MANURES, LIME AND FERTILIZERS 67 
of sand or coal ashes, and the deficiency made up as above stated, 
but the feasibility of this plan has not been tested. 
“The problem, however, was not to determine to what extent 
stable manure may be displaced by commercial fertilizers, but rather 
to what extent the latter may be used in connection with an abun- 
dance of the former. We have taken the conditions as we find them 
in most gardens and greenhouses, and the verdict of our experi- 
ment is that under such circumstances, and with the crops grown 
in this experiment, there is likely to be no profit arising from the 
use of the commercial fertilizers named.” 
In the same connection, Prof. Green writes: “The 
growth of plants upon the separate plots was noted from 
time to time, and weights and measures taken at time of 
harvesting. No effect from the use of any fertilizer could 
be detected; the plots were as uniform as though the 
same treatment had been given to all. The crops grown 
were lettuce, radishes and tomatoes.” 
Complete fertilizers were used in larger amounts than 
is customary out of doors, but not so freely as to injure 
the plants. It is probable, though, that with the decreas- 
ing supply of city stable manure, greenhouse growers and 
market gardeners will be forced to resort more largely to 
the use of commercial fertilizers. It is also probable that 
less manure and the skillful use of fertilizers would give 
just as good results as the exclusive use of large amounts 
of manure. 
Sources of nitrogen.—Some nitrogenous fertilizers be- 
come available much more quickly than others. High 
solubility is desirable, for the grower can then adjust the 
supplemental applications more accurately to the needs of 
the crop. It is assumed that every grower is using at least 
some stable manure, and the practical and often perplex- 
ing problem is, how much and what kind of fertilizer is 
needed to produce the best results. 
Of the mineral materials which contain nitrogen, 
nitrate of soda is used the most generally, and no doubt 
more largely as a source of nitrogen than any other 
