450 MISCELLANEOUS FARM SUBJECTS 



They thus require an abundance of easily available plant food. 

 Other plants grow more slowly and take a long time to mature. They 

 can utilize the more difficultly available forms of plant food which 

 would be almost useless to the plants first named. These differences 

 account for the fact that different plants require different fertilizers 

 even on the same soil. 



It is not possible to prepare formulas for fertilizers which are 

 best for this or that crop. This is seen by the fact that fertilizers put 

 up for special crops by different manufacturers may vary widely in 

 composition. The best fertilizer to use depends both on the soil and 

 the kind of crop, though it is always safe to apply an abundance of 

 plant food if the crop is valuable. However this may lead to waste 

 of plant food. Some fertilizer formulas are based on the analyses of 

 the plants, but plants vary in their power to secure food, as well as 

 in their needs, and they take up an excess (especially of potash) 

 when they can get it. 



The legumes a class of plant which, includes the various 

 clovers, peas, beans, vetches, etc. differ from other plants in being 

 able, under proper conditions, to acquire their nitrogen from the 

 air through the aid of organisms working in their root tubercles, 

 and can, therefore, make perfect growth without depending upon 

 soil nitrogen. On the other hand, the various grasses and grains 

 are not only dependent upon soil nitrogen, but they must have an 

 abundance during their period of most rapid growth in order to 

 attain their maximum development. For the latter class of plants 

 favorable results are secured from the proper use of nitrogenous 

 manures, while for the former class the application of nitrogenous 

 manures simply results in supplying an element which could have 

 been secured quite as well by the plant itself without expense. Illus- 

 trations could be multiplied, though they be less striking than this, 

 showing that the variations in crops in respect to their power of 

 acquiring food are really very great, and a right knowledge of this 

 fact has a most important bearing upon the economical use of com- 

 mercial manures. 



Soils that will furnish nitrogen for large crops of corn and oats 

 will also furnish some of the nitrogen for the clover crop, certainly 

 as much as is left in the clover roots and stubble after both hay and 

 seed crops are removed. Consequently if we are to enrich the soil 

 in nitrogen by growing clover, the clover must be returned to the 

 soil, either by plowing under directly or in the form of manure 

 from pasturing or feeding. 



In practical agriculture the fertility of the soil is of the first 

 importance, for if the soil is so poor that satisfactory yields cannot 

 be obtained then the difference between the cost of producing a crop 

 and its market value may be so small that no adequate profit re- 

 mains, while if a crop is sufficiently large then the cost of produc- 

 tion tends to become relatively smaller, and the profits larger. 



It is of course important to select crops adapted to the soil and 

 climate and which have either directly or indirectly a high market 

 value. It is important to select the right variety ; to plant good seed 



