Empirical Application of Polarimetric Synthetic Aperture Radar for Rice Phenology Monitoring in Irrigated and Favorable Rainfed Ecosystems
Jean Rochielle F. Mirandilla1 3*, Megumi Yamashita1, Mitsunori Yoshimura2

1 Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan- s235342z[at]st.go.tuat.ac.jp (J.R.F.M)- meguyama[at]cc.tuat.ac.jp (M.Y.)
2 College of Bioresource Sciences, Nihon University- yoshimura.mitsunori[at]nihon-u.ac.jp
3Philippine Rice Research Institute- jrfmirandilla[at]exchange.philrice.gov.ph (J.R.F.M)
*s235342z[at]st.go.tuat.ac.jp

Abstract

Rice in the Philippines is cultivated under two primary ecosystems, irrigated and rainfed. Rainfed areas can be further categorized as favorable or unfavorable based on rainfall distribution. Management and challenges in production in these ecosystems are observed to be different. This study focused on monitoring rice phenology in irrigated and favorable rainfed ecosystems in Iloilo Province, Philippines, using multi temporal polarimetric Synthetic Aperture Radar data. Multitemporal SAR datasets were used to capture the temporal dynamics of rice growth across two cropping seasons, 2019 semester 2 and 2020 semester 1. A total of 37 dual polarization SAR images were acquired from Sentinel 1B, C band, VV and VH polarizations, and ALOS PALSAR 2, L band, HH and HV polarizations. All images underwent preprocessing, followed by the generation of 2 x 2 covariance matrices, which were analyzed using H A alpha decomposition to extract polarimetric parameters. Six key rice growth stages were identified and used to compare the polarimetric bands such entropy, alpha and anisotropy, land preparation, seedling, tillering, reproductive, ripening, and harvested. Statistical analysis such as segmented regression were performed to identify growth stage specific changes. The approach enabled the characterization of key phenological stages and the comparison of crop development patterns across the two rice ecosystems. Moreover, notable differences were observed between the two SAR sensors, particularly in relation to water presence in rice paddies. This study demonstrates the potential of dual-polarization SAR for operational rice monitoring and for distinguishing phenological behavior under different water management regimes in rice ecosystems.

Keywords: Irrigated Rice Ecosystem, Favorable Rainfed Rice Ecosystems, Polarimetric SAR

Topic: Topic B: Applications of Remote Sensing