New York Agricultural Experiment Station. 323 



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.i 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 teuch 

 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 mod<n'ate 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 beloiv that which tvould be given on the same kind of soil 

 with less manure. 



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 



Mmer. Oard., Supplement of Jan. 22, 1»98; Rural N. T., 1898:871. 



