NITROGEN GROUP OF FERTILIZERS 13 



In both cases changes have to take place in the soil 

 before the constituents of the fertilizer are suitable for 

 absorption by the plant ; indeed, in both cases a water culture 

 of either super-phosphate or sulphate of ammonia, or both 

 together, would be absolutely injurious to the plant, and the 

 plant would probably refuse to grow altogether. After, 

 however, these materials have acted upon the soil they are 

 rendered suitable to the plant's needs. 



When sulphate of ammonia acts upon ths soil a complete 

 chemical change takes place. This change can be easily 

 demonstrated so far as the broad effects are concerned by 

 the following simple experiment : — A couple of glass tubes, 

 about 2 1 or 3 inches in diameter, and about a foot in length, 

 are partially closed at one end with cork and cotton-wool, 

 and a depth of 6 or 8 inches of soil placed in the tubes. 

 Into one tube is poured some distilled watei^sj^^ to perceive 

 the effect of plain water upon the soil J^^^o tl^-^her tube 

 is poured a solution of sulphate of agm^^^ ^ter. If 

 a quantity of sulphate of ammonia ^^e^lti^'^al^t one- 

 tenth of a gramme be used for one of tl|^f^.c tubes it would 

 correspond to an application of 2 cwt. sulphate of ammonia 

 per acre, a quantity comparable to practice. 



A litre of water poured on to the quantity of soil men- 

 tioned above would correspond to a rainfall of about ten 

 inches. 



If the drainage from the two tubes be now collected, the 

 addition of a small quantity of '* Nessler's," solution will 

 give a coloration due to the ammonia, and it will be at once 

 observed that whilst the original manure employed shows 

 a large amount of ammonia present, the drainage from the 

 manured soil only shows a fraction of that amount. The 

 distilled water itself will be found to have washed a little 

 ammonia out of the soil, unless the soil chosen was a 

 particularly poor one. We perceive at once from such an 

 experiment that the ammonia has in some way been removed 

 from aqueous solution, or in other words, the anunonia 

 has been fixed by the soil. These fixations of fertilizer 

 ingredients are always partial reactions which follow the 



