902 



Observations of the cliaii'ie ni coinixisitiun of dininase \vat«'r from 2 

 ]>lats (Mi which aiiiinoiiiiim salts \vei«' applied on Maich 12 and October 

 25 serve to illustrate this fact, as well as to show that the chlorides 

 are a more reliable index of the movement of soluble salts in the s«)il 

 than the nitrates. 



The principal constituent in drainage water is calcium carbonate. 

 Application of fertilizers, especially ammonium salts, increases the pro- 

 ])ortion of this ingredient. 



If we take the meau of ten series of analyses of drainage waters by Voelcker ami 

 Frankland (1866-73), and assume the average drainage in Broadbalk fiehl as 10 inches 

 per annnm, we have 223 pounds of lime and magnesia as the annual loss per acre 

 upon the unmanured plat ; 297 pounds on the plat receiving sniierphosphat*', with 

 sulphates of jiotassium, sodium, and magnesium ; 284 pounds on the plat receiving 

 sodium nitrate, with half a dressing of superph<»s}ihate and alkali sulphates; 389 

 pounds on the i>lat manured with ammonium salts only; 443 pounds wlnre saper- 

 phosjdiate is used with the aunnoiiiiiiii salts; and a mean of iK'i jxuiutls w iu-rt' alkali 

 siiljihates are also aiii)lied. 



Potash and jihosphoric acid were ]>resent in only small (iuantities(.i.C 

 and 2.1 i>ounds per acre, resi>ectively, for 10 inch drainage), anil it is 

 ]>robable tlmt without drainpipes the greater part of both would be 

 retained in the soil. Soda was present in larg*' (piantity, as soils have 

 slight retentive power for this constituent. 



The average proportion for 5 years of nitrogen as nitnitaes in drain- 

 age waters of 12 ]tlats differently manured, is given in a table. In 

 the case of plats receiving nitrogenous manure, "the spring jn-riod 

 shows a considerable diminution in the amount (»f nitiatesin the drain- 

 age water, which is followed by their abiiosi entire disiippearanc«> in 

 summer. Autumn shows the maxinuim amount of nitrates for the year, 

 and winter stands second in the richness of the drainage water. The 

 jdat re«*eiving ash constituents shows a little more nitrate in the drain- 

 age water than the i)ermanently unmanured land.'' In the case of phits 

 receiving ammonium salts in March the drainage water was richest in 

 nitrates in the si)ring and disappeared in Juiu' or July, and ewu as 

 early as May. With nitrate of soda the loss was mu«'h less than with 

 ainmonium salts. When nitrogenous manures were apjjlied in tlie fall 

 the greatest loss of nitrates occurred during the winter months. 



The deep wclht of JIarpenden. — "The water supply of Harpenden is 

 deriv^ed entirely from wells sunk in the chalk, which «'omes in some 

 l)laces to the surface, and is prob;ibly never incu-e than 2r> feet beneath 

 it. The water in the wells is in the valley al»out (i(» feet ami on the hills 

 about 120 to 14") feet below the surftice. The water level of the <listrict 

 exhibitsa rather steep gradient, the undergr(»und flow of water being 

 ai)parently from northwest to southeast. This flow of underground 

 water consists of the mixed drainage of a large are:i of agricultural 

 laud." 



