FORTY-FIRST ANNUAL CONVENTION 45 



would not be discovered by analysis of the soil or crop. This is 

 really a very considerable supply that comes from the atmosphere 

 in the rainfall. Every form of combustion throws sulphur into the 

 air. If you stand at the top of a smokestack where soft coal is 

 being burned, you can easily determine sulphur in the fumes. 

 If an apparatus for making gas fails to work properly in remov- 

 ing the sulphur compounds from the gas, when you burn that 

 gas, you can detect sulphur. All forms of combustion throw 

 sulphur into the air in the form of sulphur dioxide and it re- 

 turns in the rain fall. It is possible some may be absorbed by 

 contact of the soil and air even though there is no rainfall. A 

 great many soils have a good deal of pore space. That means 

 that with changes in the pressure of the atmosphere air will be 

 forced into the soil and will be forced out of the soil. With a 

 high barometer there w^ill be heavy pressure of the air. Then 

 the air will be forced into the pores, and with a lower pressure 

 the air would come out again. So there may be considerable 

 movement into and out of the soil of the air, and sulphur will 

 be absorbed. We do not know how much. The amount of sul- 

 phur added would be different in a greenhouse where the rain 

 fall w^as shut off and water used from the laboratory than in the 

 open field. 



There is another very important question, wdiether the sul- 

 phur contained normally in the plant is required. No doubt 

 some of it is essential, but it is not at all sure that all the sulphui 

 (^ommonly found in plants is needed for their growth. In fact, 

 sodium is found in plants in very considerable amounts. It is 

 one of the abundant elements found in the ash of plants, but 

 it is not at all essential to plant growth. It is not a fertilizer 

 or plant food. Silicon is another element of the same character 

 and is very abundant in all soils. It is taken up by plants, but 

 has no value, but if we analyze the plant and decide from that 

 basis that all the silicon present is an essential part of the plant 

 structure, then we would have to count it as a fertilizer. There 

 are several factors that must be considered before we dare draw 

 any such conclusion. Because this is in the press more or less, 

 even getting into text books, I think we have a right to con- 

 sider it here. 



