and smooth downstream drainage, the grain output increased significantly.

In order to solve the flood problem, the ancients excavated ponds and weirs around the fields at the same time, thus gradually forming a pond polder system with horizontal ponds and vertical ponds.

Putting aside the field, also known as dividing the field, is to make a shelf with wooden stakes in the swamp, select aquatic plants such as fenugreek roots and mix them with soil, spread them on the shelf, and plant rice. Crops planted in this way float on the water, competing with water and not being submerged. During the Song and Yuan Dynasties, there were such fields in Jiangnan, Huaidong, Guangdong and Guangxi.

In order to expand the cultivated land, the ancients required the fields to be terraced fields in mountainous areas and enclosures on the water surface. For example, "farmland" in Sichuan and Hunan provinces, and "farmland" in northern Guangdong and eastern Jiangxi. There are also ancient books called Koutian, Leimingtian, Yamada and Iwata.

As for the farming system of rice, rice can only be planted once a year. Since the emergence of early rice varieties, the planting range has gradually advanced to the Yellow River basin with long sunshine in summer, while in the south, it can be planted for two or even three seasons a year. For example, the three-season rice that appeared in the Ming Dynasty is.

From Song Dynasty to Qing Dynasty, double cropping rice has been the main farming system in Fujian and Zhejiang coastal areas. The proportion of double-cropping rice is very small. Winter wheat has been planted in late rice fields in Taihu Lake Basin since the Tang and Song Dynasties, and it has continued to this day.

The above-mentioned farming system gradually formed in history is the reason why the multiple cropping index in China's rice areas has increased, the grain output has continued to increase, and the soil fertility has never declined.

After the original rice cultivation distinguished upland rice from rice, rice was directly broadcast for the first time. North and south are the same. As for the invention and application of seedling technology, the reasons are different. Seedling transplanting in the north aims at reducing grass damage, and seedling transplanting in the south can also reduce grass damage, but it is closely related to the development of multiple cropping system, especially multiple cropping system.

After the system is developed, transplanting is an effective measure to solve seasonal contradictions.

At first, rice irrigation water was developed into a paddy field where rice could be planted by using natural rivers, digging ditches, storing water in ponds and using dams to prevent the invasion of external water, which became a quite perfect farmland water conservancy project. Dujiangyan, for example, has been used for more than two thousand years and is the basic guarantee of Sichuan granary.

The focus of rice production was in the south, which was not fully developed in Qin and Han dynasties, so water conservancy construction was mainly in the north. After the Tang and Song Dynasties, the national economic center of gravity shifted to the Yangtze River basin, the population increased, rice fields were reclaimed, and the water conservancy conditions were guaranteed to develop rapidly. In addition, the ancients used irrigation tools such as rollover, bucket wheel, bucket and orange peel in places with low water level.

As early as the Book of Fan Sheng Zhi in the Western Han Dynasty, there was an incisive description about the irrigation technology of rice fields: when the weather is still cold in spring, the water temperature of rice seedlings should be kept warm, so that the water in the fields can stay in the fields and get more sunshine, so the water inlet and outlet should be in a straight line. In summer, in order to prevent the water temperature from rising too fast, the water inlet and outlet are staggered, which makes the water flow in the field and is beneficial to cooling down.

The discussion on fertilization in paddy fields was first seen in Chen Fang's Agricultural Book in the Southern Song Dynasty. Among them, it is thought that soil fertility can be continuously updated and strengthened, manure should be used as medicine, and fertilization should be based on soil conditions. These thoughts are still instructive.

In the relationship between applying base fertilizer and topdressing in rice, previous agricultural books all emphasized base fertilizer, because topdressing is the most difficult to master. However, the long-term practical experience made ancient farmers gradually create the technology of topdressing according to seedling color, which was described in detail in Shen Shi Agricultural Book in the late Ming Dynasty.

Tangpu polder system