Annual Increase of Underground Materials in Three Range Grasses

Any thoughtful student who has seen the mellow, granular, fiber-filled soil of virgin midwestern prairie and the same soil that has been cropped with maize or wheat for only a decade has cause for deep concern. For the cropped soil has lost its mellowness, the granular structure of discrete crumbs has largely disappeared as has also the binding root fiber. The soil when dry is often like dust, dust that pours between the fingers and is dispersed by the wind before it reaches the ground. Throughout the Midwest soil drifting has greatly increased, and erosion by water has become accelerated with length of time of cultivation and the cropping of more arid lands. Such soils have lost much of their fertility. They are greatly reduced in water-absorbing and waterholding capacity, and because of their small percentage of aggregates or their single-grain condition they may readily drift. Grasses not only provide the soil with a protective cover against the forces of erosion but they also bring about a recovery of soil fertility which has been partly exhausted by continuous cropping. Under a cover of grass, a favorable crumb structure (the amount of which is a rough measure of the fertility of a given soil) is produced. These aggregates, a high percentage of which are large, are much more resistant to movement by wind and water than are the particles of dust. They promote rapid absorption of water and permit freer movement of both water and gases within the soil. Soil aggregation under grassland as brought about biologically is partly through the accumula-