In speaking of soil selection (228. Best Soil and Location for Vineyard) the need of fertilizing soils after several crops have been gathered was indicated. In this connection the absolute need of humus in the soil continually cultivated must be considered more in detail. Even on good corn soils continued culture soon uses up or "burns out" the fresh vegetable humus that has much to do with the physical texture of the soil. An experiment conducted by the writer illustrated this fact forcibly. For a period of five years crops were grown on half an acre of quite rich prairie soil that could be taken away, including the roots, such as beans, currant cuttings, and apple and plum seedlings. The sixth year the plot including the adjacent field with the same soil was sown to barley. The crop made fine growth on the untreated ground, but did not get high enough on the experimental plot to be reached by the cutting sections of the reaper. In this case the beans gave nitrogen to the soil, but nothing was left to give the needed humus. In the orchard the use of cover-crops (126. Shading of Orchard Soils) give nitrogen and a plentiful supply of humus to the soil. In the vineyard the cover-crop cannot be used and we must rely on barnyard manure with possible use of nitrate of soda, potash, and phosphoric acid as the vineyard attains age.