Development and testing of vehicle-mounted soil bulk density detection system

Soil bulk density (BD) reflects the soil's ability to function for structural support, water and solute movement, and soil aeration. It is used to express soil physical and biological measurements on a volumetric basis for soil quality assessment and comparisons between management systems in precision agriculture. In order to solve the problem that it is difficult to directly obtain the BD with large sample size, this study introduces a self-developed vehicle-mounted BD detection system, which is a composite sensor. Through the collection and analysis of soil electrical conductivity (ECa), soil mechanical resistance (MR) and soil surface images (SIMG), BD is estimated. A systematic verification test was carried out in the experimental field in North China, the study depth was 0.2 m. The R2 and RMSE between the estimated BD and actual BD measured by core sampling were 0.647 and 0.173 (using Multiple Linear Regression), 0.591 and 0.160 (using Ridge Regression), 0.719 and 0.090 (using Gradient Boosting Decision Tree). Soil moisture content (SMC) was included into the model of BD and R2 of the model was increased from 0.719 to 0.775, RMSE was reduced from 0.090 to 0.073. The system can estimate the degree of soil compactness with R2 = 0.708 and RMSE = 0.049. SMC can also be estimated from ECa and MR (R2 = 0.481, RMSE =1.658). These results show the potential of the vehicle-mounted BD detection system, which can provide the basis for fast, economical, and efficient soil physical property analysis.