EXPERIMENT STATION BULLETINS. 233 



to secure a proper development of the trees and it will also increase the 

 amount of sugar and heighten the color of the fruit. 



The best source of phosphoric acid is from bones, either ground or as bone 

 charcoal. The value of ground bone depends to a considerable extent upon 

 its fineness, and the action will be hastened if it has been treated with acid 

 and rendered soluble, in which case it forms what is known as a superphos- 

 phate. Fresh bones contain a small amount of nitrogen which adds to 

 their value. A fair sample of ground bone should contain rather more than 

 20 per cent of phosphoric acid, of which about one third can be utilized by 

 plants; while the remaining 15 per cent, is in an insoluble form, it will grad- 

 ually become available. The amount of nitrogen in ground bones is quite 

 variable but is seldom less than 2, or more than 5 per cent. In addition 

 to the fresh bones, bone charcoal in the form of dissolved bone-black is also 

 used as a source of phosphoric acid, it containing some 16 to 20 per cent., 

 nearly all of which is immediately soluble. Nitrogen is not present in 

 bone-black, having been removed by the burning. Phosphoric acid is also 

 obtained from various waste products of slaughter-houses, from guano and 

 tish scraps and, in less valuable forms, is mined at Charleston, South 

 Carolina, and in Florida, and is found in iron slag. The Charleston phos- 

 phate rock is largely used in fertilizers, but its phosphoric acid is less val- 

 uable than that from bones. The iron slag phosphate, sometimes known 

 as "Odorless," is highly commended by many who have tried it. Although 

 it has some value, the extravagant claims made for it can hardly be sus- 

 tained. Analysis shows that it contains about 20 per cent, of phosphoric 

 acid, of which some 3 to 4 per cent, is soluble. 



The nitrogen supply, except as furnished incidentally in the bones 

 and waste animal products, is obtained from nitrate of sodium and 

 sulpliate of ammonium. In both of these salts it is readily soluble and 

 is considered more valuable than when from other sources. The quantity 

 of the salts required varies with the character of the soil as well as with 

 the age of the trees. Stable manure is preferable as the source of nitro- 

 gen, but if it can not be obtained, and the condition of the soil is such that 

 some form of nitrogen is needed to give a fair growth to the trees, 100 to 

 150 pounds of either of these chemicals per acre would generally be ample, 

 while a considerably smaller quantity would suffice for young trees. There 

 is much danger if it is used in large quantities, particularly if it comes in 

 close contact with the roots. One can determine the relative value of the 

 various fertilizers, as their guaranteed analysis must be furnished, and with 

 this and the value per pound of potash, phosphoric acid, and nitrogen it can 

 readily be computed. Potash is reckoned as worth about 6 cents per pound 

 when in the form of sulphate and five cents as a muriate. Phosphoric acid 

 when soluble is valued at eight cents, reverted at seven, and when insolu- 

 ble in bones it is valiled at from three to seven cents, while in rock and 

 similar materials it is only worth from one to two cents at the most, while 

 from some materials it has little if any value. The variation in the value 

 of nitrogen is still greater, as in nitrate of soda it is worth sixteen cents 

 per pound; as sulphate of ammonia eighteen cents; in blood, meat, and fish 

 scraps fifteen cents ; in bones from ten to fifteen cents according to the fine- 

 ness of grinding. In stable manure nitrogen would be worth about 

 eight cents per pound. As they are for the most part readily soluble, it is 

 best to apply the fertilizers in the spring; if this is done just before the 

 land is to be harrowed it will be better than to plow it in. In seasons when 

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