The ordinary practice of the British farmer is to grow his wheat in rotation with other crops. Various rotations are practised to suit the special circumstances of different districts, one might almost say of special farms. This short account of wheat-growing does not profess to give a complete account of even English farming practice. It is only necessary to describe here one rotation in order to give a general idea of the advantages of that form of husbandry. For this purpose it will suffice to describe the Norfolk or four course rotation. This rotation begins with a root crop, usually Swede turnips, manured with phosphates, and potash too on the lighter lands. This crop, as already described, provides the opportunity of cleaning the land. It produces also a large amount of food for sheep and cattle. Part of the roots are left on the land where they are eaten by sheep during the winter. The roots alone are not suitable for a complete diet. They are supplemented by hay and by some kind of concentrated food rich in nitrogen, usually linseed cake, the residue left when the oil is pressed from linseed. Now an animal only retains in its body about one-tenth of the nitrogen of its diet, so that nine-tenths of the nitrogen of the roots, hay and cake consumed by the sheep find their way back to the land. This practice of feeding sheep on the land therefore acts practically as a liberal nitrogenous manuring. The trampling of the soil in a wet condition in the winter also packs its particles closely together, and increases its water-holding power, in much the same way as the special cultural methods employed in the arid western States under the name of dry farming. The rest of the roots are carted to the homestead for feeding cattle, usually fattening cattle for beef. Again the roots are supplemented by hay, straw, and cake of some kind rich in nitrogen. The straw from former crops is used for litter. Its tubular structure enables it to soak up the excreta of the animals, so that the farmyard manure thus produced retains a large proportion of the nitrogen, and other substances of manurial value, which the animals fail to retain in their bodies. This farmyard manure is kept for future use as will be seen later.