184 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Table IX. 
Ratio of increase in Turnip Crop to ash-free organic matter buried. 
Spring Section. 
Y - Yc 
R - Rc 
OM-OMc 
OM-OMc 
Mustard 
4-8 
3-8 
Rape . . 
2-4 
1-4 
Turnip 
2-9 
1-4 
Rye .... 
3-9 
2-6 
Oats . 
(11 - 9 ) 
(8'3) • 
Vetches 
13-2 
6-o 
Crimson Clover . 
yi 
3-2 
Red Clover 
19-0 
n-7 
Medick 
Lupine 
Control 
In the autumn section it is seen that equal weights of organic 
matter are most effective in the order — red clover, rye, oats, vetches, 
mustard, crimson clover, turnip. Again, in the spring section, weight 
for weight, red clover is easily the most effective, followed by vetch 
and crimson clover. The figure for oats is not trustworthy owing 
to the dying-off and resprouting of the tops already mentioned. Of 
course, these relations do not express the practical value of the different 
crops, for which the actual yield of turnips must be taken (Table VI.), 
but they afford an interesting preliminary analysis of the results. 
It is not intended that any special mathematical significance should 
be attached to the actual ratios ; not only are the data too scanty 
for statistical treatment, but also the magnitude of main crop yield 
depends on other factors besides organic matter and the curve for 
the relation of yield to any one factor, in this case organic matter, 
would not be linear, the ratio being lower where the actual values 
of Y-Yc and OM-OMc are high. 
It is, however, amply demonstrated by these results, that mere 
bulk of green stuff turned under is by no means the only important 
factor in determining the relative value of different crops as green 
manures, at any rate in a moist season. From other results to be 
dealt with below, it will be seen that the amount of nitrogen in the 
green crop had an important bearing on the results obtained. 
The main conclusions to be drawn from these cropping results 
are : 
(1) The superiority of spring green-manuring over autumn 
digging in. 
(2) The superiority of a quick-growing leguminous crop like 
crimson clover or vetches over a non-leguminous one like 
mustard, rape, or rye, for turning under in the spring. 
That is to say, the results do not support those of Voelcker, but 
