848 



JOURNAL OF FORESTRY 



Crop Plants. — Several of the commoner crop plants were tried on 

 the same soils, for the physical factors controlling tree growth apply to 

 herbs as well as to trees. In addition to the three soils above described, 

 a fourth, a partly decomposed humus from a small opening in the forest, 

 was used in these experiments. This soil showed an acidity of .0013 



^ 



J J 4 t 



bate 



by duseo-sc before Av^ttsCi% 

 by imiijhC after Auyuitn 



DfiCeof M eu i ij le m en t 

 Fig. 4. — Influence of soil on the growth of wheat and clover. See figure i for acidities. 



normal by the Coville method, or approximately half as much acidity 

 as the undecomposed humus, though by the Truog test it was more 

 strongly acid than the undecomposed humus. The physical properties 

 of this soil appeared to be similar to those of the undecomposed humus, 

 the moisture-holding capacity at saturation being 451 per cent of the 

 air-dry weight, or 65 per cent of the air-dry volume. 



