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In this research, a model for the estimation of antioxidant content in cherry fruits from multispectral imagery acquired from drones was developed, based on machine learning methods. For two consecutive cultivation years, the trees were sampled on different dates and then analysed for their fruits' radical scavenging activity (DPPH) and Folin-Ciocalteu (FCR) reducing capacity. Multispectral images from unmanned aerial vehicles were acquired on the same dates with fruit sampling. Soil samples were collected throughout the study fields at the end of the season. Topographic, hydrographic and weather data also were included in modelling. First-year data were used for model-fitting, whereas second-year data for testing. Spatial autocorrelation tests indicated unbiased sampling and, moreover, allowed restriction of modelling input parameters to a smaller group. The optimum model employs 24 input variables resulting in a 6.74 root mean square error. Provided that soil profiles and other ancillary data are known in advance of the cultivation season, capturing drone images in critical growth phases, together with contemporary weather data, can support site-and time-specific harvesting. It could also support site-specific treatments (precision farming) for improving fruit quality in the long-term, with analogous marketing perspectives.

Abstract:The objective of this study was to develop a methodology for mapping olive plantations on a sub-tree scale. For this purpose, multispectral imagery of an almost 60-ha plantation in Greece was acquired with an Unmanned Aerial Vehicle. Objects smaller than the tree crown were produced with image segmentation. Three image features were indicated as optimum for discriminating olive trees from other objects in the plantation, in a rule-based classification algorithm. After limited manual corrections, the final output was validated by an overall accuracy of 93%. The overall processing chain can be considered as suitable for operational olive tree monitoring for potential stresses.

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The objective of this research is to assess the potential of satellite imagery in detecting soil heterogeneity, with a focus on site-specific fertilization in rice. The basic hypothesis is that spectral variation would express soil fertility variations analogously. A 100-ha rice crop, located in the Plain of Thessaloniki, Greece, was selected as the study area for the 2016 cropping season. Three RapidEye images were acquired during critical growth stages of rice cultivation from the previous year (2015). Management zones were delineated with image segmentation of a 15-band multi-temporal composite of the RapidEye images (three dates × five bands), using the Fractal Net Evolution Approach (FNEA) algorithm. Then, an equal number of soil samples were collected from the centroid of each management zone before seedbed preparation. The between-zone variation of the soil properties was found to be 33.7% on average, whereas the within-zone variation 18.2%. The basic hypothesis was confirmed, and moreover, it was proved that zonal applications reduced within-zone soil variation by 18.6% compared to conventional uniform applications. Finally, between-zone soil variation was significant enough to dictate differentiated fertilization recommendations per management zone by 24.5% for the usual inputs.

This research is an outcome of the R&D activities of Ecodevelopment S.A. (steadily supported by the Hellenic Agricultural Organization—Demeter) towards offering precision farming services to rice growers. Within this framework, a new methodology for topdressing nitrogen prediction was developed based on machine learning. Nitrogen is a key element in rice culture and its rational management can increase productivity, reduce costs, and prevent environmental impacts. A multi-source, multi-temporal, and multi-scale dataset was collected, including optical and radar imagery, soil data, and yield maps by monitoring a 110 ha pilot rice farm in Thessaloniki Plain, Greece, for four consecutive years. RapidEye imagery underwent image segmentation to delineate management zones (ancillary, visual interpretation of unmanned aerial system scenes was employed, too); Sentinel-1 (SAR) imagery was modelled with Computer Vision to detect inundated fields and (through this) indicate the exact growth stage of the crop; and Sentinel-2 image data were used to map leaf nitrogen concentration (LNC) exactly before topdressing applications. Several machine learning algorithms were configured to predict yield for various nitrogen levels, with the XGBoost model resulting in the highest accuracy. Finally, yield curves were used to select the nitrogen dose maximizing yield, which was thus recommended to the grower. Inundation mapping proved to be critical in the prediction process. Currently, Ecodevelopment S.A. is expanding the application of the new method in different study areas, with a view to further empower its generality and operationality.

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SUMMARYThe determination of time for grape harvest is probably the most important decision for wine making producers, because grapes are not climacteric fruits and if they are harvested before fully ripe their quality is compromised. This is because sugar content, aroma and color compounds increase only before harvest for non-climacteric fruits. The current practice for determining berry ripeness includes measurements of berry samples for total soluble solids (TSS) and pH, but this procedure is time consuming and laborious. On the other hand, with the development of unmanned aerial vehicles (UAV) and modern ultralight cameras the grower can now obtain data rapidly and also spatial information for crop's physiological status at farm scale. Berry samples were collected from grapevines (cv. Malagousia) and their reflectance spectra were used to estimate TSS and pH by Multiple Linear Regression (MLR) and Support Vector Machine (SVM). The highest classification accuracy was achieved using the SVM model. Moreover, berries taken by grapevines with low Carotenoid Reflectance Index 2 (CRI2) had higher TSS, pH and terpenes, and gave wine with higher alcohol by volume. The importance for constructing a model for predicting TSS in berries is obvious, because this can aid in the prediction of wine quality. The current work is a preliminary compilation of methodologies for making a monitoring tool of berry ripeness, using statistical techniques, remote sensing and crop physiological data. RESUMOA determinação da época de vindima é provavelmente a decisão mais importante para os produtores vinícolas porque as uvas não são frutos climatéricos e se forem vindimadas antes de estarem completamente maduras, a sua qualidade fica comprometida. Isto ocorre porque o teor de açúcar, assim como os compostos responsáveis pelo aroma e pela cor aumentam apenas antes da colheita de frutos não climatéricos. A prática atual para determinar a maturação da uva inclui medições de amostras de uva quanto a sólidos solúveis totais (TSS) e pH, mas este procedimento é demorado e trabalhoso. Por outro lado, com o desenvolvimento de veículos aéreos automatizados (UAV) e câmaras ultraleves modernas, o produtor pode agora obter dados rapidamente e também informação espacial sobre o estado fisiológico da cultura à escala da propriedade. Foram recolhidas amostras de uvas de videiras (cv. Malagousia) e os seus espetros de reflexão foram utilizados para estimar o TSS e o pH através de Regressão Linear Múltipla (MLR) e de uma Máquina de Vetores de Suporte (SVM). A precisão da classificação mais alta foi obtida com a utilização do modelo SVM. Além disso, as uvas de videiras com baixo Índice de Reflexão de Carotenoide 2 (CRI2) alcançaram valores de TSS, pH e terpenos mais elevados, dando origem a vinho com mais álcool por volume. A importância para a construção de um modelo de previsão de TSS em uvas é óbvia, porque pode auxiliar na previsão da qualidade do vinho. O presente trabalho é uma compilação preliminar de metodologias para criar uma ferramenta de monito...