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)

Carbon stocks in different carbon pools of a tropical lowland forest and a montane forest with varying topography

Increasing atmospheric carbon dioxide concentrations at alarming rates have triggered the need to revisit potential opportunities in conserving and monitoring carbon (C) stocks for climate change mitigation. The dynamic nature of tropical forests based on topographic variations and biomass components needs reliable estimation of forest C to support conservation and forest monitoring strategies. This study was aimed to determine C stocks of varying components (i.e. litter, soil, aboveground biomass and roots) in a tropical lowland forest and a tropical montane forest at varying topographic positions. Systematically designed 10 m × 10 m plots were 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 due to minimal topographic variability. Basic soil characteristics and botanical distribution of both forest sites were determined. Carbon stocks were significantly higher in the tropical montane forest, where litter and soil C stocks at the summit were three and five folds significantly higher compared with the lowland forest. No significant differences were found in vegetation structure (mean diameter at breast height, mean height and stand basal area) but the aboveground biomass ranged from 100 to 120 Mg C ha-1 and was the most dominant pool (> 40%) for all sites. Soil C pools were comparable (100 to 120 Mg C ha-1) with aboveground biomass pools at the summit and toeslope position of the montane forest

Spatial variability of selected forest soil properties related to carbon management in tropical lowland and montane forests

A better understanding of spatial variability of forest soil properties related to carbon (C) sequestration will improve management strategies towards conserving forest areas that project higher C stocks. This study was aimed at determining spatial variability of soil C, C:N (nitrogen) and forest floor depth in tropical lowland and montane forests at varying topographic positions. Quadrants of 10 m ×10 m were established for soil (0-15 cm depth) and forest floor sampling along three slope positions. This amounted to 120 quadrants at the montane forest and 60, in the lowland forest. Soil and forest floor samples were geo-referenced using global positioning system. Univariate statistics, including normality check, non-spatial outlier detection and data transformation were performed on test variables, followed by variography and kriging analyses to quantify spatial variability. Results showed that spatial structure of test variables differed across topographic positions and within the lowland forest. Surface maps showed distinct spatial clustering and displayed acceptable accuracy of interpolated values. Soil C stocks were highest in the summit, followed by toeslope, sideslope and Jengka Virgin Jungle Reserve. Site specific management for carbon sequestration monitoring in tropical forest should be based on topographic delineation

Spatial variability of forest floor thickness for estimation of refined carbon stocks in a tropical montane forest

Spatial variations of forest floor thickness in tropical montane forest influences carbon stocks estimates in forest floor and soil, microbial decomposition and soil conservation. Delineation of forest floor thickness according to decomposing layers (litter, hemic, sapric) and total forest floor will provide refined measurements of forest floor carbon stocks to improve site-specific carbon management. This study was aimed at determining spatial variability of the depths of decomposing forest floor layers in a tropical montane forest at varying topography. Sampling grids (10 m × 10 m) were established along three slope positions (summit, sideslope and toeslope) with 120 quadrants and their depths measured. Forest floor samples were georeferenced using a global positioning system. Variables were first explored using univariate statistics, including normality check, non-spatial outlier detection and data transformation. Variography and kriging analyses were used to quantify spatial variability of forest floor depths. Results showed that spatial structure of test variables differed across topographic positions. The coefficient of variation for test variables ranged from 27 to 64%. Surface maps displayed distinct spatial clustering and acceptable accuracy of interpolated values. Hemic and total forest floor were highest at the toeslope where hemic constituted approximately 80% of total forest floor. Site-specific management of forest floor carbon stocks in tropical montane forest should be based on topographic delineation

Effects of three rainfall patterns on soil chemical properties in black pepper cultivation in a hilly topography

