28 Mr. A. D. Hall and Dr. N. H. J. Miller. [Mar. 30, 



will be in proportion to the size of the crop. In this way the following 

 results are obtained : — 



Table XIV. 





Broadbalk Field. 



Hoos Field. 





Plot 3. 



Plot 9. 



Plot 4o. 



Plot 4n. 





lbs. 



lbs. 



lbs. 



lbs. 





1936 



6133 



2343 



5524 



Bases restored to the soil as calcium carbonate, cal- 













53 



167 



73 



171 



Mean rate of loss of calcium carbonate from the soil . . . 



800 



564 



675 



465 



Total annual consumption of calcium carbonate ... 



853 



731 



748 



636 



The agreement between the figures in the last line is not very close, but 

 indicates that the restoration of base to the soil, as calculated from the 

 increase of crop on the plots receiving nitrate of soda, is approximately 

 equivalent to the lower rate of loss of calcium carbonate found on analysis of 

 the soil of these plots. 



The results, as a whole, go to show that the action of plants, in leaving 

 behind a basic residue from the neutral salts in the soil upon which they 

 feed, is a very essential feature in the chemistry of the soil, explaining, 

 amongst other things, the maintenance of healthy conditions on the many 

 soils poor in calcium carbonate. It also serves to explain one or two other 

 points which have been observed in connection with the use of sodium nitrate 

 as a manure. It has long been noticed that the continued use of sodium 

 nitrate is very destructive to the texture of a clay soil, intensifying all the 

 clay properties, rendering the soil persistently unworkable when wet, and 

 forming hard and intractable clods when dry. The ultimate cause of such an 

 effect is the " deflocculation " of the fine particles composing the soil ; they 

 are no longer bound together in loose aggregates, but are separated so as to 

 give the soil its most finely grained character. Such deflocculation of the soil 

 can be brought about by a trace of any soluble alkali, just as the opposite state 

 of flocculation is induced by a slightly acid reaction. The Eothamsted soils 

 continuously manured with sodium nitrate show marked signs of defloccu- 

 lation, the drainage water from the nitrated plots in the Broadbalk Field is 

 always more turbid than that from the other plots, and as one of us has 

 shown,* there results in time on the nitrated plots a perceptible washing 



* Hall, ' Trans. Chem. Soc.,' 1904, vol. 85, p. 964. 



