The first flowering date of apples is a key phenological stage in the annual growth cycle of fruit trees. Its occurrence timing is directly associated with pollination efficiency, fruit set rate, and subsequent fruit development, and it also serves as an important basis for orchard management practices, including flower and fruit thinning, pest and disease control, as well as early risk warning and emergency management for low-temperature frost events during the flowering period. Existing studies still have room for improvement in the fine-scale extraction of temperature time-series information and in the representation of model adaptability across different spatial locations. Therefore, the purpose of this research is to develop a prediction method for the first flowering date of apples that can effectively characterize time-varying temperature patterns and achieve regional adaptability, thereby providing more reliable technical support for refined orchard management and disaster prevention.

A deep learning-based forecasting framework for predicting the first flowering date of apples was developed based on observation sites in Luochuan county, Shaanxi province. First, daily near-surface air temperature (NSAT) data from 2019 to 2021 were collected for the period from apple harvest to the subsequent flowering season in the study area, including daily maximum, mean, and minimum temperatures. In addition, elevation, latitude, and longitude were introduced as static geographic factors, forming a combined input composed of dynamic temperature sequences and static spatial attributes. Second, in terms of the model design, a bidirectional long short-term memory network (Bi-LSTM) was employed as the temporal encoder to learn bidirectional dependencies within the temperature time series. On this basis, a customized multi-head attention (MHA) mechanism was integrated, consisting of a local dependency head, a global trend head, and a cumulative feature head, which were designed to represent short-term pre-flowering temperature fluctuations, overall temperature trends, and cumulative temperature effects, respectively. This configuration enhanced the extraction of time-varying information across multiple temporal scales. The attention outputs were then fused with the static geographic factors, and the predicted first flowering date was generated through a regression layer, enabling regionally adaptive prediction. To ensure comparability of results, LSTM and Bi-LSTM models were simultaneously constructed as baseline models using identical data preprocessing and training procedures. Third, Bayesian optimization was applied for automatic hyperparameter tuning, during which key parameters, including learning rate, number of network layers, number of hidden units, regularization terms, and optimizers, were systematically searched, and the optimal configuration was selected based on validation performance. Finally, a cross-year validation strategy was adopted to evaluate model generalization ability: Data from 2019 to 2021 were used as the modeling dataset (training and validation), while the observed first flowering date in 2022 served as an independent test dataset. The predictive performance of all models was evaluated using three widely recognized metrics: root mean square error (RMSE), mean absolute error (MAE), and correlation coefficient (R).

The proposed model achieved an RMSE of 1.34 d, a MAE of 1.13 d, and the R of 0.84 on the test dataset, with most prediction errors concentrated within a range of 0-2 d. Validation results indicated that the proposed approach was capable of providing stable predictions approximately 15-20 d in advance within the study area. Further comparative analysis demonstrated that the Bi-LSTM architecture more effectively exploited both forward and backward dependencies in the pre-flowering temperature time series, thereby offering a more stable temporal representation for regression-based prediction of the first flowering date. Building upon this structure, the introduction of three attention heads: the local dependency head, the global trend head, and the cumulative feature head, enabled the model to more explicitly distinguish and utilize short-term fluctuations, stage-wise trends, and cumulative temperature effects. This targeted extraction of multi-scale time-varying information contributed to reduced prediction errors and improved overall prediction accuracy. Ablation experiments involving static geographic factors further verified the necessity of the spatial adaptability component. When the elevation was removed, the RMSE increased from 1.34 d to 1.45 d. Removing latitude and longitude led to a larger increase in RMSE to 2.54 d, and when both elevation and geographic coordinates were excluded, the RMSE further rose to 2.69 d accompanied by a decrease in correlation. These results indicated that geographic factors provided effective spatial constraints, which supported the learning of location-specific phenological responses across different sampling sites. In addition, spatial prediction maps revealed that the first flowering date in the study area exhibited a gradient distribution with respect to elevation to a certain extent. This spatial pattern was consistent with the modeling rationale of incorporating geographic factors into a unified prediction framework.

This study proposes a deep learning-based prediction method for the first flowering date of apples that integrates multi-dimensional temperature features, a multi-head attention mechanism, and geographic factors. The proposed method achieves relatively high prediction accuracy in cross-year forecasting and enables spatially adaptive prediction of the first flowering date of apples. These findings provide a new data-driven technical pathway for refined prediction of apple flowering phenology and offer important technical support for orchard flowering management, frost damage prevention, and agricultural production decision-making.

The explosive development of agricultural big data has accelerated agricultural production into a new era of digitalization and intelligentialize. Agricultural big data is the core element to promote agricultural modernization and the foundation of intelligent agriculture. As a new productive forces, big data enhances the comprehensive intelligent management decision-making during the whole process of grain production. But it faces the problems such as the indistinct management mechanism of grain production big data resources, the lack of the full-chain decision-making algorithm system and big data platform for the whole process and full elements of grain production.

Grain production big data platform is a comprehensive service platform that uses modern information technologies such as big data, Internet of Things (IoT), remote sensing and cloud computing to provide intelligent decision-making support for the whole process of grain production based on intelligent algorithms for data collection, processing, analysis and monitoring related to grain production. In this paper, the progress and challenges in grain production big data, monitoring and decision-making algorithms are reviewed, as well as big data platforms in China and worldwide. With the development of the IoT and high-resolution multi-modal remote sensing technology, the massive agricultural big data generated by the "Space-Air-Ground" Integrated Agricultural Monitoring System, has laid an important foundation for smart agriculture and promoted the shift of smart agriculture from model-driven to data-driven. However, there are still some issues in field management decision-making, such as the requirements for high spatio-temporal resolution and timeliness of the information are difficult to meet, and the algorithm migration and localization methods based on big data need to be studied. In addition, the agricultural machinery operation and spatio-temporal scheduling algorithm based on remote sensing and IoT monitoring information to determine the appropriate operation time window and operation prescription, needs to be further developed, especially the cross-regional scheduling algorithm of agricultural machinery for summer harvest in China. Aiming to address the issues of non-bi-connected monitoring and decision-making algorithms in grain production, as well as the insufficient integration of agricultural machinery and information perception, a framework for the grain production big data intelligent platform based on digital twins is proposed. The platform leverages multi-source heterogeneous grain production big data and integrates a full-chain suit of standardized algorithms, including data acquisition, information extraction, knowledge map construction, intelligent decision-making, full-chain collaboration of agricultural machinery operations. It covers the typical application scenarios such as irrigation, fertilization, pests and disease management, emergency response to drought and flood disaster, all enabled by digital twins technology.

The suggestions and trends for development of grain production big data platform are summarized in three aspects: (1) Creating an open, symbiotic grain production big data platform, with core characteristics such as open interface for crop and environmental sensors, maturity grading and a cloud-native packaging mechanism for core algorithms, highly efficient response to data and decision services; (2) Focusing on the typical application scenarios of grain production, take the exploration of technology integration and bi-directional connectivity as the base, and the intelligent service as the soul of the development path for the big data platform research; (3) The data-algorithm-service self-organizing regulation mechanism, the integration of decision-making information with the intelligent equipment operation, and the standardized, compatible and open service capabilities, can form the new quality productivity to ensure food safety, and green efficiency grain production.