THE OTTAWA I(ATURALIST. 



Vol. XIV. OTTAWA, JULY, 1900. No. 4 



SOILS AND THE MAINTENANCE OF THEfR FERTILITY 

 THROUGH THE GROWTH OF LEGUMES. 



By Frank T, Shutt, M.A., F.I.C., F.C.S., F.R.S.C, 



Chemist, Dominion Experimental Farms. 



{Continued.) 



The chief value of green manuring", as the system of plough- 

 ing under a growing crop of clover is called, lies in the addition 

 of nitrogen, otherwise unobtainable. By the subsequent decay in 

 the soil of the turned-under clover, this nitrogen is set free and 

 converted by nitrification into available food for future crops of 

 grain, fruit trees, roots, etc., as the case may be. The growth 

 and harvesting of the nitrogen-consumers leave the soil poorer in 

 nitrogen, the growth of clover and other legumes — even when the 

 crop has been harvested and the roots only left — leaves the soil 

 invariably richer in this constituent. But there are other advant- 

 ages, though ol less importance, to be obtained by this method. 

 Humus in large amounts is formed in the soil from the organic 

 matter of the clover. To the great value of this constituent we 

 have already referred to in detail. All that we have said respect- 

 ing" its functions and importance might be repeated with emphasis 

 for this method of manuring with clover. There is the mechanical 

 as well as the chemical improvement of the soil, the addition of 

 food materials, and the encouragement of microbic life within the 

 soil. 



Further, considerable amounts of potash, phosphoric acid 

 and lime are during the growth of the clover absorbed and built 

 up into its tissues. These, in part at least, are obtained from 

 depths of the soil not reached by the roots of other farm crops, 



