Legume Damage by Tractors 



by 

 (iordon L. Bvers and Robert F. Lucev* 



Mo(l(Mn farming necessitates moving tractors and equipment 

 over fields where plants are in various stages of growth. In- 

 corporated in modern farming methods has been the trend 

 towards employing more tractors with greater power at the 

 drawhar. Increased drawhar horsepower was obtained without 

 increasing the overall weight of the tractor. 



Heavier loads are being pulled by the tractor now that 

 tractors have the ability to do so. As a result, tractor drive 

 wheel slippage, in the normal process of operations, has in- 

 creased. Tractor tire treads have been designed to provide 

 adequate traction along with roadaljility. Little or no attention 

 lias ])een given to the effect that weight, area of contact, or 

 slippage may have on yields of alfalfa or other legumes. 



Barger and Roberts ( 1 ) found that larger drawhar pull was 

 obtained on green grass because of the ability of new tires to 

 cut or shave off the grass and reach firm ground. Worn tires 

 which had greater contact area, slipped on the grass after it 

 had been matted down. 



The studies reported in this bulletin were concerned with the 

 extent of damage inflicted on alfalfa and red clover plants by 

 ( 1 ) increasing drawbar pull and ( 2 1 increasing the area of 

 contact between the tire and the ground. Increasing the draw- 

 har pull increases the ground pressures under the rear wheels 

 by transferring weight from the front of the tractor to the rear 

 of the tractor. Drive wheel slippage also increases as the draw- 

 bar load increases. Increasing the area of ground contacted by 

 the tire exposes more plants to damage. Tractor tires that ai"e 

 badly worn have a larger contact area than tires with new 

 tread. 



Materials and Methods 



A paxton loam soil located in Northwood Ridge. Northwood. 

 New Hampshire, was used in this study. Soil test results showed 

 that the soil was strongly acid and low" in available plant nu- 

 trients. 



* Associate Agricultural Engineer and former Assistant Agronomist, re- 

 spectively, in the Agricultural Experiment Station. 



3 



