DEPARTMENT OF AGRICULTURE. 



FUNCTION OF PLANT-FOOD CONSTITUENTS. 



To intelligently use fertilizers a knowledge of the functions of the plant-food 

 materials added to the soil is necessary. The kind of fertilizer to use upon a given 

 soil will depend upon the character of the soil and the crop it is proposed to raise. 

 For example, it would be poor economy to fertilize heavily with nitrogen when 

 clover is to be the crop, because of the ability of that plant to obtain its own supply 

 of that element. 



FUNCTION OF NITROGEN AS A FERTILIZER. 



Nitrogen stimulates the growth of the vegetative parts. Truck-crops such as 

 lettuce, celery, and cabbage are greatly improved by its use owing to the fact that 

 it stimulates rapid growth. 



With certain crops there is a danger of an overapplication. If too much 

 nitrogen is applied to potatoes the growth of vine will be stimulated at the expense 

 of tubers. 



When the season is short and the grain-crops have a tendency not to ripen, the 

 use of nitrogen may not be advisable. On the whole, this fertilizer tends to lengthen 

 the growing season. When trees appear to be stunted nitrogen is frequently 

 beneficial, in that it will induce a more luxuriant growth. 



Clover, alfalfa, peas, beans, vetches, and other legumes are seldom benefited by 

 using a nitrogen fertilizer, in that this group of plants can use the free nitrogen of 

 the air. In farm practice inclusion of a legume at short intervals in the rotation 

 will dispense with nitrogen fertilizers. 



FUNCTION OF PHOSPHORIC ACID AS A FERTILIZER. 



Phosphoric acid hastens the maturity of crops. It has a ripening effect and 

 serves to hasten grain and fruit formation ; it stimulates root-development in young 

 plants. The proportion of grain to straw is usually higher with ample phosphoric 

 acid. In a very general way grain-crops are heavy phosphoric-acid feeders. It is 

 required to build up protein and consequently should be liberally supplied to the 

 legume crops that are rich in protein. 



FUNCTION OF POTASH. 



Potash is essential to the formation of starch, sugar, and cellulose in plants. 

 The flavour and colour of fruits is generally credited to potassium. Potatoes and 

 sugar-beets in particular require an abundant supply of potash owing to the quantity 

 of starch and sugar they contain. Experiments show that soils without sufficient 

 potash do not produce as heavy grain-crops. This is probably due to the effect of 

 potash in prolonging the growing season of grains. However, the growing season of 

 all crops is not prolonged by the use of potash. With roots the reverse is found to 

 be true. 



FUNCTION OF CALCIUM OR LIME. 



Calcium seems to impart hardness to the plant. It has been noticed that soils 

 containing an abundant supply of lime usually produce well-nourished crops that are 

 capable of standing unfavourable climatic conditions, such as drought or early frost. 

 It has also a decided beneficial effect on the texture or physical condition of the 

 soil. Lime acts as a liberator of plant-food, particularly potash, held in insoluble 

 forms in the soil. It neutralizes soil-acidity, a condition that is not favourable to 

 the normal development of a great many farm crops. 



TYPE OF SOIL AND FERTILIZER REQUIREMENT. 



On most soils and for most crops a judicious mixture of nitrogen, phosphoric 

 acid, and potash will give the best results. Clays or clay loams if adequately 

 supplied with lime may not require potash. Peat soils as a rule only require lime, 



