They clear a forested slope by burning; rake over the ashes in which they sow their grain, and reap a fairly good crop in the fertilized soil.

The second year the clearing yields a reduced product and the third year is abandoned.

When the hamlet of five or six families has exhausted all the land about it, it moves to a new spot to repeat the process.[113] The same superficial, extensive tillage, with abandonment of fields every few years, prevails in the Tartar districts of the Russian steppes, as it did among the cattle-raising Germans at the beginning of their history.

Tacitus says of them, _Arva per annos mutant et superest ager_,[114] commenting at the same time upon their abundance of land and their reluctance to till.

Where nomadism is made imperative by aridity, the agriculture which accompanies it tends to become fixed, owing to the few localities blessed with an irrigating stream to moisten the soil.
These spots, generally selected for the winter residence, have their soil enriched, moreover, by the long stay of the herd and thus avoid exhaustion.[115] Often, however, in enclosed basins the salinity of the irrigating streams in their lower course ruins the fields after one or two crops, and necessitates a constant shifting of the cultivated patches; hence agriculture remains subsidiary to the yield of the pastures.