1. The^Crop Adaptation. While the chemical condition 

 of a soil is not altogether without influence in determining the 

 crops to which it is suited, this, as a rule, at least within such 

 range of soil variation as exists in this state, plays a much less 

 important part than mechanical and physical peculiarities. The 

 crops to which a soil is suited are determined chiefly by its drain- 

 age, its capacity to hold and to conduct water, its temperature 

 and its aeration; and these in turn are determined by the 

 mechanical structure of the soil and sub-soil. Variations in the 

 proportions of gravel, sand, silt, and clay, and not in chemical 

 composition, cause the usual differences in these respects. The 

 varying proportions of these, therefore, usually determine the 

 crops to which a soil is suited. 



2. Fertilizer Requirements. The results of a chemical 

 analysis of a soil do not, as a rule, afford a satisfactory basis for 

 determining manurial requirements. The chemist, it is true, can 

 determine what the soil contains, but no ordinary analysis 

 determines with exactness what proportion of the several 

 elements present is in available form for the crop. Indeed, there 

 is no such thing as a constant ratio of availability. While one 

 crop finds in a given soil all the plant food it requires, another 

 may find a shortage of one or more elements. Further, on the 

 very same field one crop may find an insufficient amount of 

 potash, another may find enough potash for normal growth, but 

 insufficient phosphoric acid; while a third may suffer only from 

 an insufficient supply of nitrogen. 



Most of our soils are of mixed rock origin, and, as a rule, possess 

 similar general chemical characteristics, providing they have been 

 farmed under usual conditions. The manurial and fertilizer re- 

 quirements are determined more largely for most soils by the crop 

 than by peculiarities in the chemical condition of the soil. 



3. Crop Diseases. In some cases, the correspondent reports 

 that his crop is diseased, and that he desires a chemical analysis 

 in order to ascertain what is the cause. The chemical composition 

 of the soil may in some instances exercise a controlling influence 

 in determining a condition of health or disease, and is never 

 unimportant from the standpoint of vigorous, normal and healthy 

 growth ; but in the case of most diseases, the immediately active 

 cause is the presence of a parasitic fungus, and this fungus is 

 usually capable of fixing itself upon the plant whatever may be 

 the composition of the soil. A knowledge of the chemical com- 

 position of soils, therefore, will not make it possible to advise such 

 manurial or fertilizer treatment as will insure immunity from 

 disease. 



