XII. 



CHOPS 



253 



16 per cent. One hundred tons of grass will yield from 30 to 40 tons 

 of hay, while the same weight of freshly cut clover will yield, on an 

 average, about 33 tons of hay. 



Of great importance is the time of cutting. Since fodder crops 

 are essentially straw, the proper time is before the nutrient ingredients 

 are moved from the foliage into the seed. Hence hay should be cut 

 when the grasses are flowering. If grass is left until too ripe, the re- 

 sulting hay is found to be poorer in albuminoids and ash, though richer 

 in carbohydrates and indigestible fibre. 



The changes in Timothy grass during ripening are well seen from 

 the following table l : 



It will be seen that the nitrogenous matters are practically not 

 increased by the later growth, but that carbohydrates and fibre are 

 largely augmented after blossoming. On June 26, the grass was in full 

 bloom ; on July 23, its seeds were almost ripe. 



Grass and clover are always abundantly supplied with micro- 

 organisms, including bacteria, moulds and yeasts ; these act upon the 

 sap and woody fibre of the grass when cut, producing oxidation and 

 evolving carbon dioxide and small quantities of other gases. The act 

 of oxidation is attended with the evolution of heat. These changes 

 take place in the open air with little rise of temperature, because the 

 heat is carried away by conduction and convection almost as fast as it 

 is evolved. Moreover the activity of the micro-organisms soon di- 

 minishes if the materials dry. 



An investigation into the changes produced in grass by fermentation 

 was made in 1897 by Emmerling. 2 Freshly cut grass of the following 

 composition, calculated on the dry matter 



Proteids 



Ash .... 

 Ether extract 

 Woody tissue 

 Non-nitrogenous extract 



Per cent. 

 11-80 

 7-62 

 1-86 

 26-40 

 52-32 



10000 



was placed in a large vessel provided with thermometer and delivery 

 tube. In twenty-four hours the temperature rose several degrees ; 

 during four weeks a slow current of carbon dioxide (6-i per cent) and 

 nitrogen (36 per cent) was evolved. 



1 Hunt, Bui. 5, U.S. Dept. of Agrio. 



2 Ber., 1897, 1869; Jour. Chem. Soc., 1897, Abstracts, ii. 579. 



