ARTICLES , 589 



should a dry September follow the harvest period, ploughing 

 immediately after harvest — a much more feasible operation with 

 the tractor plough than the slower horse-drawn implement — 

 is more easily done and more readily breaks up the moist soil ; 

 whereas later ploughing, when the land has dried out further, 

 owing to the removal of the protecting vegetation, brings 

 about less crumbling of the soil and often produces hard clods 

 needing considerable weathering before they crumble into a 

 good tilth. The factors which enter into the two cases must first 

 of all be separated and measured before it is possible to synthe- 

 sise them, and to say that certain factors, operating in a given 

 manner, will cause certain results. Briefly stated, the study 

 of soil cultivation must proceed first from results to causes, 

 and then from causes to results. 



Whatever form of plough is used, it has an effect on the soil 

 besides the mere mechanical inversion, or breaking, of the 

 furrow-slice. In some complicated and, at present, little 

 understood way it brings about conditions conducive to the 

 formation of compound particles, or it may produce the opposite 

 effect, when used incorrectly. The farmer has a traditional 

 knowledge of ploughing problems, and has developed soil 

 cultivation into an art. That is, in fact, its present position 

 — an art, but not a science. There can be no doubt that the 

 development of soil physics now taking place under the impetus 

 of our increasing knowledge of the colloidal state of matter 

 will lead not only to a scientific understanding of the funda- 

 mental phenomena in soil cultivation, but will open up many 

 possibilities of improvement. 



