OPERATION OF MANURING AGENTS. 



151 



The operation of manuring agents, severally or 

 jointly applied, is even more marked upon soils which 

 are poorer in nutritive substances than the field at 

 Schleissheim above mentioned. 



The following results were obtained on a field broken 

 up for the purpose, which had not been touched by the 

 plough for fifteen years, and had served as a pasture for 

 sheep. The entire surface-layer of the ground at 

 Schleissheim is 6 inches deep at most ; below this there 

 is no more soil, but a bed of rubble stones, which might 

 be compared to a sieve with meshes an inch wide, 

 through which the water runs freely ; the crop ob- 

 tained from the unmaiiured portion will give some idea 

 of its sterility. Another portion was manured with 

 superphosphate of lime ; the quantity used per hectare 

 ( 2f acres) was 525 kilogrammes ( = 10 cwt.) of 

 phosphorite decomposed by sulphuric acid, containing 

 193 kilogrammes of phosphoric acid, or 420 kilo- 

 grammes ( = 8 cwt.) of phosphate of lime. 



Crop of winter-rye in 1858 at Schleissheim, per 

 hectare : 



Dr. Zoeller found by analysis that this field con- 

 tained, per hectare, to a depth of 6 inches, only 727 

 kilogrammes ( 14 cwt.) of phosphoric acid. 



The plot manured with phosphoric acid produced 

 six times more corn and five times more straw than the 

 unmanured plot. It will be observed that, however 



