PRINCIPLES OF PLANTING AND CULTIVATION 49 



Phosphoric acid. Phosphoric acid is one of the most essential 

 ingredients of the soil and, at the same time, one that is most often 

 lacking. Phosphoric acid is intimately associated with the growth 

 of the stems and roots and with the development of the seed of 

 nearly all plants. In most of the commercial fertilizers prepared 

 for the use of truckers or market gardeners, phosphoric acid is the 

 leading or important constituent. It is generally used in larger 

 proportions than either nitrogen or potash. Since it is intimately 

 associated with the process of seed production, it is an important 

 fertilizer to be used in connection with beans, peas, and all crops 

 in which seed production is the end sought. 



Potash. Potash, the third element of plant food, is less apt to 

 be lacking in soils than either of the other two. It ranks next in 

 importance to phosphoric acid and is intimately associated with it 

 in the work of producing stems and seeds. Potash, as a rule, has 

 a tendency to counteract the work of nitrogen in that it tends to 

 hasten maturity rather than to continue growth. This is particularly 

 true of the muriate of potash which is prepared by treating crude 

 rock with hydrochloric acid, making it potassium chloride instead 

 of potassium sulphate, which results when the crude salts are treated 

 with sulphuric acid. Both forms of potash are available and are 

 used by truckers to a considerable extent. Potash can be obtained 

 as high-grade sulphate or muriate of potash, each of which carries 

 about 50 per cent of available potash; or it may be obtained as 

 kainite, a low-grade salt carrying about 14 per cent potash. The 

 high grades cost much more per ton, but, on account of the greater 

 amount of potash which they carry, they are in reality cheaper. 

 Where large quantities of potash must be applied, it will be found 

 safer to use the sulphate. 



Stable manure. While stable manure must be looked upon as 

 the most complete and desirable form of plant food, yet, unless 

 very carefully handled, it is frequently deficient in nitrogen and 

 phosphoric acid. In truck work the aim should be to supply any 

 deficiency which may exist in the stable manure used ; that is, the 

 stable manure should be supplemented by the addition of a small 

 percentage of nitrogen and of phosphoric acid. 



How to apply manure. When coarse, only partially decom- 

 posed manure is to be used, it is best to apply it either in the fall 



