ORCHARD MANAGEMENT 133 



potash, for granite contains feldspar, a mineral which carries 

 large quantities of potassium. As a rule, therefore, where 

 soils have been derived from a nearby granite source, they 

 contain an abundance of potash, and it is not necessary to 

 add any in the form of fertilizer. On the other hand, swamp 

 soils generally contain an abundance of organic matter and 

 ample nitrogen, but are frequently so deficient in potassium 

 that they are practically worthless until this element is 

 added. 



Potassium in the soil becomes available very slowly. In 

 this it differs from nitrogen. It has already been stated that 

 about 2 per cent of the total nitrogen content becomes avail- 

 able each year. Of the potassium in the soil, only about one- 

 fourth of one per cent becomes available in any one year. 

 Thus, the nitrogen becomes available approximately eight 

 times as fast as the potassium. Phosphoric acid stands as 

 regards availability about half way between these two. 



One of the best methods whereby the amount of available 

 potash and phosphoric acid can be increased is by the addi- 

 tion of organic matter. This is especially true in the regions 

 of relatively small rainfall, where humus is already deficient. 

 The raising of cover-crops and the plowing under of manure 

 constitute the most rational processes of fertilization in these 

 parts of the country. 



221. Fertilizers for fruits. In fruit-growing the use of 

 fertilizers gives a better quality of fruit, a larger yield, and 

 in orchards fertilized year after year, a longer period of 

 profitable bearing. But fertilizers must be applied intelli- 

 gently. The character of the soil, the nature of the crop, the 

 prices of fertilizing materials, all must be taken into account. 

 No specific recommendations can be made since each locality, 

 and indeed each orchard, is a separate problem. There are 

 a few general rules that it is well to keep in mind : (1) Nitro- 

 gen induces wood and leaf growth, and beyond a certain 

 point these compete with fruit growth. (2) The most cheaply 



