VALUE OF MANURE 269 



206. Manure an Unbalanced Fertilizer. — As a complete 

 fertilizer manure is not well balanced. It contains 0.5 per 

 cent, of nitrogen, 0.25 per cent, of phosphoric acid, and 0.5 

 per cent, of potash. Proportionately expressed this is a 

 2-1-2 fertilizer. A common fertilizer for general farm crops 

 is a 1-6-4 combination (Section 212), and for garden crops a 

 4-8-10 fertilizer is used. Manure is very deficient in phos- 

 phoric acid, and in order to obtain enough of this con- 

 stituent it is necessary to apply in many cases more manure 

 than is economically profitable. While it is possible to 

 maintain the fertility of a soil for a long period of years, at 

 least with no other fertilizer than manure, it is not a practice 

 to be recommended. Manure reinforced with phosphoric 

 acid is more satisfactory and, better yet, a judicious use of 

 commercial fertilizers and manure, properly distributed in 

 a rotation according to the crops, is to be recommended. 

 It is by no means a good practice to add such excessive 

 amounts of manure as are used in some sections of the country 

 on tobacco land where an average of eighteen tons of manure 

 per acre have been applied annually. Under these con- 

 ditions the loss of the fertilizing constituents from the 

 surface soil have been enormous. 



207. Value of Manure. — The proper use of barnyaVd 

 manure is something to be earnestly recommended on every 

 farm. No other single material will do so much for the 

 soil, and no other material is so cheap and easily obtained 

 in most cases. Manure adds organic matter to the soil, 

 and organic matter, it will be remembered, improves the 

 physical condition of the soil, increases the moisture holding 

 capacity and the temperature of soils. Moreover, organic 

 matter is the source of carbon dioxide and organic acids 

 which aid in making mineral compounds soluble. This is 

 particularly true of fresh manure which decomposes easily. 

 Manure also adds large numbers of bacteria to the soil, 

 and the benefits to be derived from bacteria are too numerous 

 to mention. And finally manure adds nitrogen, phosphoric 

 acid, potash, and even calcium to the soil. Fig. 68 shows 

 the effect of manure on a soil which does not respond to 

 liming, although somewhat acid. It is probably the effect 

 of the plant food in the manure which is here most important. 



