Before leaving the question of manuring one more point from the Rothamsted experiments must be referred to. It has already been mentioned that when manured with nitrogen alone the Rothamsted soil produced 21 bushels of wheat per acre. When, however, a complete manure containing both nitrogen and minerals was used the crop rose to 35 bushels per acre which is about the average yield per acre of wheat in England. This shows that although the yield of wheat is dependent in the first place on the nitrogen supplied by the soil, it is still far from independent of a proper supply of minerals. A further experiment on this point showed that minerals are not used up by the crop to which they are applied, and that any excess left over remains in the soil for next year. This is not the case with nitrogenous manures. Whatever is left over from one crop is washed out of the soil by the winter rains, and lost. Translated into farm practice these results mean that nitrogenous manures should be applied direct to the wheat crop, but that wheat may as a rule be trusted to get all the minerals it wants from the phosphate and potash applied directly to other crops which are specially dependent on an abundant supply of these substances. At Rothamsted, Lawes and Gilbert adopted the practice of growing wheat continuously on the same land year after year in order to find out as quickly as possible the manurial peculiarities of the crop. This however is not the general system of the British farmer, but it has been carried out with commercial success by Mr Prout of Sawbridgeworth in Hertfordshire. The Sawbridgeworth farm is heavy land on the London clay. Mr Prout’s system was to cultivate the land by steam power, to manure on the lines suggested by the Rothamsted experiments, and to sell both grain and straw. Wheat was grown continuously year after year until the soil became infested with weeds, when some kind of root crop was grown to give an opportunity to clean the land. A root crop is not sown until June so that the land is bare for cleaning all the spring and early summer. Such crops also are grown in rows two feet or more apart, and cultural implements can be used between the rows of plants until the latter cover the soil by the end of July or August. After cleaning the land in this way the roots are removed from the land in the winter and used to feed the stock. By this time it is too late to sow wheat, so a barley crop is sown the following spring, and with the barley clover is sown. Clover is an exception to the rule that crops must get their nitrogen from the soil.