l86 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Table XI. 
Autumn Section. 
Amounts of nitrogen added to the soil by turning under green crops. 
Nitrogen in Green 
Yield of Turnips 
Green Crop. 
Crops. 
(Roots). 
lb. per acre. (mean). 
Tons per acre (mean). 
Rye . 
5° 
6-3 
Oats .... 
68 
6-3 
Mustard 
49 
5'9 
Vetch 
78 
5 *5 
Turnip .... 
74 
4'3 
Red Clover . 
9 
4-i 
Crimson Clover 
22 
4-0 
Rape .... 
67 
3-2 
Lupine . . 
9 
3-5 
Black Medick 
6 
2-4 
In the spring section, where the green crops were turned in only 
a short time before the sowing of the main crop, it is seen that the 
yields of turnips obtained decrease with the amount of nitrogen 
added to the soil. (The apparent exception of mustard is probably 
partly to be explained by the fact that a considerable part of the 
nitrogen in this crop is not accounted for by the analyses, owing to 
the crop having been dying down at the time of turning in, and 
having previously shed a large part of its leaves, whose additional 
nitrogen would have been added to the soil.) The case is somewhat 
different with the autumn section ; here the yields of turnips bear 
no relation to the amount of nitrogen added to the soil in the green 
crops. This is without doubt to be explained by the long interval 
which elapsed between the turning in of the green crops in early 
December and the sowing of the turnips in the following May. The 
rainfall during the intervening five months was considerable, and 
without doubt a large part of the nitrogen originally turned under 
in the green crops was lost by nitrification and leaching. This 
explains the proved smaller effect of the green manures in the autumn 
section, as compared with those in the spring section, where the 
opportunities for such leaching were very much less. The results 
would also appear to indicate that the rates of decomposition of the 
buried green crops varied considerably, so that the amount of avail- 
able nitrogen in the soil during the growth of the main crop bore 
no direct relation to the amount of nitrogen turned under in the green 
crop five or more months before. 
These considerations find strong support in the nitrate estimations 
which were carried out on the soils of the green-manured plots. 
Typical results of these estimations are shown in Table XII., and 
the turnip yields obtained from the plots in question are included 
again for purposes of comparison. 
