42 



moved the toxic body, although the root development 

 was not so good as m the leached series. In still an- 

 other series the soil was leached before planting, and 

 the leachings slowly returned to the pots in the water 

 applied to the growing plants. The plants iii this se- 

 ries grew about as well as those in the limed series. 



In all cases above discussed, each extract from the 

 high nitrate soil had a very high concentration of man- 

 ganese. The extracts contained not more than traces 

 of iron, and very small amounts of aluminum. The 

 data obtained justify the conclusion that the toxic 

 body in this soil is easily removed by leaching; or is 

 made non-toxic by the addition of lime. That the in- 

 fertility is not due to the concentration of the soil so- 

 lution is shown by the yields obtained from the pots 

 to which nitrate of soda was returned to replace the 

 nitrates leached out. Since manganese was the only 

 unusual constituent found in quantity in the extracts, 

 it was apparent that the infertility was due to this ele- 

 ment, or to some soluble organic compound. 



Experiments to Determine the Cause of the Infer- 

 tility OF THE 'Soil with a High Nitrate Content 



Since thorough leaching of the soil carrying a high 

 nitrate content greatly reduced its toxicity, the leach- 

 ings from this soil should contain the substance re- 

 sponsible for the low productive power of the soil. In 

 ordfer to test this, the following methods were used: 

 Pint jars were fitted with paraffined corks, through 

 which five holes had been bored with a small cork 

 borer. After the jars had been prepared and treated 

 as indicated in Table II, germinated oat seedlings were 

 inserted in the holes in the corks, and held in place by 

 a wrapping of cotton. The cultures were then so plac- 

 ed in the laboratory as to receive maximum light. At 

 the end of about three weeks, the plants were taken 

 down, carefully air dried and weighed. The data so 

 obtained are given in Table II. 



