Design, construction and field evaluation of a multiple blade soil mechanical resistance sensor

• Soil mechanical resistance sensor (SMRS) could measure soil mechanical resistance.
• SMRS measures soil mechanical resistance index (SMRI) continuously at four depths.
• SMRS was sensitive enough to measure changes in soil moisture content and operational depth.
• Good correlations were obtained between SMRI and soil cone index at different depths.
• Low soil disturbance and low variations in measurement are some advantages of SMRS.

A multiple blade soil mechanical resistance sensor (SMRS) that could measure soil mechanical resistance index (SMRI) continuously at four depths was designed, constructed and tested in two field conditions. Results showed that the effects of soil moisture content and depth on SMRI were significant (P < 0.01) while the effect of travel speed ranging from 1.78 to 3.57 km h−1 on SMRI was not significant. Comparison between SMRI and tractor-mounted soil cone Penetrometer measurements (CI) indicated that the coefficient of variation of SMRI was lower than CI. Also, there were good correlations between SMRI and CI at the depths of 10–20, 20–30 and 30–40 cm with the coefficient of determination (R2) of 0.84, 0.83 and 0.80, respectively due to same failure mode between the two systems. Lower correlation obtained at the depth of 0–10 cm (R2 = 0.63) was due to the difference between the failure mode of SMRS (crescent mode) and tractor-mounted cone penetrometer (bearing-capacity). Low soil disturbance, high correlation with CI and low oscillations in measurement are some advantages of SMRS.