food, of all kinds, than the guano, but
it is so 'lasting' that it does not do half as much good as its
composition would lead us to expect. Its 'lasting' properties are a
decided objection, rather than an advantage. If we could make it less
lasting--in other words, if we could make it act quicker, it would
produce a greater effect, and possess a greater value. In proportion to
its constituents, the barn-yard manure is far cheaper than the guano,
but it has a less beneficial effect, because these constituents are not
more completely decomposed and rendered available."

"That," said I, "opens up a very important question. We have more real
value in manure than most of us are as yet able to bring out and turn to
good account. The sandy-land farmer has an advantage over the clay-land
farmer in this respect. The latter has a naturally richer soil, but it
costs him more to work it, and manure does not act so rapidly. The
clay-land farmer should use his best endeavors to decompose his manure."

"Yes," said the Doctor, "and, like John Johnston, he will probably find
it to his advantage to use it largely as a top-dressing on the surface.
Exposing manure to the atmosphere, spread out on the land for several
months, and harrowing it occasionally, will do much to render its
constituents available. But let us return to Mr. Lawes' wonderful
experiments."

"On eight plots," said I, "300 lbs. of ammonia-salts were used without
any other manures, and the _average_ yield on these eight plots was
nearly 26 bushels per acre, or an average increase of 9 bushels per
acre. The same amount of ammonia-salts, with the addition of
superphosphate of lime, gave an increase of 13 bushels per acre. 400
lbs. ammonia salts, with superphosphate of lime, gave an _increase_ of
nearly 16 bushels per acre, or three bushels per acre more than where 14
tons of barn-yard manure had been used four years in succession.

"I hope, after this, the Deacon will forgive me for dwelling on the
value of available nitrogen or ammonia as a manure for wheat."

"I see," said the Deacon, "that ground _rice_ was used this year for
manure; and in 1845, _tapioca_ was also used as a manure. The
Connecticut Tobacco growers a few years since used _corn-meal_ for
manure, and you thought it a great waste of good food."

I think so still. But we will not discuss the matter now. Mr. Lawes
wanted to ascertain whether _carbonaceous_ matter was needed by the
growing wheat-plants,