Evaluation of Soil Hardness in Paddy Fields by Cone Penetrometer as a Simple Soil Physical Diagnosis Method

Abstract

To enable quantitative soil physical diagnosis by cone penetrometer, this study investigated time-course changes in the three-dimensional (3D) distribution of soil hardness and quantified the effect of land leveling on soil compaction. The most important result is that the 3D distribution of soil hardness in the field can be mapped quickly. One person could survey 1 ha to 60 cm depth in 90 min. The method allows several fields to be screened in a short time. The results of cluster analyses based on the horizontal distribution of soil hardness show that the distribution did not change significantly throughout the year. Although absolute values can change, this method can be used to measure soil hardness at any time of the year. Measurement of soil hardness by depth can detect the range or position of the plow pan. Comparison of the distribution of soil physical properties between fields revealed that field management affects hardness, especially in the plow layer and plow pan.