A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in Maize
This study presents the MSPAT (Multispectral Soil Plant Analysis Tool), a device designed for assessing leaf nitrogen concentrations in maize crops under field conditions. The MSPAT includes the AS7265x sensor, which has 18 bands and covers the spectrum from 410 to 940 nm. This device was designed t...
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2025-06-01
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| author | Felipe Hermínio Meireles Nogueira Adunias dos Santos Teixeira Sharon Gomes Ribeiro Luís Clênio Jario Moreira Odílio Coimbra da Rocha Neto Fernando Bezerra Lopes Ricardo Emílio Ferreira Quevedo Nogueira |
| author_facet | Felipe Hermínio Meireles Nogueira Adunias dos Santos Teixeira Sharon Gomes Ribeiro Luís Clênio Jario Moreira Odílio Coimbra da Rocha Neto Fernando Bezerra Lopes Ricardo Emílio Ferreira Quevedo Nogueira |
| author_sort | Felipe Hermínio Meireles Nogueira |
| collection | DOAJ |
| description | This study presents the MSPAT (Multispectral Soil Plant Analysis Tool), a device designed for assessing leaf nitrogen concentrations in maize crops under field conditions. The MSPAT includes the AS7265x sensor, which has 18 bands and covers the spectrum from 410 to 940 nm. This device was designed to be portable, using the ESP32 microcontroller and incorporating such functionalities as data storage on a MicroSD card, communication with a smartphone via Wi-Fi, and geolocation of acquired data. The MSPAT was evaluated in an experiment conducted at the Federal University of Ceará (UFC), where maize was subjected to different doses of nitrogen fertiliser (0, 60, 90, 120, 150, and 180 kg·ha<sup>−1</sup> N). Spectral readings were taken at three phenological stages (V5, V10, and R2) using the MSPAT, an SPAD-502 chlorophyll meter, and a FieldSpec PRO FR3 spectroradiometer. After the optical measurements were taken, the nitrogen concentrations in the leaves were determined in a laboratory by using the Kjeldahl method. The data analysis included the calculation of normalised ratio indices (NRIs) using linear regression and the application of multivariate statistical methods (PLSR and PCR) for predicting leaf nitrogen concentrations (LNCs). The best performance for the MSPAT index (NRI) was obtained using the 900 nm and the 560 nm bands (R<sup>2</sup> = 0.64) at stage V10. In the validation analysis, the MSPAT presented an R<sup>2</sup> of 0.79, showing performance superior to that of SPAD-502, which achieved an R<sup>2</sup> of 0.70. This confirms the greater potential of the MSPAT compared to commercial equipment and makes it possible to obtain results similar to those obtained using the reference spectroradiometer. The PLSR model with data from the FieldSpec 3 provided important validation metrics when using reflectance data with first-derivative transformation (R<sup>2</sup> = 0.88, RMSE = 1.94 and MAE = 1.28). When using the MSPAT, PLSR (R<sup>2</sup> = 0.75, RMSE = 2.77 and MAE = 2.26) exhibited values of metrics similar to those for PCR (R<sup>2</sup> = 0.75, RMSE = 2.78 and MAE = 2.26). This study validates the use of MSPAT as an effective tool for monitoring the nutritional status of maize to optimize the use of nitrogen fertilisers. |
| format | Article |
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| publishDate | 2025-06-01 |
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| spelling | doaj-art-8d19530f5a9743c0bfbcf40ba002e2932025-08-20T02:36:31ZengMDPI AGSensors1424-82202025-06-012513392910.3390/s25133929A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in MaizeFelipe Hermínio Meireles Nogueira0Adunias dos Santos Teixeira1Sharon Gomes Ribeiro2Luís Clênio Jario Moreira3Odílio Coimbra da Rocha Neto4Fernando Bezerra Lopes5Ricardo Emílio Ferreira Quevedo Nogueira6Department of Agricultural Engineering, Federal University of Ceara, Fortaleza 60455-760, BrazilDepartment of Agricultural Engineering, Federal University of Ceara, Fortaleza 60455-760, BrazilSoil