This study was conducted to determine the effect of the rainfall pattern on cation nutrients in black pepper cultivation in a hilly topography. A field study was conducted in black pepper cultivation in a hilly topography around Bintulu, Sarawak, Malaysia, with a 26o slope during the Northeast monsoon in 2020. Six blocks were established on 462.56 m2, with four subsequent soil samples (0-20 cm) collected per block after the rainfall. Soil samples were analysed using the standard pH, total organic carbon (TOC), soil texture, total nitrogen (TN), available phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and manganese (Mn) in triplicate. Rainfall pattern (October December) affects TN (300.31-1422.90 mg/kg) and K availability (13.54-166.68 mg/kg), especially during peak season in November 2020. Available P, Ca, Mg, Fe, and Mn exhibit minimum rainfall effect but are closely related to combined interaction with parent material and topography. Therefore, proper soil management, such as applying fertiliser using top dressing, foliar spray, and manure amendment, including growing cover crop, is recommended to improve nutrient availability

Leaf litter decomposition and soil carbon dioxide fluxes across climatic gradient in tropical montane and lowland forests

Leaf litter decomposition and soil respiration are of great interest in climate change studies due to their roles in recycling carbon and nutrients. These processes can be markedly different in tropical montane and lowland forests. Litterbag technique was used to determine the decomposition and nutrient dynamics of leaf litter in two different tropical forest types in Pahang, Malaysia for 480 days. Soil CO2 fluxes were measured periodically for up to 360 days. Mass loss, total C, N, S, P, K, Mn, lignin, cellulose as well as C:N and lignin:N dynamics of decaying leaves were quantified. Various mathematical models and regression analysis were used to describe litter mass loss trends. Rapid decomposition (k: -0.004 day-1) and weight loss (> 80%) took place in the lowland forest compared with the montane forest. Significant linear regression relationships between mass loss and litter quality were obtained for all sites except for cellulose (montane forest). Low soil CO2 fluxes (two to three folds) and 38% slower decomposition due to reduced soil and air temperatures were found in the montane forest, suggesting its role as potential temporary C sink. Decomposition rate, C:N, lignin:N and soil respiration can be used as potential indicators to predict C balance in forests

Mudflats to marvel: soil health of a successfully restored mangrove coastline in Sungai Besar, Selangor

Mangrove forest plays an important part in our ecosystems. Mangroves functions include coastline protection, marine produce, firewood, charcoal production and for the conservation of floral and faunal species. This unique ecosystem is under tremendous stress due to erosion, excessive anthropogenic activities and natural disasters such as tsunamis. The coastlines of Malaysia have witnessed drastic decline in the recent years whereby 29% of the Malaysian coastal areas were reported to be vulnerable to serious erosion (Wan Rasidah et al., 2015). In order to restore this vulnerable ecosystem, efforts have been undertaken by replanting of mangrove seedlings and placing geotubes to control soil erosion and accretion. Geotubes are intended to slow erosion along coast line, breakwater and to provide some protection to mangrove seedlings. It consists of permeable geotextile fabric folded and sewn together and hydraulically filled with dredged sand (Shin et al., 2002). Since the installation of geotubes, we monitored the soil physical and chemical properties of an old growth mangrove forest and a newly regenerating mangrove stands over the years. This paper highlights the important changes that took place from 2007 to 2017 in an established mangrove and a newly regenerating mangrove plots which have been restored

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

Phosphogypsum Organic, a Byproduct from Rare-Earth Metals Processing, Improves Plant and Soil

Phosphogypsum organic (PG organic) is a soil conditioner, derived from residues, water leach purification (WLP) and neutralisation underflow (NUF) from rare-earth metals processing in combination with composted organic material. There was no report available with regards to the effectiveness of this byproduct for crops improvement in a sandy soil texture. Therefore, a field trial involving a multi-crop was conducted by the addition of PG organic on a sandy texture soil for 23-month period. Guinea grass or guinea grass intercropping with teak wood trees, corn and kenaf showed an improvement in cumulative fresh yield in plot treated with PG organic either with a half- or full-fertilizer recommended rate for the respective crop as compared to control. The same trend was also observed in teak wood trees in hole planting systems and pandan coconut seedlings in the polybags. Application of PG organic in each season showed a consistently higher cumulative fresh yield or yield for certain crop types due to soil ability to maintain the soil pH buffering capacity (pH 5.8–6.0). Therefore, the application of PG organic as soil conditioner promotes plant growth and development due to the improvement of soil condition by creating suitable ecosystem for nutrients absorption by roots