38 



MISCELLANEOUS PUBLICATION NO. 1065, U.S. DEPARTMENT OF AGRICULTURE 



applied to farms, Verduin - has carefully exam- 

 ined the evidence and finds that most of the phos- 

 phorus enrichment in surface waters is coming 

 from sewage treatment plants and only second- 

 arily from agricultural fertilizers. 



The sediment delivered into farm ponds by soil 

 erosion is usually insufficient to provide enough 

 nutrients to support aquatic plant growth for 

 fish food. Most recommendations (16, 89) on the 

 management of ponds specify the addition of 100 

 pounds of 8-8-2 fertilizer per acre of pond sur- 

 face to permit the growth of an adequate supply 

 of miscroscopic plants for fish food. If the pond 

 averaged 13 feet deep, the fertilizer would supply 

 0.1 p.p.m. of elemental phosphorus in the water, 

 assuming the phosphorus was entirely soluble. 



The extensive use of fertilizers in farm ponds 

 for fish production is an indication that land run- 

 off is a poor source of the needed phosphorus. 



Phosphorus is getting into streams from farm- 

 land; however, it mainly gets into surface water 

 through runoff and erosion of topsoil. Water seep- 

 ing down through the subsoil or moving laterally 

 through the soil carries virtually no phosphorus 

 because of the high capacity of soil particles to 

 adsorb phosphate. Topsoil contains on the average 

 about 200 p.p.m. of phosphorus adsorbed on soil 

 particles. The clay fraction of a soil usually con- 

 tains about 1,000 p.p.m. of adsorbed phosphorus. 

 Thus, the richer a particular soil happens to be in 

 clay, the more adsorbed phosphorus that can be 

 carried into the stream by soil erosion. 



Soil particles have a tremendous affinity for 

 holding onto phosphate molecules. Even when the 

 fine suspended particles in a river water contain 

 1,000 p.p.m. of phosphorus adsorbed on their 

 surfaces, the phosphorus in true solution may be 

 only 0.005 to 0.0005 p.p.m. Water samples, there- 

 fore, should be analyzed in a way that distin- 

 guishes between phosphorus in true solution and 

 phosphorus adsorbed on suspended sediment. 



Barnyard waste carries around 1,000 p.p.m. of 

 phosphorus. Runoff that flows directly from feed- 

 lots and barnyards into stream channels may be 

 an untoward source of phosphorus. 



The conclusion is obvious that the best way to 

 control the phosphorus content of surface water 



2 Verduin, J. Eutrophication and Agriculture. Pre- 

 sented at Amer. Assoc. Adv. Sci. Symposium, Dec. 27, 1966, 

 Washington, D.C. 



that might arise from agricultural practices is to 

 use soil conservation practices and structures that 

 minimize runoff and sediment delivery from farms 

 and farmsteads. 



Certain aquatic plants such as cattails and sedges 

 that have their roots in bottom sediments offer a 

 more difficult problem. These plants may be a 

 serious nuisance in canals and waterways, and on 

 the edges of ponds and lakes. They can obtain their 

 phosphorus supply by their roots permeating the 

 bottom sediment. They appear to flourish best 

 when this furnishes some adsorbed phosphorus and 

 the water of submersion also contains a trace of 

 phosphorus. 3 



Nitrate in Well Water 



The Public Health Service (125) states : 



Serious and occasionally fatal poisonings in in- 

 fants have occurred following ingestion of well 

 waters shown to contain nitrate (NO.)). This has 

 occurred with sufficient frequency and widespread 

 geographic distribution to compel recognition of 

 the hazard by assigning a limit to the concentra- 

 tion of nitrate in drinking water. 



From 1947 to 1950, 139 cases of methemoglo- 

 binemia (blue babies), including 14 deaths due 

 to nitrate in farm wellwater supplies, have been 

 reported in Minnesota alone. Wastes from chemi- 

 cal fertilizer plants and field fertilization may be 

 sources of pollution. 



The observation that nitrate moves into ground 

 water is not new. As early as 1910, W. P. Headden 

 published extensively on nitrate (53). He found 

 high quantities of nitrate in ground water 80 feet 

 below the surface at a time when chemical fer- 

 tilizers had not been used in Colorado. He reasoned 

 that the nitrate was formed in the surface soil by 

 natural processes and leached to deep horizons. 



Vernon Michael (80) District Health Officer, 

 Franklin County, Wash., implied that heavy use 

 of nitrogen fertilizer in that county resulted in 

 relatively high concentrations of nitrate in drink- 

 ing water. 



De Laguna (31) found high nitrate (about 10 

 p.p.m.) in wells in the vicinity of Suffolk County, 

 N. Y. He concluded that the nitrate in the wells was 

 obviously caused by high applications of fertihzer 

 to the potato fields in the area. 



3 Martin, J. B., and Clements, L. B. National Fert. Devel. 

 Cent., Tennessee Valley Authority, Muscle Shoals, Ala. 



