Nitrogen status assessment for multiple cultivars of strawberries using portable NIR spectrometers combined with cultivar recognition and multivariate analysis

Abstract

Abstract Background The assessment of nitrogen status non-destructively in strawberry was performed to indicate its growth and provide guidance for precise management of N fertilizer using near-infrared reflectance (NIR) spectroscopy with leaf spectral reflectance. The Leaf soil plant analysis development (SPAD) value was thought as an indicator data that indirectly reflects nitrogen status in strawberry. However, the variation of cultivars would lead to differences in the cell structure and light scattering and/or reflection effects of strawberry leaves when assessed strawberry N status, which caused that no single leaf SPAD threshold value or same N demand can be applied for all strawberry cultivars. As a result, accurate detection of SPAD values and N status in strawberries with multiple cultivars is still challenging.Results In this study, Individual-cultivar model, hybrid-cultivar model and multi-cultivar model were developed for the determination of SPAD values, and the performance of the models in lessening the impact of cultivar variation were studied and compared. Individual-cultivar model was constructed on the basis of the single cultivar of strawberry leaf; hybrid-cultivar model was developed by merging the spectrum reflectance data and SPAD values of all studied leaf samples, and multi-cultivar model was built in combination with cultivar identification, individual-cultivar models, and model search strategy.Conclusion The results indicated that multi-cultivar model was more superior to the other two models for SPAD values estimation of strawberry leaves from different cultivars, with the overall Rp and RMSEP value respectively being 0.966 and 0.468. We demonstrate that the leaf N content per strawberry is profoundly affected by cultivar variation, and establishing a multi-cultivar model might be more useful in monitoring nitrogen status and guiding N fertilization recommendations for different strawberry cultivars.

Plant phenotyping relevance

携帯型NIR分光と品種認識・多変量モデルにより、イチゴ葉のSPAD値および窒素状態を非破壊推定する手法を開発・比較しており、表現型取得と解析手法が研究の中心である。

Code and data availability

The paper's strawberry leaf NIR spectral reflectance data and SPAD measurements are not publicly deposited; the authors state the datasets are available from the corresponding author on reasonable request. No public code, models, or data URLs are provided.

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