REPORT OF THE CHEMIST 



173 



&E5STGNAL PAPEH No. 16 



NITROGEN-ENRICHMENT OF SOILS THROUGH THE GROWTH OF 



CLOVER. 



The importance of clover as a manurial agent led us to inaugurate in 1902 a 

 number of experiments with the object of learning to what extent the nitrogen-content 

 of a soil could be increased through the growing and turning under of this crop. 

 Of these one plot has been constantly in clover since it was first seeded, the crop being 

 cut as often as occasion required and the material allowed to decay on the soil. Every 

 second year, the plot has been dug over and re-sown. At the outset it was dressed with 

 superphosphate at the rate of 400 lbs., and muriate of potash at the rate of 200 lbs. per 

 acre. The plot was limed at the rate of one ton to the acre in the spring of 1909. 



From time to time, the soil of this plot has been sampled and its nitrogen-content 

 determined. The following table presents the results to date : — 



Nitrogen-Enrichment of Soil due to Growth of Clover. 



Before experiment 

 After two years 

 After four years. . . 

 After five years . . 

 After six years. . . . 

 After seven years . 

 After nine years . . 



Increase in nitrogen due to nine years' growth 



Date of 

 Collection. 



13-5-02 

 14-5-04 

 15-5-06 

 30-5-07 

 23-5-08 

 4-5-09 

 5-5-11 



Nitrogen. 



Percentage 



in 



Water-free 



Soil. 



0437 

 •0580 

 •0608 

 •0689 



0744 

 •0750 

 •0824 



•0387 



Pounds ]ier 

 Acre to 



Depth of 4 

 Inches. 



533 



708 

 742 

 841 

 908 

 915 

 1,005 



472 



This soil, it will be observed, continues to increase in nitrogen, though the figures 

 afford evidence of a falling in the rate of increase as the experiment progresses. It is 

 equally evident, however, that the limit of enrichment has not yet been reached. 



The total nitrogen of the soil has practically doubled in the nine years of the 

 experiment; averaging the results there has been an annual increase of 52-4 lbs. per 

 acre. 



