looking up the lime matter. I find that a lime is being advertised,
and sold in small amounts, that is called hydrated lime, and it is
especially prepared as an agricultural lime. It is recommended by
some dealers as being fully equal to the ordinary commercial
fertilizer which sells at about $25 a ton, while this hydrated
agricultural lime can be bought for $8 a ton, and I think for a
little less in larger amounts. You mentioned also that you had seen
some one who had used hydrated lime, but it didn't seem to make much
of a clover crop. Of course, I understand from what you said that
his soil contained only one hundred and sixty pounds of phosphorus,
and I take it that lime alone could not markedly improve his soil;
but still I would like to know why, if he has one hundred and sixty
pounds of phosphorus in his plowed soil, he could not produce a few
good crops of clover. HOW much phosphorus does it require for a ton
of clover?"

"One ton of clover contains only five pounds of phosphorus," Percy
replied, "and of course the roots must also require some phosphorus,
although after the crop is produced and removed, the phosphorus
contained in the roots remains for the benefit of subsequent crops.
Thus we might suppose the land which contains one hundred and sixty
pounds of phosphorus ought to furnish the phosphorus needed for a
three ton crop of clover every year for ten years; but in actual
practice no such results are secured. The invoice of the plant food
in the soil is a matter of very great importance, for it reveals the
mathematical possibilities, but another matter of almost equal
importance is the problem of liberating plant food from this supply
sufficient for the crops to be produced year by year.

"Decaying or active organic matter is one of the great factors in