1921.] 



Notes on Manures for December. 



831 



Use of Superphosphate and Basic Slag on Arable Land.— 



A correspondent has asked for an opinion on the following 

 manurial scheme : — 



Super, per acre. Super, per acre. 



cwt. cwt. 



Mangolds ... 8 to 10 Swedes 6 to 8 



Wheat ... ... none Barley and seeds 3 to 4 



Oats none Two to three 



years leys ... none 



The rainfall is 40 in., the climate mild, the soil on the light 

 side and the locality in the west country. 



Superphosphate has so great a value as a fertiliser that it 

 is a pity to use it for unsuitable purposes, as prejudice may 

 thereby be created against it. There may be some sufficient 

 reason for the dressing given to the mangolds, but so far as 

 one can see it is probably unnecessary to give so much; in 

 general 2 to 4 cwt. of superphosphate per acre is sufficient; 

 indeed at Rothamsted the entire omission of superphosphate 

 has not depressed the crop. There are a few special cases 

 where larger dressings have been proved to be beneficial, and 

 in the fen districts as much as 6 cwt. gave good results. The 

 need for high dressings of superphosphate would seem to arise 

 only when the plant has difficulty in starting or when very 

 heavy dressings of dung are applied, e.g., the 60 or 70 loads 

 formerly used by some of the dairymen near London. In 

 other cases the manuring for mangolds should rather be on 

 the basis of : — 



Up to 20 loads of dang. 



1 cwt. nitrate of soda or sulphate of ammonia, 2 to 4 cwt. super- 

 phosphate or basic slag 1 , 4 cwt. French or German kainit or 1 cwt. 

 sulphate or muriate of potash, 2 to 4 cwt. salt in the drills. 

 H cwt. nitrate of soda as a top dressing when the plants are hoed and 

 singled. 



Naturally this recommendation must be modified to suit local 

 soil and climatic conditions. 



The swedes could quite well receive slag in place of super- 

 phosphate. This has not infrequently proved a useful sub- 

 stitute, and wherever finger-and-toe is prevalent slap" should 

 be preferred. In some centres, however, e.g., at Newton Rigg 

 and in the Devon experiments, superphosphate came out 

 better, except where the soil was deficient in lime. 



Barley following roots that have been folded can nearly 

 always receive superphosphate with advantage; the straw is 



