120 AGRICULTURE. 



In the spring- it may be used as green manur- 

 ing for corn or cotton fields, or for soiling or 

 spring pastures, or it may be allowed to grow 

 for hay ; but it must be cut bcfoi'c it is in full 

 bloom, for when the blossoms are fully ripe the 

 bristly hairs and the calyx are liable to form 

 balls in the stomach or intestines of horses or 

 cattle, which cause their death. 



III. Alfalfa {Medicago sativa). 



Alfalfa cannot be grown on all soils. It is a 

 deep feeder, the roots penetrating the ground 

 to a depth of from eight to twenty-five feet 

 ( Fig. 32 ), and cases have been reported where, in 

 loose sandy soils, alfalfa roots have been found 

 at a depth of from fifty to sixty feet. 



It must have a subsoil which its roots can 

 penetrate. The soil must be well drained and 

 well ventilated, so that the nitrogen-fixing 

 organisms (bacteria) which work upon its roots 

 may be well supplied with nitrogen from the 

 air. It thrives best in a soil rich in lime, potash, 

 magnesium, and phosphorus — lime being the 

 most essential. 



The soil must be thoroughly prepared. A 

 field should be selected which is free from the 

 seeds of weeds, and plowed thoroughly and 

 deeply. If no subsoil plow is to be had, "the best 

 substitute is two turning plows, the one follow- 

 ing in the furrow made by the other." The Soil 

 must then be thoroughly pulverized and made 



