78 



centages of phosphoric acid and potash so small that in 

 the case of the absence or deficiency of lime, the soil is prac- 

 tically sterile. 



(d.) It tends to secure the proper conditions of nitrifica- 

 tion whereby the inert nitrogen of the soil is rendered 

 available. 



(e.) It exerts a most important influence upon the floccu- 

 lation and therefore upon the tillability of the soih" 



For many purposes, gypsum is employed instead of lime, 

 itself, and many of the functions performed by the latter 

 can be quite efiectively accomplished by the substitution 

 of the gypsum (or land plaster), while for certain other 

 purposes, gypsum can be used to better advantage than the 

 lime. 



On account of the tendency which gypsum (sulphate of 

 lime) in a moist condition, has to fix certain volatile ammo- 

 nia compounds, it is highly esteemed for use in covering 

 compost and manure heaps, and effects a saving of consid- 

 erable proportions of valuable plant food, which would 

 otherwise be lost. 



The continuous employment of stimulant manures to the 

 exclusion of nutritive fertilizers, however, is one of the surest 

 and quickest means of impoverishing the soil, since noth- 

 ing of value is added to the stores of plant food, and the 

 pre-existing supplies of nutritive materials are all the more 

 readily removed by virtue of the presence of the lime or 

 kindred stimulants. 



NUTRITIVE MANURES. 



The nutritive manures, in contradistinction to the stimulant, 

 contribute directly to the plant valuable supplies of nutri- 

 ment, and any excess of nutritive ingredients left uncon- 

 sumed by the plant or crop, adds so much to the stores of 

 plant food available for the use of subsequent crops. The 

 various forms and descriptions of commercial fertilizers 

 upon the market are designed to fulfill the office of nutri- 



