Weed Species Composition and Distribution in Rice Fields in Comparison Between Off- and Main-Season of 2014/2015 in KADA Granary Area of Malaysia

This study aimed to identify weed composition, distribution, and dominance under water-scarce conditions in 45 fields across three locations in the KADA granary area of Malaysia during the main- and off-season of 2014/2015. The survey employed a quantitative method using 0.5 m & times; 0.5 m quadrats, with 20 samples per rice field laid out systematically in an inverted W pattern. Resultantly, the survey revealed variations in weed composition and prevalence between rice planting seasons, driven by varying moisture stress levels that favored specific weed survival traits under fluctuating water availability. A total of 30 weed species were identified from 14 different families, comprising 6 grasses, 6 sedges, and 18 broadleaved weeds. Based on the relative abundance and ranking of the weeds in the surveyed rice fields, Fimbristylis miliacea (84.2%), followed by Leptochloa chinensis (41.6%), Scirpus grossus (30.1%), and Ischaemum rugosum (23.6%) were the most prevalent and abundant species in the off-season 2014. Conversely, the 2014/2015 main-season was highly dominated by Echinochloa crus-galli (62.8%), followed by L. chinensis (37.3%), Limnocharis flava (25.1%), and F. miliacea (22.3%). Sorenson's index values (92.9%-100.0%) during the 2014 off-season indicate high weed species similarity across districts, while lower values (59.6%-76.6%) in the 2014/2015 main-season suggest slight variations in weed composition between districts. These findings provide critical baseline data for developing targeted weed control strategies to enhance rice yield and promote sustainable agricultural practices.