ENRICinN({ SOIL— COMMERCIAL RESOURCES 81) 



soluble in soil wator; hy its being of such com- 

 position that tli»» plant will nso it. 



l.')l!. ()ii»» ])ri)l)l('in for tlio airricultnrist is to 

 secure available plant-food, and to dt't»^rinine 

 .vhotlicr it i^ better to indoek tlic itlant-food 

 in tho soil by means of tillas^e, or to supply 

 tho elcnuMits in some mamu'o or ftn-tilizci-. 



in.'>. Barn nianni'fs an* not always to Ik^ had, 

 and they an^ varialjle in cotnjtosition. It is often 

 advisable, therefore, to substitute conunercial or 

 eoneontratod fertilizers, in which the constituents 

 aro of known amounts and often readily avail- 

 able. Barn manures are bulky. Even manure 

 of cattle from a covered yard contains a> 

 hiji^h as 70 or 7.") pn- cfiit of \\at«'r, and usu- 

 ally less than I j)cr cent of nitrogen, phos- 

 phoric acid or potash. If it were not for its 

 influence in improvinjLT thf jiliysical effects of the 

 soil, stable manure would have comparatively 

 little value. 



2. Nitrngrfi 



134. Nitrop^en is the most important element 

 which the farmer adds to his soil. It comprises 

 part of all prreen and woody parts of })lants. 

 It seems to l)e the element most intimately 

 associated with rapid ^-rowth in plants. Plants 

 that feed excessively on nitrogen tend to pro- 



