12 



by the cultivation processes are investig-ated, especially those con- 

 cerned with tilth, water supply and resistance to the passage of 

 implements ; and the actual working- of typical implements is 

 studied by means of dynamometer tests so as to see what power 

 is required to do a given piece of work and how this is affected by 

 the design of the implement. The first of these enquiries is 

 needed to find out exactly what work has to be done and, if 

 possible, to state the result in engineering terms ; the second 

 shows how far our present types of implements are efficient, and 

 if they are not, where the wastage of power occurs. 



It is fully recognised that the nature of the soil larg-ely deter- 

 mines the amount of power required to do certain cultivation work. 

 The measurements are showing that the farmer can alter his own 

 soil so as to reduce the power requirement. Thus, on our heavy 

 soil at Rothamsted the drawbar pull on a plough turning three 

 furrows is of the order of 1,500 lb. and the "power factor" {i.e., 

 drawbar pull in lb. multiplied by time in seconds taken to ploug-h 

 1 ft. length of furrow) is of the order of 550. But when the land 

 is chalked there is a saving of power, which may vary from almost 

 nothing up to 15%, according to the condition of the soil. The 

 following are some of the data : — 



When the land is very dry or very wet, the chalking shows its 

 effects least, but in moist conditions it acts strikingly. 



Farmyard manure and coarse ashes also reduce the power re- 

 quirement in ploughing. On Hoos field the reduction has been, 

 as compared with unmanured soil : — 



Due to Farmyard Mamire Coarse Ashes 



22.6% 12.3% 



(values for unmanured soil: drawbar pull = 

 1,472 lb. ; power factor = 614.) 

 Even artificial manures have some action. This has been studied 

 in the first instance on the Hroadbalk wheat field where, however, 

 the effects are much intensified from the circumstance that the 

 same manures are applied year after year. The reduction in 

 power requirement brought about by the use of artificial manures 

 has been : — 



