RESEARCH REGARDING THE FACTORS THAT INFLUENCE THE PHYSICO-CHEMICAL PROPERTIES OF THE SOIL

Abstract

Through the tractor’s tires, the soil is solicited by the forces caused by the weight (assigned on the tires) and by the other forces that are present between the tire and the soil: indirect forces of traction (the driving wheel), retardation forces, rolling resistance, direction forces. The influence of different constructive (type, dimensions) and running factors (air pressure, burden, spin) over the sliding, on the scale of iso static curves, in different soil conditions:  Even though the average pressure of the contact area between the tire and the soil is the same, the depth of the propagation of the pressure in the soil is higher than on the contact pressure between the tire and the soil. Reducing the pressure on the contact area between the wheel and the soil is generally obtained by increasing the contact area and is done mainly by using low pressure in the tires. In order to achieve that, special low pressure tires (those are relatively expensive) or double tires are being used. Experimental research has shown that by rising the loading time, the depth of propagation of iso static curves increases. The speed of the tractor will also influence the degree of soil application. Compacting the soil depends on the tangible physic-mechanical properties of this one (density, porosity, humidity), as well as on the constructive parameters (type and size of the tire) and the running of the tires (the air pressure, weight placed on the tire and the number of passing on the same trace). The degree of compacting the soil is characterized by resistance to penetration, indicator that is established by using a cone penetrometer (built according to SAE standards). Reducing the compactation of the soil can be obtained through decreasing the pressure in the tire, as well as by augmenting the contact area between the soil and the tire. After various experiments, it is recommended to reduce the traffic on the field, to control the traffic by using technological paths, to lower the number of works by using the non-till system, to use low weight equipments, to use agricultural equipments with the tires placed in tandem, to rotate the crop using plants that have profound roots and a high force of penetration.