PLANT FOOD FOR HORTICULTURAL CROPS. 427 



necessary. The rate at which a nitrogenous manure should be ap- 

 plied will, of course, depend entirely upon the soil and crop. 



Another plant food element which frequently requires some at- 

 tention on the part of the horticulturist is potassium, or potash, as it 

 is more commonly called. This element has much to do with im- 

 parting vigor and stimulating plant growth ; it is always found the 

 most abundantly in plants in the active or growing parts. It takes 

 an important part in the building up of the plant and the production 

 of new cells. It is important in plant growth that the potash be as- 

 similated in the early stages of plant life, otherwise restricted growth 

 results, and a plant of low vitality is obtained. Potash alone will 

 not accomplish these results, but it must be associated with nitrogen, 

 phosphoric acid and other elements. The need of potash for our 

 horticultural crops is, perhaps, not as imperative as the need of nitro- 

 gen, because, as a rule, our soils are more liberally supplied with 

 potash than with nitrogen or phosporic acid ; nevertheless, there are 

 some soils in the state that could be benefited for horticultural pur- 

 poses if some form of potash dressing were employed. 



In addition to the nitrogen or potash, the only other element 

 which crops may possibly require on ordinary soils is phosphorus 

 in the form of phosphates. The amount of phosphorus in a fer- 

 tilizer is usually referred to as its phosphoric acid content. The 

 phosphates are associated with the nitrogenous compounds and 

 stored up largely in the seeds of plants. In the production of seeds 

 of the highest vigor and vitality, a good supply of phosphates is es- 

 sential. Fruiting and seeding are stimulated by phosphate fer- 

 tilizers. Not only is the seed, but also is the brilliancy of the flower 

 influenced by different plant food elements, particularly phosphoric 

 acid. As in the case of a nitrogenous or potash fertilizer, a phos- 

 phate fertilizer when used alone may fail to fulfill its mission unless 

 it is properly combined and works in harmony with the other es- 

 sential elements of plant food. 



Definite rules for the combination of the essential elements of 

 plant food can not be formulated because soils differ so widely in 

 their composition, and then, too, crops differ materially as to their 

 demands for plant food. For general horticultural purposes, 

 medium or average dressings of commercial manures are preferable 

 to heavy applications. In the case of well rotted manure, as high 

 as thirty tons or more per acre may be safely used upon many crops, 

 particularly corn, but in no case should more than 500 pounds of a 

 commercial fertilizer be used for any crop, and in many cases less 

 than half this amount is sufficient, unless, of course, experience 



