OUR INVESTIGATIONS FROM 1898 TO 1901. 
GENERAL CONDITIONS. 
OBJECT OF TESTS. 
We have called attention on pages 323 and 327 to the methods 
of using stable manure which are often practiced by gardeners 
in forcing lettuce and to the investigations bearing upon this 
subject which were published in Bulletin 146 of this Station. 
The experiments which are now reported form a portion of the 
series of investigations begun in 1895 concerning the selection 
and preparation of soils for forcing lettuce and the economical 
use of stable manure and commercial fertilizers for this crop. 
In the fall of 1898 the experiments were directed to the question 
of the use of nitrogenous fertilizers. It was decided to try com- 
mercial nitrogenous fertilizers for forcing lettuce both with and 
without stable manure. Director Jordan assisted in formulat- 
ing the plans for testing these fertilizers. His counsel has also 
been sought at various times during the progress of the work. 
In the fall of 1900 Mr. Hasselbring became associated in the 
work. He has assisted in taking notes and in preparing this 
account of the experiments for publication. 
THE HOUSER. 
The experiments were conducted in the forcing house which 
had been used for the preceding investigations. Its arrange- 
