io POPULAR SCIENCE MONTHLY 



lands, to choke the reservoirs, to waste the water-power, and to bar up 

 the navigable rivers. The highest solution of the problem for the 

 tiller of the soil essentially solves the whole train of problems. 



How is this control to be effected? All the known and tried 

 methods of preventing wash and turning the rainfall into the soil 

 should be duly employed. It is obvious that all methods of culture 

 and all crops that increase the granularity and porosity of the soil con- 

 tribute to the end sought. Deep tilth to promote soil granulation and 

 deep-rooting plants to form root-tubes are specific modes of great 

 value. Artificial underdrainage by preventing water-logging and pro- 

 moting granulation aids the end sought. Contour cultivation by 

 arresting and distributing the surface wash may also assist. Alternate 

 strips of protected and cultivated land, reservoirs for catching and 

 distributing concentrated rainfall, and other devices, serve to limit the 

 wash of the slopes and give the surface waters the right direction. 



It is possible that some of the more radical and permanent remedies 

 will be found by a closer study of nature's methods. Nature has been 

 working at this complex problem of balance between soil formation, 

 soil waste, surface slope, plant growth and stream development, for 

 millions of years. Looking closely at her methods, we note that she 

 uses a much larger variety of plants to cover and protect the soil than 

 we do, and that these plants have a wider range of adaptation to the 

 special situations where protection is needed. We may, therefore, in- 

 quire whether we should not follow this precedent farther by develop- 

 ing more kinds of profitable plants and by using the protective varieties 

 more freely on slopes especially subject to wash. Forest trees are a 

 resource of this kind and should be employed as fully as practicable, 

 as will, no doubt, be urged with great cogency by those who discuss 

 the problem of forestry. We also have many shrubs, vines and fruit 

 trees, whose employment to the maximum in covering areas subject to 

 wash is likewise urged, either alone or in conjunction with trees. We 

 are forced to recognize, however, that for the greater part the berries 

 and fruits which render these profitable are perishable and have limita- 

 tions of preservation, transportation, market, etc. But if shrubs and 

 vines could be evolved by modern selective methods, whose nut-meats or 

 dry seeds should be available for food in place of the watery pulp, and 

 which could be treated much as cereals are, and have similar wide 

 year-round markets, there would be a larger choice of crops to grow 

 in soils subject to wash, and we might secure soil-protection with less 

 crop-limitation. There would then be less need to press the culture of 

 the cereals so far as we do now, and they could be limited more largely 

 to surfaces less subject to harmful soil-loss. 



Another of nature's marked methods is the formation of plant- 

 societies, or, from our point of view, combination-crops. No doubt 



