ILLUSTRATION OF THE EFFECT OF PREVIOUS VEGE- 

 TATION ON A FOLLOWING CROP: CABBAGE AFTER 

 SESAME. 



J. J. SKINNER 



Bureau of Soils, Washington, D. C. 



A peat soil was sent to the laboratory of Fertility Investiga- 

 tions from Middle River, California, by Mr. W. W. Mackie, of 

 the Soil Survey of the Bureau of Soils, with the statement that 

 the soil had failed to grow cabbages. A crop of sesame had 

 previously grown on the soil and was cleared from the land about 

 a month before the cabbages were planted. The cabbage plants 

 had entirely withered away and died whereas the adjoining rows 

 which had not previously grown sesame produced good healthy 

 cabbages. 



In the course of a laboratory examination an aqueous extract 

 of the soil was made by shaking the soil with three parts of water 

 and filtering through a Chamberlain Pasteur filter. By this proc- 

 ess a clear extract of the soil was obtained and the extract used 

 as a culture solution for plants. 



Cabbage plants were grown in the solution of the soil so as to 

 determine if the water extract was also harmful. Culture jars 

 holding 250 cc. were used as containers of the solution. Ten 

 young cabbage plants were supported in the solution by means 

 of a cork which had been notched for the purpose. The tech- 

 nique and details of this water culture method are described in 

 Bulletin 70 of the Bureau of Soils. An extract of another soil 

 known to produce good cabbages was made and young cabbage 

 plants grown for comparison. 



The cabbage plants in the extract of the sesame soil made very 

 poor growth, showing that the constituents of the soil harmful to 

 cabbage had been transmitted to the solution. The growth in 

 extract of the good soil used for comparison was very good. At 



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