NATURAL MANURES. 63 



Ashes are probably one of the best sources of potash 

 that we have, so far as its form and combination are 

 concerned, being in a very fine state of division, and in 

 such a form as to be immediately available to plants. 

 Ashes also have a very favorable physical effect upon 

 soils, the lime present, of course, aiding in this respect. 

 Canada is now the main source of wood-ashes, the sub- 

 stitution of coal for wood making the supply in this 

 country for commercial purposes very limited. Owing 

 to the variability of this product, it should always be 

 bought subject to analysis, and to a definite price per 

 pound for the actual constituents contained in it ; which 

 should not be greater than the price at which the same 

 constituents could be purchased in other quickly available 

 forms. 



Marl. Marl may contain one or more of the constit- 

 uents, phosphoric acid, potash, and lime. Shell marls 

 are usually very rich in lime, but contain only traces of 

 phosphoric acid and potash. The green sand marls of 

 New Jersey often contain very considerable amounts 

 of phosphoric acid and potash, though they vary widely 

 in composition. They contain on the average two and 

 two-tenths per cent of phosphoric acid, four and seven- 

 tenths per cent of potash, and two and nine-tenths per 

 cent of lime. These constituents, particularly the potash, 

 are, as a rule, slowly available. 



Marl, however, is an important amendment to soils, 

 not only because of its content of mineral constituents, 

 but because these constituents are associated with pro- 

 ducts that have a very favorable mechanical effect upon 

 soils. Large areas of land in the State of New Jersey 



