FERTILIZERS 137 



fertilizing elements required by plants in forms that insure 

 plentiful crops and permanent fertility to the soil. It not only 

 enriches the soil with the nitrogen, phosphoric acid and potash, 

 which it contains, but it also renders the stored-up materials of 

 the soil more available, improves the mechanical condition of 

 the soil, makes it warmer, and enables it to retain more mois- 

 ture or to draw it up from below." It has a forcing effect 

 when fresh. 



Barnyard manure rapidly undergoes change and deteriora- 

 tion. The latter results mainly from two causes: (1) Fermen- 

 tation, and (2) weathering or leaching. Losses from leaching 

 may be prevented by storage under cover or in pits, while 

 proper absorbents and preservatives, such as gypsum, super- 

 phosphate and kainit, will almost entirely prevent destructive 

 fermentation. The manure should be kept moist and compact. 

 The loss is less in deep stalls than in covered heaps. The fer- 

 tilizing constituents of well rotted manure are more quickly 

 available to plants than those of fresh manure, and the former 

 should be used when prompt action is desired. In the wheat 

 lands of California manure is more or less visible for four or 

 five years after its application to the land, and in the semi-arid 

 region it must be used cautiously on unirrigated land. The 

 light soils of the Pacific coast lack the moisture requisite for 

 the absorption of wheat straw plowed under, and consequently 

 it must be burned. This wastes the nitrogen element of the 

 straw, but saves the ash ingredients for the land. Land treat- 

 ed with stable manure for 6 years gave an increase of 60 

 per cent in the yield of wheat. Ten tons has been given as a 

 reasonable amount to apply to one acre of wheat land. 



Guano. The first shipload of Peruvian guano was imported 

 by England in 1840. Two years later a company was organized 

 to trade regularly in this substance. From 1.5 to 2 cwt. per 

 acre of wheat was harrowed in with the seed. In the United 

 States it quickly gained in popular favor. By 1876 the trade 

 was regulated by national treaties, and millions of dollars 

 were engaged in its transportation. Peruvian guano was used 

 chiefly for its ammonia. The later guanos of the West Indies 

 were rich in phosphates, and of greater advantage to some 

 crops than the Peruvian. Guano was also one of the principal 

 1 Yearbook U. S. Dept. Agr., 1895, p. 570. 



