186 POMOLOGY 



soils, but rather to maintain continuously a vigorous con- 

 dition of the trees. 



154. Fertilizing tilled and non-tilled apple orchards. — 

 The source of much error in studying the fertiUzer problem 

 in the apple orchard hes in a failure to recognize the all but 

 universal experience in fertilizing a tilled and a sodded plan- 

 tation. The fundamental or underlying reasons for this 

 difference lie in the effects of stirring the soil on its nitrate 

 and moisture-content. As a general rule, a well-cultivated 

 apple orchard (including the use of cover-crops) will respond 

 slowly to the use of chemical fertilizers, and one which is 

 not tilled will give prompt returns. An outstanding ex- 

 ception is in the impoverished soils of southern Ohio where 

 the fertilizers gave as great and as prompt results in tilled 

 as in sod orchards. The author believes this is of such im- 

 portance that the fertilization of tilled and untilled orchards 

 are considered separately. 



155. Moisture and fertility intimately related. — Moisture 

 is of first importance in the proper growth and develop- 

 ment of plant and fruit, and when it is lacking the elements 

 of fertility are not available. If the soil is too dry at a crit- 

 ical period, the fohage suffers and the fruit is small and of 

 poor quality. On the other hand, too much water in the soil 

 is equally serious, resulting in stunted growth, yellow foli- 

 age, and eventually death of the trees. Of the ten or more 

 chemical elements that enter into the composition of the 

 plant, only four are likely to require special attention in the 

 way of amendments to the soil. These are nitrogen, phos- 

 phorus, potassium, and calcium. Of these most of the cal- 

 cium (lime) remains in the wood and leaves, while a large 

 proportion of the potassium (potash) finds its way to the 

 leaves and fruit. 



156. Relative importance of the different essential 

 elements. — While each of these so-called essential elements 



