REPORTS OF EXPERIMENTS WITH DIFFERENT TOP-DRESSINGS. 73 



The nitrogen contained in 56 lbs. ammonia (NH 3 ) is taken as 

 a useful standard amount to be applied per acre. Thus, each 

 plot of T ^ acre receives such quantity of the nitrogenous manures 

 as contain h lb. ammonia, or of those which contain nitrogen 

 equivalent to that in | lb. ammonia. 



The plots were carefully measured and marked out by strings 

 fastened at the corners of each plot, and left there till the grass 

 was cut. Thus the manures could be spread exactly ; and when 

 they were in such a fine powder as to be liable to float in the air, 

 a broad plank was placed edgeways on the string to prevent the 

 dust flying on to the adjoining plots. 



The dressings, which were carefully weighed out for each indi- 

 vidual plot, were applied on May 10 and 11, 1865. 



This was late in the season to reap the full advantage from 

 them; but an unforeseen delay arose, from the nitrate of ammonia 

 and nitrate of lime having to be manufactured expressly, and 

 then analysed. 



It may, however, be safely inferred that the beneficial influence 

 of the various dressings would have been greater had the dress- 

 ings acted on the first crop for a longer time. This supposition 

 is borne out by the fact, that the rest of the field in which the 

 plots lay had received on April 18th a dressing of nitrate soda and 

 sulphate ammonia, rather smaller than that applied on the expe- 

 riments three weeks after, and had in that time grown 6 or 7 

 inches more than the part reserved to receive the trial dressings ; 

 and this advantage it continued to keep, after the experimental 

 plots had received their dressing, up to the time of cutting. 



The plots received as follows : — 



1, 11, 21, 1 Nothing, being left as standards of comparison. They 

 31, 10, 40. J were interspersed as evenly as possible among the 



manured plots. 



2, 12, 1 Each 2 lbs. 10 oz. glue (estimated to contain 15 per cent. 

 22, 32. J nitrogen, equivalent to 18 per cent, ammonia), containing 



nitrogen equal to that in £ lb. ammonia. The glue being very 

 tough and unbreakable, was dissolved by heating the 2 lbs. 10 

 oz. in 3 gallons of water. This solution was poured on from a 

 gardener's watering-can with a rose-end. The object of this 

 experiment was to ascertain whether nitrogen contained in unde- 

 composed animal matter is as valuable as when decomposed, and 

 in the form of an ammonia salt, or a nitrate. Glue, though far 

 too expensive to apply as a manure, is taken as typical of other 

 undecomposed animal matter, and as one which does not contain 

 other substances liable to interfere with the result of the nitrogen. 

 It serves to test if it is expedient to allow the gelatine to be 

 abstracted from the bones before using them for manure, and then 

 supplying its loss by ammonia salts, or whether it is more econo- 

 mical to apply the gelatine itself in the bones. 



