RESULT OF FREQUENT MANURING WITH BONES. 495 



and phosphoric acid which the earth of bones contains are almost the only 

 kinds of inorganic f)od required by plants that are returL'^d to the soil. 

 By the aid of the animal matter and the small supply of other substances 

 in the bones,* good crops — and especially the turnips and tlie corn which 

 immediately follows them — may be raised for a few rotations, but at 

 every return the clover and wheat will become more unhealthy, till they 

 at length appear to sicken upon the land. Neither bones nor rape-dust 

 nor any such single substance can replace farm-yard manure for an in- 

 definiie period, because it does not contain all the substances which the 

 entire rotation of crops requires. 



If wood-ashes be used along with the bones, the bad effects I have des- 

 cribed will be much longer delayed — they may even be delayed indefi- 

 nitely, since wood-ashes are said to be especially favourable to the growth 

 of clover and other leguminous plants, (p. 353), and this because they 

 contain those substances which the clovers require. 



It thus appears, therefore, that while the failure, upon a given spot, of 

 a crop which formerly grew well there, is explained generally upon the 

 principle that the soil has become deficient in something which the crop 

 . requires — the cause of this deficiency may not unfrequently be found in 

 the mode of culture, or in the species of manuring which the land has 

 received. The cause being discovered, the remedy is easy. Cease to 

 employ exclusively the manure with which your land has hitherto been 

 dressed. Mix your bones or rape-dust with wood-ashes, with gypsum, 

 or with other portable manures in which the necessary food of your 

 crops is present — or employ farm-yard manure now and then in their 

 stead, and you will apply the most likely remedy. Unless this be done, 

 it will be of comparatively little service to vary the species, — to substi- 

 tute tares or beans for the clover, — since these also will refuse to grow 

 while the same incorrect system of manuring is persisted in. 



I have already drawn your attention (p. 477) to the falling of the 

 clover crops in certain parts of Staffordshire, where the turnips are 

 raised by means of rape-dust — and of the mode of improving them by a 

 top-dressing of farm-yard manure. Were this manure laid in with the 

 turnips, the after top-dressing would most probably not be required. 



§ 6. Of the theory of fallows. 

 , By fallowing, it has been known in all ages that the produce of the 

 land was capable of being increased. How is this increase to be ac- 

 counted for ? We speak of leaving the land to rest, but it can never 

 really become wearied of bearing crops. It cannot, through fatigue, lie 

 in need of repose. In what, tlien, does the efficacy of naked fallowing 

 consist ? 



1°. In strong clay lands one gfeat benefit derived from a naked fallow 

 is the opportunity it affords for keeping the land clean. In such soils it 

 is believed by r^any that weeds cannot possibly be extirpated without an 

 occasional fallow. It is certain that naked fallows are had recourse to 

 in many places for the purpose of cleaning the land, where if it could 

 easily have been kept so by other means they would not have been 

 adopted. Is it not the case on some farms that a neglect of other avail- 

 able methods of extirpating weeds has rendered necessary the assistance 

 * For the composition of bones, see page 446. 



