322 Report or THE HortTIcULTURAL DEPARTMENT OF THD 
Those portions of soil which received applications of 5 per ct. 
of manure in combination with the commercial fertilizers always 
showed a very great increase in yield over corresponding soils 
which were treated only with the commercial fertilizers. Fur- 
ther increase in the manure, however, was not followed by a 
corresponding increase in the yield. 
When soils similar to those under test are used for the first 
time for forcing a crop of lettuce, much more manure may doubt- 
less be used with profit than would be profitable where manure 
has been used abundantly with previous crops. 
Where the use of manure is continued year after year on soil 
originally not rich enough to force good lettuce the optimum 
amount may be expected to decline first towards 10 per ct., 
eventually to approach 5 per ct. 
The amount of manure which may be used with good economy 
in forcing lettuce varies with the character of the soil and of 
the manure, and also with the differences in prices received for 
fancy lettuce and ordinary lettuce. For these reasons no definite 
amount can be recommended. 
Repeated applications of excessive quantities of manure to the 
Same soil are not good economy. Manure is thus wasted and 
the yield may be reduced. 
Where large amounts of manure were incorporated in the soil 
for forcing lettuce the yield was increased by compacting the 
soil. This shows that unfavorable effects which follow excessive 
applications of manure may be caused in part, at least, by 
thereby loosening the soil so much as to put it in an unfavorable 
mechanical condition for the lettuce plant. 
The clay loam used in these experiments has always proved 
superior to the light sandy loam for forcing lettuce when both 
were fertilized with equal amounts of stable manure. - 
INTRODUCTION. 
In forcing lettuce may nitrogenous commercial fertilizers be 
used profitably either with or without the addition of stable 
manure? This is a question of considerable importance to those 
