五土五音
Five Soils and Five Tones
夫管仲之匡天下也，其施七尺。瀆田悉徙，五種無不宜，其立後而手實。其木宜蛾、菕與杜、松，其草宜楚棘。見是土也，命之曰五施，五七三十五尺而至於泉。呼音中角。
When Guan Zhong brought order to all under heaven, his survey extended seven chi deep. Irrigated fields fully cultivated are suitable for all five grains, with yields established subsequently. Their trees are suited to the yuan, lin, du, and pine; their grasses are suited to thorn-bush and bramble. When you observe this soil, call it the 'Five Applications' — at five times seven, thirty-five chi, you reach the spring. Its tonal resonance corresponds to the jue note.
Notes
This extraordinary chapter is one of the world's earliest systematic soil classification treatises. It categorizes ninety types of soil across nine grades, correlating soil composition with suitable crops, trees, grasses, water depth, and even musical tones. It demonstrates remarkably advanced empirical agricultural science for its era.