"This accumulation of nitrogenous plant-food, specially useful to cereal
crops, is, as shown in the preceding experiments, much greater when
clover is grown for seed, than when it is made into hay. This affords an
intelligible explanation of a fact long observed by good practical men,
although denied by others who decline to accept their experience as
resting upon trustworthy evidence, because, as they say, land cannot
become more fertile when a crop is grown upon it for seed, which is
carried off, than when that crop is cut down and the produce consumed on
the land. The chemical points brought forward in the course of this
inquiry, show plainly that mere speculation as to what can take place in
a soil, and what not, do not much advance the true theory of certain
agricultural practices. It is only by carefully investigating subjects
like the one under consideration, that positive proofs are given,
showing the correctness of intelligent observers in the fields. Many
years ago, I made a great many experiments relative to the chemistry of
farm-yard manure, and then showed, amongst other particulars, that
manure, spread at once on the land, need not there and then be plowed
in, inasmuch as neither a broiling sun, nor a sweeping and drying wind
will cause the slightest loss of ammonia; and that, therefore, the
old-fashioned farmer who carts his manure on the land as soon as he can,
and spreads it at once, but who plows it in at his convenience, acts in
perfect accordance with correct chemical principles involved in the
management of farm-yard manure. On the present occasion, my main object
has been to show, not merely by reasoning on the subject, but by actual
experiments, that the larger the amounts of nitrogen, potash, soda,
lime, phosphoric acid, etc., which are removed from the land in a
clover-crop, the better it is, nevertheless, made thereby for producing
in the succeeding year an abundant crop of wheat, other circumstances
being favorable to its growth.

"Indeed, no kind of manure can be compared in point of efficacy for
wheat, to the manuring which the land gets in a really good crop of
clover. The farmer who wishes to derive the full benefit from his
clover-lay, should plow it up for wheat as soon as possible in the
autumn, and leave it in a rough state as long as is admissible, in order
that the air may find free access into the land, and the organic remains
left in so much abundance in a good crop of clover be cha