WASTES IN RELATION TO AGRICULTURE AND FORESTRY 



95 



roads and highways, and on other construction 

 sites is a new requirement of great urgency. 



Increasing demands for greater quantities of 

 water of improved quality may soon require that 

 positive steps be taken to stabilize and control crit- 

 ical sediment source areas in urban, agricultural, 

 and forested environments. In urban areas, erosion 

 from construction and development sites is a po- 

 tent contributor to the sediment content of streams. 

 Studies have shown that erosion in the Washing- 

 ton, D.C. metropolitan area is a primary source of 

 sediment polluting the Potomac River estuary and 

 will have to be controlled before this portion of 

 the Potomac River can be restored to its natural 

 beauty and used for its full potential. 



Economically feasible erosion-control techniques 

 are needed for use in suburban development and 

 preparation of industrial construction sites. Better 

 means of channeling and trapping uncontrollable 

 sediment delivery from these sites must be de- 

 veloped. 



Soil erosion by water, the dominant problem on 

 179 million acres of cropland, is feasible to treat 

 with measures that reduce soil losses {25). Highly 

 mechanized farming on large tracts, monoculture, 

 and intensive culture, all focus on the need for new 

 technology that will provide for more economic- 

 ally feasible systems of erosion control under these 

 systems. 



More than 40 million acres of forest and related 

 rangelands are eroding because of disturbances or 

 destruction of cover. They produce an estimated 

 100 million tons of sediment each year. Approxi- 

 mately 90 percent of this sediment is produced by 

 roads, logging skid trails, and burned areas. Not 

 only are these lands reduced in productivity, but 

 they are sources of sediment-laden floods and mud- 

 rock flows, which destroy crops, homes, roads, and 

 other improvements, and impair water quality for 

 irrigation, industrial, and domestic use. 



Research towards diminution of forest fires, 

 gully development, and overgrazing of rangelands 

 would contribute very much to reduction in sedi- 

 ment delivery. 



Strip mining for coal and minerals has become 

 more economic with the advent of large, powerful 

 machinery. Tremendous spoil banks and barren 

 areas are formed. These piles of raw earth ma- 

 terials are usually highly erodible. Revegetation 



of these barren areas is frequently very difficult 

 because of high acidity and low content of mineral 

 nutrients. 



Revegetation is difficult on gullies, spoil banks, 

 roadbanks, strip mine areas, overgrazed range- 

 lands, forest burns, and other badly disturbed, un- 

 stable, or deteriorated sites where growing condi- 

 tions are severe. Adapted species, varieties, or 

 strains must be found or developed to revegetate 

 and stabilize these critical sediment source areas. 

 This will require extensive research on selection, 

 evaluation, and culture of promising plant ma- 

 terials. Revegetation may involve a succession of 

 species, with the first cover probably involving 

 plants that can become established quickly under 

 conditions of low fertility and drought. 



Engineering modification of barren surfaces 

 and addition of specific soil amendments will need 

 research attention for effective revegetation of 

 many of these deteriorated sites. 



Plant Nutrients 



Concern is growing over the eutrophication of 

 lakes and rivers. The enrichment of these waters 

 with plant nutrients, particularly nitrogen and 

 phosphorus, enables the growth of algae and 

 other water plants that are the base of the eutroph- 

 ic process. These nutrients may come from many 

 different sources: Domestic sewage, including: the 

 phosphate in detergents; processing wastes; gar- 

 bage and refuse dumps ; animal wastes ; land run- 

 off ; and land drainage. 



More and more evidence is appearing on the 

 prevalence of nitrate in ground waters. Possible 

 sources include fertilization of farmland, feedlots 

 and barnyards, septic tanks and other domestic 

 sewage, processing effluent, and natural sou: 

 such as niter spots in semiarid regions. 



When phosphorus or nitrate is found in water, 

 the relative importance of possible sources of ori- 

 gin is largely conjecture. This provides fertile 

 ground for arguments. To the extent possible, con- 

 jectures should be replaced by sound information. 



Very little modern information is available on 

 the phosphorus content of runoff from land vary- 

 ing in geochemica] characteristics, treatment with 

 chemical amendment and fertilizers, cultural prac- 

 tices, and hydrologic conditions. The data avail- 

 able indicate that total quantities of phosphorus 



