Preliminary assessment of the effect of waterseeding technique and herbicide application on weedy rice tillers

Metsulfuron methyl has been recommended to control weedy rice under wetseeded conditions (Zainal and Azmi, unpubl. data, 1994). Another weed control method involves broadcasting pregerminated seeds using the water-seeding technique. This study was undertaken to evaluate the effect of seeding methods and herbicide application on weedy rice tillers 45 d after sowing (DAS). A factorial experiment was carried out in a glasshouse at Putra University Malaysia. Treatment 1 (T1) was the wet-seeding method—broadcasting seed on saturated soil and introducing water up to 10-cm flooding depth 7 d after seeding with (H1) and without herbicide (H0). Treatment 2 (T2) was water seeding—continuous flooding at 10-cm depth from seeding to date of data collection with H1 and H0. All treatments were replicated five times and arranged in a factorial randomized complete block design. Both weedy rice seeds and pregerminated MR219 seeds were sown on the soil surface (Tropic Fluvaquent) into 25.5-cm-diameter × 40-cm-high experimental containers using the MARDI-recommended seed rate (500 seeds m–2) (MARDI 2004) to achieve uniform establishment. Herbicide (metsulfuron methyl 1.75% combined with bensulfuron methyl 8.25%) was applied 14 DAS at 0.05 kg ai ha–1. Water was brought in 7 DAS for treatments with herbicide (T1) to facilitate herbicide application. The effects of water seeding and herbicide application on tillering ability of weedy rice (45 DAS) were analyzed using ANOVA. The means of these treatments were compared using Duncan’s new multiple range test. Only the seeding method was significantly different at P ≤0.05. There were no significant effects or interactions for the other sources of variation tested (see table). Weedy rice tillers decreased in both seeding methods (see figure)

Contribution of forest floor fractions to carbon storage and abundance patterns of arbuscular mycorrhizal fungal colonisation in a tropical montane forest

Forest floor carbon stocks, which include different components of litter, hemic and sapric materials, have not been empirically quantified in tropical montane forest, although they influence soil carbon (C) pools. To date, the contribution of arbuscular mycorrhizae in C sequestration potentials in tropical montane forests have not been clearly investigated. This study determined the amount of C stocks in the different decomposing layers of forest floor, mainly litter, hemic and sapric materials. The abundance of arbuscular mycorrhizal root colonisation differed among forest floor fractions. Forest floor was measured for depth, area density, dry mass and carbon fraction separately in Sungai Kial Forest Reserve, Pahang, Malaysia to calculate C stocks. Percentages of root colonisation in the hemic and sapric materials were investigated. The results showed that forest floor C stocks were significantly higher in hemic (5 Mg C ha−1) and sapric (7.7 Mg C ha−1) compared with the litter fragments (1.5 Mg C ha−1). Mycorrhizal root colonisation was significantly higher (75%) in the toeslope compared with the summit area in the hemic materials. Segregation of forest floor layers provided greater accuracy in forest floor C stocks reporting

Control of Weedy Rice Infestation by Enhancing Rice Establishment in Anaerobic Direct Seeding

Weedy rice or ‘padi angin’ is a serious threat to the rice industry of Malaysia. Its easy grain shattering characteristics has been reported to reduce rice yield up to 74%. The shift from transplanting techniques to direct seeding of planting rice has increased the weedy rice infestation. Preliminary study had shown that pre- treated rice seeds used in anaerobic seeding technique were able to out compete the growth of weedy rice and simultaneously increase the rice establishment. The objectives of this study were; a) to evaluate different rice seed germination enhancers in anaerobic (water) seeding, b) to evaluate seedling emergence in different water temperatures in anaerobic seeding and c) to evaluate rice establishment using pre-treated seeds and herbicide in controlling weedy rice in anaerobic seeding. Three rice seed varieties (MRQ 50, MR 167 and MR 219) were given treatments. The treatments tested were rice seeds soaked in water (control, T1); rice seeds coated with calcium peroxide (sodium silicate binding agent), [T2]; seeds treated with 1% peroxide base material [T3], seeds treated with 0.2% dilute acid [T4] and seeds treated with seaweeds [T5]. The seedling emergence was evaluated at three days after sowing (DAS) and the rice seedling growth was evaluated fourteen days after sowing (DAS) in glasshouse trials. The number of emerged seedlings for T3 was significantly higher for MR167 and MR219 compared to control at three DAS. However, there were no significant differences for MRQ 50 for emerged seedlings compared to control. Generally, there were no interaction effects between varieties and treatments tested for seedling height, root length and root surface area. T3 showed a significant increase of 7% for seedling height compared to control. However, the performance of T2 was inferior to the other seed treatments as well as control for all varieties tested. The seedling height, root length and root surface area of rice seedlings of T2 were reduced significantly to 27%, 38% and 90%, respectively compared to control at fourteen DAS. T4 and T5 performed the same as control for seedling height, root length and root surface area. In a laboratory study, pre-treated rice seeds were sown in soil –filled petri dishes and placed in water bath. Water level was maintained at 5 cm and temperatures were adjusted according to treatments (T1: 30°C, T2: 35°C, T3: 40°C and T4: 45°C). Seedling height increased significantly by 11% at 35°C compared to control (30°C). Water temperature of more than 40ºC significantly inhibited the rice seedling emergence and growth. In a glasshouse trial, the effect of pre-treated cultivated rice seeds and herbicide application on the tiller establishment of cultivated rice and weedy rice in aerobic (wet) and anaerobic (water) seeding were evaluated. There were no significant differences for herbicide effects on weedy rice tillers. However, seedling emergence of weedy rice at 14 DAS and tiller establishment at 45 DAS was significantly reduced in water seeding compared to wet seeding. In a field trial, pre-treated seeds were sown into divided plots, T1: wet seeding (control) and T2: water seeding and the weedy rice population and rice yield were evaluated at harvest. Water seeding technique significantly reduced weedy rice population almost 52% compared to control at 90 DAS. In this trial, farmer’s received a surplus in yield using water seeding technique compared to wet seeding technique as water seeding increased net rice yield by 15% (almost one ton/ha). The use of pre-treated seeds for the anaerobic direct seeding technique had an advantage on seedling vigor that out competed the weedy rice growth, and increased the rice seeds viability

