CONTRIBUTIONS FROM THE WISLEY LABORATORY. 183 
plots manured with rye, oats, mustard, and vetches have given very 
similar yields, between 50 per cent, and 75 per cent, above the control. 
Of the remainder, it is not immediately apparent why the yields 
from the plots manured with black medick should be less than the 
control, but this needs confirmation before speculation is justified. 
The results for the spring section show a very marked increase over 
those for the autumn section. Here the plots manured with crimson 
clover and vetch have given yields well ahead of all the others, 
though the plots manured with red clover, rye, oats, rape, and turnip 
all give distinctly bigger yields than the controls. On the average, 
the spring green-manured plots give about 50 per cent, bigger yields 
than the autumn-treated ones. It is to be noticed that correspond- 
ing to the partial dying down of the mustard before the spring 
application, the yields of turnips show a slight decrease. This is 
the only case of a smaller yield after spring treatment. 
A rough idea of the relative green manurial value of equal 
amounts of organic matter from the different green crops is given 
by Tables VIII. and IX., in which are shown the ratios of the excess 
of yield after each green crop, over the control to the excess of amount 
of organic matter buried by that crop, over that buried on control. 
In these tables — 
Y = Turnip yield (whole plant) from plots manured with green 
crop. 
Yc = Turnip yield (whole plant) on control plots. 
R = Turnip yield (roots only) from plots manured with green 
crop. 
Rc = Turnip yield (roots only) on control plots. 
OM == Ash-free organic matter buried on plots manured with 
green crop. 
OMc = Ash-free organic matter buried on control plots (weeds) . 
Table VIII. 
Ratio of increase in Turnip Crop to ash-free organic matter buried. 
Autumn Section. 
Y - Yc 
R - Rc 
OM-OMc 
OM-OMc 
Mustard 
3-8 
2 -O 
Rape 
Turnip 
0-9 
P-4 
Rye .... 
9-6 
4-8 
Oats .... 
6-3 
3-4 
Vetches 
5'8 
2*5 
Crimson Clover . 
2-2 
o-6 
Red Clover 
I5.O 
Black Medick 
Lupine 
^Control 
