574 



Journal of Agricultural Research 



Vol. X, No. II 



The soil from the new Citrus station has been cultivated very little and 

 therefore retains much of its original organic matter. It is higher in 

 that respect than the average of the soils from the much cultivated Citrus 

 groves in the vicinity. When planted to Citrus seedUngs in pots it pro- 

 duced much better plants than the neighboring soils, at least during the 

 period that these plants have been under observation. This is quite 

 likely due to the higher percentage of active organic matter in the soil 

 and would tend to explain the fact that young Ckrus groves when planted 

 on virgin soil usually grow well at first and show little mottling until they 

 have reached an age of 8 years or more. By this time under the system 

 of intensive cultivation now in common practice, the active organic mat- 

 ter is necessarily reduced to a minimum. 



Four samples of hydrochloric-acid-treated soil were washed and placed 

 in pieces of apparatus resembling lantern chimneys, and set in shallow 

 reservoirs. They were given the treatments outlined in Table XXXVII. 

 Distilled water and 20 per cent solutions of sodium nitrate were placed 

 in the reservoirs beneath and allowed to pass up through the soil and 

 evaporate on the surface. After four days the surface crust was 

 scraped ofiF and the amount of organic matter brought into solution was 

 determined. 



Table XXXVII.- 



-Solubility of organic matter of black alkali soil treated with sodium- 

 nitrate solutions 



1. Under the conditions of this experiment, when the soil contained 

 calcium carbonate and was treated with distilled water, Httle or no organic 

 matter was brought into solution. 



2. When the soil contained no carbonates and was treated with a 

 sodium-nitrate solution, a moderate amount of organic matter was dis- 

 solved, representing the solubility of the organic matter of the soil in 

 sodium nitrate. 



3. When sodium nitrate and calcium carbonate were brought together 

 in the reservoir, the reaction with the formation of sodium carbonate took 



