SU = 560 
Iiiflaence of Chemical Discoveries on 
There are soils which, like pure sands, may be called per- 
manently barren ; that is to say, they naturally contain bareh 
any mineral or organic elements of plant-food to produce ir 
their natural or normal conditions a paying crop. Such soils 
by dint of manures of the proper kind, may be made to acquin 
a certain amount of fertility, which, however, is rapidly ex 
raised by con- pended on the crops grown ; and they require constant manurin; 
stant ma- in order to yield any kind of agricultural produce in payinj 
nurings. . quantities. 
But the term permanent fertility is hardly applicable in it 
full sense to any kind of land ; for however rich land mav b 
naturally, its productive power or standard of natural produc 
will be impaired, it may be very slowly in some cases, bu 
surely in all, if such land is cropped from year to year, and n 
provision is made to restore to it the elements of fertility whici 
have been removed by a long succession of crops. Whilst full 
admitting this, it is nevertheless a fact that, in the case of th 
majority of soils under cultivation in England, nothing short c 
the most wilful and long-continued cropping, without any retur 
whatever, can materially injure the staple of the land ; and, o 
the other hand, however much the acquired fertility of naturall 
poor soils may have been raised by the liberal application ( 
dung and artificial manures, or the consumption of cake upo 
the land, such soils will soon return to their natural state ( 
sterility, or fall to the level of their standard natural product 
if they be left unraanured for a few years. 
CHAPTER IL 
Continuous Cropping. 
Experiments MESSRS. Lawes and Gilbert's experiments on the continuoi 
oropp^ng"°"'^ growth of corn-crops show, that on moderately stiff soils ' 
considerable depth, containing naturally an abundance of a 
the mineral elements of fertility, corn-crops may be gro« 
without manure of any kind for more than twenty-five years 
succession, without material injury to the natural or standai 
fertility of the land. 
Mineral manures alone have given very little increase ■ 
produce when they have been applied to wheat, but rath 
better results when applied to barley in an adjoining fie 
similar in character to the experimental wheat-field. On tl 
other hand, nitrogenous manures alone in the form of ammoni 
salts, or nitrate of soda, have given considerably more prodtt 
than mineral manures alone; and a mixture, of mineral ai 
nitrogenous manures has yielded much more still, and more, 
