No. 7. DErARTMENT OF AGRICULTURE. 237 



regard to the great nitrogen problem, and this is, th^^t there is no 

 such problem except in the minds of people who ignore these facts." 



We cannot too often repeat the fact that the farmer who prac- 

 tices a good short rotation, in which the legumes come frequently 

 on the land, needs never to buy a complete fertilizer, that is one con- 

 taining nitrogen as one of its constituents. The importance of this 

 fact can be seen when we reflect that in the usual complete fer- 

 tilizers on the market the cost of the nitrogen equals or at times 

 exceeds that of the phosphorus and potassium in the mixture. It has 

 been proven bej'ond any reasonable doubt that the agents which en- 

 able the legume plants to combine the free nitrogen of the air are 

 the bacteria which live parasitically on the legume roots. It has 

 been shown that unless these are pre sent the legumes do not get 

 the nitrogen, and that when they are present they do get it. Various 

 theories have been promulgated to explain just how these bacteria 

 do their work, but the exact method is still unknown, and it mat- 

 ters little to the practical farmer, since, for his purposes it is suflQ- 

 cient to know that they do get it. But every now and then some 

 one rises up to say that the scientists are wrong. In a recent Eng- 

 lish daily paper one of these know -it-alls says that the idea that 

 the bacteria do the work is all wrong, for that all plants have the 

 same power, and all get nitrogen from the air through their leaves, 

 and that the best way to increase the nitrogen in the soil is to use 

 Thomas slag liberally. Since this slag is entirely composed of phos- 

 phorus, lime and magnesia it is hard to see how it can increase the 

 nitrogen in the soil unless used to promote the growth of the legume 

 crops. As a rule farmers should pay no attention to the science 

 of the daily papers, for the average newspaper reporter is the most 

 gullible of mortals about anything relating to scientific agriculture. 



While we can get all the nitrogen we need in general farming 

 from the air, we cannot get phosphorus or potassium, and when 

 these are deficient they must be restored to the soil in some way. 

 The element most generally deficient in our old cultivated soils is 

 phosphorus. It is taken from the soil to form the bones of every 

 animal raised on the farm, and the grain crops use it up radily. 

 Potassium exists in most of our clay soils in abundance, but is apt 

 to be deficient in sandy and especially in peaty soils like reclaimed 

 swamp lands. In our clay soils it exists in the form of an insoluble 

 silicate, which is slowly made available by the carbonic acid in 

 rain water, and can be made more readily available by the use of 

 lime or plaster. The chief problem for the farmer is to determine 

 whether it is cheaper for him to get at the potassium in his soil or 

 to use the potash salts. 



The question is then narrowed down to the keeping up in the 

 most economical way the supplies of phosphorus and potassium and 

 putting them in a shape most readily available to crops. 



W^hen these are deficient, they must be added in some artificial 

 w^ay to the soil, and it depends very largely on the conditions sur 

 rounding the farmer as to how he shall do this. If he is so situated 

 that he can profitably buy and feed the grain which has been grown 

 on some other man's land, he can restore these elements and can 

 keep up the fertility of his soil without the purchase of commercial 

 fertilizers. Where he cannot do this with profit, he must buy these 

 elements in the forms in which they are sold on the market. It is 



