THE SHRINKAGE OF MARKET HAY. 9 



Forage plants contain comparatively large amounts of water at 

 harvest time. The average water content of timothy, redtop, John- 

 son grass, and other grass hays is from 60 to 70 per cent. The water 

 content of alfalfa, clovers, cowpeas, etc., is somewhat higher, ranging 

 from 70 to a little more than 80 per cent. The maximum water 

 content of hay plants occurs, not at harvest time, but when they are 

 young and are growing vigorously. As the plant approaches ma- 

 turity its water content is gradually lessened, 12 because the growing 

 has almost stopped and the plant requires only sufficient food to 

 mature its seed. The minimum water content is found at this stage. 



There is a rather wide difference between the maximum and 

 minimum water content of grasses and legumes at the time they are 

 cut for hay, depending largely on the length of the harvest season, 

 which sometimes exceeds three weeks. Hay cut at the earliest 

 possible date will have a much larger water content than that cut 

 at the end of the haying season. The variation in the quantity of 

 water in timothy cut at these two extremes amounts to almost 32 

 per cent. (See Table I.) A slightly greater difference is found in 

 some of the legumes, clover and alfalfa, for example.- 



This great variation in the quantity of water in hay when cut is 

 alone ample cause for a considerable difference in the amount of 

 shrinkage that occurs in the barn or stack. This is the first im- 

 portant factor that influences shrinkage of hay. In actual practice 

 it frequently happens that hay cut at the end of the haying season 

 is more throughly cured than that cut at the beginning of the season, 

 because the late-cut hay will lose a greater percentage of its total 

 water content in a given length of time, other things being equal, 

 than will early-cut hay "full of sap." Therefore it is obvious that 

 there may be a considerable difference in the water content of two 

 lots of hay when they are removed from the field and, consequently, 

 a difference in the amount lost by shrinkage. The water content of 

 field-cured hay varies considerably, as is shown in Table II. 



12 See Utah Agricultural Experiment Station Bui. 48, 1897. Alfalfa or lucern for water content of alfalfa 

 from May 4, when plant was 6J inches high, until August 24, when leaves were dry. 

 U. S. Department of Agriculture. Bui. 353, 1916. 



183958°— 20— Bull. 873 2 



