Using field measurement of saturated soil hydraulic conductivity to detect low-yielding zones in three Swedish fields

Within-field variability in crop yield is subject to research within the framework of precision agriculture. The objectives of this study were to investigate relationships between crop yield and soil structure at the field level, and to evaluate whether field-saturated hydraulic conductivity could be used as a simple and quickly measurable indicator of crop yield. We hypothesized that the long-term average crop yield is influenced by the subsoil properties. Measurements were carried out on three fields in Sweden, at three geo-referenced locations (representing a high-, medium- and low-yielding zone, respectively) on each field. We measured significantly lower field-saturated hydraulic conductivity, Kfs, in low-yielding zones than in high- and medium-yielding zones. Aggregate mean weight diameter tended to be higher and bulk density larger in low-yielding zones, and soil structure was more blocky. Field-saturated hydraulic conductivity showed to be a good indicator of (low) yield. A model with a high R2-value was found that explained yield as a function of Kfs, on the basis of relative values. Our results indicate that degraded soil structure was the reason for low yield. The findings further suggest that subsoil plays an important role for temporally stable within-field features. The results have implications for precision framing in practice, in that (i) soil structure should be accounted for, and (ii) attention should be paid to subsoil properties. Further research is needed to generalize the findings presented here.