"Limited rainfall is the controlling factor in crop production in the Great Plains. The average yields of a series of years can be foretold from the records of past years; but because the rainfall is fluctuating in amount and uncertain in distribution, the yields of a simple year can not be foretold with any certainty. The chances of success are, however, much better when the soil is wet to a considerable depth at seeding time than they are when the soil contains little or no available water at that time. The relation between the amount of water in the soil at seeding time and the yield is much closer with winter wheat than with other crops. This crop should, therefore, be seeded on the best-prepared land and that in which the greatest amount of water is stored. Except in the southern section, the response of winter wheat to summer tillage is greater than that of any other crop. Summer-tilled land should be seeded to winter wheat wherever this crop can be grown. The growth of corn is one of the best preparations for winter wheat, especially north of Kansas. With increase in the length of season and the time between harvest and seeding, there is an increase in the value of early preparation for winter wheat. In the northern section the crop can be replaced with spring wheat without serious loss. In the central section winter wheat has a greater advantage over spring wheat and can not be replaced by the latter without serious loss. In the southern section, winter wheat is less certain and less productive than farther north and can not be replaced by spring wheat. It is, however, profitably raised under favorable conditions of oil, season, and preparation. In this section particularly it should be recognized that the chances of producing a crop are low when it is seeded on land that does not contain water enough in storage to wet the soil to a depth of 3 feet."--Page [2].