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Precision-farming applications are mainly based on site-specific information of soil properties at the field scale. For this purpose, a number of novel sensor techniques have been developed but not intensively tested under different field conditions. This study presents a combined application of a self-developed dual-sensor vertical penetrometer (DVP) for measuring volumetric soil water content (VSWC) and cone index (CI), and an EM38 for soil apparent electrical conductivity (ECa) in a pasture (1.4 ha). To verify the feasibility of the DVP for interpreting the depth-specific information in the field, not only the soil physical properties and their geographical coordinates were measured, but also geo-referenced yield data were collected. We found that the yield pattern was quite similar to the soil water-content pattern of each layer (layer-1: 5–15 cm; layer-2: 15–25 cm, layer-3: 25–35 cm) and ECa pattern. Using the map-based comparisons in conjunction with the statistical analyses, the effect of each measured soil physical property (VSWC, CI, and ECa) on the yield was investigated. The regression between the yield and VSWC at each layer fitted a quadratic equation (R2 = 0.515 at 5–15 cm; R2 = 0.623, at 15–25 cm; R2 = 0.406 at 25–35 cm). The negative correlation between yield and CI at each layer fitted a linear model with R2 ≥ 0.510.

A combined penetrometer is an appropriate tool to measure the soil cone resistance and the water-content profile. As a relatively new technique, a combined capacitance-penetrometer for the simultaneous measurement of cone index and soil water content was developed at the Department of Agricultural Engineering of Bonn University in 2002. The objective of this study was the evaluation of the effectiveness and applicability of the innovated penetrometer with a focus on three aspects: (1) A capacitance sensor with two electrode configurations was calibrated for silt loam, sandy loam, and sand. The calibration results show that both electrode configurations have sufficient water-content sensitivity, but soil-specific calibrations seem necessary. (2) Under laboratory conditions, the dynamic resolution and response of the capacitance-penetrometer were validated, and its radius of influence was determined. (3) The field measurement results demonstrate that this measurement technique can be used to improve the interpretation quality of soil cone index data. Bewertung eines Penetrometers zur gleichzeitigen Bestimmung von Eindringwiderstand und Bodenfeuchte Fur die Ermittlung von Bodenprofilen fur den Eindringwiderstand und die Bodenfeuchte erscheint die Kombination aus Penetrometer und Bodenfeuchtesensor als geeignete Losung. Ein solcher Kombinationssensor wurde im Jahr 2002 am Institut fur Landtechnik der Universitat Bonn fur die simultane Messung des Eindringwiderstandes und der Bodenfeuchte entwickelt. In diesem Beitrag wird die Tauglichkeit und Anwendbarkeit fur Feldmessungen in folgenden Schritten dargestellt: (1) Ein kapazitiver Sensor mit zwei Elektrodenkonfigurationen wurde fur die drei Bodenarten schluffiger Lehm, sandiger Lehm und Sand kalibiriert. Die Kalibrationsgleichungen zeigen, dass beide Elektrodenanordnungen uber ausreichende Empfindlichkeit zur Bodenfeuchtemessung verfugen. Es sind aber bodenartspezifische Kalibrierungen notwendig. (2) Die dynamische Auflosung und das Ansprechverhalten des Feuchtesensors wurden fur beide Elektrodenanordnungen untersucht, und die Ausbreitung des dielektrischen Feldes wurde bestimmt. (3) Die Ergebnisse der Messungen im gewachsenen Boden zeigen, dass die Messmethode zur Verbesserung der Interpretation der Konus-Indexwerte herangezogen werden kann.