Introduction
The document discusses the determination of Carbon-Nitrogen (CN) concentration ratios in sandy soils using the vario MICRO cube. This analysis is crucial for assessing soil fertility, especially given the typically low CN content in such soils, which necessitates high detection sensitivity.

Methodology
Soil samples were weighed into tin boats without any pretreatment. Due to the finely ground nature of the soil, a very low sample weight was used to demonstrate the instrument's performance. The vario MICRO cube is designed for analyzing low element concentrations, making it suitable for this purpose.

Results
The CN content in soil was determined with high precision even at low sample weights. The results showed:

• Carbon (C) content ranged from 0.125% to 0.133%.
• Nitrogen (N) content was consistently around 0.020% to 0.021%.
• The average C content was 0.130% with an absolute standard deviation of 0.004.
• The average N content was 0.020% with an absolute standard deviation of 0.001.

These results indicate that small homogeneous samples in the lower mg-range are sufficient for reliable analysis due to the sensitive TCD detector with a stable baseline.

Instrument and Sample Details
The analysis was conducted using the vario MICRO cube in CN mode. The sample used was 10 mg of finely ground solid soil.

Conclusion
The vario MICRO cube effectively determines CN content in sandy soils with high precision, even at low sample weights, making it a reliable tool for soil fertility analysis.