THE APPLICATION OF NITROGEN-CARRYING FERTILIZERS 207 



nutrients and with the actual reduction in the total nitrogen supply of 

 cultivated soils taking place each year it is easy to see how the margin of 

 safety may disappear entirely. Increased vegetative growth follows 

 the apphcation of nitrogen-carrying fertilizers only when the supply 

 of available nitrates in the soil is less than the plant must have for its 

 best growth and there is a limit to what the plant can use. Within 

 limits, surplus amounts of available nitrogen, like surplus amounts of 

 available potassium or calcium or other materials, are simply tolerated. 

 Analyses are not at hand showing the exact amounts of available nitrates 

 in the West Virginia and Oregon soils to which reference has just been 

 made, but it may be presumed that they contained very small amounts 

 or amounts smaller than those required by the trees for maximum 

 growth and production. 



Many orchards will not respond to nitrogenous fertilizers because 

 the soils and the methods of soil management are of such a character 

 that nitrogen is not a limiting factor. On the other hand experience 

 shows that there are many orchards in which nitrogen is a limiting factor 

 and in which, consequently, nitrogen-carrying fertilizers can be used 

 profitably. To conclude from one experiment or a series of experiments 

 giving negative results that orchard fertilization in general is not needed 

 or that it does not pay is as erroneous as it is to conclude from striking 

 returns on a nitrate deficient soil that orchards generally should be 

 regularly fertilized with that element. Statements that have been made 

 give some idea of the symptoms of nitrogen starvation. Short, slender 

 shoot growth and small pale leaves are perhaps the most frequent indices 

 of this condition, though there are many others. However, some of 

 these symptoms likewise characterize injuries resulting from deficient 

 water supply, borer attack or other troubles and care should be exercised 

 to identify the real cause or causes of the trouble before deciding upon 

 fertilization of any considerable area. 



A given supply of available nitrogen in the soil though entirely ade- 

 quate for the requirements of one fruit crop may not prove sufficient for 

 the best growth of another. Thus Chandler-'^ has found that in a certain 

 clay loam in New York applications of nitrogen-carrying fertilizers 

 resulted in greatly increased shoot and leaf growth in gooseberries and 

 red raspberries, though currants and black raspberries showed but little 

 response. Reimer^^^ reports that in the Rogue River of southern Oregon 

 the Yellow Newton apple does not respond to fertihzer applications so 

 readily as Esopus (Spitzenburg). Much yet remains to be done toward 

 determining the actual total yearly nitrate requirements of different 

 fruit crops and also their varying requirements from season to season 

 with increasing age. 



Influence of Nitrogen On Blossom Bud Formation. — It is not the 

 intention at this point to discuss in detail the many factors influencing 



