STATE POMOLOGICAL SOCIETY. II9 



one-half inches. In iqii it was twenty and three-fourths inches 

 and in 1912 nineteen and one-half inches, or an average 

 annual increase of two and one-half times that of the three 

 preceding years combined. It should be remembered that, 

 as has been previously stated, these trees have produced in 

 succession two fair crops of apples while making this growth. 

 It should also be remembered that during the last three years 

 they have not been competing with a hay crop which would eat 

 up the food materials and make great demands on the water 

 supply just at the time that the trees needed it the most. The 

 only thing which has been grown in the orchards aside from 

 apples has been a fall cover crop which has been plowed under 

 the following spring. 



It is the common practice to speak of the ordinary natural 

 and artificial fertilizers as plant food. Strictly speaking this is 

 incorrect. Fertilizers furnish some of the crude food materials 

 which the plant takes in along with water and certain other 

 materials dissolved in water. From these and with the carbon 

 dioxide gas from the air and through energy obtained from 

 the sun's rays it builds np food substances suitable for the nour- 

 ishment and growth of its various tissues. There are certain 

 chemical elements such as calcium, magnesium, sulphur, iron, 

 nitrogen, phosphorus, and potassium which must be present in 

 the soil to properly nourish the plant. The most of these are 

 present in ordinary soils in sufficient quantity but the supply of 

 nitrogen, phosphorus and potassium is not usually sufficiently 

 abundant to withstand repeated cropping so that they must be 

 replaced by some means or other. All complete artificial fertil- 

 izers contain each of these elements in some form. The active, 

 living part of the plant cell in which the work of food manu- 

 facture goes on is a nitrogenous compound. Potassium is pre- 

 sumably active in assimilation or the absorption of carbon from 

 the air and in the formation of this living substance, while 

 phosphorus and sulphur rank with nitrogen as important con- 

 stituents of it. Until quite recently it has been taught that 

 sulphur was present in ordinary soils in sufficient quantity for 

 plant growth. The work of Hart and his associates at the 

 Wisconsin Experiment Station and that of certain German 

 investigators raises a question as to the soundness of this 

 teaching and it is possible that in the near future the use of 



