SAR Backscater Response of Various Growth Stages of Wetland Rice Paddy in Malaysia
Saiful Bahari B. Abu Bakar and Abdul Talib B. Shaari
Malaysian Center for Remote sensing
CB 100, 5th Floor
City Square Center
Jalan Tun Razak Malaysia
Tel:+603-2645640 Fax: +603-2645650
H.T.Chuah and H.T.Ewe
faculty of Engineering
Telekom University
Bukit Bruang, Jalan Keroh Lama
Melaka Malaysia
Tel: +606-2523420 Fax:+606-2318696
Abstract
This paper investigates the capability of space-borne multi-data SAR images ( ERS-1/2) for monitoring of growth stages of wetland rice paddy crop. Four study sites were selected in the Kedah State, located in the northern part of Peninsular Malaysia, which produces 39% of total rice paddy output in ht country. The period of study was form April to September 1996, which cover the first cropping in the year. Ground data collection on soil and rice paddy plants were conducted around the days of the SAR data acquisition. in general, the phonological growth of wetland rice paddy could be classified into five main stages: land preparation, seeding, vegetative, ripening and harvesting. Preliminary results indicated that space-borne radar imagery has a great potential for delineation and monitoring different growth stages of wetland rice paddy.
Introduction
Rice is the staple food in Malaysia. The growing areas for rice paddy ( Oryaza sative ) form about 12.7% of total agricultural areas in country. Double cropping is practiced in Malaysia, where the first cropping is planted in April and harvested in September, while te second cropping covers the period form October to February in the foloowing year. The identification and real-time monitoring of rice paddy areas is therefore essential for econmonic reasons. traditionally, this has been done by using optical remote sensing data such as Landsat TM and SPOT data. However, due to cloud cover over the country, year-round optical data are ot possible. the ue of microwave remote sensing technology is a logical choice. Some work has recently been reported in the use of ERS-1 data for rice monitoring in temperate regions [1]. This paper reports on a similar investigation of the capability of using SAR images to monitor the phonological growth characteristics of wetland rice paddy in the tropical region. The study site is in kedah (MADA) * which accounts for about 97,200 hectares out of 144,900 hectares for the whole kedah State [2]. The images use are multi-date images from ERS ½. Ground measurements were conducted during the day of data acquisition. These include soil moisture content, soil composition, water depth, plant height, plant density, sizes and moisture contents of leaves, stems and stalks. the study covers the period from April to September 1996.
Fieldwork
Four rice paddy field in the Kedah State have been selected for the study: Kampung Tanah Seratus ( Lat. 601'50. 5"N, Long. 100021' 53.1" E), Kampung Rambai(Lat.602' 6.7"N, Long 100027'8"E), Kampung Hutan Kandis ( Lat. 6011'1.4", Long. 1000 24'33.1"E) and Kampung Telok Jawa ( Lat. 6013'24.9"N, Long. 100019'36.9"E). Six fields trips were conducted during the period of study from April to September 1996 (i.e. on April 27, May 19, June25, August 11, and September 15, 1996). During each field trip, the following ground truth measurements were made at the sites, the positions of which were checked by a GPS system
- composition and moisture contents of soil
- average height of paddy crops above the water.
- Moisture content and sizes of paddy rice plant constituents such as leaves and tillers
- Weather conditions.
At each site, there were 5 plots, where each plot containing 5 replications were measured Table 1 gives a typical measurement results on the rice paddy plants for kampung Tanah Sratus.
Table 1: Typical Measured Data for Paddy at Kampung Tanah Seratus, Kedah State, Malaysia
| Date |
Apr27 |
May. 19 |
June.1 |
June.25 |
Aug. 11 |
Sep. 15 |
| Average height above water(cm) |
17.2 |
59 |
59.0 |
76.8 |
89.7 |
0 |
| Average leaf width (cm) |
0.42 |
0.88 |
0.9 |
1.1 |
1.13 |
0 |
| Average leaf thickness (mm) |
0.11 |
0.14 |
0.14 |
0.17 |
0.22 |
0 |
| Average stalk diameter (cm) |
0.4 |
0.4 |
0.5 |
0.6 |
0.6 |
0 |
| Average of moisture content of plant (%) |
76.2 |
- |
79.8 |
75.2 |
53.2 |
0 |
| Average No. of tillers in a 0.5m x 0.5m plot |
176 |
186 |
186 |
132 |
90 |
0 |
| Average No. of leaves per tiller |
4 |
8 |
8 |
5 |
4.5 |
0 |
