1102 
Journal of Agricultural Research 
Vol. XXXI, No. 12 
All studies were conducted at the Priest River field station, with 
the exception of duplicate experiments in the study of the depth of 
cover begun at the Savenac and Boulder nurseries in 1912 and at the 
Trapper Creek nursery in 1914, under the direction of the experiment 
station. 
The 1912 depth of cover bed at Priest River was located at the 
Benton Flat nursery, a dry flat with a sandy loam soil and thin 
sandy subsoil. The 1913 studies of depth of cover, and all studies 
on the other three phases, were located m a group of sixteen 4 by 12 
foot beds known as the Meadow nursery. These beds were on a 
gentle southerly slope just above a flat meadow near Benton Creek. 
They had about a 10 per cent gradient, and were terraced to make 
their surfaces level. The natural soil was a fine silt loam 12 to 18 
inches deep with a reddish color and a marked tendency to become 
compact or caked on the surface. It was underlaid by a light gray, 
claylike silt subsoil so compact and hard that water penetrated very 
slowly. To overcome the heavy nature of the soil, sharp granitic 
sand was mixed with the top 6 inches of each bed, rendering the soil 
loose and loamy and largely overcoming the tendency to pack on 
the surface. 
In all of the experiments included in this series, counts of germina¬ 
tion and of loss were made approximately once a week throughout 
the germinating period of the first season in the seed bed. A survival 
count was made at the end of the season to check the totals which 
had been carried forward. Each seedling, as soon as its germination 
was noted, was marked by sticking a toothpick in the ground just 
north of it. Toothpicks were colored to indicate the month in which 
germination occurred. Dead seedlings and the corresponding 
toothpicks were removed at each weekly count and the cause of death 
noted. Pamping-off was found to be the most prevalent cause of 
death of first-year seedlings. 
In the fall or following spring, at the time of removing the seedlings 
from the seed beds, measurements and weights were obtained of 
representative plants to show relative development under different 
conditions. From one to five seedlings, depending on the number 
available, and representing as nearly as possible the average develop¬ 
ment of each lot of plants, were preserved for future record. Photo¬ 
graphs were made of these specimen plants in the winter of 1916-17 
to illustrate differences in development due to varying treatment in 
the seed beds. 
DEPTH OF COVERING IN SEED BED 
SUMMARY • 
Depth of covering layer has a direct effect on the temperature 
and moisture of the soil in contact with the seed, upon the amount 
of mechanical obstruction to the growth of the stem toward the 
surface, and on the favorable conditions for the development of 
injurious fungi as well as the vigor and resistance of the plants to 
fungus attack. It is because of these effects that variations in depth 
cause differences in germination and survival of seedlings. 
In all of the experiments the shallower covers very uniformly show 
a more rapid germination, a larger total germination, a smaller loss 
