44 HORTICULTURE, FORESTRY, FLORICULTURE 



portions. Our knowledge of soil conditions is as yet too incomplete 

 to enable us to know the precise amount of each fertilizing ingredient 

 to apply in order to exactly supplement the available fertility in the 

 soil. Each grower must study his own soil conditions and test the 

 effects of different manures on it in order to get the best results. 



The chemical elements that compose our fruit and agricultural 

 crops are oxygen, hydrogen, nitrogen, phosphorus, sulphur, iron, 

 potassium, sodium, calcium, magnesium, chlorin, and silicon. Nitro- 

 gen, potassium, and phosphorus are the elements commonly lacking 

 in the soil and it is these that we look for in fertilizers. These ele- 

 ments each act differently in affecting vegetation. To be used by 

 plants, they must be soluble. Soil that has large amounts of soluble 

 nitrogen in it produces a vigorous soft growth of wood and a dark 

 green color in the leaves. On such land trees are liable to grow late 

 in autumn and to winterkill. The fruit is likely to be low colored 

 and of poor keeping quality. For peaches such soil is more injurious 

 than for apples or other hardy crops. Nitrogen encourages a growth 

 of wood rather than fruit. Large amounts of potash and phosphoric 

 acid in the soil cause a firm, solid growth of wood, early maturity of 

 plant, and firm, bright colored, long keeping fruit. Nitrogenous fer- 

 tilizers in sufficient quantity can usually be supplied by the use of 

 barnyard manure or by plowing under leguminous catch crops. Of 

 the commercial forms nitrate of soda, sulphate of ammonia, dried 

 blood, and tankage are most common. Potash fertilizers seldom need 

 be applied heavily on well-tilled clay soils, as such are usually well 

 supplied with potash. Wood ashes afford potash in a readily available 

 form. Unleached hardwood ashes are most useful. The leading com- 

 mercial forms of potash are the sulphate and muriate and a lower 

 grade product known as kainit. Phosphoric acid is more often lack- 

 ing in the soil than potash. It is supplied by applications of ground 

 bone, finely ground rock phosphate, either raw or after treatment with 

 sulphuric acid, which renders the phosphoric acid much more readily 

 available to plants. Treated ground bone or ground rock is known as 

 acid phosphate or superphosphate. 



To secure the best results each of the elements nitrogen, phos- 

 phoric acid, and potash must be available to the plant in the proper 

 proportions. These elements are all necessary for healthy plant 

 growth. The following table shows the amount of plant food, nitro- 

 gen, potash, and phosphoric acid taken from the land by a crop of 

 75 barrels of apples. This amount is here used, as it represents a good 

 average crop of apples per acre : 



To raise this crop of apples there must be about 50 trees, each 

 one of which is fifteen years old. The branches, trunk, and roots of 

 such a tree will weigh about 1,400 pounds, of which 40 per cent is 



