Characterization of rice agriculture in the Southern Province of Rwanda by means of microwave remote sensing

Wetlands can be considered as one of the most vulnerable and endangered ecosystems on the planet. The threat is even more emphasized when the "kidneys of the landscapes" are used for agricultural purposes. The agricultural intensification in Rwanda resulted year-round cultivation in most of the wetlands. Despite its higher water and labor demand than other crops paddy rice is the preferred and policy recommended food and cash crop in the wetlands of the country. For effective management planning processes to ensure food security there is a serious need for accurate and up-to-date information on the agriculture sector. The objective our study is to contribute to this effort by using spaceborne Synthetic Aperture Radar (SAR) data to retrieve phenological parameters of paddy rice in the Southern Province of Rwanda. High spatial resolution dual polarized Sentinel-1 SAR data were obtained for the time period covering Season B of the two rice cropping seasons of 2017. For the derivation of the selected phenological indicators (start, end, middle and length of season) time series analysis was performed. Based on the temporal pattern of radar backscatter values, the temporal and spatial distribution of SAR derived phenological indicators considerable differences were identified among the investigated four paddy rice fields. These differences are related to the different level of management harmonization, embedding other crops in the paddy rice fields, and as well as to the topographical characteristics of the valley bottoms where the cropping activity takes place. The study confirms that using SAR is a promising technology for agricultural monitoring especially in regions where cloud cover is the main reason for the limited use of optical imagery.