## 3 Materials and Methods
### Studied Zone  
We selected the \"Encin Golf Course\" located in Alcala de Henares (Madrid, Spain) (Lat. 40\({}^{\circ}\)31'21''; Long. 3\({}^{\circ}\)18'43'') as the sampling area to deploy a batch of soil moisture sensors provided by PLANTAE. This region is characterized by very hot and short summers; and dry, very cold, and long winters. Generally, throughout the year, the temperature varies from 1 to 33 \({}^{\circ}\)C. The temperature rarely cools down below \(-4\)\({}^{\circ}\)C or increases above 37 \({}^{\circ}\)C [7]. Therefore, the golf manager must water the grass regularly in summer to keep it healthy and in optimal conditions to play.  
The golf course was built on a plot used for agriculture previously, on the upper terraces of the Henares River. Originally this area was characterized by a slope of less than 0.5% and surface horizons Ap and AB with the following characteristics: Ap between 0 cm and 18 cm, clay loam texture (22.7% gravel, 44.1% silt, 33.2% clay), weak structure, medium angular blocks, firm consistency when wet and hard when dry, thin and zonal clay films, few very fine pores, abundant roots of all sizes; and AB between 18 cm and 32 cm, clay loam texture (24.9% gravel, 41.1% silt, 34.0% clay), weak structure, medium angular blocks, firm consistency when wet and hard when dry, thin and zonal clay films, few pores fine and very fine, with an abundance of roots of all sizes [19]. In addition, it was designed in different areas, which account for different types of soil and grass management: (1) tee, fairway, and green, where the grass is tightly trimmed, regularly watered, and the soils are sandy; (2) rough surrounding the fairways, where the grass is kept longer, regularly watered and soils are sandy-clay; and (3) wild areas, with native plants and zero maintenance or watering, except from the rainfall (see Figure 1). Thus, only soil 1 and 2 were amended to adapt their texture to that required by the golf course designer.  
We placed three sensors, see Figure 2a in different spots of every area, at a depth of 5 cm and covered by soil, to measure the shallow soil moisture. Thus, we have nine different sets of data. Small patches of grass were cut, and soil was removed to install the sensors; see Figure 2b. After placing the sensor, the hole was filled with soil, and the patch of grass was relocated. The soil moisture sensors, provided by PLANTAE, are a resistive sensor type, with temperature compensation [20]. The GPS coordinates and the sensor number were registered for each point. Then, they were configured to send data every 15 min. The data was received in a hub placed close to the golf house. These records were uploaded and processed in a cloud service managed by PLANTAE. Data was provided as gravimetric water content (%): the mass of water per mass of dry soil. The soil moisture sensors were calibrated by the service provider (PLANTAE), according to the texture of soil samples taken during the installation of the sensors.  
Figure 1: “Encin” Golf Course (Alcalá de Henares, Madrid, Spain) and sensors location.  
The moisture values during the sampling period ranged between 5% and 35%, depending on the irrigation, rainfall, and environmental temperature. The sandy and sandy-clay areas showed a lower humidity value (average 10% to 15%) compared to clay soil ones (average 20%) due to the better drainage of these soils.