LABORATORY MANUAL IN FIELD CROPS 53 



Snyder's Soils and Fertilizers. 



Wilson and Warburton's Farm Crops. 



United States Department of Agriculture, Year Book 1907, pp. 385-398. 



Bureau of Plant Industry Bulletin No. 142. 



United States Department of Agriculture, Year Book 1902, pp. 519-532. 



Livingston's Field Crop Production, pp. 14-25. 



