January, 1922 



GROWTH OF TREE SEEDLINGS AND WHEAT 



81 



was a noticeable difference in health and vigor. On humus the green weight 

 of the lightly much surpassed that of the heavily limed plants; the snialler 

 application of calcium did not mask the benefits of the humus. Table 7 gives 

 the green weight per plant on the lightly limed soils. 



The growth of wheat was remarkably stimulated by the small amount of 

 lime added, and far surpassed that on the other soils both in height and in 

 green weight (see fig. 6 on the extreme right). Table S gives the green and 

 dry weight per plant of wheat, exclusive of roots, on this series. 



Table 8. Green and dry weight of wheat on lightly limed soils 



Green weight per plant. Dry weight per plant, 

 Soli grams grams 



Sand 060 .017 



Sand with humus 777 .080 



Humus 1.99 .219 



Summary 



The growth of certain coniferous trees, of a broadleaf tree, and of wheat, 

 on soils of varying humus content, and on similar soils rendered alkaline by 

 the addition of air-slaked burnt lime, was determined. 



To eliminate the influence of humus on moisture-holding capacity, all soils 

 were watered. 



Growth in height, root growth, and green weight were very much greater 

 on pure humus than on pure sand, and were intermediate on the mixture of 

 sand with 4 percent humus by weight, though nearer that on the sand. 

 Height growth on humus continued till the middle of September ; on sand It 

 fell off early in July, and on the mixture of sand and humus it diminished 

 by the middle of July. 



The favorable influence of humus is attributed to its nitrogen content. 

 The value of humus as a nutrient and its influence on the rate of growth in 

 certain forests, independently of its influence on moisture, appears to be 

 amply demonstrated. 



