Submitted:
19 September 2025
Posted:
19 September 2025
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Abstract
Keywords:
1. Introduction
- Estimation of the amount of nutrients removed by the harvested crop.
- Estimation of profitability [Lambert and Lowenberg-DeBoer, 2000].
- Delineation of management zones.
- Analysis of the impacts of different experimental treatments.
- Evidence provision to a farmer in terms of scientific data as a backed proof for low-yielding zones notified from before by the farmer [Tsouvalis et al. 2000].
- Identifying all possible sources of rice yield data, e.g., yield monitors, field measurements, remote sensing, institutional reports, etc.
- Assessing the reliability and accuracy of rice yield data from harvesters.
- Exploring the necessity for post-processing rice yield data from harvesters, including cleansing, homogenization, calibration, etc.
- Homogenizing rice yield data derived from different harvesters to enable comparisons between fields and across years.
2. Study Area
3. Data and Methods
3.1. Data Preprocessing
3.2. Data Analysis
- i.
- one implementing precision fertilization in Axios River Plain (denoted as PrecAg);
- ii.
- another non-implementing precision fertilization in Axios River Plain (denoted as Non-PrecAg), and
- iii.
- the generic group of rice farmers all over Greece, as reported by JRC/MARS (denoted as JRC).
- i.
- Spectral detail=10;
- ii.
- Spatial detail=15;
- iii.
- Minimum segment size=20 pixels
4. Results
- a)
- DATA ORGANIZATION DESCRIPTOR, which serves a set of functions for data collection from the various rice yield monitors, their ingestion in a common geodatabase, and their projection to WGS84.
- b)
- DATA CURATION DESCRIPTOR, which serves a set of functions for geometry repair of rice yield data and cleansing them from various outliers and abnormal values, through spatial filtering.
- c)
- DATA HOMOGENIZATION DESCRIPTOR, which serves a set of functions for data conversion from polygon to point type, layer merging and unification, unit conversion into a single one (t/ha), transformation of the irregular point grids into regular ones (5x5m), their final transformation into raster layers with IDW interpolation, and their calibration with in-situ weighting records.
- d)
- DATA ANALYSIS DESCRIPTOR, which serves a set of functions for exploring data through descriptive stats and autocorrelation, calculated from the vector data and yield surface segmentation calculated from the raster data.
- e)
- DATA VISUALIZATION DESCRIPTOR, which serves a set of functions for displaying yield data in raster format -either original or classified- within the GIS and in vector format after transferring to the ifarma platform.
| Nr | DESCRIPTOR | Function | Layers | Data Type | Commands | Parameters |
|---|---|---|---|---|---|---|
| 1 | ORGANIZATION | Collection | YIELD(s) | POINT/POLYGON | Copy/Download | From yield monitors |
| 2 | Ingestion | YIELD(s) | POINT/POLYGON | Add Data | ||
| 3 | Transformation | YIELD(s) | POINT/POLYGON | Project | WGS84 [WKID=32634] | |
| 4 | CURATION | Correction | YIELD(s) | POLYGON | Repair Geometry | Esri |
| 5 | Correction | YIELD(s) | POLYGON | Add Field | AREA[m2] | |
| 6 | Correction | YIELD(s) | POLYGON | Select by Attributes | AREA<30m2 | |
| 7 | Correction | YIELD(s) | POLYGON | Delete Selected | ||
| 8 | HOMOGENIZATION | Transformation | YIELD(s) | POLYGON | Feature to Point | Inside |
| 9 | Merging | YIELD(s) | POINT | Merge | ||
| 10 | Conversion | YIELD | POINT | Add Field | YIELD[t/ha] | |
| 11 | Conversion | YIELD | POINT | Calculate Field | YIELD=[yield fields] | |
| 12 | Unification | YIELD | POINT | Delete Field(s) | All FIELDS except YIELD | |
| 13 | Transformation | YIELD->GRID | POINT | Spatial Join | Join one to one; Closest geodesic | |
| 14 | Enhancement | GRID/FIELDS | POINT | Select By Location | Within | |
| 15 | Enhancement | GRID | POINT | Switch Selection | ||
| 16 | Enhancement | GRID | POINT | Delete Selected | ||
| 17 | Calibration | GRID | POINT | Select by Attributes | 0<YIELD<=20 [t/ha] | |
| 18 | Transformation | GRID->SURFACE | POINT | IDW Interpolation | Output cell size=5m, Power=2, Number of Points=12 | |
| 19 | Calibration | SURFACE->MEAN | RASTER | Zonal Statistics | Mean | |
| 20 | Calibration | MEAN | RASTER | Raster Calculator | Cor-Factor=In-situ-weight/MEAN; SURFACE=Cor-Factor*SURFACE | |
| 21 | ANALYSIS | Classification | SURFACE | RASTER | Segmentation | Spectral detail=20; Spatial detail=20; Minimum segment=1pxl |
| 22 | Exploration | GRID | POINT | Descriptive Stats | ||
| 23 | Exploration | GRID | POINT | Autocorrelation | ||
| 24 | VISUALIZATION | Classification | GRID | POINT | Expoirt to CSV | To ifarma |
5. Discussion
- The soil properties derived from soil sampling and interpolation, were found with a within-field variability of about 33.7% on average [Karydas et al. 2020].
- The spectral properties, derived from satellite imagery, were found with a within-field variability of about 35.3% on average [Karydas et al. 2020].
- The yield, derived from yield monitors mounted on the harvesters, was found with a within-field variability of about 8.6% on average.
- Bad tillage and tractor traces, which either compact surface soil or create crust.
- Rapidly drained or flooded locations, due to very sandy soils or ground lowering, respectively.
- Presence of several obstacles, such as electricity column or trees, which affect the passes in the nearby locations.
- Presence of birds under protection, such as flamingos, as a major part of the study area is inside a Ramsar site; these birds may destroy part of the production.
- Weed infestations.
- Spraying of weed management substances, which may affect the crop.
- Tillage and compaction issues on specific areas of poor tillage.
- Irrigation problems, such as waterlogged or rapidly drained spots.
- Weed and pest outbreaks that can be correlated with low-yield spots in the yield maps.
6. Conclusion
- Identify all possible sources of rice yield data; specifically rice yield monitors of different types, in situ measurements, and institutional reports based on satellite imagery and farmers’ communication.
- Assess the reliability of rice yield data recorded by harvesters as high, with an accuracy ranging between 91.7 and 96.6% yearly; only one extreme was noticed on a field basis.
- Verify the necessity for post-processing rice yield data from harvesters, including organization, curation, homogenization, analysis, and visualization.
Acknowledgments
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| Year | PrecAg | Non-PrecAg | JRC |
|---|---|---|---|
| 2014 | 8,85 | - | 7,59 |
| 2015 | 9,00 | - | 7,12 |
| 2016 | 8,20 | - | 7,69 |
| 2017 | 10,11 | - | 8,42 |
| 2018 | 9,44 | - | 8,51 |
| 2019 | 9,86 | - | 6,98 |
| 2020 | 9,69 | 9,40 | 7,04 |
| 2021 | 9,74 | 9,04 | 7,78 |
| 2022 | 10,20 | 9,19 | 8,10 |
| 2023 | 9,54 | 8,50 | 7,64 |
| 2024 | 10,18 | 9,41 | 7,86 |
| Avrg[2014-23] | 9,53 | N/A | 7,70 |
| Avrg[2020-24] | 9,87 | 9,11 | 7,68 |
| Std[2020-24] | 0,30 | 0,37 | 0,40 |
| CV[2020-24] | 3,1% | 4,1% | 5,2% |
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