in] SUPERPHOSPHATE 27 



development is especially valuable for shallow rooted crops and 

 for short lived crops which have to grow quickly : thus, it acts 

 well for barley, swedes, and potatoes. 



For the same reason it is very useful on heavy land after a wet 

 winter in helping the young plants to form roots. 



The effect of the early start persists throughout the life of the 

 plant, and ripening is hastened. Wherever there is danger of late 

 harvests superphosphate should be used for the corn. 



All heavy soils and soils inclined to be sticky in spring respond 

 to superphosphate, and two classes of soil respond in an extra- 

 ordinary degree: the clay fen soils, which often want nothing 

 else in the way of artificial manures, and the heavy soils in wet 

 regions, e.g. the north country, on the Boulder Clay, Wales, etc. 

 Light soils do not usually want phosphates so much except in 

 cold or wet climates, or after a crop has been eaten on the land by 

 sheep receiving also cake or corn. 



The dressings may be liberal, from 3 to 5 cwts per acre; 

 there is no fear of loss, and whatever is left by one crop remains 

 for the next. It can safely be mixed with sulphate of ammonia 

 so as to put on the two together. If necessary it can also be 

 mixed with nitrate of soda, but this mixture should be applied 

 at once as it does not keep well. 



As a rule the yield does not go on increasing with the dressings 

 as in the case of sulphate of ammonia or nitrate of soda, and it 

 is not usually worth while giving more than 5 cwts per acre. In 

 some of the special cases above mentioned, however, the crop goes 

 on responding long after this dressing is exceeded. Thus the 

 Cambridge experiments on fen soils gave the following results 

 per acre 1 : 



With mangolds With potatoes 



tons cwts tons cwts 



No manure ... ... 11 2 No manure ... ... 5 12 



3 cwts superphosphate ... 16 2 4 cwts superphosphate ... 7 15 



6 ... 21 13 8 ,. ... 8 10 



1 Cambridge Farmers' Bull. No. 6. Two of the soils overlay clay, the third 

 was over gravel. 



