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." * * * "While the 

 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 iplace it under cover away from rain, and to 

 intermix it thoroughly and frequently, and to keep it in 

 rather shallow heaps." 



