MANURES 53 



like the same degree ; (3) weeds are stifled and killed ; 

 and (4) the root stocks of the green crop burrow deep 

 into the ground, break up the subsoil and make way for 

 our real crops. 



There is no necessity to dig the land before thickly 

 sowing the above seed, but when it has grown and the 

 land is required for vegetables, the surface is well turned 

 and the green matter dug in. 



Not only must the grower who wishes to proceed on 

 scientific lines consider the value of the various manures 

 at his disposal in connection with the composition of the 

 land, but he must also bear in mind that some manures 

 tend to assist the spread of certain diseases whilst others 

 operate as checks to them. Accordingly, if such diseases 

 are likely to occur, he will have to regulate his manuring 

 accordingly. For instance, acid manures, though 

 valuable in themselves, are amicable to the spread of 

 club-root. We must, therefore, withhold dissolved bones, 

 superphosphate, sulphate of ammonia if this dread com- 

 plaint is prevalent and use basic slag or steamed bone 

 flour instead. Again, where diseases occur through the 

 land degenerating into a sour condition, lime must be 

 used freely as a dressing. And where blight is trouble- 

 some the potato crops must be fed liberally with potash 

 in order to make them robust and more immune. 



Lastly, we may point out that artificial manures 

 should not be placed together in a haphazard way. 

 Sulphate of ammonia must not be mixed with a manure 

 holding free lime, notably . basic slag and precipitated 

 phosphate. The immediate result of making such a 

 mixture is the liberation of free ammonia. If it is 



