524 FORAGE PLANTS AND THEIR CULTURE 



bean seed is very important, poor stands frequently re- 

 sulting from too deep covering. The depth should not 

 exceed two inches, since with shallow planting chance of 

 failure due to formation of a soil crust is lessened. In a 

 test under favorable conditions with the Mammoth and 

 Peking varieties, 100 seeds each were planted respectively 

 1, 1J, 2, 2|, 3 and 4 inches deep. The percentages of plants 

 reaching the surface one week after planting are shown in 

 the table : 



GERMINATION OF SOYBEANS AT DIFFERENT DEPTHS OF PLANTING 



At the Tennessee Experiment Station, it was found that 

 seed of the Ito San variety failed to reach the surface when 

 planted 6 inches deep. At 5 inches the stand was very 

 poor, but it was apparently perfect at any depth of plant- 

 ing between 1 and 4 inches. 



639. Inoculation. Natural inoculation now occurs 

 quite generally throughout much of the soybean region 

 in southern United States. In localities, however, where 

 this crop has not been previously grown it is advisable 

 to inoculate. 



The inoculation of the soybean by means of artificial 

 cultures has been found to be unusually difficult, the rea- 

 sons for which are obscure. In soil supplied with nitro- 

 gen, the plants grow fairly well without nodules, and 

 according to Kirchner nodules were not detected on Euro- 



