64 MANAGEMENT OF THE FORCING-HOUSE. 
Tests made at the Connecticut Station itself confirmed 
these general results. The investigation was carried to 
mixtures of nitrates with garden loam and to potting soil, 
as well as to mixtures with fresh manure. The garden 
soil had very little effect in reducing the nitrates. 
In another experiment, fresh horse dung and potting 
soil were used. The potting soil ‘‘was made of pasture 
sod and the soil just beneath, composted with about one- 
third their bulk of mixed horse and cow manures. The 
mixture, made in the summer of 1894, had stood in a 
conical, compact pile, exposed till the fall of 1895. The 
soil for this experiment was taken from the interior of 
this pile at a depth of 2-3 feet.” * (7) =) Sime ime 
surface soil of the garden, although heavily dressed each 
year with stable manure, had little or no effect in destroy- 
ing nitrates, the potting earth (made by composting con- 
tiguous pasture sod and a few inches of underlying soil 
with stable manure), reduced nitrates to about half the 
extent caused by fresh horse dung. 
“This result is in accord with familiar facts. The 
surface soil of tilled ground is commonly or always 
charged with oxidizing and nitrifying organisms. Fresh 
and damp compost heaps where vegetable or animal 
matters are abundant and the soil of forests, low mead- 
ows and bogs, contain little or no nitrates, and their 
bacterial growths are of the deoxidizing or reducing 
kinds. It is probable that, near the surface of the heap 
of potting earth, nitrifying organisms were abundant at 
the very time when the sample taken from the interior 
was found to have a denitrifying effect. Accordingly, the 
use of potting earth from the exterior of a compost heap 
may occasion no loss of nitrate-nitrogen, while earth from 
the interior of the heap may reduce nitrates and cause 
serious waste of any nitrate that is applied as a fertilizer. 
It is therefore advisable, some time before using potting 
compost, to place it under cover away from rain, and to 
intermix it thoroughly and frequently, and to keep it in 
rather shallow heaps.’’ 
