754 



Notes on Manures for November. 



[Nov., 



quite certainly advise him that he would gain nothing, and 

 probably lose, by adding still another 2 cwt. of sulphate of 

 ammonia, making 13 cwt. of artificials in all. So far as dressings 

 of this size are concerned there is no reason at all to suppose 

 that they are profitable. 



No farmer nowadays, however, uses anything like these quan- 

 tities of artificials on wheat, not even the 4 cwt. of sulphate of 

 ammonia which Lawes spoke of as the possible limit, and there- 

 fore the results are not directly applicable to modern practice. 

 The experiment tells us nothing at all about the behaviour of 

 the wheat crop with smaller dressings such as 1 cwt. or cwt. 

 of nitrate of soda or sulphate of ammonia with or without 1 to 

 2 cwt. of superphosphate. Is it worth while using these? It 

 is obviously very unsafe to say that because it does not pay to 

 give 13 cwt. of artificials to wheat, therefore it does not pay to 

 give 1 or 2 cwt. The experiment, in other words, cannot properly 

 be quoted in relation to the modern problem. A more applic- 

 able experiment is now in hand at "Rothamsted, and while the 

 results are not all available those to hand suggest that the old 

 conclusion does not apply to dressings of the size ordinarily given 

 by farmers. There are also recent experiments on other crops 

 that do not agree with this old conclusion. At the Midland Agri- 

 cultural College an interesting experiment was made on Arran 

 Chief potatoes in 1921. The whole field received 12 tons of farm- 

 yard manure per acre, but the various plots received different 

 quantities of a mixture of artificials (3 cwt. superphosphate, 

 1 cwt. sulphate of ammonia and 1 cwt. sulphate of potash). The 

 results were as follows : — 



Plot 



Manuring. 



Yield 

 in tons 

 per acre. 



Per- 

 centage 

 Ware. 



■ 



Per- 

 centage 

 Seed. 



Value of 

 Crop at 

 £6 per ton, 

 Seed and 



Chats 

 £2 per ton. 



Cost of extra 

 Manure at 

 41- cwt. for 

 Superphos- 

 phate, 15/- 

 cwt. Sulph. 

 Am?n., 151- 



cwt. Sulphate 

 of Potash. 



Profit or 

 loss from 

 additional 

 Di-essing. 





Dung 



Artificials 











£ S. 



d. 





s. 



d. 



£ s. 



d. 



1 



12 tons 



6 cwt. 



11-31 



53-1 



42-3 



46 13 

















2 



12 „ 





13-63 



56-9 



39-3 



58 5 











17 







+ 10 15 







3 



12 „ 



10 „ 



14-36 



60-6 



35-7 



63 10 







1 



14 







+ 15 3 







4 



12 „ 



12 „ 



13-19 



61-7 



33-2 



58 18 







2 



11 







+ 9 14 







5 



12 „ 



14 „ 



13-18 



52-9 



41-2 



54 5 







3 



8 







+ 44 







6 



12 „ 



16 „ 



11-34 



58-4 



38-3 



49 3 







4 



5 







- 1 15 







