barn-yard manure.

Similar experiments have been made on barley, with even more striking
results. The plot dressed with 300 lbs. superphosphate of lime, and 200
lbs. ammoniacal salts per acre, produced as large a crop as 14 tons of
farm-yard manure. The average yield of barley for nineteen crops grown
on the same land each year was 48 bus. and 28 cwt. of straw per acre on
both plots. In other words, 41 lbs. of nitrogen, in ammoniacal salts,
produced as great an effect as 200 lbs. of nitrogen in farm-yard manure!
During the nineteen years, one plot had received 162,260 lbs. of organic
matter, 16,492 lbs. of mineral matter, and 3,800 lbs. of nitrogen; while
the other had received only 5,700 lbs. mineral matter, and 779 lbs. of
nitrogen--and yet one has produced as large a crop as the other.

Why this difference? It will not do to say that more nitrogen was
applied in the farm-yard manure than was needed. Mr. Lawes says: "For
some years, an amount of ammonia-salts, containing 82 lbs. of nitrogen,
was applied to one series of plots (of barley), but this was found to be
too much, the crop generally being too heavy and laid. Yet probably
about 200 lbs. of nitrogen was annually supplied in the dung, but with
it there was no over-luxuriance, and no more crop, than where 41 lbs. of
nitrogen was supplied in the form of ammonia or nitric acid."

It would seem that there can be but one explanation of these
accurately-ascertained facts. The nitrogenous matter in the manure is
not in an available condition. It is in the manure, but the plants can
not take it up until it is decomposed and rendered soluble. Dr. Voelcker
analyzed "perfectly fresh horse-dung," and found that of _free_ ammonia
there was not more than one pound in 15 tons! And yet these 15 tons
contained nitrogen enough to furnish 140 lbs. of ammonia.

"But," it may be asked, "will not this fresh manure decompose in the
soil, and furnish ammonia?" In light, sandy soil, I presume it will do
so to a considerable extent. We know that clay mixed with manure retards
fermentation, but sand mixed with manure accelerates fermentation. This,
at any rate, is the case when sand is added in small quantities to a
heap of fermenting manure. But I do not suppose it would have the same
effect when a small quantity of manure is mixed with a large amount of
sand, as is the case when manure is applied to land, and plowed under.
At any rate, practical farmers, with almost entire unanimity,