# Effect of Precision Nitrogen Fertilization of Grassland on Soil Microbial Structure
## 2 Materials and Methods  
### Experiment Detail  
The study site where various experimental tests were conducted was located at a family farm in Zedowice, Poland, with a total agricultural land area of 25 hectares (coordinates of the test site--50\({}^{\circ}\)34\({}^{\prime}\)47.7\({}^{\prime\prime}\) N 18\({}^{\circ}\)30\({}^{\prime}\)32.9\({}^{\prime\prime}\) E). The structure of the farmland was characterized as a single-purpose farm focused on crop production. Of the total land, approximately 15 hectares was arable land, where cereals, corn, and alfalfa were cultivated, while 10 hectares consisted of grassland. The farm's soils are predominantly podzolic and pseudo-podzolic, with smaller areas of proper chemozem and a weak rye complex.  
For the selection of the experimental plots, data archived at the farm were utilized, assuming that the soil tillage practices had been consistent for at least five years, and the degree of implementation of Agriculture 4.0 systems was well understood. Additionally, the CORINE Land Cover database, the Copernicus Program, and the SatAgro service were employed to aid in selecting plots from which laboratory samples were taken. Existing databases on agrotechnical practices, soil chemistry, and crop yields at the farm were also used to identify plots with notable production potential.  
A training ground was selected (Figure 1a,b), where no soil tillage had been performed but precision fertilization treatments had been applied using a parallel driving system. The soil profile in this area exhibited significant variation in the vertical plane (Figure 1c). The number of measurement points depended on the initial measurements, but there was no fewer than one measurement point per hectare of the experimental field. Samples were collected after the harvest, and the processes were repeated over three consecutive cycles.  
Weather conditions were recorded by WH 2600 weather stations (Hirschau, Germany), which are equipped with an internet protocol that allows real-time data visualization, archiving, and export in a selected frequency regime. These stations were equipped with a wind vane, wind speed sensor, solar panel, temperature and humidity sensors, a UV sensor, a light sensor, and a rain sensor. The technical specification of the station included: transmission range in open space up to 100 m, frequencies of 433 MHz/868 MHz/915 MHz, temperature range from \(-\)40 \({}^{\circ}\)C to 60 \({}^{\circ}\)C (accuracy \(\pm\)1 \({}^{\circ}\)C, resolution 0.1 \({}^{\circ}\)C), relative humidity measurement in the range of 1% to 99% (accuracy \(\pm\)5%), rainfall measurement in the range of 0-9999 mm (accuracy \(\pm\)10%, resolution 0.3 mm for rainfall \(<\)1000 mmand 1 mm for rainfall >1000 mm), wind speed of 0-50 m/s (accuracy \(\pm\)1 m/s for wind speed <5 m/s, \(\pm\)10 m/s for wind speed >5 m/s), and light measurement in the range of 0-400 kLux (accuracy \(\pm\)15%). During the study, the average temperature was 14.4 \({}^{\circ}\)C, the average dew point temperature was 8.2 \({}^{\circ}\)C, the average air movement speed was 4.9 km/h, the average humidity was 67.8%, the average solar radiation was 164.6 W/m\({}^{2}\), and the average rainfall was 3.2 mm. The pH value remained in the range of 5.4-6.2 at the studied depths of the soil profile.