82 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



scientist who can devise means of bringing it into an available condition 

 so that our crops can utilise it will confer upon horticulture one of the 

 greatest of blessings. 



Botanical texts-books teach that plants absorb their food from the 

 soil in the form of inorganic salts, such as nitrates, phosphates, 

 sulphates, and chlorides, of potash, soda, lime, magnesia, and iron. We 

 accept this teaching because at present there is no other to offer in its 

 place ; but when the source of soil fertility is discovered we shall not 

 attach so much importance to these inorganic dead earthy chemical 

 substances, for by then we shall have discovered what the millions of 

 soil microbes are doing for the benefit of plants. Much has already 

 been achieved in this direction, and many very able men are engaged in 

 the work ; but would not more rapid progress be made if the prevailing 

 idea were given up that the inorganic salts are the only substances which 

 constitute the soil food of crops ? 



I think the time will come when we shall find that plants have two 

 kinds of soil food — the one the inorganic salts, the other some organic 

 compound made or formed by soil bacteria. That plants absorb and use 

 as food these salts is a fact beyond dispute ; but that they need something 

 else which every soil does not seem capable of supplying is also a fact 

 very evident to all observant cultivators. 



It does not require much reasoning to show indirectly that there is 

 truth in my statement. The scientist says that plants absorb their food 

 as soluble inorganic salts. Let us for a moment suppose they do. Sand 

 forms a splendid rooting medium for most plants. If what the scientist 

 says is correct, we ought to be able to grow splendid plants in sand by 

 judiciously feeding them with what, from their point of view, is the very 

 essence of plant food, i.e. the salts in a soluble condition. Those who 

 have tried this know what miserable specimens are produced compared 

 with others grown in fertile soil which supplies everything necessary for 

 perfect growth. 



Whence do plants get their nitrogen, and in what form is it absorbed ? 

 The teaching of to-day is that plants absorb their nitrogen from the 

 soil principally as nitrates of lime, potash, or soda, and to a less extent as 

 salts of ammonia ; and also that the leguminous plants are able to use free 

 nitrogen from the atmosphere. 



So far as I know no writer has ever said that plants could and do 

 absorb their nitrogen from the soil in the form of organic nitrogen and 

 as ammonium nitrate. 1 know that plants have been fed with urea and 

 one or two other organic salts of this description, but what I mean by 

 " organic " is some form of organic nitrogenous food made by bacteria in 

 which the other elements of nutrition are blended. 



It was thought at one time that the conversion of soil-food from an 

 unavailable to an available form was of a purely chemical nature, but this 

 idea is now giving way to another, for now the change is known to be 

 more or less the work of soil-microbes. 



If we apply organic matter to soil, the nitrogen in it being present as 

 organic nitrogen is changed by different kinds of bacteria, first of all into 

 ammonia, secondly into nitrous acid, and thirdly into nitric acid. The 

 nitric acid then unites with lime or potash, forming nitrate of lime 



