96 



MISCELLANEOUS PUBLICATION NO. 10G5, U.S. DEPARTMENT OF AGRICULTURE 



in water derived from either surface or subsurface 

 land runoff are at levels that are completely in- 

 significant in terms of agricultural production, but 

 may be approaching significance for growth of 

 algae which respond to as little as 0.05 p.p.m. of 

 phosphorus in the growth medium. 



Far more study is needed on the method of de- 

 termining phosphorus content of water in terms 

 of biological significance. Trying to interpret the 

 significance of values for total phosphorus con- 

 tent of river water is analogous to grinding up a 

 whole cow and then testing a bit of the resulting 

 hamburger to see if the animal had ketosis. 



The development of suitable analytical proce- 

 dures may help us to distinguish at least four dif- 

 ferent states of phosphorus in water samples: (a) 

 That which is in true solution as orthophosphate ; 

 (b) that which is in solution in a nonpolar form 

 as an organic polyelectrolyte ; (c) that which is 

 adsorbed on the surface of suspensoids; and (d) 

 that which is a component part of the mineral 

 of the suspensoid. Information is especially 

 needed as to the degree of liability of phosphorus 

 in entities (i) and (c) in terms of growth of water 

 plants. 



It is urgent that we rapidly alleviate the grave 

 dearth of qualitative and quantitative information 

 on the phosphorus in runoff and drainage water 

 from agricultural and forested lands as affected by 

 soil type, fertilizer practices, cultural practices, 

 vegetative cover, and climatic conditions. 



The lability of phosphorus in bottom sediments 

 in streams is little understood in terms of its avail- 

 ability for growth of algae even if it is available 

 to bottom-rooted plants. We need to know how tur- 

 bulence in stirring up bottom sediments, presence 

 of organic matter, prevalence of aerobic vs. anaer- 

 obic conditions, and the activity of metallic ions 

 such as iron and aluminum, affect release of phos- 

 phorus adsorbed on sediment particles. 



In terms of eutrophication of surface waters, 

 we also need information on nitrogen and potas- 

 sium moving from the land into streams, even 

 (hough need for information pertaining to these 

 two elements does not appear to be as pressing as 

 that for phosphorus. 



Whereas phosphorus appears to be the nutrient 

 that limits the growth of free-floating plants, 

 such as algae, different circumstances may control 

 the growth of bottom-rooting plants which have 



direct access to the phosphorus reserves in the bot- 

 tom muds. Evidence shows that when nitrogen 

 supplies are adequate, the growth will be con- 

 trolled by the supply of potassium in the water. 

 The extent to which this is supplied from ferti- 

 lizers is not known. 



Nitrate is found in ground water and there is 

 concern on the readiness with which this anion may 

 be reduced to nitrite and cause methemoglobinemia 

 in babies or nitrite poisoning in ruminants. There 

 is evidence that nitrate in ground water does not 

 come from fertilizers applied to fields ; and there is 

 evidence to the contrary. Supplementary informa- 

 tion to fully explain this apparent contradiction 

 must be attained. 



Nitrate is formed naturally in soils. In arid or 

 semi a rid regions, it accumulates near the surface 

 as caliche or as "brown alkali'' — niter spots — in 

 the surface soils. No one has adequately explained 

 whence this nitrate came. Under the right hydro- 

 logic conditions, it may be leached into ground 

 water. If it is formed in humid regions, it is so 

 leached. 



Evidence is at hand that nitrate does enter the 

 ground water system in leachate from cattle pens 

 and feedlots. In a restricted locality such down- 

 ward movement of nitrate may be appreciable, but 

 little is known of the total contribution of this 

 source to overall content of nitrate in an aquifer. 



Domestic sewage is certainly a source of nitrate 

 in ground water. This may be the main source of 

 such nitrate in rural communities. Certainly there 

 is need to replace unwarranted supposition with 

 irrefutable evidence. 



As nitrate and associated entities move down- 

 ward from the surface soil to the water table, there 

 is much need for information on the prevalence of 

 conditions for the formation of nitrite at various 

 horizons as well as in the ground water. 



Inorganic Salts and Minerals 



Inorganic salts and minerals in the effluent from 

 certain metallurgical and chemical industries, and 

 the acidic drainage from many operating and 

 abandoned mines, can seriously impair the quality 

 of water. All fish may be killed. Use of an afflicted 

 stream for recreation areas in forests or in other 

 parts of upstream watersheds may be seriously im- 

 paired. Such water is generally unusable for irri- 



