FARMYARD MANURE CONTAINS. 47 



different crops to obtain the ingredients from the soil. 

 If we take into account these two considerations in 

 estimating the value of farmyard manure as a general 

 manure, we shall find that they accentuate the inade- 

 quacy of the ratio existing between the nitrogen and 

 the mineral ingredients. Messrs Lawes and Gilbert 

 have found in the Eothamsted experiments with farm- 

 yard manure that while it restored the mineral ingredi- 

 ents, it was inadequate as a sufficient source of nitro- 

 gen. Nitrogen is, of all manurial ingredients, in least 

 abundance in soils. It is consequently found that the 

 ingredient in w r hich farmyard manure requires to be 

 reinforced is nitrogen. With regard to phosphoric acid 

 and potash, it has already been shown that the ratio 

 between them is probably greater than that in a good 

 average manure. We should, arguing from this alone, 

 be inclined to think that farmyard manure would 

 be best reinforced with potash. The reverse, as every 

 farmer knows, is the case, however. This is due, first, 

 to the fact that the potash, unlike the phosphoric 

 acid, is entirely of a soluble nature, and therefore 

 immediately available for the plant's needs ; and 

 secondly, to the fact that the necessity for the appli- 

 cation of potash as a manure is generally not nearly 

 so great as in the case of phosphoric acid. The result 

 is that farmyard manure will be, as a rule, more 

 valuably supplemented by phosphoric acid than by 

 potash. 



Another point of great importance in estimating 



