48 GARDEN FARMING 



preference but one of economy. Growers conducting intensive 

 cultivation on expensive land with high-priced labor can better 

 afford to purchase plants than to grow them. The special rates 

 and quick transportation facilities now available to plant growers 

 will tend to build up this important accessory to truck farming. It 

 cannot be denied that to be able to purchase plants to make up a 

 shortage or to replace those lost through misfortune or poor seed 

 is a great advantage to the market grower. 



Fertilizers. In market-garden work and in agriculture the terms 

 " fertilizers " and " manures " are usually synonymous. A fertilizer 

 or manure may be defined as any substance applied to the soil 

 which increases the soil's supply of available plant food. There 

 are two classes of such manures : (i) those which add to the sum 

 total of the plant food in the soil, such as stable manure, green 

 crops plowed under chemical fertilizers which contain nitrogen, 

 phosphoric acid, and potash ; (2) manures which by their chemical 

 action upon the soil make available an increased amount of the 

 plant food already contained in it. The latter act in the way of a 

 stimulant rather than as a true manure, yet, according to the defi- 

 nition, they are just as much manure or fertilizer as is any sub- 

 stance which increases the actual quantity of available plant food 

 in the soil. Such fertilizers as land plaster, lime, salt, etc. belong 

 to this class, since they add nothing to the sum total of the plant 

 food in the soil, but by their chemical action render available an 

 increased amount of the existing plant food. 



The action of fertilizers on the growth of plants is determined 

 by the predominance of one or another of the three important ele- 

 ments which usually make up a fertilizer, namely, nitrogen, phos- 

 phoric acid, and potash. 



Nitrogen. Nitrogen, which, in stable manure, is in the form of 

 ammonia, and in commercial fertilizers may be in the form of dried 

 blood or other animal products or nitrate of soda, is the most active 

 principle in all our so-called manures or fertilizers. This particular 

 ingredient stimulates leaf growth, intensifies the green color of 

 most plants, and has a tendency to promote an abnormal growth 

 of herbage and to delay maturity. For lettuce, spinach, cabbage, 

 and leafy plants in general, where it is desirable to get a large 

 quantity of herbage, nitrogen is a most important manure. 



