AGRICULTURAL PROGRESS AND EXPERIMENTS. 581 
soil, and especially in its manner of disposing 
of the vegetable substances which are on the sur- 
face, it differs entirely from the turn-over plough, 
comparative experiments ought to be made 
for the purpose of ascertaining the effects which 
follow from the continued use of each of these 
ploughs, as well on the plant-food ingredients of 
the soil as on the crop-yields and their per- 
manence. It is possible that instead of using 
either plough exclusively, the two used in con- 
junction may be found to give better results 
than either by itself; and if this be the case, 
we ought to find out in what manner they can 
be made to best supplement each other. I am 
inclined to expect good results from a system of 
covering the stubbles immediately after the 
harvest with a many-furrow stubble plough, 
followed after an interval of a few months by a 
rotary disc plough for stirring the soil deeply. 
