53 



increased nitrification cannot be the cause of the in- 

 creased yields in tiie limed pots, since in tlie sandy soil 

 lime apparently retarded nilrilication in the unferti- 

 lized pots, but increased the plant growth five fold. 

 The manganese leached from the unlimed fertilized 

 pot of the sandy soil is quite sufficient to cause the poor 

 growth obtained, as can be seen from the following 

 considerations. The optimum water content of this 

 soil is probably about 10 per cent. On this basis the 

 water content of the approximately 20 pounds of soil 

 per pot would be about 1,000 cc. Assuming that the 

 manganese recovered in the leachings existed in the 

 soil in readil}' soluble form, and calculating the man- 

 ganese as sulphate, the concentration of the soil solu- 

 tion would be above 280 p. p. m. While the amount of 

 manganese leached from the plot 4 soil is not as great 

 as that obtained from the nitrification plot soil, still 

 the amounts obtained are sufficient to cause injury to 

 plants, according to the assumptions above. Repeated 

 leachings from this soil continued to show manganese, 

 even after about 7 liters had been percolated, and it 

 is doubtful if all the soluble manganese could be re- 

 moved by a much more thorough leaching than this. 



Most of the pots used in the above work were planted 

 to cow peas on June 17, and harvested August 25, 1917. 

 In the early stages of growth, the plants in the pots to 

 which ammonium sulphate or dried blood had been 

 added, were yellow, and had a very unhealthy appear- 

 ance. Later, all plants took on a healthy green color, 

 and made a good growth, all pots yielding about alike. 

 At harvest time, it was found that the root system of the 

 plants in the unlimed fertilized pots was very poorly 

 developed, and had a scant development of tubercles. 

 Aside from this, there was little or no apparent injury 

 to peas, as judged by final weights of tops producc(i. 

 This result with cow peas is in strong contrast with 

 sorghum in these same pots, and with cow peas in the 

 field. In all probability, however, these plants with 

 poor root growth would have made a poor showing 

 under field conditions in time of drought. 



After the cow pea harvest, the pots used in this work 

 were left undisturbed in the green house until Septem- 

 ber 24, 1917, at which time, 5 grams of ammonium sul- 

 phate and () grams of dried blood were applied, respec- 

 tively, to tliose pots which had received these substan- 

 ces in the j)rcvious treatment. No further addition of 

 lime was made. On October 16, one set of pots was 