Science Graduate Program, Federal University of Ceara, Fortaleza 60455-760, BrazilDepartment of Agronomy, Federal Institute of Education, Science and Technology of Ceara, Limoeiro do Norte 62930-000, BrazilDepartment of Agricultural Engineering, Federal University of Ceara, Fortaleza 60455-760, BrazilDepartment of Agricultural Engineering, Federal University of Ceara, Fortaleza 60455-760, BrazilDepartment of Metallurgical and Materials Engineering, Federal University of Ceara, Fortaleza 60455-760, BrazilThis study presents the MSPAT (Multispectral Soil Plant Analysis Tool), a device designed for assessing leaf nitrogen concentrations in maize crops under field conditions. The MSPAT includes the AS7265x sensor, which has 18 bands and covers the spectrum from 410 to 940 nm. This device was designed to be portable, using the ESP32 microcontroller and incorporating such functionalities as data storage on a MicroSD card, communication with a smartphone via Wi-Fi, and geolocation of acquired data. The MSPAT was evaluated in an experiment conducted at the Federal University of Ceará (UFC), where maize was subjected to different doses of nitrogen fertiliser (0, 60, 90, 120, 150, and 180 kg·ha<sup>−1</sup> N). Spectral readings were taken at three phenological stages (V5, V10, and R2) using the MSPAT, an SPAD-502 chlorophyll meter, and a FieldSpec PRO FR3 spectroradiometer. After the optical measurements were taken, the nitrogen concentrations in the leaves were determined in a laboratory by using the Kjeldahl method. The data analysis included the calculation of normalised ratio indices (NRIs) using linear regression and the application of multivariate statistical methods (PLSR and PCR) for predicting leaf nitrogen concentrations (LNCs). The best performance for the MSPAT index (NRI) was obtained using the 900 nm and the 560 nm bands (R<sup>2</sup> = 0.64) at stage V10. In the validation analysis, the MSPAT presented an R<sup>2</sup> of 0.79, showing performance superior to that of SPAD-502, which achieved an R<sup>2</sup> of 0.70. This confirms the greater potential of the MSPAT compared to commercial equipment and makes it possible to obtain results similar to those obtained using the reference spectroradiometer. The PLSR model with data from the FieldSpec 3 provided important validation metrics when using reflectance data with first-derivative transformation (R<sup>2</sup> = 0.88, RMSE = 1.94 and MAE = 1.28). When using the MSPAT, PLSR (R<sup>2</sup> = 0.75, RMSE = 2.77 and MAE = 2.26) exhibited values of metrics similar to those for PCR (R<sup>2</sup> = 0.75, RMSE = 2.78 and MAE = 2.26). This study validates the use of MSPAT as an effective tool for monitoring the nutritional status of maize to optimize the use of nitrogen fertilisers.https://www.mdpi.com/1424-8220/25/13/3929spectroradiometryprecision agriculturetechnological development<i>Zea mays</i> L. |
| spellingShingle | Felipe Hermínio Meireles Nogueira Adunias dos Santos Teixeira Sharon Gomes Ribeiro Luís Clênio Jario Moreira Odílio Coimbra da Rocha Neto Fernando Bezerra Lopes Ricardo Emílio Ferreira Quevedo Nogueira A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in Maize Sensors spectroradiometry precision agriculture technological development <i>Zea mays</i> L. |
| title | A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in Maize |
| title_full | A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in Maize |
| title_fullStr | A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in Maize |
| title_full_unstemmed | A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in Maize |
| title_short | A Handheld Multispectral Device for Assessing Leaf Nitrogen Concentrations in Maize |
| title_sort | handheld multispectral device for assessing leaf nitrogen concentrations in maize |
| topic | spectroradiometry precision agriculture technological development <i>Zea mays</i> L. |
| url | https://www.mdpi.com/1424-8220/25/13/3929 |
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