# Advancing Crop Yield Predictions: AQUACROP Model Application in Poland's JECAM Fields
## 2 Materials and Methods
### In-Situ Measurements  
The field site, covering an area of 25 km \(\times\) 25 km, underwent meticulous planning of cultivation and harvesting schedules for various crops from 2018 to 2023. This planning aimed to synchronize with the specific requirements of each crop type and the prevailing meteorological conditions. Winter wheat, sown in September and harvested in August, underwent its growth cycle during the cooler months, while maize, planted in mid-April and harvested in November, thrived during the warmer seasons. Sugar beet, sown in early April and harvested in November, followed a growth pattern similar to maize. Rapeseed, sown at the end of August and harvested in mid-August of the following year, had a longer growth period extending over two seasons.  
These cultivation and harvesting timelines were synchronized with the JECAM field campaigns, conducted from April, marking the onset of the vegetation season, until early July. The selection of 42 fields during the initial campaign formed the basis for the continuous monitoring of plant conditions throughout the growth period, covering each vegetation season over the span of six years. These fields comprised 15 winter wheat fields, 12 rape-seed fields, 10 maize fields, and 5 sugar beet fields. The geographical coordinates of the selected points were recorded using GPS receivers, facilitating precise spatial referencing for subsequent analyses. The distribution of the measurement fields within the JECAM area in the Wielkopolska Voivodeship is illustrated in Figure 1.  
During each campaign, a suite of parameters was measured to comprehensively assess the physiological and environmental aspects of the selected crops. The measured parameters included electromagnetic radiation reflectance using ASD FieldSpec 4 Hi-Res (Malvern Panalytical, Malvern, UK) (depending on weather conditions), LAI using the LAI-2200C  
Figure 1: Sampling points’ distribution in the JECAM tested area and cultivation types for the tested year 2018.  
Plant Canopy Analyzer (LI-COR, Lincoln, NE, USA), soil moisture using TRIME PICO (IMKO Micromodultechnik GmbH, Ettlingen, Germany), accumulated photosynthetically active radiation using AccuPar, chlorophyll content using FieldScout CM 1000 Chlorophyll Meter (Spectrum Technologies, Aurora, IL, USA), plant development phase, and plant height.  
Simultaneously, samples of each observed crop type were collected, with each sample covering an area of 1 m\({}^{2}\). Subsequently, laboratory measurements were conducted, including fresh biomass weight, dry biomass weight, water content in plants, 250-grain weight, and 1000-grain weight. Additionally, during the sample harvesting process, the number of plants within the 1 m\({}^{2}\) frame and the quantity of spikes were recorded. The meticulously measured parameters played a crucial role in determining the in-situ yield per hectare (t-ha\({}^{-1}\)) for each wheat field. It is worth noting that, for wheat, samples were collected for each field in each of the six test years to determine the yield from each measurement point, whereas for the other crops, the yield was determined as the average yield from all cultivated plots specifically for that crop within the studied region.  
The selection of these parameters aimed to capture a holistic understanding of crop health, growth dynamics, and environmental interactions.