Development of a Soil Bin Compaction Profile Sensor

Development of sensors to detect the location and depth of hard pans in real time is a major restriction on the application of Site Specific Crop Management (SSCM). In this study, a soil compaction profile sensor equipped with four horizontal operating penetro-meters for on-the-go sensing and mapping of the location and intensity of hard pans arti-ficially formed in a soil bin was developed and tested. The leading edge of a ۶۰۰ mm long vertical soil cutting blade held four ۸ mm diameter, ۸۰ mm long, and ۳۰ degree conic tip stainless steel soil penetrating rods equally spaced at ۱۰۰ mm vertical intervals. With this arrangement, when the cutting blade was driven into the soil up to a ۵۰۰ mm depth, the conic tips sensed soil penetration resistances at ۱۰۰, ۲۰۰, ۳۰۰ and ۴۰۰ mm depths. The penetration resistance force was transmitted by the rod end to the elastic diaphragm of a hydrostatic oil chamber beneath each rod. Each oil chamber was connected to a force magnifying piston and cylinder located off the soil engaging tools. The penetration force was magnified five times before being sensed by a strain gage load cell. Software pro-grams with the capability of discriminating ۱۶ levels of soil compaction intensity were de-veloped for monitoring soil impedances sensed by the soil probes and for converting them to soil compaction maps. For conducting the tests in the soil bin, the sensor mounted on the tool carrier frame was moved along the bin, where artificially formed compacted soil blocks with various densities (۱.۴۵, ۱.۶۵ and ۱.۸۵ Mg/m³) were placed at different loca-tions and depths (up to ۵۰۰ mm deep at ۱۰۰ mm increments). While the probe was cutting and advancing through the soil, the corresponding compaction map was simultaneously displayed on a PC monitor, and the soil penetration resistance data of all four sensing tips was displayed and stored in program files.