ILLUSTRATIONS. 



Page. 

 Fig. 1. Diagram showing the parts per million of water-soluble nitrates in dry 

 soil in the fallow plat in each 6-inch soil layer to a depth of 2 feet; 

 also precipitation curve 12 



2. Diagram showing the parts per million of water-soluble nitrates in dry 



soil in the spring-wheat plat in each 6-inch soil layer to a depth of 2 



feet; also weekly increase of wheat plants 14 



3. Diagram showing the average parts per million of water-soluble nitrates 



in dry soil to a depth of 2 feet in the summer-fallow, spring-wheat, 

 and corn plats; also weekly increase of wheat plants and precipita- 

 tion curve 16 



4. Diagram showing the parts per million of water-soluble nitrates in dry 



soil in each 6-inch soil layer in the corn plat to a depth of 2 feet 17 



5. Diagram showing the average parts per million of water-soluble nitrates 



in dry soil in the fallow plat to a depth of 2 feet; also soil-moisture 

 curve and precipitation curve 19 



6. Diagram showing the average parts per million of water-soluble nitrates 



in dry soil to a depth of 2 feet in the spring- wheat plat; also soil- 

 moisture, precipitation, and weekly crop-increase curves 20 



7. Diagram showing the time and location of the maximum amount of 



nitrates in the wheat and fallow plats 21 



173 

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