Informative value of infrared survey data for detecting properties of arable soils

Possibility of detecting soil fertility parameters based on the use of thermal survey data was studied on the test area of Yasnogorsky District, Tula region, Russia. The test area has gray forest slightly eroded arable soils located in the flat part of the slope. During the field works, an open soil surface was photographed using a FLIR VUE 512 thermal imager (range 7.5-13.5 mkm), soil samples were also taken from a layer of 0-5 cm and soil moisture was measured in a layer of 15-20 cm. For almost all parameters of soil fertility (pH, humus content, potassium content, exchange cations - Mg++, K+, Na+), a statistically significant correlation was established (r =0.4-0.7) between them and the survey data in the thermal range of the spectrum. For moderate correlations, polynomial regression equations were compiled. Among the studied fertility parameters, the pH of the salt extract, the content of potassium oxide and potassium exchange cations had significant coefficient of determination (R2 0.60) with the thermal range of the spectrum - R2= 0.61, R2 =0.60 and R2 = 0.63, respectively. The obtained results have shown that thermal imaging can be used to map some parameters of soil fertility for the region. Nevertheless, it turned out to be impossible to reliably detect all the main parameters of soil fertility of the test field on the basis of thermal survey data. However, the thermal soil survey data can be used as auxiliary data when shooting in the visible and nearIR ranges, which helps to improve the accuracy of contactless soil monitoring.