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New YorkK AGRICULTURAL EXPERIMENT STATION. Silex 
who are engaged in growing lettuce under glass. In preparing 
the soil for forcing lettuce it is not unusual for market gardeners 
to cover it from 2 to 3 inches deep with manure and then work 
the manure in. Some growers recommend applications 1 or 2 
inches deep.t If another lettuce crop is to follow the first one 
immediately, another, though perhaps less heavy, application of 
manure is made as soon as the first crop is removed. In some 
lettuce houses, and especially in those of modern type, the soil 
is not often renewed and the repeated heavy applications of 
manure supply it with humus and plant-food in great abundance. 
May there not be an extravagant use of manure under kuch 
circumstances? 
One of the authors reports in Bulletin 146 of this Station some 
investigations bearing on this point. It is there shown that the 
amount of manure which may be profitably used.in forcing let- 
tuce varies with different soils; also that the use of excessive 
quantities of manure has a detrimental effect on the crop as 
compared with more moderate use. It appears, therefore, that 
many gardeners in trying to make the soil very rich for forcing 
lettuce overdo the matter and not only waste that portion of the 
manure which exceeds the requirements of the crop but reduce 
the yield below that which would be given on the same kind of soil 
with less mamre. 
On subsequent pages there is given an account of our inves- 
tigations bearing upon the economical use of manure in forcing 
lettuce and also upon the question of profitably combining nitrog- 
enous commercial fertilizers with stable manure or substituting 
them for it in forcing this crop. Before passing to the consid- 
eration of this work it will be well to inquire what has been 
previously published on the subject. 
PREVIOUS INVESTIGATIONS, 
Scarcely any mention of fertilizer experiments on lettuce 
under glass is found in European literature. The investigations 
on this subject which have thus far been reported have been 

*Amer, Gard., Supplement of Jan, 22, 1898; Rural N, Y., 1898 : 871, 
