SAR-Based Monitoring of Maize Phenology in the High-Yielding Mpumalanga Province of South Africa.
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| Title: | SAR-Based Monitoring of Maize Phenology in the High-Yielding Mpumalanga Province of South Africa. |
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| Authors: | Kimura, Reiji1 (AUTHOR) rkimura@tottori-u.ac.jp, Moriyama, Masao2 (AUTHOR), Tsubo, Mitsuru1,3 (AUTHOR), Moeletsi, Mokhele Edmond3,4 (AUTHOR), Bello, Zaid Adekunle5 (AUTHOR) |
| Source: | Remote Sensing. Sep2026, Vol. 18 Issue 18, p3231. 15p. |
| Subjects: | Backscattering, Phenology, Corn farming, Remote sensing, Crop yields |
| Geographic Terms: | Mpumalanga (South Africa), South Africa |
| Abstract: | Highlights: What are the main findings? Sentinel-1 VH backscatter and the VH:VV ratio showed distinct temporal peaks associated with the expected heading and maturity periods, respectively, with consistent patterns across the 2019–2021 growing seasons. The peak VH backscatter was negatively associated with maize yield (R2 = 0.79, p < 0.01), suggesting that temporal SAR characteristics may provide useful information on maize phenological development and production conditions. What are the implications of the main findings? Sentinel-1 VH and VH:VV temporal patterns provide potential phenological indicators for maize in high-yielding agricultural areas where cloud cover can limit optical observations. The identified SAR–phenology relationships provide a basis for developing field-level maize monitoring, while independent field observations are needed to calibrate and validate these indicators for operational applications. Maize is one of the most important crops in South Africa, making timely information on its growth and phenological development essential for effective production management and yield forecasting. This study investigated the potential of Sentinel-1 SAR to characterize maize phenological periods in Mpumalanga Province, one of South Africa's highest-yielding maize-producing regions, during the 2018–2019, 2019–2020, and 2020–2021 cropping seasons. Sentinel-1 vertical transmit-horizontal receive (VH) polarization and vertical transmit-vertical receive (VV) polarization gamma naught backscatter coefficients and the VH:VV cross-polarization ratio were analyzed together with the Sentinel-2 Normalized Difference Vegetation Index (NDVI) and field survey data. Unsupervised classification was used to assist in identifying candidate maize fields, and the seasonal variations in SAR indices showed patterns similar to those previously observed in North West Province. The increase in the VH:VV cross-polarization ratio was associated with the expected emergence period, and NDVI-derived emergence dates generally fell within the emergence periods indicated by SAR. The peak of VH gamma naught occurred several days after or coincided with the NDVI peak, suggesting its potential as an indicator of the expected heading period, whereas the peak of the VH:VV cross-polarization ratio was consistent with the expected mature period, as was the second peak of VH gamma naught. Peak VH gamma naught exhibited a significant negative relationship with maize yield (R2 = 0.79, p < 0.01). Compared with North West Province, Mpumalanga showed lower peak VH gamma naught values despite substantially higher yields, suggesting that differences in planting density and canopy structure reduced the contribution of volume scattering within the maize canopy. These results suggest that Sentinel-1 SAR has potential for providing phenological indicators of maize in both semi-arid and high-yield production environments. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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