90 



Journal of Agricultural Research 



Vol. XVII, No. 3 



It was decided to apply sulphur in the form of sodium sulphate 

 (Na2S04), calcium sulphate (CaS04), and elemental sulphur. The ele- 

 mental sulphur was mixed with the soil at the time of planting, but the 

 sulphates were added daily in the form of a solution. This daily addi- 

 tion of sulphates maintained a continuous supply of sulphates for the 

 plant and it was thought that through the growth of the plants in the 

 pots receiving the different forms of sulphur one could ascertain whether 

 the elemental sulphur was able to supply the necessary sulphate. In 

 order to eliminate nitrogen as a limiting factor, sodium nitrate (NaNOg) 

 in solution was added daily. By keeping up an available supply of 

 nitrogen, a study could be made of the influence of sulphur fertilizer on 

 the amount of nitrogen taken up by the plant. Nitrogen and sulphur 

 enter into the composition of proteins and mustard oils so that an abund- 

 ant supply of sulphates and nitrates in the plant may increase the elabo- 

 ration of those organic compounds containing sulphur and nitrogen. 



In addition to growing the plants on soil, they were also grown in sand 

 pots receiving extract from the soil plus any nutrient that was added to 

 the soil. For example, for a soil receiving a solution containing calcium 

 sulphate and sodium nitrate, there was a corresponding sand pot re- 

 ceiving a water extract of the soil plus calcium sulphate and sodium 

 nitrate. The foUowdng statement shows what each pot growing clover 

 received : 



SOIL 



Pot I : 



Calcium sulphate. 



Sodium nitrate. 

 Pot 2: 



Sodium sulphate. 



Sodium nitrate. 

 Pots: 



Sodium nitrate. 



Calcium carbonate. 



Sulphur. 



Pot 7: 



Soil solution. 



Calcium sulphate. 



Sodium nitrate. 

 Pot 8: 



Soil solution. 



Sodium sulphate. 



Sodium nitrate. 



Pot 4: Sodium nitrate. 



Pots: 



Sodium nitrate. 

 Calcium carbonate. 



Pot 6: No fertilizer. 



SAND 



Pot 9: 



Soil solution. 



Sodium nitrate. 



Calcium carbonate. 



Sulphur. 

 Pot 10: 



Soil solution. 



Sodium nitrate. 



Pot 4 (PI. 9, A, B, and C) is a control to compare with i and 2, and 

 5 is a control on pot 3. Pot 10 receives no sulphur except that in the 

 original soil extract. The pots growing oats and rape were treated in 

 the same way, and this was repeated for each soil, making in all 90 pots 

 (PI. 9-12). 



