1 88 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
shown that, under the wet conditions obtaining, the nitrogen supply 
was probably a dominant factor. 
But there is no doubt that the physical effect of groen manuring, 
especially on light soils, is one of the most important of its effects, 
and merits closer investigation. The actual growth of green crops 
may deplete the soil moisture by transpiration, and by keeping light 
showers off the soil, and their burial may break the capillary channels 
too low ; but when decomposed they give 'rise to humus material 
which has a profound effect on the texture of the soil, rendering 
light soils more water-retaining and drought-resisting, and heavy 
soils more open and less liable to water-logging. The " direct " 
effects of green manures on plant growth — e.g. the supply of nitrogen 
and other nutrient elements — though important, can all be fulfilled 
by artificial manures, but the physical effects can only be attained 
by the addition of organic matter, and, now that dung is so scarce, 
green manuring seems to offer the greatest possibilities as a source 
of this organic matter. 
Although the author is now no longer at Wisley, the trials, of 
which the first year's results are here reported, are being continued 
there ; the author is also continuing and extending the work at the 
Rothamsted Experimental Station, and it is hoped that as a result 
of this work it will be possible to indicate the best methods for the 
application of green manures to both light and heavy soils, under 
the variety of different conditions obtaining in horticultural and 
agricultural practice. 
In conclusion, the author's thanks are due to the Director of 
Wisley, Mr. F. J. Chittenden, for much valuable advice in planning 
and carrying out this investigation, which was aided by a grant 
from the Development Commissioners ; to Dr. F. V. Darbishire, for 
his assistance in sampling and analysing the crops ; and to Mr. J. 
Wilson, for his practical supervision of the crops. 
