218 INTRODUCTION TO GENERAL SCIENCE 



gen is obtained, both from the bacteria of decay acting on 

 the green manures, and from the nitrogen-fixing bacteria which 

 have grown on the roots of these plants. Green manures are 

 the only salvation for the land when it has run out completely. 

 Green manures need not interfere with the regular crops, 

 unless the land is very poor, 'for they may be planted in the 

 fall or early spring, as catch crops, being plowed under before 

 planting the regular crop. It means a little more labor to the 

 farmer, but in no other way could he get so much return for 

 the time he spends in thus increasing the available plant food. 



References : 



1. 1601 : 190-192. Early Seeding and Catch Crops. 



2. 1605 : 147. Green Manures. 



3. Farmers' Bulletin No. 245 : 12-15. Green Manures. 



4. Farmers' Bulletin No. 278. Leguminous Crops for Green 



Manuring. 



5. Farmers' Bulletin No. 374 : 5-7. Inoculation and Lime for 



Alfalfa. 



6. Bureau of Plant Industry, Circular No. 71. Legume Inocula- 



tion and the Litmus Reaction of Soils, 

 a. 1602 : 45-48. How Clover Helps the Farmer. 

 6. 1603:33-35. Root Tubercles. 



c. 1606:78-81. The Kinds and Management of Green 



Manure. 



d. 1607 : 201-202. Danger from Green Manuring. 



e. 1610 : 44-47. Green Manuring and Suitable Plants. 

 /. 1611 : 141-143. Green Manure. 



g. 1612 : 289. The Help from Green Manure. 



h. 1902 : 95-110. Legumes and Bacteria. 

 i. 1903 : 237-263. Green Manures. 



156. BARNYARD MANURE 



This source of plant food is by far the most important that 

 the farmer can apply to his land. It has been long known, 



