The usefulness of legumes in strip cropping, crop rotations, pasture improvement, and other soil-conserving agronomic practices is now recognized, and the wildlife technician operating on agricultural lands should know the part legumes play in controlling erosion as well as in improving wildlife habitats.

The majority of legumes at our disposal are herbaceous plants, although some that are important are woody forms, such as the black locust. For obtaining rapid, efficient control of eroding lands, herbaceous cover is often better than woody vegetation. Grasses are usually most effective, but in soil rehabilitation grass-legume mixtures are preferable to grasses alone. The legumes supply nitrogen to the soil, and the grasses prevent the soil heaving characteristic of some herbaceous legumes when grown alone. Such mixtures also provide denser ground cover, tend to prevent weed growth, and produce better forage or hay. The exclusive use of a single species of legume may nevertheless prove efficient in controlling erosion and improving wildlife habitat, as shown by the use of Lepedeza sericea on the berms of terrace outlet channels and unproductive field borders in the Southeast. In this connection it is well to remember that it is not only the roots but the aerial parts of plants and the mulch they lay clown in the form of fallen leaves that are effective in controlling erosion. Even dead vegetation affords protective cover; thus mulching the ground when planting has in itself an erosion-control value.

The following criteria may be useful in choosing herbaceous plants for controlling erosion:

1. Adaptability to the climate and soil in which they are to be planted.
2. Ability to compete with plants that may already occur on the site or are likely to volunteer there.
3. Capacity to spread by stolons, rhizomes, root shoots, or suckers, to form dense foliage, to be thicket-forming, mat-forming, or trailing, and to produce water-absorbing litter.
4. Tendency to resist drought, insect damage, or disease, and ability to grow on infertile or depleted soils.
5. Possession of perennial habit and ability to become rapidly established by direct seeding, mature quickly, and reseed readily. (The seeds should be, easily obtainable, preferably in the open market.)

Plants for erosion control can be of value to the wildlife manager if those are selected that provide wildlife cover and food throughout the year. Van Dersal has already stated the erosion-control qualifications for woody plants, and Leopold has discussed the properties that make plants valuable to wildlife. The similarity between the demands of the soil conservationist and the wildlife manager emphasizes the desirability of developing vegetation for erosion control and wildlife hand in hand.

The fact that many legumes are plants that pioneer on bare areas and abandoned land is of significance to the soil conservationist. Man has only started to learn the use he can make of such plants in revegetating eroded sites. On poor soils and steep slopes where grass is thin, legumes often form a larger proportion of the flora, both species and individuals, than where soil is good and the slope gentle. Warren observed that legumes developing on poor, steep sites in Nebraska and Kansas slowly enriched the soil until other plants, ecologically more mature, finally invaded and crowded out the legumes. Man may learn to use legumes on such sites to aid natural plant succession and secure the soil. In Maryland, on many thousands of acres of waste land, more than one-half of the plant species are legumes naturally rehabilitating the soil with no help from man. In the plant succession of an old gravel pit in Indiana, legumes decreased from almost a pure stand of white sweetclover, with 8 associated herbs on gravel 1 year from the shovel, to one-fifth as much white sweetclover associated with Desmodium laevigxtum, 12 other herbs, 3 shrubs, and 1 tree on gravel 10 years from the shovel. Practically no legumes occurred in an adjoining woods on unstripped gravel. The total pounds of nitrogen per acre in the gravel pit was also observed to increase as the succession advanced.

The available information on soil and water losses under various types of vegetal cover has recently been summarized by Bennett. These data show that among farm crops legumes are as capable of preventing erosion and run-off as any of our commonly cultivated plants. 1-or example, in experimental plots of 1/100 acre on Vernon fine sandy loam, 7.7-percent slope, at Guthrie, Okla., in a 3-year rotation of cotton, wheat, and sweetclover (wheat seeded in cotton in the fall and in sweetclover the ensuing winter) for the period 1930-35, there was consistently less run-off and less soil lost per acre annually from the plots when in sweetclover than when in any of the other crops used in the rotation. The averages are shown in table 1.

(tables missing due voluntary work)

Likewise, from 8-percent slopes on Shelby silt loam at Bethany, Mo., for the period 1931-35, inclusive, there was less soil and water lost from experimental plots in continuous alfalfa than from those in fallow, corn, rotations of corn, wheat, and clover, and even slightly less than from those plots in continuous grass. During drought the soil in alfalfa cracked to depths of 2 to 4 feet. This tendency for soil to fracture when under alfalfa increases its capacity to absorb water, and thus aids in preventing rim-off. On the basis of this experiment Bennett makes the following estimate of the time necessary to erode 7 inches of soil from Shelby silt loam on an 8-percent slope under four conditions of cover:

(tables missing due voluntary work)

The above figures are given, not to suggest that legumes are the panacea of soil conservationists, but rather to indicate that in addition to their other values, such as their adding nitrogen and organic matter to the soil, the use of legumes may be a mechanical soil-conserving measure of the first rank.

Jason Ladock

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