On Compouvd'mg Mineral Manure.^. 



419 



manuring: in such cases the abundance of the substance applied pro- 

 bably enables the plants to assimilate more of those other substances 

 than they otherwise would have done had this one been deficient; the 

 effect thus produced is called stimulation. If, however, the same manure 

 be continued to be used alone on the same land, the other constituents 

 of plants will soon be exhausted, and it will cease to have any effect. 

 If, on the other hand, the manure so applied, or the elements of which it 

 is composed, exist already in the soil in sufficient abundance, the effect 

 will be less, or not at all, perceptible, in which case some other substance 

 than that applied might be deficient, and would produce the desired 

 effect, if chance had led to its application instead of that which failed. 

 This view of the subject corresponds with the varying effect of the same 

 substance on the same soil in different years. 



Seeing the great uncertainty of the effect of such manures, and it 

 being very diflScult, if not impossible, to know what substances are 

 deficient in the soil, it is desirable, in using a substitute for farm-yard 

 dung, that it should contain, not two or three only, but most or all the 

 substances or elements which the dung-cart supplied. These may be 

 united factitiously ; but those substances are the best, and can more 

 surely be relied upon, which are derived from refuse animal matter in 

 which the elements of plants are already compounded.* If this view of 

 the subject be well considered by agriculturists, 1 think it will have the 

 effect of preventing the losses and disappointments so often attendant 

 upon the empirical application of such imperfect manures as those above 

 mentioned. A few well-conducted experiments instituted with this 

 particular object would, I have no doulDt, prove the correctness of the 

 views I have taken, and thereby solve a deeply interesting problem 

 which has so long perplexed the agricultural community. 



13, Camden Terrace^ Camden Toivn, London, 

 Oct. I8th, 1841. 



* The salts of ammonia and the earthy phosphates are the most important substances 

 in concentrated manures ; not because the muriates and sulphates of potass, soda, and 

 lime are less essential to most plants and to general fertility, but because they are more 

 abundantly supplied by the hand of nature ; and therefore it is always found that 

 manures containing a large portion of the salts of ammonia and the earthy phosphates 

 are more constantly successful than such as consist entirely of inorganic salts. In 

 order, however, to have a perfect manure, all the inorganic salts should be included, 

 unless it be clearly ascertained that those which may be omitted exist already in the 

 soil. — F. Burke. 



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