14 BULLETIN 873, U. S. DEPARTMENT OF AGRICULTURE. 
SIXTH FACTOR—EFFECT OF TIME ON SHRINKAGE. 
The sixth factor in the shrinkage of hay is that of time. The time 
factor is not nearly as important as 1t would seem to those who have 
not given the matter careful consideration. A study of the 25 experi- 
ments given on pages 4 to 7 will show that, in general, there is no 
correlation between percentage of loss and lapse of time, as affecting 
hay in the barn or stack. In other words, the amount of loss that 
may occur during three months has absolutely no mathematical 
relation to the amount occurring during six months, nine months, etc. 
The average loss by shrinkage in the 25 experiments amounted to 
about 16 per cent. The average length of the experiments was about 
six months, the shortest experiment lasting four months and the 
longest about nine months. The average loss of weight in these 
experiments has no significant relation to average time. (See rule 
for measuring shrinkage, p. 21.) The relation of time to amount of 
shrinkage of barn and stack hay is significant only during a com- 
paratively short period, that is, while the hay is going through that 
part of the curing process commonly known as “‘sweating ” (heating and 
fermentation), which lasts from three to six weeks, or perhaps a 
little longer. Whilethis process or change is taking place in the stack 
or mow, the greatest reduction in water content also takes place, and 
very soon after sweating ceases the hay will be found to contain its 
normal percentage of water. The amount of shrinkage that takes 
place after the first month or two is comparatively small, and 
humidity or condition of the weather becomes a much more important 
factor than does that of time. The factor of time is important, 
however, while hay is curing in the field, in that it affects shrinkage 
later on. 
SHRINKAGE OF NEWLY MOWN HAY. 
It has been pointed out (see Table I) that newly-mown hay con- 
tains a large amount of water, and that about three-fourths (see 
Table IT) of the water must be ‘“‘cured out” in the field before hay 
is ready to be put into the barn or stack, if it is desired to make 
first-class hay. The prime question regarding shrinkage is not how 
much hay will shrink from the time it is cut until it can be stored, 
but how much the haymaker should allow hay to cure in the field. 
During ideal hay-making weather hay loses water rapidly and in a 
comparatively short time, if not handled properly, will lose as much 
as 90 per cent or even more of its water content, becoming so dry 
that there will be no further loss by shrinkage in the stack or barn. 
When this happens there is liable also to be a decided loss of color, 
and with legume hay there may be a large loss of leaves by shattering 
when the hay is handled. 
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