New York Agricul,tural Experiment Station. 355 



1. Very much better crops of lettuce may be forced by using 

 stable manure for enriching the soil than by using only commer- 

 cial fertilizers of the kinds tested. 



2. When the soil is used for the first time for forcing a crop 

 of lettuce, an abundance of manure may be used with good re- 

 sults but where the use of manure is continued with the same 

 soil year after year the optimum amount may be expected to 

 decline towards the 5 per ct. rate. It is evident that the amount 

 which it is economical to use varies with the character of the 

 soil and of the manure and also with the relation of the prices 

 for a fancy product to those paid for ordinary lettuce. For 

 these reasons no definite recommendations can be made as to 

 the amount of manure which it is profitable to use in forcing 

 lettuce. 



3. In forcing lettuce it is not good economy to make repeated 

 applications of manure in excessive quantities to the same soil. 

 Not only is manure thus wasted but the yield may be actually 

 decreased. 



WHY DO THE SMALLER AMOUNTS OP MANURE GIVE RESULTS BBTTE'R 

 THAN THOSE OBTAINED WHERE THE MANURE IS APPLIED IN 

 EXCESSIVE QUANTITIES? 



With the smaller amounts of manure applied to soils which 

 had received an abundance of nitrogen, phosphoric acid and 

 potash in commercial fertilizers the yield was much greater than 

 it was on similarly treated soils without any manure, but where 

 the manure was used in excessive quantities the yield, as has 

 been shown above, dropped below that obtained with less 

 manure. Why is this so? What factors of fertility does the 

 manure introduce into the soil aside from the plant-food which 

 it contains? The data bearing upon this question which have 

 been obtained in carrying out the experiments under discussion 

 have not all been presented in this account of the work. Other 

 experiments which may throw light on this subject are now in 

 progress. The discussion of this question will therefore be de- 

 ferred till further data have been secured. 



