Why Combining MIR (Alpha) and XRF Improves LIAB Accuracy

The Alpha (MIR) and XRF instruments use different analytical methods that complement each other. 

• XRF (X-ray fluorescence) is an elemental method. It directly measures the elemental composition of a sample. However, due to the intrinsic characteristics of the methods, it cannot detect light elements such as B, C, and N. 
• Alpha (MIR) uses mid-infrared spectroscopy (600–4000 cm⁻¹). It is a molecular method that measures how specific chemical bonds (such as C–O, N–O, H–O, and C–H) absorb light.

Why They Work Better Together

Soil is a complex and variable material. Because of this:

• XRF provides direct measurements of elements 
• MIR (Alpha) predicts properties indirectly, using proxies such as clay content and organic matter

Each method has strengths and limitations. When used together, they compensate for each other. 

Because of the direct measurement of total elements used by the XRF, the XRF comes in to complement on the strength of the predictions in addition to elements whose predictions are not strong for the alpha instrument. For example: 

• XRF is more accurate for total phosphorus (P)
• MIR provides broader insight into soil composition and structure

Figure 1: Comparison of reference vs prediction for P exchangeable: XRF only (upper left), Alpha only (upper right) and fusion approach (below)

The Fusion Approach

Combining data from both instruments (fusion) results in:

• Higher overall accuracy 
• Better prediction of soil properties 
• More reliable results across different soil types 

A complete LIAB setup is therefore a hybrid of direct measurement (XRF) and predictive modeling (MIR).

In essence, combining both data enhances the prediction providing results of the entire range of properties with a high accuracy. Therefore, the fusion approach of the two instruments is highly recommended for increased accuracy.