Research On Measuring Soil Mechanical Resistance On-The-Go And Exploring Its Primary Application

Soil mechanical resistance is an important mechanics property of soil. The relationship between soil mechanical resistance and several soil physical parameters (such as soil dry bulk densities, soil moisture content, plasticity index, cone index and so on) is closely, and soil mechanical resistance is unfavourable to corn growing and soil tillage. So, we should appreciate researching on its measuring and applying. Amongst the numerous instruments developed to measure soil mechanical resistance, penetrometer is widely used to measure stop-and-go. The method is convenient but labour-intensive, time-consuming. In addition, soil mechanical resistance data is limited to a few discrete points within a field, relationship between soil mechanical resistance and several soil property parameters or crop growing from point data have an accuracy limitation due to a relatively small achievable measurement density. In the context of precision agriculture, soil mechanical resistance should be on-line and on-time measured, and used to build the model of soil-crop. Measuring stop-and-go do not meet the need. Therefore, a set of continuous testing system was developed, which was consisted of hardware and software. The designed dynamometer and the associated measurement chain is efficient, it will suit to precision agriculture if it is integrated with GPS, GIS and DSS.A laboratory calibration of the sensor showed good linear relationship between the applied solicitations and the output electrical tensions of the Wheatstone bridge. The experiment in this study was performed in a field. After spectrum analysis and filtering, the results showed that soil mechanical resistance is lower frequency signal and the lower spectrum density occurs at 2Hz; the soil mechanical resistance at a constant depth was correlated to the cone penetrometer measurements for the same depth, so, the continuously measurement could be used to evaluate soil strength; spatial variability and fractal dimension of soil mechanical resistance was primary studied: (1) autocorrelation function was calculated, autocorrelation length was found, the results showed that existed spatial correlation phenomenon in a limited range, value of undetected points could be interpolated by points from neighbor area. (2) the fractal dimension of soil mechanical resistance were estimated in semi-variograms (1.78845-1.9124) and power spectral densities(2.12-2.296), which were all very close to 2, and it showed that the variation of soil mechanical resistance in all measuring routings were the same complex, random and irregular.