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基于无人机多光谱影像和机器学习的水稻产量与氮素利用率预测

Prediction of rice yield and nitrogen use efficiency based on UAV multispectral imaging and machine learning

  • 摘要: 为了筛选对产量与氮素利用率(nitrogen use efficiency, NUE)敏感的遥感特征,构建准确的产量及NUE预测模型,该研究开展为期2a的多氮素水平与多水稻品种田间试验,获取了3个关键生长阶段的无人机(unmanned aerial vehicle, UAV)多光谱影像,采用递归特征消除(recursive feature elimination, RFE)算法筛选敏感植被指数(vegetation indices, VIs)、纹理特征(texture features, TFs)和二者的混合特征,利用6种机器学习算法构建“敏感特征-产量和NUE”直接预测模型,并根据NUE属性提出一种“敏感特征-产量-NUE”间接预测模型,通过两种模型的对比验证了UAV在水稻NUE精确预测中的应用潜力。研究结果表明:(1)尽管对产量和NUE敏感的特征因生长阶段而异,但DVI(difference vegetation index)、VARI(visible atmospherically resistant indices)和mNDblue(modified normalized difference blue index )以及纹理均值(Mean)在多个生长阶段对产量敏感;repRVI(reciprocal ratio vegetation index)、相关性(correlation, Cor)和Mean在多个生长阶段对NUE敏感。(2)深度神经网络(deep neural network, DNN)模型对产量和NUE直接预测性能最佳。在灌浆期,基于TFs的产量预测精度最高(R²=0.938,RMSE=479.591 kg/hm2);在分蘖期,基于混合特征的NUE预测精度最佳,农学氮素利用率(agronomic nitrogen use efficiency, aNUE)和氮素偏生产力(nitrogen partial factor productivity, NPFP)的预测精度分别为R2=0.711,RMSE=4.448 kg/kg和R2=0.781,RMSE=12.787 kg/kg。(3)与直接预测模型相比,间接预测模型对NUE预测精度更高,对aNUE和NPFP的预测R2分别提高了18.589%和14.733%,RMSE分别降低了54.411%和90.015%。研究结果可为田块尺度下利用无人机遥感技术快速准确预测水稻产量和NUE提供新思路。

     

    Abstract: Rice is one of the most important staple crops worldwide, with China being the largest rice producer. Rice yield and nitrogen use efficiency (NUE) are critical factors determining food security and agricultural sustainability. Nitrogen (N) is an essential nutrient for rice growth; however, excessive nitrogen fertilizer application reduces NUE, increases production costs, and causes environmental pollution. Therefore, accurately predicting rice yield and NUE is crucial for optimizing nitrogen management, improving rice production efficiency, and mitigating environmental impacts. In recent years, the development of remote sensing technology, particularly the application of unmanned aerial vehicle (UAV) multispectral imagery, has significantly enhanced the precision management of agricultural production. UAV remote sensing technology enables efficient acquisition of crop growth status information and, when combined with machine learning approaches, facilitates the construction of accurate predictive models, thereby providing data support and decision-making assistance for agricultural production.A two-year field experiment was conducted in Fengyang County, Anhui Province, China, involving multiple nitrogen levels and rice varieties. UAV multispectral images were collected at three key growth stages (tillering, heading, and grain filling stages) to obtain remote sensing data. The recursive feature elimination (RFE) algorithm was used to select sensitive vegetation indices (VIs), texture features (TFs), and their combined features. Six machine learning models-random forest (RF), support vector machine (SVM), multilayer perceptron (MLP), gradient boosting machine (GBM), deep neural network (DNN), and long short-term memory (LSTM)-were employed to establish direct prediction models based on “sensitive remote sensing features–yield and NUE” Additionally, an indirect prediction model based on “sensitive remote sensing features–yield–NUE” was proposed using calculated features. The potential of UAV remote sensing technology for accurate NUE prediction was evaluated by comparing the performance of direct and indirect models.The results showed that: (1) The prediction of rice yield and NUE at different growth stages exhibited varying dependencies on remote sensing features. At the tillering stage, spectral-based vegetation indices contributed more to prediction accuracy, whereas at the grain filling stage, texture features played a more significant role in NUE prediction. Difference vegetation index (DVI), visible atmospherically resistant indices (VARI), and modified normalized difference blue index (mNDblue), as well as the texture mean (Mean), were sensitive to yield across multiple growth stages. Similarly, reciprocal ratio vegetation index (repRVI), correlation (Cor), and Mean were consistently sensitive to NUE. (2) Among all models, the deep neural network (DNN) achieved the highest accuracy in direct predictions of yield and NUE. At the grain filling stage, the TF-based model provided the most accurate yield predictions (R²= 0.938, RMSE = 479.591 kg/hm2). At the tillering stage, the hybrid feature-based model demonstrated the best predictive performance for NUE, with agronomic nitrogen use efficiency (aNUE) and nitrogen partial factor productivity (NPFP) achieving R² values of 0.711 (RMSE = 4.448 kg/kg) and 0.781 (RMSE = 12.787 kg/kg), respectively. (3) Compared to direct models, the indirect model significantly improved NUE prediction accuracy. The R² values for aNUE and NPFP increased by 18.589% and 14.733%, while RMSE values decreased by 54.411% and 90.015%, respectively. The proposed indirect prediction framework for NUE overcomes the limitations of traditional methods that rely on data from the maturity stage, enabling nondestructive and dynamic assessment at earlier growth stages. This study demonstrates that UAV multispectral imagery combined with machine learning techniques effectively enhances the prediction accuracy of rice yield and NUE. The DNN model outperforms traditional machine learning models in predictive accuracy, and the indirect prediction method surpasses the direct approach. These findings provide a novel methodology for precision management in rice production and offer valuable technical support for intelligent agricultural management.

     

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