FERTILIZERS, OTHER THAN NITROGENOUS 221 



as in others; whilst the difference in the average annual amount of it taken up 

 over a given area is more than five times as much on some plots as on others — 

 dependent on the supplies of it by manure, and the consequent description of 

 plants, and amount, and character, of growth induced. The percentage and 

 acreage amounts of phosphoric acid also vary very strikingly; and ao again it is 

 with other mineral constituents, but in a less marked degree.""* 



Li7ne. — Calcium has been mentioned as an element practically always 

 present in quantities far greater than orchard trees require. Indeed 

 very large amounts are likely to lead to chlorotic conditions through mak- 

 ing the soil reaction alkaline and thus rendering iron unavailable. Never- 

 theless liming the soil accelerates nitrification and may thus indirectly 

 help the orchard plants to obtain a larger supply of nitrogen. The 

 strawberry has been mentioned particularly as a plant preferring an acid 

 soil and as being actually harmed by applications of lime. Yet it is 

 common experience that strawberries do exceptionally well following 

 clover, though clover is very sensitive to acid soils and usually profits 

 greatly from liming. In this case it is entirely practicable to apply lime 

 to the clover field a year before the sod is turned under for the strawberry 

 plants. The lime stimulates the growth of the clover and its effect on 

 soil reaction wall have largely, if not wholly, disappeared by the time the 

 ground is ready for the strawberries. Ultimately the strawberries will 

 profit greatly from the lime applied to the clover that preceded them, 

 though its direct application would result in serious injury. 



Illustrations might be given of other indirect influences of fertilizers, 

 but enough has been said here and at other places in this section to afford 

 some idea of the many ways in which they may affect orchard trees. 

 Enough has been said, also, to make it clear that these indirect are often 

 as important as the direct influences, for there may be no occasion to 

 supply the plant with more nutrients. With our present knowledge it 

 is impossible to predict with certainty all of the effects, direct and 

 indirect, that any particular fertilizer will have in a given orchard. How- 

 ever, this should not prevent the careful study of each situation as it 

 arises. 



Plant Nutrient Carriers ; Different Forms of Fertilizers. — The neces- 

 sity that the different plant nutrients be in certain forms if they are 

 to be taken up by the tree has been discussed under the subjects of Solu- 

 bility and Availability in Chapter VII. This does not mean, however, 

 that fertilizers must contain these elements in these particular forms, 

 for as soon as applied they become subject to numerous changes through 

 the physical, chemical and biological factors always at work in the soil. 

 Nevertheless there are certain advantages and certain disadvantages 

 inherent in different fertilizers because of the form in which they carry 

 the elements for which they are valued. A brief discussion of this matter 

 as it applies to orchard problems is included at this point. 



