Monitoring and Mapping of Rice Cropping Pattern in Flooding Area in the Vietnamese Mekong Delta Using Sentinel-1A Data: A Case of An Giang Province

Huynh Vuong Thu Minh,Geetha Mohan,Masaaki Kurasaki,Ram Avtar,Prakhar Misra

doi:10.3390/ijgi8050211

Abstract

Cropping intensity is one of the most important decisions made independently by farmers in Vietnam. It is a crucial variable of various economic and process-based models. Rice is grown under irrigated triple- and double-rice cropping systems and a rainfed single-rice cropping system in the Vietnamese Mekong Delta (VMD). These rice cropping systems are adopted according to the geographical location and water infrastructure. However, little work has been done to map triple-cropping of rice using Sentinel-1 along with the effects of water infrastructure on the rice cropping intensity decision. This study is focused on monitoring rice cropping patterns in the An Giang province of the VMD from March 2017 to March 2018. The fieldwork was carried out on the dates close to the Sentinel-1A acquisition. The results of dual-polarized (VV and VH) Sentinel-1A data show a strong correlation with the spatial patterns of various rice growth stages and their association with the water infrastructure. The VH backscatter (σ°) is strongly correlated with the three rice growth stages, especially the reproductive stage when the backscatter is less affected by soil moisture and water in the rice fields. In all three cropping patterns, σ°VV and σ°VH show the highest value in the maturity stage, often appearing 10 to 12 days before the harvesting of the rice. A rice cropping pattern map was generated using the Support Vector Machine (SVM) classification of Sentinel-1A data. The overall accuracy of the classification was 80.7% with a 0.78 Kappa coefficient. Therefore, Sentinel-1A can be used to understand rice phenological changes as well as rice cropping systems using radar backscattering.

Highlights

Rice (Oryza. sativa L.) is one of the major crops and the primary daily grain consumed in Asian countries [1,2,3]
An Giang receives slightly lower average annual rainfall compared to the Vietnamese Mekong Delta (VMD), at 2000 mm per year, because the province is located in the inland delta with a minimal effect of the southwest monsoon
This study clearly shows the strong response of dual-polarization (σ◦VV and σ◦VH) to rice phenology and cropping system by using Sentinel-1A synthetic aperture radar (SAR) data

Summary

Introduction

Rice (Oryza. sativa L.) is one of the major crops and the primary daily grain consumed in Asian countries [1,2,3]. Most of the rice produced in Vietnam comes from the Vietnamese Mekong Delta (VMD). It feeds a population of nearly 95 million and provides food security in Southeast Asia [13,14,15]. In the VMD, these rice cropping systems were adopted according to the geographical location and water infrastructure [16]. The rapid intensification of agriculture, mainly in irrigated areas, has been explained by the renovation policy, by which the delta was turned into the rice bowl of Vietnam by the mid-1990s [20,21,22,23]. Since 2009, the double-rice crop has gradually been replaced by a triple-rice crop to increase rice production for food security and economic development [29,30]

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