When did the Chinese begin using night soil as fertilizer?

Question

Farmers in China, Japan and Korea use human waste as fertilizer. But farmers in other parts of Asia where the main crop is paddy rice, like Thailand and Malaysia, do not.

Some sources (like King 1911) argue that this was necessary in order to maintain soil fertility and support large populations over centuries of continuous use of fields. But online sources are quite vague about when the practice started – the Wiki entry on night soil mentions the 9th century in Japan, and McGarry gives the Yuan dynasty (circa 13th century). Often it’s just “thousands of years.”

Do we know anything about when precisely the use of night soil began? Presumably it originated in China. It would be interesting if we could show that this was an innovation that resulted from population pressure or some other change in the ecosystem.

References from this page: http://www.agroecology.org/Case%20Studies/nightsoil.html

Answer 1

The Old Chinese character for fertilisers is the same as the word as fecal matter. Thus, we cannot assume that the fertilisers mentioned in Spring and Autumn texts were actually excrement. It is known that at least in some cases, they were referring to (presumably compost) weed or grass.

The earliest explicit reference of using human waste as fertilisers seems to date to the late Western Han dynasty. The Book of Fan Sheng-Chih, which was written around the reign of Emperor Cheng discussed various methods of raising agricultural productivity extensively, including, of course, applying fertilisers.

While the bulk of the original text has been lost, part of the surviving 3,500 characters mentions that:

《漢·氾勝之書》 種麻，豫調和田。二月下旬，三月上旬，傍雨種之。麻生布葉，鋤之。率九尺一樹。樹高一尺，以蠶矢糞之，樹三升；無蠶矢，以溷中熟糞糞之亦善，樹一升。

Growing hemp ... One foot tall, fertilise with silkworm excrement, three cupsper tree; if lacking silkworms excrement, then fertilising with feces from toilets is good too ...

It is in all likelihood impossible to know precisely when a practice like this began. Nonetheless, based on the above, we can probably date the start of wider adoption to around the Qin or Han dynasties and possibly late Warring States.