Design of portable near infrared soil nutrient measuring instrument

The aim of the present work was to design a portable instrument to predict the constituents of total nitrogen and organic matter in soil. Data from recent reports as well as our experiments show that these constituents exhibit absorption peaks in the near-infrared region around 850 nm and 940 nm. We designed a portable instrument that adopted diffuse reflectance spectroscopy. Subsequently, we conducted instrument performance tests to obtain the curves relating the actual and calculated values. Experimental results showed that the coefficients of determination (R2) for predicted total nitrogen and organic matter in oven-dried soil sample were 91.84% and 81.06%, respectively, and the corresponding values in wet samples were 90.17% and 80.24%. For soil organic matter and total nitrogen content in the samples, we found clear correlations between the actual values and calculated values.