Performance of in situ vs laboratory mid-infrared soil spectroscopy using local and regional calibration strategies

•The accuracy of various calibration strategies for field vs lab MIRS requires investigation for key soil properties.•Principal components of field vs lab spectra correlated with water content vs C, N, pH, and clay.•Field MIRS requires a more arduous calibration procedure than lab MIR to achieve satisfactory results (RPIQ ≥ 1.89).•Regional field MIRS models with spiking accurately detected tillage effects on soil C.•Moisture most negatively affected MIRS accuracy for sandier soils, with greater affects for C than clay prediction. Comparison of in situ mid-infrared spectroscopy (MIRS) with laboratory MIRS is required to demonstrate the accuracy of field-scale prediction of soil properties. Application of MIRS to investigate soil management questions must also be tested. Our objectives were therefore to determine i) the accuracy of lab vs in situ calibrations using various numbers of local and/or regional soils for prediction of organic carbon (OC), total nitrogen (TN), clay and pH; ii) effects of soil moisture content and variability on model performance for coarser and finer soils; and iii) if the method of OC determination (dry combustion vs MIRS-estimation) affects evaluation of tillage effects. Surface field MIRS measurements were made at three loess sites in Germany, each featuring three tillage treatments. Material (0–2 cm) was collected for lab MIRS measurements on dried/ground (