1922.] 



Notes on Manures for March. 



1141 



might have accrued had the fertiliser been used for some more 

 responsive crop. This matter has been tested by Professor 

 Somerville, and his conclusions are justified by the later 

 Eothamsted work. These experiments show that if the yield 

 of swedes does not run to more than about 15 tons per acre 

 there is no advantage in using both dung and artificials : a 

 farmer may use dung if he can spare it, and then his artificials 

 could go on to some other crop : or, if he could make better 

 use of his dung somewhere else, he could grow his swedes 

 on artificials only, except where the soil is likely to dry out. 

 This is shown in an experiment made at Eothamsted in 1915, 

 when the yields per acre were : — 



Artificials + 



No manure. 10 tons dung. Artificials only. 10 tons dung. 

 tons cwt. tons cwt. tons cwt. tons cwt. 



9 12 12 18 12 15 12 18 



The addition of artificials to the dung gave no increase in yield. 



The case is different when the climatic conditions allow of 

 larger crops. In the north of England yields are considerably 

 heavier than at Eothamsted, running to 25 tons per acre or 

 more, and Professor Gilchrist finds that under ordinary circum- 

 stances they justify the addition of 4 cwt. basic slag or 3 cwt. 

 superphosphate, as well as 1 cwt. sulphate of ammonia to the 

 12 tons of good dung per acre. 



It is usually safe in manuring to aim at as large a crop as the 

 climate will allow, but also to recognise that fertilisers must 

 not be expected to overcome the effects of the weather. , 



Muriates or Sulphates as Manure. — Farmers are now offered 

 the choice of muriate or sulphate of potash, and it is possible 

 that they may at a future date be able to obtain muriate of 

 ammonia. Experiments are being carried out at Eothamsted 

 and elsewhere to ascertain the manurial value of these newer 

 substances. Before the War the problem never arose : all the 

 available potash salts came from one source and it was no 

 advantage to the farmer to obtain muriate rather than sulphate. 

 Nowadays, however, there is more than one source of supply, 

 and the possibility of competition accordingly exists. It is 

 therefore imperative that the relative values of the two sub- 

 stances should be carefully and impartially tested. This is being 

 done, but as everyone familiar with agricultural experiments 

 will realise, the tests must go on over several seasons before 

 anything very definite emerges. 



There already exists, however, a certain amount of information 

 which may easily prejudice the matter because it is not strictly 



