354 FIELD CROPS 



why a good stand is often obtained after repeated failure. 

 Special inoculation is not often necessary except for alfalfa, 

 and is not always essential for the success of that crop. A 

 liberal application of barnyard manure, particularly that 

 from stock fed alfalfa hay, is very helpful and often meets 

 all requirements. 



LABORATORY EXERCISES 



Dig up any of the common legumes carefully when they are grow- 

 ing rapidly during the late spring or early summer, and examine the 

 nodules on their roots. These nodules are of quite different shapes and 

 sizes on different plants. If they can be examined under a high- 

 power microscope, they will prove still more interesting. It may be 

 possible to find fields of alfalfa or some other legume where the nodules 

 are not present and others where they are. Note the difference in 

 growth. The instructor may provide an illustration of this kind by 

 planting seeds of red clover or some other legume common in the 

 neighborhood in ordinary soil in one pot, and seed which has been care- 

 fully washed to free it from nitrifying bacteria in soil that has been 

 baked long enough to sterilize it in another pot. This should be done 

 long enough before this lesson is reached to allow the plants several 

 weeks' growth or, if there is sufficient time between this lesson and the 

 close of the school year for the plants to make the necessary growth, 

 the pupils may do the planting and watch results. 



SUPPLEMENTARY READING 



Farmers' Bulletins: 



278. Leguminous Crops for Green Manuring. 



315. Legume Inoculation. 



Bureau of Plant Industry Circular 63, Methods of Legume Inoculation. 

 Cyclopedia of American Agriculture, Vol. II, pp. 291-295. 

 Conn's Agricultural Bacteriology, pp. 95-110. 

 Hall's Feeding of Crops and Stock, pp. 120-148. 

 Hunt's Forage and Fiber Crops in America, pp. 121-139. 

 Shaw's Clovers and How to Grow Them, pp. 38-26. 

 Vivian's First Principles of Soil Fertility, pp. 21-30. 

 Wing's Meadows and Pastures, pp. 133-149. 



