element of food, and its value as an element is measured ^°°^ ^^^ 



largely by the content of minerals in the 'pi, -d 4.tt f —^- 



soil, with which it must associate and com- „. _ ^^7 



bine, in order to fully meet the food needs of 



I TT 1 AT- • quires an 



plants. Hence, where JNitrogen m any ^, , ^ 



j: , , r •^■ ■ Abundance of 



form IS recommended as a lertilizer, it _,, t. • a -j 



, , , , 1 ,1 , , , . Pnosphonc Acid 



should be understood that the phosphoric , -X j. ^ - 



. , , , r 1 1 and Potash in 



acid and potash necessary tor the growth , _ „ 



of the crop must either be supplied with it, 

 or have been previously applied, or should have existed 

 naturally in the soil. On poor soils, therefore, the 

 application of the minerals must be made with the 

 Nitrogen, while in cases where the soil is naturally 

 rich in minerals, if Nitrogen only is added, the crops are 

 largely increased, because, by virtue of the presence of 

 Nitrogen, they are able to gather the phosphoric acid and 

 potash needed from the natural supplies in the soil, previously 

 inaccessible to them, because of the deficiency in Nitrogen. 

 Under such circumstances, it is a commendable practice to 

 use Nitrogen only, as it enables a use of soil constituents, 

 which are of no service while in the soil. The fear that such 

 use of Nitrogen will result in an undue exhaustion of phos- 

 phoric acid and potash, which is sometimes expressed, is not 

 well founded, since, where an increase in crop is caused by 

 the use of Nitrogen only, the amounts of phosphoric acid and 

 potash removed in the crop would not be relatively greater than 

 the amounts removed were some other condition responsible 

 for the increased yield. 



The chances of recovering, in the form of produce, the 

 minerals used in excess are greater than are the chances of 

 recovering all of the Nitrogen used in excess of the needs of the 

 plants, or even that used in moderate amounts, because of the 

 differences in the fixing power of soils for the different elements 

 when in a condition to feed plants. The Nitrogen, when in its 

 available form, the Nitrate, does not form again any fixed 

 compounds with the soil; hence, if the plant does not take 

 it up, it may be lost by virtue of further changes of form, 

 which results in its loss as a gas. This applies to the Nitrogen 

 in organic and ammonia forms, as well as to the Nitrate. 

 In the use of Nitrogen, the aim should be to feed the plant; 

 in the case of the minerals, excessive quantities may be used, 

 as the accumulations are not liable to escape. 



