THE ORANGE IN CALIFORNIA — FERTILIZATION. 147 



If groves are on very moist land, as is frequeiitlj^ the case in 

 Florida, where the necessity is to lessen the moisture rather 

 than to increase it, some form of organic manure, as muck or 

 blood and bone, might be found of benefit. 



Effect of Fertilizers on the Orange in Health. — The elements 

 which need to be supplied in fertilization to most Florida orange 

 groves are nitrogen, potassium, and phosphorus; or, using the 

 terms in which they are expressed in most analyses of fertil- 

 izers, ammonia, potash, and phosphoric acid. The application 

 of lime would also prove of benefit to many groves. Probably 

 no element of plant-food used in the fertilization of orange 

 groves sliould be more carefully considered, with respect to 

 both form and quantitj^, than nitrogen. It is the most costlj' 

 and at the same time the most dangerous element to use, as 

 excessive applications are liable to result in extensive dropping 

 and splitting of the fruit or in the production of the serious 

 disease known as die-back. 



Effect of Nitrogen. — A grower may with considerable certainty 

 determine by the appearance of his trees the condition of his 

 grove in respect to the supply of nitrogen available in the soil. 

 An abundance of nitrogen is indicated by a dark green color of 

 the foliage and rank growth. The fruit shows the effect of an 

 abundance of nitrogen by being, in general, large, with a com- 

 paratively thick and rough rind. If the trees have a yellowish 

 foliage, with comparatively small leaves, and show little or no 

 growth, there is probably a lack of nitrogen. In this case there 

 is but little fruit formed, and that formed is small and usually 

 colors early. If the tree is starving from a lack of nitrogen, 

 the foliage will become very light yellow and sparse, and the 

 small limbs will die, as will also the large limbs in extreme 

 cases. If the starvation is continued, no fertilizer being added, 

 the tree will finally die back nearly to the ground and prob- 

 ably die out entirely. The extreme symptoms of general 

 starvation from lack of all elements are probably nearly the 

 same. The nitrogen used in fertilization is commonly derived 

 from mineral or organic sources. Of the former, sulphate of 

 ammonia and nitrate of soda are the forms most used; of the 

 latter, muck, dried blood, blood and bone, cottonseed meal, 

 tankage, fish scrap, stable manure, etc., are the forms most 

 commonly employed. 



