Corn, potato and sweet potato are the three staple foods that we are used to in our life. In fact, their hometown is far away in America, and they were introduced to China in the Ming and Qing Dynasties, and gradually spread to become an indispensable food on the table in China.

so, what are the advantages of these three crops from America? What impact has it had on China's population growth? Listen to the botanist Shi Jun's careful analysis for us.

Wen shi jun

Tu Zhang Yang

In 1368 AD, Zhu Yuanzhang made Nanjing his capital and began the rule of the Ming Dynasty. In the following more than 5 years, China maintained a unified state during this period, although it experienced wars and changed dynasties. The population of China has been growing rapidly, especially during the Qianlong period of Qing Dynasty, from 143 million in the six years of Qianlong to over 2 million and 3 million, which is only a few decades.

Ming and Qing Dynasties were very frequent and serious natural disasters in the history of China, which was obviously not a good thing for ancient agriculture, which almost depended on the weather. So what is the reason for the rapid population growth in this period?

Many historians believe that the introduction and extensive cultivation of various crops in the New World in the late Ming and early Qing dynasties was one of the important promoters. To understand this problem, we still need to know the introduction time of potatoes, sweet potatoes and corn, and their special abilities.

corn, a defective super grain

There is no doubt that as a grain that nourishes American civilization, corn has an irreplaceable position in the grain circle. Compared with wheat and rice, corn has stronger environmental adaptability and good yield. Corn is suitable for planting in arid mountainous areas. Besides their developed roots, it is more important to have a special photosynthesis pathway-C4 pathway.

Generally speaking, when plants carry out photosynthesis, they use the carbon dioxide that enters the stomata of leaves. However, the concentration of carbon dioxide in the air is limited after all, which greatly limits the efficiency of photosynthesis. C4 plants, such as corn, have a brilliant idea, that is, first concentrate carbon dioxide, and then carry out photosynthesis. Carbon dioxide entering maize mesophyll cells will combine with phosphoenolpyruvate (PEP) to produce oxaloacetic acid with four carbon atoms (hence the name C4 pathway), which will be converted into malic acid or aspartic acid. Subsequently, these special acids will be concentrated and sent to the leaf sheath, where they will be decomposed into carbon dioxide and pyruvate again. In this way, the concentration of carbon dioxide in leaf sheath cells is increased, and the photosynthetic efficiency is naturally improved.

not only that, C4 plants also have amazing water use efficiency. C4 plants only need 23-25ml of water to make 1g of dry matter, while C3 plants need two to three times as much water. Because of this, corn has become an important food crop in arid areas at middle and high altitudes.

In addition to good varieties, corn is rich in a lot of nutrients needed by human body. The carbohydrate in fresh corn accounts for 74% of dry matter, and there is 9.4% protein. Because of its rich nutrition, corn has been used as a staple food by Mayans in America as early as 8 years ago.

But compared with rice and wheat, corn has an inherent disadvantage-if it is not treated with alkaline solution, the nicotinic acid contained in corn seeds cannot be released. Because of the lack of nicotinic acid, a special vitamin, people who rely on corn for food will suffer from pellagra. Fortunately, China people's recipes are rich in food, which naturally solves this problem.

the strength of sweet potato, a natural genetically modified crop

Although the status of sweet potato has not been as high as that of corn in South America, sweet potato is also a food crop with its own aura. Sweet potato is a natural genetically modified crop, which happened about 1 million years ago. Yes, we humans didn't do it, but nature arranged it.

actually, the roots of the ancestors of sweet potatoes are not stout, but more like Adenophora adenophora and Platycodon grandiflorum that we see today. However, just a million years ago, a sweet potato was invaded by a bacterium called Agrobacterium tumefaciens. It survived tenaciously and obtained a special gene, which made the offspring embark on the road of "getting fat".

In today's laboratory, Agrobacterium tumefaciens is the most commonly used tool for scientists. This kind of bacteria has a special DNA—— called plasmid in their bodies-they can "carry" some genes on themselves like "porters" and send them to the genome of infected organisms. One million years ago, the plasmid of Agrobacterium tumefaciens inserted gibberellin gene into the genome of sweet potato, thus making today's sweet potato.

