To illustrate these facts, it may be mentioned that horn 

 shavings and Nitrate of Soda contain, in equal weights, about c ^ ltivation o 

 the same quantity of nitrogen, and nevertheless their value ltrus 

 as fertilizers is very different. The nitrogen of the nitrate l i 



of soda is in a form in which it is immediately assimilable 

 by plants, whilst that contained, in organic form, in the horn 

 shavings nitrifies slowly, three or four years being required 

 for the completion of the process. The like is the case with 

 barn-yard manure and all other animal or vegetable manures, 

 although the nitrification of the organic nitrogen of some 

 of them is completed in the course of two years or less. 



When we remember that 15 to 16 per cent, of the 

 weight of nitrate of soda of ordinary commercial purity 

 (95%) i s represented by Nitrogen, and that i cwt. of it 

 therefore contains as much nitrogen as ultimately becomes 

 available from the decomposition of a ton and a half of rich 

 barn-yard manure, the activity and rapidity of action of this 

 fertilizer, and at the same time the control which the culti- 

 vator is able to exercise over its effects, are readily to be 

 understood. 



Another important characteristic of Nitrate of Soda 

 is the freedom with which it permeates the soil. The roots 

 have not to wait for nitrogenous food until they can grow 

 down to it, neither have they to seek it immediately beneath 

 the surface, to the encouragement of shallow rooting; and, as 

 a consequence, plantations dressed with nitrate of soda suffer 

 less from drought than those deriving their nitrogen from 

 other sources. 



Although the intensive cultivation of citrus fruits can 

 only be carried on with the aid of chemical fertilizers, the 

 application of organic manures to the plantation should not 

 be omitted, if only as a means of maintaining the mechanical 

 condition of the soil. Where barn-yard manure is at dis- 

 posal, it should be spread over the grove lightly, so that 

 each tree receives only a small amount. Good results are also 

 to be obtained by ploughing under, every second or third 

 year, a leguminous crop. Among the plants suitable for 

 green-manuring tested at the Experiment Station of the Uni- 

 versity of California, a variety of Horse Bean, Ficia faba, 

 has been found to be one of the most suitable for use in citrus 

 orchards. All the horse beans make rapid winter growth, 

 and growth ceases with the coming of hot weather. Thus, 



