As each year the selection of hill and slope land for orchard sites is becoming more general, the washing and gullying of such soils under cultivation becomes an important subject for consideration. If the slope is quite decided the finer particles of soil are soon carried to lower levels and the storms and showers run off too quickly for penetration to the tree-roots. In such older States as Virginia, Massachusetts, and New York, the hill soils under culture in many cases are already ruined by the washing process. In south France tens of thousands of acres once covered with orange-, grape-, and other fruit-plantations were ruined by washing to such extent that the lands were abandoned for many years. At this time they are mainly restored by levelling, fertilizing, and a system of planting by running the rows and cultivating at right angles with the slope of the hills. In that region the rows and culture often run around the circular hills. Hence the common name of "zone-planting."
With the rows planted at right angles to the slope and the culture between the rows given in the same direction, a ridge is soon formed in the line of the rows that helps to hold the water. If the slope is quite steep the space between the trees in the row is planted with small fruits, and in south France usually with filberts to strengthen the bank by root-growth. By this plan the rows may be circular and varied in direction, but it does not seriously interfere with culture or the gathering of the fruit. Where the plan has been tried in Kansas, Missouri, and other States, it has been found that it not only conserves moisture by giving time for rains and melted snow to settle downward, but mainly stops the washing and gullying. As a rule, the best orchard soils are most subject to deep gullying. On the loess soils of west Iowa, Tennessee, Georgia, Missouri, and other States, old cultivated fields are now eroded and gullied, as shown in Fig. 55, as given in "The Soils of Tennessee." The upper slope shown was the surface of a field ten years ago. After a gully was started each heavy rain deepened it on account of the natural porosity of the soil and subsoil. On the start the water that centred in the gully might easily have been divided and scattered. Or had a zone system of culture been given, with fruit-trees or other crops, the whole surface would have been retained. The figure only shows one gully, but the visitor to the old plantation hill lands of Georgia will find a succession of such deep gullies on many fields once productive.
Fig. 55. - A gully in best orchard soils.