Estimating carbon storage of forest floor components at varying altitudes in tropical forest of Pahang, Malaysia

Increasing atmospheric carbon dioxide (CO2) concentrations at alarming rates has triggered the need to conserve and monitor carbon (C) stocks for climate change mitigation. Tropical forests are important carbon sinks which are dynamic due to topographic variations, biomass components, forest floor quality, decomposition processes and spatial variation. Precise and reliable estimation of C stocks and its confounding processes that release/store C are still absent in tropical montane and lowland forests in Malaysia. The objectives of this study were i) to quantify above and belowground biomass C stocks in a lowland forest and montane forest with varying topography; ii) to determine the potential indicators (i.e. litter and duff decomposition rate, forest floor component and properties, soil CO2 fluxes and C:N ratios) of soil C storage and iii) to determine the spatial variability of litter, soil C, C:N, and forest floor component depths of a tropical lowland forest and tropical montane forest with varying topography. A systematic design of 10 m x 10 m plots was established for soil (0- 15 cm depth), litter and aboveground biomass sampling along three slope positions at the montane forest and one plot in the lowland forest. Basic soil characteristics and botanical distribution were determined. A litter bag study and soil CO2 flux measurements were conducted for 480 days in the montane and lowland forest.Forest floor materials were carbon dated and segregated for precise bulk density and carbon fraction measurements. Soil C, C:N, litter depth and various decomposing layers were explored using geostatistics to determine spatial variability. Litter and soil carbon stocks were significantly higher (3 and 5-fold) in the montane forest compared to the lowlands. The aboveground biomass ranged from 100 to 120 Mg C ha-1 and was the most dominant pool (> 40%) for all sites. The decomposition decay rate constant, k ranged from -0.002 to – 0.004 day-1 for the tropical montane and lowland forest. Lowlands showed increased mass loss and significant linear regression relationships between mass loss and litter quality except for C, lignin and cellulose. Soil CO2 fluxes were higher in the lowlands and positively correlated with decomposition and water filled pore space (WFPS). Duff (hemic + sapric) segregation resulted higher bulk density values (0.2) compared to litter (0.04) and revealed a more precise carbon fraction for litter (0.43) and duff (0.55) to be used for forest floor C stocks predictions utilizing significant linear regressions. Duff may reside up to 60 years. Duff decomposition is impeded even at higher temperatures in Forest Research Institute Malaysia campus and retained most of its carbon, nitrogen and lignin. Relationship between soil C:N and C were strong for all plots. Soil total C, C:N, and litter depth exhibited spatial variability at both forest types. Similarly, the litter, hemic and the total forest floor depth fractions confirmed spatial variations. Most variables exhibited a strong spatial dependence with the exception of C:N at the sideslope, litter depth at Jengka VJR and hemic depth at the summit (moderate). Surface maps for total C, C:N, litter depths, hemic and total forest floor depth showed distinct spatial clustering and displayed acceptable accuracy of interpolated values. Forest floor in the montane forest acts as an important C stock in the tropical forest which needs to accounted precisely for national C accounting. Research and developments in monitoring C stocks in montane forests within national and regional areas must be explored to avoid undestimation