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

PetreVOICU1,RaduVASIU2, Mircea OAIDA3,Catalin GHEORGHIU3,Aurel DUMITRU3

1 INCDPAPM-ICPA Bucuresti, Romania

2 Universitatea Politehnica, Timisoara, Romania

3 Teraseya, Timisoara, Romania

ABSTRACT

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 main data of the paper present a part of the research contribution within the SINTARA Project.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).

Keywords: ground, sensors, measurements

INTRODUCTION

The paper aims to characterize two pilot agricultural perimeters where the sensors of the component of meteorological stations that measure the NPK content in the soil and the gravimetric humidity are tested / calibrated.

For this, two meteorological stations were placed in the analyzed perimeters and near them a microplatform was arranged where periodically controlled quantities of N, Psi K were administered and measured quantities of irrigation water were administered.

Following the laboratory determinations and the measurements performed, there were small differences, insignificant in relation to the necessity and usefulness of the remote transmission of the N, P, K content in the soil through meteorological stations equipped with high precision sensors.

The advantages of such a measurement consist in rapid transmission of meteorological data and measurement by sensors of NPK content in the soil, in situ measurements very useful for farmers given that the differences between laboratory determinations and those measured with NPK sensors are insignificant.

Weather station transmission indicators:

• Temperature: -30..70 ° C res. 0.1 ° C, ac. ± 0.5 ° C
• Humidity: 0-100% res. 1%
• Atmospheric pressure: 300-1100 hPa, according. ± 0.2 Pa
• Wind speed: 0-70.0 m / s, start 0.5 m / s
• Wind direction: 0… 359grm, ac. 1 ° + weather vane
• Precipitation: 0 to 9999.9 mm, res 0.12 mm
• UV index: 0.5-10, res 0.1
• 5in1 sun sensor
• Temperature (-30 ° C. + 70 ° C)
• Humidity 0-100% (m3 / m3) Acc: ± 3% (0 … 50%) / ± 0.5 ° C; ± 5% (50% – 100%)
• Conductivity (0-10000us / cm ac 10 us / cm), pH sol 3..9 (± 0.3 PH)
• PH 3-9 (± 0.3)
• NPK (1… 1999 mg / kg (mg / L)

The use of intelligent software solutions in agriculture helps to increase the yield of the farm by making the best use of the resources that farmers have at hand and by increasing the level of quality and health of crops. Fully equipped weather stations meet the requirement of remote measurements using the concept of smart agriculture. Remote NPK measurement is a major advantage for farmers, the results of in situ measurements being correlated with periodic determinations by laboratory tests.

In order to use the data provided by the weather station in general and the data provided by the sensors that measure NPK in particular, we undertook a comparative analysis between the measurements provided by the weather station and the determinations performed in the laboratory based on the standard methodology for pedological, agrochemical studies. and agrophysics. In this context, we chose two pilot perimeters where meteorological stations were located.

These pilot perimeters were analyzed from a pedological, agrochemical, hydrophysical point of view to see the extent to which the soil properties determined in the laboratory are correlated with the measurements of the sensors in the weather station.

The tables and graphs presented in the study regarding the NPK content show that the values ​​measured by the sensors in the weather station do not differ significantly from the laboratory determinations. But in order to have a statistically interpretable correlation, the number of determinations must increase, monitoring different crops in different vegetation phases.

In the following section we’ll be detailingthe pedological, agrochemical, hydrophysical analysis used as a reference to compare the results of the two types of information, determined in the laboratory and measured using NPK sensors.

Two pilot perimeters were chosen which were characterized based on the ICPA Methodology. Following these complex descriptions of the soil and its properties, the NPK values could be interpreted, both those determined and those measured with the sensors of the weather station.

RESULTS OBTAINED:

Cernozem from Fundulea

• Name: Cernozem cambic – Fundulea
• Location: Cîmpia Română, ICCPT Fundulea.
• Pedogenetic conditions
  • Relief: plain, flat surface, relatively horizontal.
  • Absolute altitude: 65.3 m.
  • Parental material: loessoid deposits.
  • Groundwater depth:> 8 m.
  • Global natural drainage: excessive.
  • Bioclimatic subzone: steppe.
  • Usage: arable.
  • Climatic data: Tma = 10.3oC, Pma = 500 mm.
  • Temperature regime: mesic.
  • Humidity regime: ustic.

Morphological characterization of the soil profile

• Ap 0-24 cm; dusty clay clay; very dark gray-brown (10YR 3/2) in the wet state and very dark gray-brown – dark gray-brown (10YR 3.5 / 2) in the dry state; disturbed by cultivation; moderately compact; friable in the wet state; hard in the dry state; moderate plastic; moderate adhesive; frequent small pores; frequent thin roots; smooth, straight passage;
• Apt 24-30 cm; dusty clay clay; very dark gray-brown (10YR 3/2) in the wet state and very dark gray-brown – dark gray-brown (10YR 3.5 / 2) in the dry state; structured (massive) unfolds into a medium-large angular polyhedron;  moderately compact; friable in the wet state; hard in the dry state; moderate plastic; moderate adhesive; frequent small pores; frequent thin roots; gradual transition;
• Am 30-50 cm; dusty clay clay; very dark brown – very dark gray brown (10YR 2.5 / 2) in the wet state and very dark gray brown – dark gray brown (10YR 3.5 / 2) in the dry state; well-developed medium subangular grainy and polyhedral structure; friable in the wet state; hard in the dry state; moderate plastic; moderate adhesive; frequent small pores; rare cervotocins; frequent thin roots.

