A cover-crop is one that is grown for its effect as green-manure or protection, or otherwise, rather than for its value as a product of itself. Cover-crops are used

1.  To prevent the loss of soluble plant-food, which occurs when the lands are left uncovered during the late fall and winter;

2.  To prevent the galling or surface erosion of hillsides or slopes by winter rains;

3.  To prevent root injury by excessive freezing of orchard lands;

4.  To supply humus;

5.  To improve the physical condition of the land.

Legumes used as cover-crops: red clover and Canada field-peas, widely useful in the northern tier of states; alfalfa in the western states and California; soybeans, cowpeas, and crimson clover in the central and southern states; velvet bean and beggarweed, especially useful only in the South; hairy vetch and spring vetch, most successfully used in the South, though rather generally grown in the northern states; sweet clover and, for peculiar conditions, serradella.

Non-legumes used as cover-crops: rye, wheat, oats, and barley, of the cereals, are more commonly used; rape and turnips, which are not hardy in the northern sections; buckwheat, white mustard, and spurry under special conditions.

Some of the leading cover-crops mentioned or recommended for fruit plantations (the leguminous or nitrogen-gathering species being starred): —

Living over winter: —

* Clovers.

* Hairy or winter vetch (Vicia villosa).

* Sweet clover (little used). Winter rye.

Winter wheat.

Killed by freezing: —

* Cowpea.

* Soybean.

* Velvet bean. *Pea.