Applications of empirical methods in central Italy for predicting field wheeled and tracked vehicle performance

Abstract

Due to the agricultural field traffic and to the soil tillage implements, soil compaction has been recognised as a severe problem in mechanized agriculture and has an influence on many soil properties and processes. In this paper, empirical methods originally developed by the different Authors at Waterways Experiment Station (WES) for predicting the performance of off-road vehicles were applied on agricultural soil. The models considered and based on soil–vehicles interaction were: clay–tire rubber track numeric (Nc,r), mobility index (MI), vehicle cone index (VCI), mean maximum pressure (MMP) and they included besides soil strength, the load carried by the tire or track, some technical characteristics of the tire or track of the vehicle, as well as the number of passes on the same track. These models have been validated with the tests results of a number of selected agricultural and forest vehicles over a range of soil in central Italy: Vertic Cambisol, Haplic Calcaric Cambisol and Eutric Cambisol. Significant correlations among the above indexes and among Nc,r and two tire–track performance parameters: traction coefficient and traction efficiency, have been found. In addition a correlation between the measured cone index values during field tests, and the predicted cone index values have been developed. Through the field data collected and the elaboration and validation of the indexes it was possible to frame in a coherent way, the performance of agricultural machinery of different mass and power, running gear system (wheels, tires with low aspect ratio, metal and rubber tracks, self-propelled for the harvest, transport and distribution of agricultural products), even though particular interpretative shrewdness was necessary in the application of such formulas in the cases of innovative machinery as with the rubber track system. The vehicles that have obtained the higher values of Nc,r (>20) have obtained the lowest values of both the MMP (<156 kPa) and VCI (VCI1 < 110 kPa; VCI4 < 269 kPa). These vehicles have also obtained the higher values of traction coefficient (0.7–0.9) and of traction efficiency (0.74–0.8). Agricultural field traffic is an important aspect of soil management and such indexes, based on parameters that determine the impact of the agricultural mechanization on soil qualities, can usefully be considered in the management of the agricultural farm to reduce soil compaction due to both the traffic of machinery and to tillage implements particularly when considering the aspect of altered land use.