A LITTLE AGRICULTURAL CHEMISTRY. 329 



During a warm, dry day leaves also assume the sleeping po- 

 sition, which aids in checking evaporation. 



There are more "sleeping" plants among the Leguminosae 

 than are found in all other families put together. 



A Little Agricultural Chemistry. Of the thirteen elements 

 necessary for plant growth the farmer usually need take but little 

 care, except in the supply of potassium, phosphorus and nitro- 

 gen, and of these three nitrogen is the most precious and costly 

 to obtain. All agricultural plants draw much of their food from 

 the atmosphere, and of those used by the farmer probably none 

 are much, if any, exceeded by clover in the large proportion of 

 nutriment thus derived. In this respect other leguminous crops 

 are much like red clover. 



"Clover seed is the best manure that a farmer can use." 

 Clover has been called "a trap for nitrogen," as it collects and 

 presents large quantities of combined nitrogen in a form ready 

 to nourish growing crops. 



In the words of Dr. Kedzie : " With an adequate supply of 

 combined nitrogen all the other chemicals of agriculture become 

 active, while a limited supply of active nitrogen correspondingly 

 limits the action of the rest. For high farming, or the raising 

 of exceptionally large crops, the great want is an abundant and 

 cheap supply of ammonia and the nitrates. 



"An acre of good clover will onake 5,000 pounds of hay, con- 

 taining 282 pounds of mineral matter or ash. In this ash will 

 be 97 pounds of potash, 96 pounds of lime, 34|- pounds of mag- 

 nesia, and 28 pounds of phosphoric acid. The hay will also con- 

 tain 108 pounds of combined nitrogen." 



The roots and stubble contain fully as much of these elements 

 as the hay. 



Baron J. B. Lawes found that in autumn, after tho last crop 

 of clover was cut, that remaining above ground, and to the depth 



of 72 inches was examined : 

 42 



