THE COMPLEX PEDOLOGICAL CHARACTERIZATION OF SOME PILOT AGRICULTURAL PERIMETERS IN ORDER TO CALIBRATE THE SENSORS FOR MEASURING THE NPK AND THE GRAVIMETRIC HUMIDITY OF THE SOIL FOR THE REMOTE TRANSMISSION OF THE NECESSARY DATA TO THE FARMERS
Authors: Voicu Petre , Vasiu Radu , Oaida Mircea , Gheorghiu Catalin , Dumitru Aurel 
Published: February 2023

The paper presents the complex pedological framework where the high-precision sensors from the meteorological stations are tested in order to remotely transmit the soil parameters with express reference to the NPK content and the water content of the soil.
In the context of climate change, the interest in continuous, "in situ" knowledge of soil moisture and macroelement content is high because soil properties are correlated with the mathematical simulation of how crops are formed on agricultural plots. While regional simulation has been operational worldwide for over two decades, during which prediction errors have decreased significantly, remote measurement of NPK and soil moisture with the required accuracy at the local scale, at the level of agricultural plots, is still under investigation.
It is necessary to continue the research in this context because the collection of soil samples in order to determine the properties of the soil in the laboratory is becoming more and more restrictive due to the high prices.
The determination of soil parameters in the laboratory cannot be completely replaced by remote measurements, but the latter method ensures, if the sensors are properly calibrated and calibrated, a high degree of accuracy and can complete the information provided by pedological laboratories specializing in hydrophysics or agrochemistry.
On the other hand, the development of precision agriculture exerts an important pressure in the direction of the development of research on the digitization of agricultural parameters to allow sufficiently accurate measurements at the plot scale, the hydrophysical and agrochemical properties being essential.
To be relevant on this scale, the sensors must be calibrated to provide real data, especially for the phenological phases in which the plant is sensitive to various stresses: water, nutrition, disease attacks and pests.Referring only to water stress and NPK content, in the absence of the actual value of surface moisture, and the content of macroelements, the simulation of the "sowing-sunrise" period, greatly influenced by the water available for seed germination, may be affected by significant errors., the results of the simulations being uncertain or even wrong.
To date, farmers have relied almost exclusively on the results of NPK determinations and soil moisture in the laboratory, which involves a great deal of financial effort. Now they can continuously know, in addition to the standard weather data provided by meteorological stations, the content of macroelements and the gravimetric humidity of the soil at a given time by transmitting data remotely via satellites.
The field experiments followed the methodological framework that is summarized in this paper and took place between September 2021 and May 2022, in pilot agricultural areas in different geographical areas: Baneasa (Bucharest), Fundulea (Calarasi) and Dabuleni (Dolj).