Fat sweet potatoes have amazing energy supply ability, and they are pure carbohydrate providers. 1 grams of raw sweet potato contains 24.7 grams of carbohydrates. In addition, orange potato varieties contain a lot of β-carotene, which is very beneficial for people who lack vitamin A to supplement nutrition. It is worth noting that during the cooking process, some components in sweet potato will change, especially vitamin C will be lost due to long-term cooking and baking. Therefore, a balanced and diversified diet is the real solution.

just delicious sweet potatoes can also bring some trouble. For example, eating too many sweet potatoes is easy to burn. This "heartburn" is actually a manifestation of hyperacidity. Starch and dietary fiber in sweet potato can stimulate the secretion of gastric acid in large quantities, so there is the symptom of heartburn.

However, sweet potato has gradually become an important supplementary food after entering China. Farmers in China also creatively improved the planting technique of sweet potato-cutting propagation. Like most convolvulaceae plants, sweet potato also has strong vegetative reproduction ability. Their vines can be extended continuously, and they can take root in suitable places to grow new roots. Clever farmers in China took advantage of this characteristic of sweet potato and propagated it by cutting vines, which greatly improved the efficiency of sweet potato planting.

during the Wanli period of the Ming dynasty, Jin Xueceng, the governor of Fujian province, recorded the methods of natural seedling raising and breeding on land and overwintering old vines in Seven New Overseas Biographies: "If vines are used as seedlings, they should be planted vertically and densely, such as the method of raising onions and leeks." With the popularization of these technologies, sweet potato has become an important food crop in China.

potatoes are the perfect food from heaven

If corn and sweet potatoes have some nutritional defects to some extent, then potatoes are simply the perfect food for the table. There is no shortage of starch, protein and vitamins in potato pieces, which can not only fill human stomachs, but also keep people healthy, because vitamins C, B vitamins and minerals are all full, and even dietary fiber, which is highly praised by the current nutrition circles, has not fallen.

As long as vitamin A and calcium are supplemented, potatoes can completely meet the nutritional needs of human body. This is not a problem at all for China people who have Chinese cabbage and spinach. How popular potatoes are can be seen from its many nicknames: potato, potato, ground egg and yam egg.

In South America, the origin of potatoes, people have cultivated them for more than 7 years. The cultivated potato is not a species, but a kind of plants belonging to Solanaceae, including six cultivated species such as Solanum tuberosum, the most common potato.

With its super-high species diversity and genetic diversity, potato has become the most adaptable food crop. In the alpine mountainous area where corn and sweet potato can't get involved, it undertakes the heavy responsibility of supplying food. Generally speaking, planting one acre of wheat consumes 25 to 3 cubic meters of water, which is enough for potatoes to grow on two acres of land; It's already a very severe thing that the average grain crop yields up to 1, kilograms per mu, and the yield of one mu of potatoes can easily climb to 3, kilograms. Therefore, it is reasonable that potato has become the core food species in many regions.

When did the three major crops from America enter China

So, corn, sweet potato and potato are really excellent food crops. When were these crops from America introduced to China and directly affected the population growth?

when and by which routes was corn introduced into China? There are still different answers to this question, but many scholars believe that there are three routes: southwest land, northwest land and southeast sea. Among them, the "Longchuan County Records" in the seventh year of Wanli in the Ming Dynasty recorded "pearls" juxtaposed with millet and rice, which was the earliest corn. In the thirty-ninth year of Jiajing in the Ming Dynasty, Pingliang Fuzhi recorded that "wheat is like wheat in the west", which is the earliest record of planting corn in the history of China. In the forty-second year of Jiajing in Ming Dynasty, Dali Prefecture recorded "Yumai", that is, corn. These records show that there is a parallel relationship in time between the spread of different routes of corn.

at the beginning of its introduction into China, corn was not a staple crop. Professor Han Maoli of Peking University expounded a viewpoint in the book Historical Agricultural Geography of China, that corn was still a rare food in the Wanli period, because Jin Ping Mei Ci Hua, which was written in this era, recorded that there were corn cakes in Ximen Qing's meals. It just shows that in this period, corn is relatively rare and can only appear on the table of dignitaries. It was during the Qianlong period that corn was popularized on a large scale. The planting area of maize first extended to the lower reaches of the Yellow River, and gradually extended to the north beyond the Great Wall, becoming an important food crop.

There are also many controversies about the introduction of potatoes, but it is certain that potatoes were introduced into China several times through multiple paths. Potatoes introduced to the southeast coast in the 17th century are adapted to high altitude areas, and soon disappeared in subtropical areas, only remaining in some mountainous areas in the southwest and northwest. Later, in the 18th century, western missionaries or businessmen brought ordinary potatoes, and they really started their expansion journey.

