SOILS ON WHICH STRAW ASH MAT BE USED. 357 



proportion of the several constituents of this mixture, however, is differ- 

 ent, according as the one or the other kind of straw is burned. Thus, 

 100 parts of each variety of ash — in the samples analyzed by Sprengel 

 {Cliemie^ II.) — consisted of — 



100 100 100 100 100 



The most striking differences in the above table are the comparatively 

 large quantity of potash in the oat straw — of lime in that of barley — 

 of phosphoric acid in that of wheat — of sulphuric acid in that of rye — 

 and of all the saline substances in rape straw. These differences are 

 not to be considered as constant, nor will the numbers in any of the 

 above columns represent correctly the composition of the ash of any 

 variety of straw we may happen to burn (see p. 183), but they may 

 be safely depended upon as showing the general composition of such 

 ashes, as well as the general differences which may be expected to pre- 

 vail among them. 



That such ashes should prove useful to vegetation might be inferred 

 not only from their containing many saline substances which are known 

 to act beneficially when applied to the land, but from the fact that they 

 have actually been obtained from vegetable substances. If inorganic 

 matter be necessary to the growth of wheat, then surely the mixture of 

 such matters contained in the ash of wheat straw is more likely than 

 any other we can apply to promote the growth of the young wheat 

 plant. A question might even be raised, whether or not in some soils, 

 rich in vegetable matter, the ash alone would not produce as visible an 

 effect upon the coming crop, as the direct application of the straw, either 

 iri the dry state or in the form of rotted fa<-m-yard manure. And this 

 question would seem to be answered in the affirmative, by the result 

 of many trials of straw ashes which have been made in Lincolnshire. 

 In this county the ash of five tons of straw has been found superior in 

 efficacy to ten tons farm-yard manure, (Survey of Lincolnshire, p. 

 304, quoted in British Husbandry, II., p. 334.) This is perfectly con- 

 sistent with theory, yet as vegetable matter appears really essential to a 

 fertile soil, and as the quantity of this vegetable matter is lessened in 

 some degree by every corn crop we raise, it cannot be good husbandry 

 to manure for a succession of rotatiDns with saline substances only. 

 The richest soil by this procedure must ultimately be exhausted. On 

 the other hand, where much vegetable matter exists, and especially 

 what is usually called inert vegetable matter, it may be an evidence of 



