SOILS AND FERTILIZERS 413 



The amounts of fertilizing constituents in the manure stand in 

 direct relation to those in the food. As regards the value of ma- 

 nure produced, the concentrated feeding stuffs, such as meat scrap, 

 cotton-seed meal, linseed meal, and wheat bran, stand first, the 

 leguminous plants (clover, peas, etc.) second, the grasses third, 

 cereals (oats, corn, etc.) fourth, and root crops, such as turnips, 

 beets, and mangel-wurzels, last. 



The nitrogen of the food exerts a greater influence on the 

 quality of the manure than any other constituent. It is the mosl 

 costly fertilizing constituent. It undergoes more modification in the 

 animal stomach than the mineral constituents (potash and phos- 

 phoric acid), and rapidly escapes from the manure in fermentation. 

 The secretion of urine increases with the increase of nitrogenous 

 substances in the food, thus necessitating the use of larger amounts 

 of litter and affecting both the amount and value of the manure. 

 The use of watery foods, as is obvious, produces the same result. 



Farm Manures as a Source of Plant Food. While the compo- 

 sition of farm manure varies with the conditions already enumer- 

 ated, yet they all supply more or less of the essential plant foods 

 nitrogen, phosphoric acid (phosphorus) and potash. The average 

 mixed farm manure contains these plant foods in the proportion of 

 approximately ten parts of nitrogen to six parts of phosphoric acid 

 and eight parts of potash. Mixed stable manure contains on the 

 average about 0.50 per cent, nitrogen, 0.30 per cent, phosphoric 

 acid, and 0.40 per cent potash. All manures contain as a rule both 

 the dung and urine of animals, mixed with some absorbents. The 

 dung consists chiefly of the undigested portions of the food consumed, 

 which was first ground fine by the teeth, and then saturated and 

 softened with the water and digestive fluids of the alimentary canal. 

 This dung, while composed largely of the woody tissues of the food 

 eaten, yet, being very fine and soft, will decompose and give up its 

 plant food very readily. Dung contains approximately one-third 

 of the total nitrogen, one-fifth of the total potash, and nearly all of 

 the phosphoric acid voided by animals. The plant foods in dung 

 are not soluble and must be decomposed before they can be utilized 

 by plants. The urine of domestic animals contains compounds 

 which have been formed in the body. It usually contains about two- 

 thirds of the total nitrogen, four-fifths of the total potash, and very 

 little of the phosphoric acid voided by the animal. While the ele- 

 ments found in the urine are in solution, yet they are not imme- 

 diately available as food for plants, but become so much more quickly 

 than the constituents found in the dung. 



In practice it has been found that while farm manures furnish 

 some of all of the essential plant foods, yet it is considered unbal- 

 anced, as it does not supply them in the proportions found most 

 satisfactory in practice. This is due to the fact that soils gain nitro- 

 gen through other sources, and that the potash in soils becomes avail- 

 able through various means more rapidly than the phosphoric acid. 



Physical Effects of Manures. As all farm manures contain a 

 considerable percentage of organic matter, they have a marked in- 



