RATIO OF CROP TO rilOSPIIORIC ACID IN SOIL. 149 



produce of the iinmaiiured, tlie eflect of the phosphoric 

 acid siipphed by the niauure is a]iparently twelve times 

 greater than that of the acid originally contained in the 

 soil. 



The quantity of phosphoric acid supplied (241-4 kilo- 

 grammes) amounted to y\ytli of the total quantity in tlie 

 field (2376 kilogrammes). If the action of both had 

 been alike, the surplus crop should have corresponded to 

 tlie additional supply, but instead of being ^Qtli greater, 

 it was double the crop obtained from the immanured plot. 



This fact is explained by the absorptive number of the 

 Schleissheim soil for phosphoric acid or phosphate of 

 lime. 



If the store of phosphoric acid in the field had been 

 uniformly distributed in the form of phosphate of lime 

 (5170 kilogrammes) to a depth of 25 centimetres (9-8 

 inches), each cubic decimetre (61 cubic inches) would 

 contain 2070 milligrammes (32 grains), each cubic centi- 

 metre about 2 milligrammes of phosphate of lime. 



The field was manured with 657*4 kilogrammes of 

 phosphorite in a soluble state, corresponding to 525 

 million milligrammes (525 kilogrammes) of pure phosphate 

 of lime. 



As determined by direct experiments, 1 cubic deci- 

 metre of Schleissheim soil absorbs 976 milligrammes of 

 phosphate of lime. Each square decimetre received in 

 the manure 525 milligrammes, which, thssolved by rain 

 water in its descent through the soil, would be sufiicient 

 to saturate the earth fully, with phosphate of lime, to a 

 depth of 5-4 centimetres (rather more than 2 inches), or to 

 half-saturate it to a depth of 10-8 centimetres. Hence the 

 manuring served to emlch the upper layer of the soil witli 

 phosphate of lime, not to the extent of j^^yth, but to 50 per 

 cent., and the greater part of this in a state available for 



