As far as I know, no one has ever written a history of rice cultivation in the Red River Delta. Instead, I think most people simply assume that people have been employing sophisticated irrigation techniques in order to cultivate wet rice there since the earliest of times.
As I’ve started to look at this issue, however, I’ve come to realize that there isn’t evidence to support such a view. Instead, I see evidence that would indicate that people relied mainly on broadcasting seeds in floodplains until the end of the first millennium AD, when efforts started to be made to dike the Red River and when Vietnamese came into contact with Southwestern Tai-speaking peoples, peoples who possessed sophisticated knowledge about irrigation techniques.
Some readers have been providing information from historical sources (thank you!!) that can help us determine the history of rice cultivation in the Red River Delta, and in looking at this information, it is interesting to see how it has been interpreted.
In the Hou Hanshu 後漢書 (History of the Later Han), there is a record about a Han dynasty official named Ren Yan 任延 who reportedly taught people in the area of what is now north-central Vietnam (known then as Cửu Chân/Jiuzhen 九真) how to plow with a water buffalo in the first century AD.
Keith Taylor talked about that passage in his 1983 work, The Birth of Vietnam, as follows:
“The most famous Han official in Vietnam during the Wang Mang era was Ren Yan, who was appointed prefect of Cửu Chân in A.D. 25. According to his biography, Ren Yan found that the people of Cửu Chân did not use draft animals for agriculture. As a result, productivity was very low, and grain had to be purchased from Giao Chỉ [i.e., Jiaozhi 交趾, the Red River Delta region].
“The local economy was based on hunting and fishing, and Ren Yan presumably found it difficult to collect taxes. He therefore ordered the production of iron field implements and supervised the opening up of new lands for farming.
“The land under cultivation expanded year after year, and the life of the people became more secure.” (34)
Taylor then goes on note that while some people had interpreted this information to mean that “the use of iron implements and draft animals for agriculture was introduced into Vietnam at this time,” he did not think that was accurate.
Instead, Taylor stated that “Ren Yan’s activities were confined to Cửu Chân, a relatively backward locale,” and that “If Giao Chỉ could produce a surplus of grain sufficient to supply Cửu Chân, agriculture in the [Red] River plain must have been well developed.” (34)
In other words, Taylor saw in this passage (indirect) evidence for the prosperity of grain (i.e., rice) production in the Red River Delta.
More recently, Li Tana likewise interpreted this passage in a similar way to argue that “Jiaozhi was the regional granary whose rice supplied its nearest neighbors.”
She quotes a portion of Ren Yan’s biography where it says “Customarily Cửu Chân lived on hunting and did not know ploughing with draft oxen. People often had to buy rice from Jiaozhi, and sometimes when short of it.”
The information in a passage like this, Li Tana argues, “suggests how mutually beneficial exchanges knitted the Gulf of Tongking region together.”
But was the exchange mentioned in Ren Yan’s biography really “mutually beneficial”? Does this really (indirectly) demonstrate that “Giao Chỉ could produce a surplus of grain sufficient to supply Cửu Chân”?
I would argue that this passage does not support these ideas, and the final phrase from Li Tana’s quote – “and sometimes were short of it” – although not an accurate translation, hints at what this passage was really about.
The passage in the Hou Hanshu states the following:
“[People in] Cửu Chân customarily relied on hunting for their livelihood. They did not know how to cultivate with draft animals.”
There is then an annotation here which states that “The Dongguan hanji says, ‘[In] Cửu Chân [people] customarily burned vegetation and planted fields.’ The Previous History [i.e., the Hanshu, the History of the Han] says ‘Grain Intendent Zhau Guo taught people to cultivate draft animals.”
These two annotations were meant to add information. The first indicates that while the Hou hanshu states that people in Cửu Chân relied on hunting, there is another text that indicates that they engaged in slash-and-burn agriculture. The second remark, meanwhile, tries to connect Ren Yan’s actions with those of an Eastern Han dynasty official by the name of Zhao Guo 趙過. However, Zhao Guo was famous for promoting a technique for cultivation known as the alternating fields system (daitianfa 代田法), not for teaching people to cultivate with draft animals.
The Hou Hanshu then goes on to state about Cửu Chân that,
“The people often asked to purchase grain [gaodi/cáo địch 告糴] from Giao Chỉ/Jiaozhi, and each time this caused hardship and impoverishment [kunfa/khốn phạp 困乏].
“[Ren] Yan thereupon ordered that farm implements be cast, and he taught people to open up new land. The fields expanded every year, and the common people were provided for.
What I have translated as “ask to purchase grain” (gaodi/cáo địch 告糴) is a very specific term that was used in very specific situations. Its earliest usage can be found in the Zuo Zhuan 左轉.
That text records that during a time of drought (in 576 BC), Zang Wenzhong 臧文仲, an official in the kingdom of Lu, went to the kingdom of Qi to “gaodi/cáo địch 告糴” – that is, to ask to purchase grain (大無麥禾，臧孫辰告糴于齊。).
This is thus what this term signified. It did not simply mean “to buy grain,” as this was not a verb that indicated normal trade practices.
Probably the best way to translate “gaodi/cáo địch 告糴” would be “to ask to purchase grain during a time of drought/famine.”
This was not a normal activity, and in the case of Cửu Chân “each time [it] caused hardship and impoverishment [kunfa/khốn phạp 困乏].”
Who did it cause hardship and impoverishment for? From the context it would seem that it was the people in the Red River Delta who had to provide rice for the starving people in Cửu Chân who found themselves in a difficult position.
This passage in the Hou Hanshu therefore does not describe a “mutually beneficial exchange,” and it doesn’t demonstrate that “Giao Chỉ could produce a surplus of grain sufficient to supply Cửu Chân” at that time.
In fact, it shows us the opposite of these claims. It suggests that the people in the Red River Delta might have had enough rice to pay taxes and feed themselves, but little more than that.
This is what the late Jennifer Holmgren argued in her 1980 work, Chinese Colonization of Northern Vietnam.
Although Holmgren did not discuss the above line that mentions “asking to purchase grain,” she could sense that there was something that was not “normal” or “positive” about this passage, and she attributed Ren Yan’s effort to expand agricultural production to a need to feel migrants who were arriving from China.
“When the Hou Hanshu speaks of the introduction of advanced methods of agriculture during Ren Yan’s time, it means that desperate efforts were made to accommodate and provide for the influx of new settlers and refugees fleeing the north at the end of the Former Han.
“Presumably large numbers of refugees arriving in Jiaozhi were also straining the resources of that commandery.” (6)
This was a hypothesis. but it’s worth investigating further, because Ren Yan’s biography makes it clear that there wasn’t an abundance of rice in the Red River Delta in the first century AD.
Why was that the case? Was it because Vietnamese were growing rice by broadcasting seeds in floodplains and were not yet employing the sophisticated irrigation and transplanting techniques of wet rice agriculture that lead to higher yields?
Was it because the Red River Delta had been overrun with migrants/refugees?
Was it a combination of these two factors?