Micro-Morphological characterization of the soil profile

• Ap 0-24 cm: The structure is spongy and with large isolated biogenic voids. The porosity is high, consisting of gaps created by biological activity (plant roots and soil fauna) and by physical-mechanical processes. The elementary assembly is intertextual. The plasma assembly is silaseptic. Plasma is clay-humic-ferric (clay-ferric pigmented with humons). The skeleton consists of numerous skeletal mineral granules (predominantly the size of fine sand and dust) of quartz, plagioclase feldspars (many of them altered), glauconite, calcite (sporadic). Quartz is the majority in the whole profile. Vegetable residues are few and finely chopped. Carbonized plant debris appears sporadically. Very small sclerotia (0.25 mm) occur frequently.
• Apt 24-48 cm; The structure is similar to that of the upper horizon except that the pores are larger but smaller. The elementary assembly is intertextual. The plasma assembly is silaseptic and the plasma is clay-humic-ferric. Within the horizon were observed coprolites (mostly integrated in the matrix) with material brought by the soil fauna from horizons C. In these coprolites, the plasma assembly is crystalline and the plasma is clay-ferric ± humic ± carbonate. The skeleton is similar to that of the previous horizon. Calcite is also present in the coprolites brought by the soil fauna from horizons C. Plant debris is relatively common on the horizon and occurs in various forms: fresh, located in biogol; To varying degrees of fragmentation and decomposition, most are located in coprolites or integrated into the soil matrix.
• Am 48-50 cm; The structure is spongy and glomerular. Deformed channels created by soil fauna and circular and semicircular cracks that delimit the glomerular elements (zoo-aggregates) frequently appear within the matrix. The elementary assembly is intertextual. Plasma assembly is silaseptic and crystalline in areas with a C-horizon-specific matrix. Plasma is clay-humus-ferric. Coprolites with material brought by the soil fauna from the base of the profile. The skeleton is similar to the previous horizons, but more altered. Plant debris is relatively common on the horizon and occurs in various forms: fresh, located in biogol; To varying degrees of fragmentation and decomposition, most are located in coprolites or integrated into the soil matrix.

Physical and chemical characterization of the cambic chernozem from Fundulea

• The analytical data regarding the granulometric composition highlight the following contents of the granulometric fractions: the clay (< 0.002 mm) has values between 37.8 – 40.0%. The dust content has a relatively uniform distribution, the values oscillating in the limits of 33.1 – 33.8%. The fine sand content has lower values (26.1-28.1%) than the dust content and has the same distribution per profile. From a textural point of view, this soil falls into the category of dusty clay soils.
• On the general background of a soil with relatively low clay content and weakly acidic reaction (pH has values of 6.3 – 6.8), the amount of humus is small (2.4 – 3%)
• In the area of root development of crop plants, the supply of total nitrogen is medium. Mobile phosphorus insurance is extremely low in surface and low-medium in the rest, and mobile potassium insurance is low.

CONCLUSIONS

• The results obtained by the 2 methods of measuring NPK are very close, not being significantly differentiated as it can be shown in the below table.  
• The use of intelligent software solutions in agriculture helps to increase the yield of the farm by making the best use of the resources that farmers have at hand and by increasing the level of quality and health of crops.
• The future of remote soil property measurements by satellite techniques is predictable. Fully equipped meteorological stations meet the requirement of remote measurements using the concept of intelligent agriculture.
• Remote NPK measurement is a major advantage for farmers, the results of field measurements being correlated with periodic determinations by samples analyzed in soil science reference laboratories.
• In order to guarantee the real prospects for the different types of crops it is necessary to carry out a feasibility study based on the results of hydrogeological research and the physico-chemical and physical characteristics of the soils.

REFERENCES

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 [2] LAUVERNET, C., LEDIMET, F.X., BARET, F., DEBOISSEZON, H., FAVARD, .-C.,VINTILĂ, R., LAZĂR, C şi BADEA, A., 2002, Assimilation of High Temporal Frequency SPOT Data to Describe Canopy Functioning. The Case of Wheat Crops in the ADAM Experiment in Romania. Proc. “Recent Advances in Quantitative Remote Sensing” (ISBN 84-370-5515-6, ed. J.A. Sobrino, Spain, Universidat de Valencia), p. 921-926

[3]ROSA, 2007. Hybrid method for updating the thematic inventory on land use through remote sensing / GIS technologies, support for the implementation of the European Agriculture – Environment Programs. Financing contract No. 81-058 / September 2007; PNCD