Dry belt cultures
In the Book of Genesis, we are told of another pair of brothers, Cain and Abel. Their story is the story of the dry belt. Of these two, "Abel was a keeper of sheep, but Cain was a tiller of the ground."
In its beginning in the neolithic Near East, agriculture was mixed farming, based on the combined use of crops and herds. But the growth of specialized, irrigated, crop agriculture in the hydraulic societies gradually divided people into two groups: farmers and herders. And it tended to drive the herders out into the wilderness. In this sense, Cain, the farmer, is accurately made the aggressor. We have seen how intensively the peasant had to work during the whole growing period of his crops. The passage of the seasons, however, would in theory have left him free to vary his work and diversify his farming, by keeping sheep or cattle on his farm. But, for every hour of his time that was not urgently required for growing the food surplus, the state needed him on the mass labour projects. It could not permit him any other occupations. He did indeed maintain a few beasts, oxen or buffaloes, to draw his plough and his carts. But maintenance of a sizeable herd of cattle or sheep, for meat, milk, hides, or wool, was out of the question. Moreover, livestock needs plenty of room to graze, and as the population rose and farms huddled closer together and shrank to smaller plots, there was simply no room for stock.
One immediate penalty was the loss of animal manure that provided valuable organic matter for the soil and food for the plant crop. The few draught animals did not produce sufficient manure to fertilize the croplands. One answer to the problem was the fertile silt from irrigating waters. Another was the use of green manure, that is, a plant crop grown especially to be ploughed back into the soil as food for the main crop. This technique, fully worked out, is described in Chinese documents from 1134 b.c. onward. In general, the hydraulic farmer could secure enough nourishment for his crops and organic matter for his soil without the manure from a large herd.