A multi-wave method for determining the phosphorus content in sandy soil based on the results of measuring moisture and soil absorption coefficient

The moisture content of the soil significantly affects the results of spectral methods for determining various organic substances present in the soil. Well-known studies of the effect of sandy soil moisture on the results of spectral measurements of the absorption coefficient in the spectral range of 225-2550 nm, conducted to determine the amount of phosphorus in the soil, allowed us to compile a calibration model for predicting phosphorus in sandy soil based on measurements of the spectral characteristics of the soil. Absorption spectra of sandy soil with different values of moisture and phosphorus content were determined, in which water absorption lines at wavelengths of 1450 nm and 1940 nm are clearly visible. At the same time, with an increase in moisture content, an increase in the value of the absorption coefficient is observed. At the same time, with an increase in soil moisture content, the curves obtained at different values of phosphorus content in it differ less and less. The values of the correlation coefficients between the absorption coefficient and the phosphorus concentration over the entire wavelength range λ = 225÷2550 nm were determined. It was found that the highest values of the correlation coefficient are observed in soil with minimal moisture content, in the wavelength range of 1900-2500 nm. The above results were used to predict the amount of phosphorus in the soil. On this basis, a method was proposed to determine the concentration of phosphorus in the soil, which has an error due to the inaccuracy of determining the correlation coefficient and the absorption coefficient. To eliminate this drawback, the use of multi-wave techniques is proposed in this article. A two-wave method for determining phosphorus in sandy soil is proposed, a block diagram of the algorithm for implementing the two-wave method is compiled. It is shown that when using a two- wave method for determining the phosphorus content in the soil, the total random error decreases by a factor of . It is noted that when using the m -number of wavelengths in calculations and measurements, the corresponding random error will decrease by a factor of . A general algorithm for the implementation of the multiwave method has been compiled