101 



the drainage water amounting to about 800 lbs. to iooo lbs. per 

 acre per annum. 



2. The loss is increased by the use of ammoniacil manures by 

 an amount equivalent to the combined acid of the manure. The 

 loss is diminished by the use of sodium nitrate or organic debris 

 like farmyard manure. 



3. The growth of plants normally returns to the soil a large 

 proportion of the basis in the neutral salts which the soil provides 

 for the nutrition of plants. 



4. The calcium oxalate and other organic salts of calcium present 

 in plant residues are converted by bacterial action in the soil into 

 calcium carbonate. 



5. The return of base by the growth of plants and the produc- 

 tion of calcium carbonate by the decay of plant residues are suffi- 

 cient to retain soils neutral which are poor in calcium carbonate, 

 and to replace the basis which have been consumed in nitrification 

 and similar changes." 



EXTRACTS FROM A PAPER ON "THE ANALYSIS 

 OF THE SOIL BY MEANS OF THE PLANT." 



By A. D. HALL, M. A., Director of the Rothamsted Experimental 

 Station {Lawes Agricultural Trust.) 



One of the main problems placed before the agricultural chemist 

 is the estimation of the requirements of a given soil for specific 

 manures, or the interpretation, by means of data obtained in the 

 laboratory, of the behaviour of the soil towards these manures, 

 as seen in properly arranged field experiments. For various 

 reasons the obvious method of determining the proportions of 

 Nitrogen, Phosphoric Acid, and Potash in the soil fails in many 

 cases to give the required information ; even the more modern 

 methods of measuring only the quantities of these materials which 

 are attacked by weak acid solvents, and in consequence regarded 

 as available to the plant, by no means always accord with the 

 results of experience. Hence from time to time attempts have 

 been made to attack the problem from another side and to use the 

 living plant as an analytical agent. The scheme is to take a par- 

 ticular plant grown upon the soil in question, and determine in its 

 ash the proportions of constituents like phosphoric acid and po- 

 tash. Any deviations from the normal in these proportions may 

 then be taken as indicating deficiency or excess of the same con- 

 stituent in the soil and therefore the need or otherwise of specific 

 manuring in that direction. The theory rests on two assumptions, 

 first that each plant has a typical ash composition, constant when 

 the plant is grown under similar conditions ; secondly that the 

 variations in the proportion of such a constituent as phosphoric 

 acid will reflect the amount of that plant food available in the 

 soil, as measured by the response of the crop to phosphatic 

 manuring. ..... 



From The Journal of Agricultural Science, Vol. I, Pt. I, Jan. 1905. 



