SOILS FEETILIZEES. 425 



" The soil-forming actions of the wind may be classed roughly under two 

 headings, soil removal and soil mixing. In removal the wind is but one of 

 several agents (of which running water is probably the chief) which, by remov- 

 ing weathered soil material from the land surface into the sea, progressively 

 expose the rocks beneath to the processes of decay, enabling the maintenance of 

 that balance upon which depends the permanence of the soil layer. Among 

 these agents the wind is greatest only in areas of considerable aridity, and even 

 there It is by no means the sole active factor. From our present viewpoint, the 

 second or mixing action is of far greater and more general importance. The 

 carrying of soil material from place to place across the land surface makes 

 possible, as already discussed, the existence in any particular soil of minerals 

 not present in its parent rocks, and is one cause of the well-known and remark- 

 able constancy with which the useful minerals occur in the soils of the world. 

 In this action the wind shows its greatest effectiveness. As a mixer of soils 

 already formed, it yields to none. Nor is this action, like the former, confined 

 to arid lands. . . . Even in humid regions there is much movement of soil by 

 wind and soil mixing by such movement is a factor which must not be neg- 

 lec-ted," a fact well illustrated by one of the author's observations on the wind- 

 blown sands of Anne Arundel County, Md. 



Soil erosion, W J McGee (U. 8. Dept. Agr., Bur. Soils Bui. 11, pp. 60, pis. 33, 

 fiffs. 3). — This bulletin discusses the agricultural duty of water, the duty of 

 the soil, the natural and abnormal work of water in agriculture, and remedies 

 for soil erosion based on treatment of the soil by tillage, mulching, fertilizing, 

 seasonable plowing, draining, and dust mulching; the treatment of cover by 

 tree planting, grassing, nurse cropping, cover cropping, eradication of weeds,- 

 and rotation of crops; the treatment of slopes by contouring, terracing, vine- 

 yarding, retain-walling, annular forestation, and grading; and the treatment 

 of the water supply by regulating its movement. 



The author siunmarizes the requisites for the maintaining of a natural bal- 

 ance between cover, soil, and slope as " (1) to retain mulch and humus, partly 

 to hold the waters of rains and snows, partly to temper and so increase the 

 friability and sponginess of the soil; (2) to till deeply in order that the soil 

 body may be kept open to free circulation of the soil fluid; (3) to select crops 

 partly for the sake of affording cover for the longest practicable portion of 

 the year, especially on steeper slopes; (4) to rotate crops partly for the sake 

 of alternating long and short seasons of cover and so checking any erosion 

 started by defective cover; (5) in the dearth of vegetal mulch, to maintain a 

 dust mulch tending to check evaporation from the surface and thus to promote 

 circulation through the crop plants; and (6) on all steeper slopes to plow 

 and plant on contours, thereby closing gullies and channels and retarding 

 run-off. ... 



" The several modes of treatment designed to remedy or prevent soil erosion 

 are alike in principle — all operate through regulating the movement of water. 

 The primary object is conservation of both solid and fluid parts of the soil 

 through a balanced distribution of the water supply. The ideal distribution 

 is attained when all the rainfall or melting snow is absorbed by the ground 

 or its cover, leaving none to run ofC over the surface of fleld or pasture: in 

 which case the water so absorbed is retained in the soil and subsoil until 

 utilized largely or wholly in the making of useful crops, while any excess 

 either remains in the deeper subsoil and rocks as ground water or through 

 seepage feeds the permanent streams. Although this ideal distribution can 

 commonly be brought about by proper treatment, it frequently fails on account ' 

 of (a) inequality of supply, (&) catastrophic storms, (c) defective drainage, 



