254 



GUANO. 



Increase of produce above the unmanured plot (see p. 186). 



In Cunnersdorf, the increase of produce obtained 

 in 1851, over the unmanured field, amounted to 



Corn. Straw. Eatio. 

 Ibs. Ibs. Ibs. 



By farm-yard manure (180 cwt.) ... 337 1745 = 1:5 



By guano (379 Ibs.) 765 3028 = 1 : 3'8 



The field at Cunnersdorf was naturally rich in those 

 ingredients which we have designated as St (straw) con- 

 stituents (silicic acid, potash, lime, magnesia, iron), and 

 the increase of these by the farm-yard manure aug- 

 mented the straw at the expense of the grain crop. 

 The farm-yard manure contained too little of the K 

 (corn) constituents (nitrogen, phosphoric acid). 



This explains the powerful action of guano (which 

 contains chiefly K constituents) upon this field; the 

 increase of corn by its means was more than double 

 that obtained from farm-yard manure, and a more suit- 

 able proportion was established between the. K and S 

 constituents in the ground. 



At Mausegast the increase of produce obtained in 

 1851, above that of the unmanured field, amounted to 



Corn. Straw. Eatio. 

 Ibs. Ibs. Ibs. 



By farm-yard manure (194 cwt.) ... 345 736 = 1 : 2-1 



By guano (411 Ibs.) 455 1369 = 1 : 3'0 



This field was richer in K and S constituents than the 



