APPLICATION OF MANURES 67 



them, else serious waste may occur by drainage. 

 Farmyard manure, seaweed, fish manure, blood, horn, 

 wool, meat guano, oilcakes, bones, basic slag and 

 other ground phosphates, and, to some extent, super- 

 phosphate and potassium salts, belong to the former 

 class ; while nitrates, and all manures containing 

 ammonia, belong to the latter class. It was formerly 

 supposed that the great retentive power of fertile soils 

 for ammonia would effectually prevent any loss by 

 drainage ; we know now that ammonia is speedily 

 converted into nitrates after mixing with the soil, and 

 that these nitrates are readily washed out by heavy 

 rain. 



Following these principles, an autumn manuring 

 for wheat may consist of farmyard manure, blood 

 manure, or meat guano, with or without superphos- 

 phate; but dressings of Peruvian guano, ammonium 

 salts, or nitrate of sodium should be deferred till the 

 spring. The question is, however, clearly one of 

 climate, and with a dry winter cHmate ammonium 

 salts or guano may be applied with advantage in the 

 autumn. In a wet spring loss may be avoided by 

 applying ammonium salts, and especially nitrate of 

 sodium, in small successive dressings instead of in one 

 application. Late applications of nitrogenous manure 

 are, however, apt to produce straw rather than corn, 

 and leaf rather than root. As a rule, early apphca- 

 tions of manure are more profitable than late ones. 



On soils of open texture, and little retentive power, 

 preference must often be given to manures of little 

 solubility, in order to diminish the loss occasioned by 

 heavy rain; organic manures— as farmyard manure, 

 seaweed, oilcakes, or green crops ploughed in — are ia 



