Lysimeter Experiments 79 



the tanks on which more cereal crops were raised. The tanks on which 

 clover was produced (tanks 5 and 9) lost more phosphorus than did the 

 tanks otherwise similarly cropped (tanks 3, 7, 11, and 12). There appears 

 to have been no relation between the lime applications and the quantities 

 of phosphorus removed in the crops. 



SUMMARY 



The lysimeters used in these experiments consist of concrete tanks 

 slightly over 4 feet square and of about the same depth. The bottoms 

 are funnel-shaped, with drainpipes leading to a tunnel where the drainage 

 water is collected. The tanks are lined with water-proofing asphaltum. 



Each tank was filled with 3^ tons of clay loam soil, taken from the 

 field in layers one foot in depth and placed in the tank in the order in 

 which the layers occurred in the field. 



The soil of some of the tanks was cropped and that of others was left 

 bare during the five years covered in this experiment. Certain of the 

 tanks received an application of lime at the beginning of the experiment, 

 and some received annual applications of sulfate of potash. 



All tanks received the natural rainfall but no other water. The drainage 

 water that percolated thru the soil was collected, measured, and analyzed. 



The average annual rainfall for the five years was 31.14 inches. Of 

 the annual rainfall, 24.4 inches, or 78.35 per cent, percolated thru the 

 unplanted soil, and 16.96 inches, or 54.46 per cent, percolated thru the 

 cropped soil. About one-half of the rainfall passed into the air from the 

 surface of the soil and thru the plants growing on it. In general the 

 largest flow of drainage water was during March and April. 



Applications of lime had no appreciable effect on the proportion of 

 rainfall that percolated thru the soil. 



The average evapo-transpiration ratio for the cropped soils was 1 : 580, 

 the crops being maize, oats, wheat, timothy, clover, and mixed grasses. 

 The average minimum transpiration ratio for the same crops was 1 : 290. 

 The minimum transpiration ratio was least for maize and greatest for 

 the grasses, while oats were intermediate. 



With crops of large yield, amounting in the case of maize to over 100 

 bushels of grain, there was never a deficiency of moisture in the soil, 

 which illustrates the great water-holding capacity of a well-drained soil. 



79 