The path of sweet potato introduction is relatively clear. It was first introduced to Fujian (Fuzhou Changle) from the Philippines by Fujian businessman Chen Zhenlong. According to "Seven New Biographies Abroad", "Sweet potatoes spread abroad because of their names", which is the earliest record of sweet potatoes in ancient China. Sweet potato has been introduced from Philippines to Quanzhou, Fuzhou and Zhangzhou for many times. Among them, the most influential was the introduction of Fuzhou, and the introduced seedlings were later extended to Zhejiang, Shandong, Henan and Hebei. According to the article "Introduction Test of Sweet Potato" published by Liang Jiamian and Qi Jingwen in Journal of South China Agricultural University in 198, several incidents of introducing sweet potato from Vietnam to Guangdong are also clearly recorded.

in addition to the above two main ways, there are some documents showing that sweet potatoes entered Taiwan Province through Brunei, and were introduced into Yunnan by land from India and Myanmar.

In this way, it takes time for the expansion and development of exotic crops, and how much they contribute to the explosive population growth still needs to be discussed.

Agricultural production technology improves grain output

In fact, during the Ming and Qing Dynasties, the cultivation techniques of traditional grain crops such as rice and wheat also made great progress. First of all, it is manifested in the popularization of three-cropping techniques in two years in the north, two-cropping techniques in the south and three-cropping techniques in one year. Through the improvement of rice varieties and the popularization of rice-wheat continuous cropping techniques, the land use efficiency has been greatly improved. Incidentally, after corn entered China, in some arid areas, a continuous cropping mode with corn as the core gradually formed, which is self-evident for improving grain yield.

At the same time, the technology of improving farmland fertility has also developed by leaps and bounds. Not only can the remaining sesame cakes and bean cakes from oil pressing be applied to the fields, but also the soil fertility can be improved by widely planting green manure such as alfalfa and Chinese milk vetch.

It must be said that the utilization of green manure is a milestone in the development of ancient agriculture in China, and it can be called the originator of organic agriculture. However, under normal circumstances, green manure can only alleviate the problem of lack of soil fertility to a certain extent. If we want to continue to increase the yield, we still need to add a lot of other fertilizers, such as phosphate fertilizer.

Farmers in China used animal bones to cook soup for fertilization very early. In the Ming and Qing Dynasties, this practice was upgraded to smelting ashes. Yang Bao, an agronomist in the Qing Dynasty, mentioned in the Outline of Knowing the Book: "All animal bones, hoof horns and clams are burnt yellow, ground and sieved, and the manure is used to cool rice seedlings and irrigate vegetable fields, which is more fat than other manure." This practice has greatly improved the effectiveness of fertilizer. In the Ming and Qing Dynasties, the related works "Tiangong Kaiwu Daoyi" and "Xu Guangqi's Handwriting" all mentioned the case of using animal ashes to fertilize the fields.

the application of new crop varieties and new farming techniques will greatly improve land use efficiency and total food, but we should also pay attention to the lag of crop dissemination and technology popularization. In addition, some special historical events may also have a decisive impact on population statistics. After Yongzheng carried out the New Deal, the feudal economic form in rural China developed to the extreme. It was a major reform of the taxation system in the late feudal period of China, and the dualistic taxation system of combining taxation with talent was transformed into a single land taxation system. After spreading the land into the mu, landless farmers no longer pay Ding Yin, and farmers with less land also have a lot less burden, which greatly promotes the development of agriculture.

At the same time, the introduction and extensive planting of new crops such as corn, potato and sweet potato have greatly improved the land production efficiency in high mountains and cold regions, the grain planting area has been rapidly expanded, and the living conditions of farmers have been greatly improved.

there is no doubt that the introduction of exotic crops directly affects the distribution pattern of population in China, especially the expansion of farmland utilization mode and cash crop planting area in the middle and lower reaches of the Yangtze River, which in turn affects the industrial distribution in this region. In the middle and lower reaches of the Yangtze River where cotton textile flourished, the seeds of capitalist production relations emerged, which is closely related to grain production. However, with the invasion of imperialism, China gradually became a semi-feudal and semi-colonial society. What changes have taken place on the dining table of Chinese people during this period? Listen to the next decomposition.

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