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the majority do, a complete fertiliser, in definite proportions, 

 regardless of whether all the elemeiits are needed by the plant 

 or not. If it can be determined by the appeai-ance of the tree 

 and fruit what element is lacking, this would seem to be the 

 most rational way to fertilise. It seems reasonable to suppose 

 that by careful study pathological characters induced by 

 starvation might be found, which would serve to indicate 

 clearly the lack of any particular element. Some growers 

 claim to be able to recognise these characters now, and are 

 fertilising largely on this modified plan, taking advantage of 

 what we might call the sign language of the tree. Some of 

 these characters will be mentioned below under the considera- 

 tion of the different elements nsed. 



Effect on soil moisture. 



In fertilisation, at least two factors must usually be con- 

 sidered, the element of plant food supplied and the effect of 

 this upon the soil as aiding it in supplying the plant with 

 moisture. The heavy application, in late fall or early spring, 

 of an organic manure, like blood and bone, which is extensively 

 used in Florida, is liable to lead to injurious effects during the 

 spring drought, if the trees are on high and dry land. On the 

 other hand, such soils might be ameliorated by using substances 

 which attract water and increase the surface tension of the 

 soil moisture. Nitrogen for instance, used in the form of nitrate 

 of soda, and potash, in the form of kainit, would tend to draw 

 Tip the subsoil moisture and probably aid largely in 

 supplying the necessary moisture during this trying season. 

 The use of organic manures, on the contrary, only exaggerate 

 the damage produced by drought. If groves are on very moist 

 land, as is frequently 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 fertilisers on the orange in health. 



The elements which need to be supplied in fertilisation to 

 most Florida orange groves are nitrogen, potassium, and phos- 

 phorus ; or using the terms in which they are expressed in 

 most analyses of fertilisers, 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 

 fertilisation of orange groves should be more carefully considered, 

 with, respect to form and quantity, than nitrogen. It is the 

 most costly 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, which will be discussed 

 below. 



