Green Manuring. 



[June, 



which their roots penetrated was also determined. The results 

 obtained .were: — 



Depth of rooting and yields of Potatoes after green manuring ivith lupins. 



Schultz — Lupit::. {Light sandy soil). 



After After farmyard 

 It/pins. manure. 



Depth of penetration of roots ... ... 47 in. 15-17 in. 



Yield of tubers per acre ... ... ... ( .) tons G tons 



In a similar experiment with rye the results were : — 



Bye after- potatoes Eye on poor 



Rye after and heavy dressing arable 



lupins. of artificials. land. 



Height above ground... 47-G6 in. 27-87 in. 20-35 in. 



Depth of roots 45 in. 20 24 in. 16 in. 



Yield of grain per acre 27 bush. # 12 bush. 9| bush. 



Space does not permit of a more detailed discussion of the 

 mode of action of green manures, but it is hoped that the above 

 remarks will serve to illustrate not only some of the reasons why 

 under suitable conditions green manuring may have such bene- 

 ficial results as it is known to have but also, how the attainment 

 of success with green manures depends on a careful consideration 

 of the actual conditions of soil, climate, etc., in the locality con- 

 cerned. We thus come finally to the consideration of those prac- 

 tical questions on which ultimately the success of any system of 

 manuring depends. We have seen that it is possible to obtain con- 

 siderable crop increases by green manuring, and indeed that in 

 certain districts in this country the system is used with success, 

 and we have examined the factors which are operative in deter- 

 mining the action of green manures. What we now have to con- 

 sider is how existing knowledge can best be applied in practice. 

 It is not surprising that different soils, and districts with different 

 climates, respond differently to similar methods of green manur- 

 ing, and the knowledge at our disposal at present does not enable 

 us to do more than suggest what are likely to be satisfactory 

 systems to suit specified conditions. Many more careful experi- 

 ments are needed before one can say with any degree of certainty 

 what is the best .method under given circumstances. 



The Practical Problems of Green Manuring. — The practical 

 problems fall into two parts : green manuring may be required 

 either to maintain the fertility of land already yielding profitable 

 crops; or to build up the fertility of poor waste land or of land 

 which is badly run down and in danger of being no longer profit- 

 able to farm. In the first case, that of maintaining the fertility 

 of the soil, it is obvious that the system adopted must interfere 



