4 BULLETIN 209, U. S. DEPARTMENT OF AGRICULTURE. 
gravel (20 to 40 per cent) they contain. Cultivation reduces the sur- 
face to a good mulch. When grape culture in Napa Valley and the 
adjoining foothills became important, a reputation for the superior 
qualities of its dry wines was rapidly made, especially for the excel- 
lence of the white wines. This reputation has been sustained, and 
Napa County has remained one of the leading dry-wine sections of the 
State. 
FRESNO EXPERIMENT VINEYARD. 
The Fresno Experiment Vineyard (PL I, fig. 2) was established in 
the spring of 1903. It is located 3 miles east of Fresno on the prop- 
erty of the Fresno Vineyard Company, at an elevation of 290 feet 
above sea level. The soil is the San Joaquin sandy loam. The fact 
that it is an outlying isolated portion of soil of this character accounts 
for the increased depths to hardpan and the sandier subsoil imme- 
diately above. The San Joaquin sandy loams are confined to lands 
adjacent to the lower foothills on the eastern side of the San Joaquin 
and Sacramento Valleys, where 75,000 acres near Fresno, 6,000 acres 
near Stockton, and 265,000 acres about Sacramento have already 
been mapped. The soil is light red in color, granitic in origin, and 
composed largely of sharp, angular particles. The surface is rolling 
and generally covered with hog wallows and small mounds. 
In the experiment- vineyard plat two varieties of soil were recog- 
nized, namely, adhesive sandy loam, closely approaching a true loam, 
and a friable sandy loam. The former retains moisture longer than 
the latter, which is a deeper soil of lighter texture. Leveling the plat 
disturbed the natural soil conditions, decreasing the depth of the 
sticky, adhesive sandy loam in spots and exposing free sandy loam in 
others, causing the hardpan underlying the plat to occur at depths 
varying from scarcely 20 inches to over 6 feet, whereas the average 
depth at which it occurs is 3^ to 4 feet below the surface. This hard- 
pan, which always accompanies San Joaquin sandy-loam soil, is a red 
iron-sandstone substance cemented by hydrates of iron and alumina 
combined with clay. When this occurs at 2 feet or less below the 
surface, blasting is necessary. Trees and vines thrive when the hard- 
pan is broken or where it lies at a sufficient depth below the surface. 
The soils of the plat above the hardpan contain alkali varying from 
less than 0.05 to more than 20 per cent; but in the lowest grade soil 
no alkali is visible. Of the salts, over 90 per cent are chlorids, as fol- 
lows: Calcium, 50; magnesium, 25; sodium, 15; and potassium, about 
2 per cent. The remainder consists of calcium sulphate and bicar- 
bonate of soda. The depth of the water table on the tract averages 
3 feet. 
Fresno is in the center of the raisin industry of the country, and is 
also one of the most important wine and brandy producing districts 
of California. 
