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CHAPTER XII. 



Action and Re-action of Farmyard Dung throughout a Rotation Disadvantages 

 from Use of General Manures Objections to Use of Special Manures 

 Permanent Effect of One Crop Manures Principles in applying Special 

 Manures Allegorical Expressions to be avoided Effects of Phosphatic 

 and other Mineral Manures upon the Principal Farm Crops Similar 

 Effects of Nitrogenous Manures Rothamsted Results Effects of Fer- 

 tilizer on Grass Land Basic Cinder Principles in conducting Field 

 Experiments. 



REVERTING to the division of fertilizing substances into 

 general and special, great advantages may be derived from 

 each class of fertilizers the great point in favour of general 

 manures is that they are calculated not only to keep up, but 

 increase, the entire amount of available plant food in the 

 soil they are suitable for all kinds of crops, they are genuine, 

 and less liable to adulteration than many purchased or 

 artificial manures. They are reliable when used by unskilled 

 and unscientific people. Bear in mind that general manures 

 were typified by farmyard dung, and the list of general 

 manure given in the last chapter was mostly composed of 

 refuse animal or vegetable matters. I adhere to my belief 

 in the importance of farmyard manure, and, although ex- 

 periments at Rothamsted and at Woburn have indicated 

 that artificial fertilizers may be employed with equal effect, 

 and in some cases superior effect, yet at the same time we 

 must remember that those experiments are made in a strictly 

 defined manner, and for a particular purpose. They are 

 carried out upon the same crop occupying the same ground 



