August 30, 1907] 



SCIENCE 



273 



NITBOGEN IN VAEIOUS LEGUMES 



habit of telling our farmers that in the 

 growth of red clover which takes place after 

 the harvesting of the cereal crop and before 

 the season closes (in eastern Canada we 

 advocate sowing eight to ten pounds of red 

 clover seed with all classes of cereals) there 

 should be in the neighborhood of one hun- 



dred pounds nitrogen per acre — that is, 

 provided growth has not been retarded by 

 a period of drought. The ploughing under 

 of this crop, either in the late autumn or 

 the following spring, according to the na- 

 ture of the next crop to be planted, is now 

 a system widely adopted with excellent re- 

 sults. 



Though we have shown conclusively that 

 clover can be successfully grown at many 

 points in Manitoba and Saskatchewan, there 

 is not in many parts of these provinces a 

 sufficiency of moisture during the growing 

 season for both clover and grain crops. 

 Further, the severity of the winter is such 

 as to render doubtful the survival of the 

 clover. Therefore, while advocating clover 

 wherever its growth is possible, we have 

 looked about for a legume that would better 

 fulfill the requirements of the ease, that 

 would allow the fallowing of the land, say, 

 till the middle of June, to get rid of weeds, 

 and then, being sown, would in two months 

 give such a growth for turning under as to 

 make it of practical value. We think we 

 have such a legume in pease, data regarding 

 which from two months' growth are given 

 in the table. Though the root system is not 

 extensive, it will be seen that by plowing 

 under the whole crop we can enrich the 

 soil by, approximately, two tons of humus- 

 forming material per acre containing in the 

 neighborhood of 130 pounds of nitrogen. 



INCREASE OF SOIL NITROGEN DUE TO GROWTH 

 OF LEGUMES 



For a number of years we have been en- 

 deavoring to determine directly, that is, by 

 analysis of the soil, the amount of nitrogen 

 derived from the growth of a leguminous 

 crop. I may very briefly describe one of 

 the experiments ia this series and which, 

 begun in 1902, is still in progress. A plot 

 16 feet by 4 feet was staked off and the 

 sides protected by boards sunk to a depth of 

 eight inches. The surface soil to this depth 



