Hitherto all lands had paid to the State a certain proportion of their produce, a proportion which varied, according to the estimated richness of the soil, from a tenth to one-half.

The effect was to discourage all improved cultivation, since it was quite possible that the whole profit of any increased outlay might be absorbed by the State, and also to cramp and check the liberty of the cultivators in various ways, since the produce could not be touched until the revenue official made his appearance and carried off the share of the crop which he had a right to take.

Chosroes resolved to substitute a land-tax for the proportionate payments in kind, and thus at once to set the cultivator at liberty with respect to harvesting his crops and to allow him the entire advantage of any augumented production which might be secured by better methods of farming his land.

His tax consisted in part of a money payment, in part of a payment in kind; but both payments were fixed and invariable, each measure of ground being rated in the king's books at one dirhem and one measure of the produce.

Uncultivated land, and land lying fallow at the time, were exempt; and thus the scheme involved, not one survey alone, but a recurring (annual) survey, and an annual registration of all cultivators, with the quantity of land under cultivation held by each, and the nature of the crop or crops to be grown by them.