THE SHRINKAGE OF MARKET HAY. 17 



the hay was ricked. It was also found that there was a direct 

 relation between temperature and water content of the hay, the 

 highest temperature occurring in the stack that contained the largest 

 percentage of water. 



The material for rick No. 1 — first-cut clover hay — was in ordinary good condition for 

 stacking, and when cut into in December was found to have undergone a rather low 

 fermentation, being only slightly browned and in good condition. 



The material of rick No. 2 — second-cut clover hay — was greener when stacked, and 

 as was to be expected, the maxim um thermometer readings were somewhat higher 

 than in the case of rick No. 1. The hay produced also showed a deeper brown color, 

 owing to the higher temperature of fermentation. 



The highest temperature occurring in the two stacks while under- 

 going fermentation was between 140° and 150° F. The investiga- 

 tor's conclusions are as follows: 



It seems unlikely that any harm to the dry matter will result where the hay has not 

 exceeded a temperature of 150°F. How much higher the temperature may safely rise 

 it is at present impossible to say; so much depends on the size of the rick and the 

 degree of consolidation that has taken place. The less the consolidation the more 

 ah there is present, and the higher the temperature is likely to rise. At the same 

 time imperfect consolidation is generally to be found in ricks of small size, but on 

 account of the small bulk more heat is lost by radiation, and hence there is less liability 

 to fire. 



According to Hoffman, 21 the organic matter in hay is destroyed at 

 a temperature of 226° F. or over. 



When spontaneous combustion occurs in clover, heat is generated in the hay, 

 oxygen being taken up from the air and the organic matter transformed into carbon 

 dioxid and water. The water moistens the hay, and the moistened material ferments 

 because of the presence of bacteria. The fermentation also produces carbon dioxid 

 and water, as well as small amounts of hydrocarbons, hydrogen, organic acids, enzymes, 

 etc. Heat is also produced from the fermentation. The fermentation is more rapid 

 if the clover is moistened at the beginning. However, the water produced by the 

 oxidation of the material is sufficient to start it. The fermentation of the hay causes 

 the temperature of 133° F. At this temperature a more violent oxidation takes place 

 and the temperature rises to about 194° F. Other processes then take place which char 

 the material and cause a slow rise in temperature to 226° F. When this temperature 

 is reached, the hay rapidly heats and the charring proceeds rapidly. All these 

 processes destroy at least half of the material. Theoretically the temperature may 

 reach 374° F. 



According to the tests made, clover hay may become ignited at 302° F. to 392° F. 

 Therefore the temperature may rise sufficiently high to cause spontaneous combustion. 

 Oxygen from the air is essential to combustion. 



These experiments confirm the belief that there can be no appre- 

 ciable loss by destruction of the dry matter in hay in storage when it 

 has been properly cured in the field, provided the hay is protected 

 from injury by rain. In other words, the natural sweating or curing 

 and the resultant shrinkage of hay in the stack or barn do not involve 



2i Hoffman, F. H., Zeitschr. Spirit-ind., 1897, Nos. 35, 39, 41, 42, 45, 47, 50, abs.in Biedermanns-Central- 

 blatt fur Agriculturchenue, v. 27, No. 6, 1898. p. 295, 296. 



183958°— 20— Bull. 873 3 



