Power and labour requirements in soil tillage — A theoretical approach

Data from the literature and from IMAG research concerning soil type, tool type and tractor performance were analysed and introduced into the model developed for the calculation of power requirement and task time for soil tillage. The differences in soil type with respect to tool resistance are characterized by well-known (specific) ploughing resistance data. The net energy demand (specific work) of drawn and p.t.o.-powered soil tillage implements is derived from these data on the basis of cutting or stirring intensity and acceleration impacted on the soil particles.The losses in power transmission of four-wheeled tractors are related to field conditions. Mechanical power losses inside the tractor and inside the implement (gearbox, etc.) are also included in the calculated overall efficiency. Taking into account efficiency, depth and speed, the calculated net specific work is converted to gross tractor engine power demand per m working width, which is the basis for selecting the optimal tractor-tool combination.For several tractor-implement combinations on several soil types, task times were calculated in relation to plot sizes, ranging from 0.5 to 12 ha. The formulae used are also applicable to other situations.