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XXVI. — On the Causes of the Benefits of Clover as a Preparatory 
Crop for JVIieat. By Uu. Augustus Voelckeu. 
Agricultui'AL chemists inform us, that in order to maintain 
the productive powers of the land unimpaired, we must restore 
to it the phosjjhoric acid, potash, nitroo^cn, and otlier substances 
which enter into the composition of our farm-crops ; the 
constant removal of organic and inorganic soil-constituents by 
the crops usually sold off the farm, leading, as is well known, to 
more or less rapid deterioration and gradual exhaustion of the 
land. Even the best wheat-soils of this and other countries 
become more and more impoverished, and sustain a loss of 
wheat-yielding power, when corn-crops are grown in too rapid 
succession without manure. Hence the universal practice of 
manuring, and that also of consuming oil-cake, corn, and similar 
purchased food on land naturally poor, or partially exhausted by 
previous cropping. 
Whilst, however, it holds good as a general rule that no soil 
can be cropped for any length of time without gradually 
becoming more and more infertile, if no manure be applied to 
it, or if the fertilising elements removed by the crops grown 
thereon be not by some means or other restored, it is neverthe- 
less a fact that after a heavy crop of clover carried off as hay, the 
land, far from being less fertile than before, is peculiarly well 
adapted, even without the addition of manure, to bear a good 
crop of wheat in the following year, provided the season be 
favourable to its growth. This fact, indeed, is so well known 
that many farmers justly regard the growth of clover as one of 
the best preparatory operations which the land can undergo 
in order to its producing an abundant crop of wheat in the 
following year. It has furtlier been noticed that clover mown 
twice leaves the land in a better condition as regards its wheat- 
producing capabilities, than when mown once only for hay, and 
the second crop fed off on the land by sheep ; for notwithstanding 
that in the latter instance the fertilizing elements in the clover- 
crop are in part restored in the sheep excrements, yet contrary 
to expectation, this partial restoration of the elements of fertility 
to the land has not the effect of producing more or better wheat 
in the following year than is reaped on land from off which the 
whole clover crop has been carried, and to which no manure 
whatever has been applied. 
Again, in the opinion of several good practical agriculturists 
with whom I have conversed on the subject, land whereon 
clover has been grown for seed in the preceding year, yields 
a better crop of wheat than it does when the clover is mown 
