12 BULLETIN 402, U. S. DEPARTMENT OF AGRICULTURE. 
Throughout the period of the test it has been necessary to sub- 
divide the tenth-acre units in at least a portion of the series in order 
to make sufficient divisions for all of the work being done. The 
subdivisions have usually been twentieth-acre plats, formed by 
making a 16-inch alley between the subdivisions and reducing the 
width of the alley between tenth-acre plats. Smaller plats are used 
when sufficient seed is not available to sow the standard plat. 
Usually no plats smaller than 0.01 acre in size are classed as field 
plats, but in a few instances plats contaming 0.008 acre have been 
called field plats. Nursery rows have been used for the preliminary 
tests, and many varieties tested in the nursery have proved so poorly 
adapted to conditions that they were never grown in the field plats. 
Careful agronomic and physiologic observations have been made and 
are preserved in the form of annual reports. 
REPLICATION OF PLATS. 
Until 1915 only one plat of each variety was grown each year, 
but a leading variety of each cereal was used as a check. Usually 
there were five or more check plats from which the data could be 
averaged. In 1915 all of the leading varieties were sown in duph- 
cate twentieth-acre plats. The value of repeating all the varieties 
in the experiment is apparent, and mcre extensive replication is 
planned for the future. 
SOIL TREATMENT. 
In preparing the land for experimental tests the aim has been to 
conform as closely to farm practice as possible. The plowing has 
been done at the moderate depth of 5 to 7 inches, and subsequent 
treatment has been in accord with common farm practice. The 
cultivation has been limited to that required to control weed growth. 
Most of the experimental work has been conducted on land summer- 
fallowed the previous year. ‘This was done to keep the land uniform 
and to assist in the control of weed growth. When the experiments 
were begun, summer fallowing was thought to be the most profitable 
method of production. In 1914 the spring-wheat varieties were 
grown on land which had been cropped to corn the previous year. 
Oats have been grown following potatoes or fallow. 
The usual practice in summer fallowing has been to plow in the 
spring and pack with the disk harrow. Weeds were kept in check | 
during the summer by two or three subsequent diskings. Usually | 
the last treatment immediately preceded the sowing of the grain, 
either in the fall or the spring. aI 
Rate-of-seeding and date-of-seeding tests were included in the 
same series of plats as the varietal work and were on land receiving 
the same soil treatment. | 
