THE SOIL 45 

 HOW TO DETERMINE WHAT THE SOIL NEEDS. 



When men first began to be interested in the chemical composition of 

 soils, and the improvement of their productive capacity, they jumped to the 

 conclusion that a chemical analysis would show them just what was lacking; 

 and by adding this they could restore the soil to its original productive 

 character. But chemical analysis at once showed them that there may exist 

 very large quantities of all the needed plant foods and yet the soil remain in 

 a very unproductive state, owing to the fact that the plant food it contains 

 is in a condition insoluble in the soil-water, and, as the plants cannot take 

 anything through their roots that is not completely dissolved in the soil- 

 water, they starve in the midst of potential plenty. Therefore, while soil 

 analysis has its use, it can never be depended upon to tell the farmer just 

 what his soil needs to render it productive, so far as the food supply is con- 

 cerned. The fact is, too, that soils vary widely within narrow areas, and an 

 analysis of the soil from one portion of a field will not give a correct idea of 

 the nature of the soil in another portion. As the uselessness of soil analyses 

 became apparent men began to study the needs of plants, and the way in 

 which different crops use the food elements. While all plants use the same 

 kinds of food from the soil, they use them in varying proportions, one needing 

 more nitrogen, or more phosphoric acid, or more potash than another. Acting 

 on the belief that from the analysis of the plant we could accordingly propor- 

 tion the different plant-food elements for each crop, the manufacturers of 

 fertilizers began to make what are known as special fertilizers, and recom- 

 mended one for one crop and another for another. There seemed to be a rea- 

 sonable basis for such notions, but really there is not such a serious difference 

 after all, in the manurial requirements of plants, while there is a wide dif- 

 ference in the manurial requirements of soils. 



If chemical analysis, then, will not materially help us in deciding what 

 our soils need, how are we to ascertain what we should apply and what we 

 need not buy? All farmers know that without some such knowledge they 

 are likely to be wasting money in the purchase of matters that they do not 

 need on their land. This is a matter which every farmer must find out for 

 himself, and no one can find it for him elsewhere than right on his own farm. 



Hence every farmer should be, to some extent, an experimenter. He 

 must experiment with his land not only to discover its food needs, but also 

 to find whether through imperfect preparation and imperfect drainage he 

 is not obliged to buy plant food which he does not need at all. Of the 

 methods of this experimentation we will treat in detail elsewhere. First let 

 us see what things are essential in the soil in order that plants may grow. 



