THE PHYSICO-CHEMICAL INVESTIGATION OF SOILS. 



319 



kept in view. The former interests vitally the permanent 

 settler or farmer ; the latter concerns the immediate outlook 

 for crop production, the " Diingerzustand " of the Germans. 

 The methods for the ascertainment of these two factors are 

 wholly distinct, even though the results and their causes are 

 in most cases intimately correlated. The failure to observe 

 this distinction accounts for a great deal of the obloquy and 

 reproach that has in the past so often been heaped upon chem- 

 ical soil-analysis and its advocates. 



PHYSICAL AND CHEMICAL CONDITIONS OF PLANT GROWTH. 



While it is true that plants cannot form their substance or 

 develop healthy growth in the absence or scarcity of the chem- 

 ical ingredients mentioned on page xxxi of this volume, it is 

 also true that they cannot use these unless the physical condi- 

 tions of normal vegetation are first fulfilled. Both sets of con- 

 ditions are intrinsically equally important and exacting as to 

 their fulfilment; and the farmers' task is to bring about this 

 concurrence to the utmost extent possible. The chemical in- 

 gredients of plant-food can, however, be artificially supplied 

 in the form of fertilizers, should they be deficient in the soil; 

 but as has been shown in the preceding pages, it is not always 

 possible to correct, within the limits of farm economy, phy- 

 sical defects existing in the land. Hence, however important 

 is the natural richness of the soil in plant-food, flic first care 

 should always be given to the ascertainment of the proper phy- 

 sical conditions in the soil, subsoil and substrata. Without 

 these, oftentimes, no amount of cultivation, fertilization and 

 irrigation is effective in assuring profitable cultural results. 



Condition of the Plant-food Ingredients in the Soil. But 

 even the abundant presence of the plant-food ingredients, as 

 shown by analysis, will not avail, unless at least an adequate 

 portion of the same exists in a form or forms accessible to 

 plants. Of course this condition would seem to be best ful- 

 filled by the ingredients in question being in the water-soluble 

 condition. But in the first place, plants are quite sensitive to 

 an over-supply of soluble mineral salts, as is evidenced by the 

 injurious effects produced by the latter in saline and alkali 

 lands. Furthermore, substances in that form would be very 



