Abstract
The nondestructive assessment of nitrogen status in strawberry was performed to analyze its growth and provide guidance for precise management of N fertilizer using Fourier transform near-infrared reflectance (FT-NIR) spectroscopy with leaf spectral reflectance. The leaf soil plant analysis development (SPAD) value is considered as an indicator that indirectly reflects the nitrogen status in strawberry. However, the variation of cultivars leads to differences in the cell structure and light scattering and/or reflection effects of strawberry leaves during strawberry N status assessment, which means, leaf SPAD threshold value and the specific N demand will vary with different cultivars. As a result, accurate measurement of SPAD values and N status in strawberries with multiple cultivars is still challenging. In this study, the individual-cultivar, hybrid-cultivar, and multi-cultivar models were developed for the determination of SPAD values, and the performance of the models in lessening the impact of cultivar variation was studied and compared. The individual-cultivar model was constructed on the basis of a single cultivar of strawberry leaf. The hybrid-cultivar model was developed by merging the spectrum reflectance data and SPAD values of all studied leaf samples, and a multi-cultivar model was built in combination with cultivar identification, individual-cultivar models, and model search strategy. The results indicated that the multi-cultivar model was superior to the other two models for SPAD value estimation of strawberry leaves from different cultivars, with the overall Rp and RMSEP values of 0.966 and 0.468, respectively. We demonstrate that the leaf N content of strawberry is profoundly affected by cultivar variation, and establishing a multi-cultivar model is useful in monitoring the nitrogen status and guiding N fertilization recommendations for different strawberry cultivars.
Highlights
Nitrogen (N) is crucial nutrient for strawberry growth, which increase chlorophyll concentration, improve photosynthetic efficiency, and delay aging [1]
SPECTRAL BEHAVIORS OF MULTI-CULTIVAR SAMPLES The reflectance spectrum shown in Fig. 2 shows the typical spectral characteristics of strawberry leaves with three different cultivars
The former is related to the strong reflection of chlorophyll, while the latter was ascribed to strong absorption of chlorophyll [45]
Summary
Nitrogen (N) is crucial nutrient for strawberry growth, which increase chlorophyll concentration, improve photosynthetic efficiency, and delay aging [1]. Proper nitrogen fertilizer management could promote strawberry marketable yields and improve quality. The associate editor coordinating the review of this manuscript and approving it for publication was Liandong Zhu. diagnose N status, provide accurate fertilization guidance, and indirectly correct N fertilization of different cultivars of strawberries. Conventional physicochemical assessment methods of nitrogen status, such as Kjeldahl nitrogen detection method, tissue and chemical analysis, and remote sensing with aerial images, have been successfully employed in cultivar-specific crop production management.
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