46 DEPARTMENT BULLETIN 1425, U. S. DEPT, OF AGRICULTURE 
Depreciation from knot defects is uniformly a factor with all 
grades and species because of the fact that certain knots will loosen 
in seasoning no matter what the system or methods employed. 
Degrade of this kind is usually somewhat smaller during the inac- 
tive seasoning period, owing to the relatively higher moisture con- 
tent of air-dry stock at that time. Warp-bow-twist, although the 
cause of material losses at individual plants, is of relatively minor 
consequence for the region as a whole. 
A comprehension of usual drying rates and average final moisture 
contents, which apply to air-seasoned stock during the different 
months of the year in the Inland Empire, can be obtained from 
Figure 7. Admittedly these will differ somewhat in different yards 
and in the same yard during years in which the seasons vary con- 
siderably from the normal. Nevertheless, these are indicative of 
the average results obtainable in air seasoning 4/4 pine stock in 
this region and point to some very definite problems. 
With present yard practice, stock will reach a moisture content of 
15 per cent in 90 days or less only if piled during May, June, July, 
and August. If piled during the period from September to Jan- 
uary, more than six months is required to reach the same level. 
It is also shown that during only half the year, April to Septem- 
ber, it is possible to obtain a moisture content as low as 15 per 
cent. Furthermore, stock which may have reached a moisture con- 
tent lower than 15 per cent by the middle of September will begin 
to pick up moisture at a comparatively rapid rate if left on crossers 
in the yard, and by February may contain 23 per cent or more mois- 
ture. Such conditions necessarily mean a relatively heavy carrying 
charge for the stock and high shipping weights and unsatisfactory 
moisture contents during certain periods of the year. 

