204 Bureau of Farmers* Institutes. 



ing sue!) quantities of phosphorous as are needed in building pro- 

 teids and in forming other phosphorus plant compounds. 



2. Phosphorus affects the development of seeds and fruit. 

 More phosphorus is found in the seeds than in any other portion 

 of a plant. Plants do not come to maturity and so do not pro- 

 duce seeds, unless the plants can get phosphorus compounds to 

 feed on. Owing to the intimate connection between phosphorus 

 and seed formation, a liberal application of available phosphorus 

 compounds to plants in the earlier stages of growth appears to 

 hasten somewhat their maturity. In this respect, it acts upon 

 plants in a manner opposite to nitrogen, whose presence in large 

 amounts retards ripening. 



3. Certain forms of phosphates render the proteids sufficiently 

 soluble to enable them to be carried from the growing parts of 

 plants to the seeds, in which they accumulate in quantity. 



Potassium. 



(a) Source. — The metal potassium is never found uncombined 

 in nature. It is a constituent of many minerals. The decom- 

 position of these minerals give rise to the presence of potassium 

 compounds everywhere in the soil. It is taken up by plants; 

 and when vegetable material is burned, the potassium remains 

 behind, chiefly as potassium carbonate. When wood ash is 

 treated with water, or " leached," the potassium carbonate is 

 dissolved out, forming " lye," and this, evaporated to dryness, 

 leaves impure potassium carbonate, which is commercially known 

 as potash. 



In using the term potash in connection with fertilizers, potas- 

 sium oxide is always meant. The compounds of potassium are 

 commonly called potash compounds, because it was formerly sup- 

 posed that potassium oxide or potash was present in all of them. 



Potassium combined with chloride forms potassium chloride or 

 chloride of potash or muriate of potash, etc. Potassium and sul- 

 phuric acid form potassium sulphate or sulphate of potash. Potas- 

 sium and nitric acid form potassium nitrate, also called nitrate of 

 potash and saltpetre. 



(b) Relation to Fertilizers. — Experiments show that when po- 

 tassium (or potash) compounds are lacking in the soil, the plant 

 suffers greatly, though it does not necessarily die. The develop- 

 ment of the woody parts of plants and the fleshy portions of 

 fruits seems to be largely dependent on the influence of potas- 



