[SHUTT & charron] NITROGEN-ENRICHMENT OF SOILS 



61 



In these results wc have further evidence of a very satisfactory 

 character concerning the manurial vahie of clover. From two seasons' 

 gro■^^i:h the clover in one set of trials enriched the soil in nitrogen to 

 the amount 'of 179 lbs. per acre, calculated to the depth of 9 inches, 

 and in the other, calculated to a depth of 4 inches, the increase was 

 175 lbs. nitrogen per acre.^ This nitrogen 'was associated with readily 

 decomposable organic matter and would be set free for the use of suc- 

 ceeding crops, as will be sho\\Ti in 'the concluding part of this paper. 



Evidence from the Crop Yield. 



That the growth and turning under of clover and other legumes 

 exercises a beneficial influence on the yield of subsequent crops has 

 been kno-^m more or less widely for a very long time. Nevertheless, 

 it was thought desirable to institute 'field experiments to estimate the 

 extent or degree of the increased yield of succeeding crops of varying 

 character and the period "over which the influence would be perceptible. 

 A large number of such experiments have been carried on during the 

 past twelve years on the Dominion 'Experimental Farms, from which 

 we may select two series as illustrative of the plan of procedure and of 

 the results 'obtained. 



Series I: — Two plots, A and B, of equal size were marked off in 

 the spring of 1900 on soil selected as being of uniform quality. A was 

 seeded with Common Eed clover, B was sown with wheat. In the autumn 

 the clover of A was ploughed under and the wheat of B harvested. In 

 1901 both plots were planted with Indian Corn; A, the plot previously 

 bearing clover, giving a yield over and above that of B of 8 tons 480 

 lbs. This increased yield can only be attributed to the clover of the 



' The relatively larger increase in nitrogen obtained in the plot experiment 

 may be accounted for by the fact often observed that the greater part of the 

 root system of the clover lies in the first or upper six inches of soil- It is 

 also possible that there had been a more complete decomposition of the clover in 

 the plot than in the pots. 



