450 CAUSE OP THE PROLONGED EFFECT OF BONES. 



of lime (p. 371,) and hence the reason why the earthy matter of the 

 bones apphed does not improve the land. In so far as the efficacy of 

 bones really depends upon their earthy constituents, the use of a marl 

 containing phosphate of lime* will, no doubt, greatly supersede them ; 

 : — but in so far as it depends upon the animal matter they contain, 

 bones will exhibit their natural fertilizing action, however rich the 

 soil may already be in those compounds of which their earthy or in- 

 combustible part consists. 



5°. Yet there is reason to believe — nay, it may be assumed as cer- 

 tain — that the phosphate and carbonate of lime which bones contain so 

 largely, are not without effect in promoting vegetation. All our culti- 

 vated plants require and contain both phosphoric acid and lime, (see 

 Lee. X., § 3,) and from the vegetables on which they feed, all animals 

 derive the entire substance of their bones. This same phosphoric 

 acid and lime, therefore, must exist in the soil on which the plants 

 grow, or they will neither thrive themselves nor be able properly lo 

 nourish the animals they are destined to feed. If a soil, then, be de- 

 ficient in phosphate of lime or its constituents, it is clear that the ad- 

 dition of bones will benefit the afler-crops not only by the animal, but 

 by the earthy matter also which they contain. And that such is the 

 case, in many instances, there is good reason for believing. But that 

 this can by no means account for the whole effect of bones, even sup- 

 posing the soil to which they are applied to be, in every instance, defi- 

 cient in phosphates, is clear from the fact (see Lee. X., § 4,) that 260 

 lbs. — less than 6 bushels — of bone-dust per acre are sufficient to sup- 

 ply all the phosphates contained in the crops which are reaped during 

 an entire fourshift rotation of turnips, barley, clover, and wheat. Yet 

 the quantity of bones actually applied to the land is from three to five 

 times the above weight, repeated every time the turnip crop comes 

 round. 



6°. Still, granting that the chief effect of bones upon the immedi- 

 ately succeeding crops is due to their organic part, upon what does 

 their prolonged good effect depend ? Some lands remember a single 

 dressing of bones for 16 or 20 years, and some after the appHcation 

 of 2 or 2\ tons of bones have yielded 10 to 15 successive crops of 

 oats, and have been sensibly benefitted for as many as sixty years 

 after the bones were applied. (See Appendix, No. I., and British 

 Husbandry, I., p. 398.) 



This prolonged effect is also due m part to both constituents. When 

 not crushed to powder, the organic matter of bones is always slow in 

 disappearing, and slower the deeper they are buried. In some soils, 

 also, the process is more slow than in others. The long-buried bones of 

 the bear and of the stag, of which the analysis is given above (p. 449.) 

 had lain in the soil for an unknown period, and yet they still contained 

 a sensible proportion of animal matter. So it is with the bones used for 

 manure, when they are not crushed too fine. They long retain a por- 

 tion of their organic matter, which they give out more slowly, and 



* Most lime-stones and shell sands contain an appreciable quantity of this phosphate, and 

 will, therefore, to the same extent, supersede the use of the earthy matter of hones. Much 

 of the marl of Holsfein consists of the detritus of chalk rocks, anciently broken up and 

 carried off— by the waters of the sea with which that part of Europe was covered at no 

 very remote geological epoch. 



