ON THE ESSENTIAL CONSTITUENTS OP MANURES. 37 



of lime to supply our cultivated crops with abundance of sulphuric acid. 

 This appears to me the chief reason why sulphates rarely show any effect 

 upon turnips and other crops. 



5. The bone-ash dissolved in acid did not contain any nitrogen, notwith- 

 standing 3 cwt. produced as large an increase as 15 tons of well-rotten farm- 

 yard manure. 



6. Sulphate of ammonia proved inefficacious when used by itself, or in 

 conjunction with soluble phosphates. 



It is possible, however, that the quantity of ammonia used in the experi- 

 ments was too large. Similar experiments, which I have since undertaken 

 and hope to continue for a number of years, induce me to believe that on the 

 soils in our neighbourhood ammonia has no beneficial effect whatever upon 

 Swedes. And yet it is quite possible that ammonia may prove beneficial 

 on other soils, which, like sandy soils, do not possess in a high degree the. 

 power of absorbing ammonia from the atmosphere, nor to accumulate largely 

 nitrogenized organic matters. But the cases in which ammonia or nitrogen- 

 ized manures are really beneficial to turnips I think are quite exceptional; 

 and I have little hesitation in saying that a great deal of ammonia, the most 

 expensive fertilizing ingredient of guano, at the present time is wasted in 

 most instances in which guano and other ammoniacal manures are exclusively 

 employed in the cultivation of root-crops. 



It is certainly a remarkable fact that many thousands of tons of turnips are 

 now raised annually with nothing else but 3 cwt. or 4 cwt. of superphosphate, 

 made exclusively of bone-ash and mineral phosphates. 



At least 90 per cent, of all the artificial manures that are now offered for 

 sale, whatever their name may be, are in reality superphosphates ; and the 

 great majority of superphosphates contains no appreciable amount of nitrogen. 

 Even those artificial manures which, like nitro-phosphate, ammonio-phosphate, 

 blood-manure, &c, convey the idea of manures rich in nitrogen or ammonia, 

 when prepared for turnips, seldom contain any considerable amount of nitro- 

 gen. It is not likely that an intelligent class of men like the makers of arti- 

 ficial manures, would cut short the supply of nitrogenized matters or ammo- 

 niacal salts in turnip-manures, if they had not found out by experience that 

 manures made from bone-ash and sulphuric acid alone, and consequently rich 

 in soluble phosphates, have a more powerful influence upon the yield of root- 

 crops than ammoniacal manures, which are comparatively poor in phosphates. 



I would likewise specially notice, that even quite dilute solutions of am- 

 moniacal salts retard the germination and early growth of turnips in a 

 remarkable degree. 



In the preceding experiments I was surprised to find, contrary to all expec- 

 tation, that sulphate of ammonia impaired the development of leaves. Am- 

 moniacal salts are generally considered as leaf-producing, fertilizing consti- 

 tuents ; I therefore fully expected to see on Plot 4 a luxuriant development 

 of tops on the expanse of the bulbs. But not only did sulphate of ammonia 

 retard the germination of the seed for a short period, instead of pushing it 

 on rapidly, but throughout the whole season the turnip-tops on Plot 4 looked 

 quite as bad, if not worse, than the unmanured plot. 



However, in Plot 5, in which sulphate of ammonia was used in conjunction 

 ■with dissolved bone-ash, I observed, to some extent, the effects which are 

 generally ascribed to ammoniacal manures. The leaves of the turnips in 

 Plot 5 had a much darker appearance than in other plots not dressed with 

 ammoniacal salts, and the plants on this plot, on the whole, looked the most 

 luxuriant. 



It would appear from this that ammoniacal salts are useless by themselves 



