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 it 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. While this 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 II) 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. 



