286 Bulletin 38. 



age of phosphoric acid and nitrogen, and is worth in the eastern 

 market from $25.00 to $35.00 per ton. This waste matter should 

 be collected and kept until sufficient quantity has accumulated to 

 make the handling practicable. For this purpose, also, a covered 

 pit is a cheap and easy means of storing it. In order that the 

 plant food in these materials may be easily available, it is neces- 

 sary that it be either decomposed or reduced to a very fine condi- 

 tion. This may be accomplished in several ways. Treatment 

 with acid, or grinding, are the two methods employed by manu- 

 facturers of fertilizers. The acid treatment is impracticable on 

 the farm, but where the supply of material is sufficient to warrant 

 it, the grinding is not. Mills for such a purpose may be found 

 advertised in agricultural journals ; and even though coarsely 

 ground, bones then more readily yield their nitrogen and phos- 

 phoric acid to the orchard trees or valuable crop plants to which 

 they may be applied. 



Another way of decomposing bones is by means of unleached 

 wood ashes. This method, however, is to be advised against, 

 owing to the fact that the ashes contain a high percentage of car- 

 bonate of potash, very similar to the "black alkali," whose in- 

 jurious effects are too well known to need further comment. 



The Station has from time to time received considerable cor- 

 respondence in regard to the fertilizing of orange trees, which in- 

 dicates the need of more concentrated fertilizing materials in the 

 citrus orchards of Southern Arizona. Our arid region soils are 

 deficient in nitrogen and organic matter, but rich in potash. This 

 deficiency has frequently been made apparent by the condition of 

 the trees, the yellow color of the leaves, or " trenching," proba- 

 bly indicating lack of nitrogen. 



In applying fertilizing materials, therefore, it should be the 

 aim to supply these deficient elements of plant food. Field obser- 

 vation also warrants the above belief; for, where green-manuring 

 has been practiced, as well as where some good nitrogenous and 

 phosphatic fertilizer has been used, the improvement in fruit, 

 foliage and trees has been very marked. Ground green bones 

 and tankage, supplemented if need be with a little potash, make 

 a very desirable fertilizer for this purpose. A fertilizer of about 

 the composition given below has frequently been advised by the 



