## 2 Materials and Methods  
### The Site, the Crop and the Mulching  
The field site was at the CREA-AA Research Unit experimental farm located in southern Italy (Rutigliano-Bari, 41\({}^{\circ}\) 01\({}^{\prime}\) N, 17\({}^{\circ}\) 01\({}^{\prime}\) E, altitude 147 m a.s.l.). The site is characterized by a Mediterranean semi-arid climate, categorized as Csa according to the Koppen-Geiger classification. Over the past thirty years, the average annual rainfall has been 535 mm, primarily occurring between autumn and late winter. The year 2023 was hot and very dry compared to the preceding twenty years. The soil, classified as \"Lithic Rhodoxerald\", features a clay texture, stable structure, shallow profile (0.6-1.1 m) and rapid drainage due to an underlying cracked limestone subsoil. The SOC content averages around 12.0 g kg\({}^{-1}\). The field capacity (FC) and the permanent wilting point (WP) volumetric water contents are 0.36 and 0.21 m\({}^{3}\)m\({}^{-3}\), respectively. Consequently, with a bulk density of 1.15 Mg m\({}^{-3}\), the available soil water ranges from 80 to 140 mm. Measurements were conducted on a watermelon crop (seedless var. Lion king), following a broccoli cabbage crop harvested in April and partially incorporated (0.81 kg m\({}^{-2}\) of fresh biomass in a soil layer depth of 0.30 m, corresponding to 0.69 kgH\({}_{2}\)O m\({}^{-2}\)) as green manure on 25 May 2023. Main tillage at medium depth ploughing (0.30 m) and seedbed preparation were performed between 25 and 30 May 2023; the biodegradable film mulch (model PC 100 d8, BASF, Italy, 1 m width) was applied on 1 June 2023. On the same day, driplines (2.1 Lh\({}^{-1}\) emitters, 0.60 m apart) and the main organic fertilization (Orga-Kem 6.11.8 + 11 CaO, 300 kg ha\({}^{-1}\)) were also applied. The watermelon plants were transplanted on 9 June at a spacing of 2.70 m between rows and 1 m between plants, covering an area of about 4.0 ha, with a density of approximately 3200 plants ha\({}^{-1}\). Every 6 rows, the inter-row distance was 5 m to facilitate machinery passage. The first irrigation was performed the day before planting. Crop management adhered to the usual treatments in the area including mechanical weed removal every 4 weeks, irrigation around three times per week to maintain optimal soil water conditions and monthly refrigeration (ammonium sulphate 50 kg ha\({}^{-1}\), magnesium nitrate 30 kg ha\({}^{-1}\), calcium nitrate 60 kg ha\({}^{-1}\), mycorrhizae 20 kg ha\({}^{-1}\)). The scalar harvest of marketable fruits occurred between 28 and 31 August 2023. After harvesting, on 25 September 2023, the fresh plant residues (0.6 kg m\({}^{-2}\) of fresh biomass, corresponding to 0.49 kgH\({}_{2}\)O m\({}^{-2}\)), unharvested fruits (4.0 kg m\({}^{-2}\) of fresh material, corresponding to 3.7 kgH\({}_{2}\)O m\({}^{-2}\)) and the mulching film were chopped by a tractor shredder and plugughed in two steps, on 2 and 13 October 2023, to a soil depth of 0.30 m. Measurements concluded at the end of November 2023, when tillage for the new winter crop commenced. For the development during the growing cycle, plants were harvested weekly or bi-weekly with randomized samples (3 plants). Each was analyzed for fresh biomass (FB) weight, dry matter (DM), leaf area index (LAI) using a Licor 3100 (Li-COR Inc., Lincoln, NE, USA) and plant height. The field coverage ratio on sampled dates was obtained by NDVI. The instrumentation for multispectral remote sensing was the Phantom 4 RTK unmanned aerial vehicle (UAV) with DJI GS PRO software (v2.0.15) for planning the survey area. The flight altitude was 33 m with 80% front and side overlap and a flight speed of 2.3 m s\({}^{-1}\). The Phantom 4 is equipped with six 1/29\({}^{\prime\prime}\) CMOS sensors in the Blue (450 nm \(\pm\) 16 nm), Green (560 nm \(\pm\) 16 nm), Red (650 nm \(\pm\) 16 nm), Red edge (730 nm \(\pm\) 16 nm), Near-infrared (840 nm \(\pm\) 26 nm) and RGB bands for visible light.