Spatial distribution of weed seedbank in rice ecosystem and abandoned land / Abdul Hayyan Basit Md Akhir

Abdul Hayyan Basit , Md Akhir (2019) Spatial distribution of weed seedbank in rice ecosystem and abandoned land / Abdul Hayyan Basit Md Akhir. Masters thesis, Universiti Malaya.

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Abstract

Seed longevity and durability in the seedbank are important traits for weed survival especially for the escape and successive mechanism in the nature. This study was developed to investigate the spatial dynamics of seedbank in rice agroecosystem and in diverse abandoned agricultural land. The objectives of the study were: (i) to characterize vertical and horizontal seedbank weedy rice distribution pattern in rice agroecosystem; (ii) to determine seedbank distribution pattern at different types of abandoned agricultural lands in Jelebu, Negeri Sembilan; and (iii) to evaluate weed infestation potential from seedbank. The weedy rice seedbank survey was conducted in IADA Barat Laut Selangor (IBLS) rice granary at two locations, Sawah Sempadan and Sungai Burung, of different land preparation practices. A total of fifty soil cores at 20 cm depth were extracted from each location and weedy rice seeds were counted from every 5 cm soil core intervals to characterize the vertical weedy rice seedbank dynamic. The horizontal seeds distribution survey was conducted by randomly placed one hundred 10 cm2 quadrat on the rice fields to count weedy rice shattered seeds on the ground. All collected seeds (vertical and horizontal) was germinated using standard germination test to evaluate the viability of the seeds. The density of weedy rice seeds at both locations has no significant difference vertically and horizontally. However, Sawah Sempadan displayed significantly higher germination rate for all soil depths indicating poor land preparation contributes to higher potential of weedy rice escape for successive season. Determination of seedbank distribution pattern in abandoned agricultural lands was conducted in Glami Lemi Biotechnology Research Center (GLBRC), University Malaya, Jelebu, Negeri Sembilan at 10 sites with three ecological types. A total of five soil samples were randomly collected at each site from 5 cm deep top soil in a 10 cm2 quadrat. The samples were put in a separate container, wetted with 10 ml distilled water and left in a room temperature with light. Germinated seeds were counted and determined for weed types (broadleaf and grass) at 3, 6 and 9 days after soaking. Another set of soil from the similar site for germination test was collected, placed in a 9 mm petri dish and air-dried for 3 days in the greenhouse. The presence of seed in the soil was counted under light microscope. The non-active sites showed the highest density of seedbank by direct seed count while the active sites with on-going agriculture activities displayed significantly higher germinated seedlings than other sites. Broadleaf weeds have higher germination rate as compared to grasses. Active land activities such as agriculture promoted weed emergence probably due to enhancement of soil suitability for seedbank germination. Abandoned lands especially from agriculture land will accumulate various weeds through seedbank. Reintroduction of these lands might provide suitable conditions for these weeds to re-emerge. The spatial distribution pattern of the weed seedbank from two agriculture landscapes of this study indicates; (i) proper land preparation will reduce weed infestation, (ii) soil depth might provide extra advantage for weedy rice seed to survive in the seedbank, and (iii) an abandoned land can be a pool for diverse weeds through seedbank. Therefore, weeds seed longevity and durability study in the seedbank need to be emphasized and strategized in the future to reduce weed infestation.

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