The soil plant transfer coefficient or f factor of 14 C-carbofuran pesticide was studied in outdoor lysimeter experiment consisting of Brassica sp. vegetable crop, riverine alluvial clayey soil and Bungor series sandy loam soil. Soil transfer coefficients at 0-10 cm soil depth were 4.38 + 0.30, 5.76 + 1.04, 0.99 + 0.25 and 2.66 + 0.71; from 1X recommended application rate in alluvial soil, 2X recommended application rate in alluvial soil, 1X recommended application rate in Bungor soil and 2X recommended application rate in Bungor soil, respectively. At 0-25 cm soil depth, soil plant transfer coefficients were 8.96 + 0.91, 10.40 + 2.63, 2.34 + 0.68 and 6.19 + 1.40; from 1X recommended application rate in alluvial soil, 2X recommended application rate in alluvial soil, 1X recommended application rate in Bungor soil and 2X recommended application rate in Bungor soil, respectively. At 77 days after treatment (DAT), the soil plant transfer coefficient was significantly higher in riverine alluvial soil than Bungor soil whereas shoot and root growth was significantly higher in Bungor soil than in riverine alluvial soil. At both 0-10 cm Brassica sp. rooting depth and 0-25 cm soil depth, the soil plant transfer coefficient was significantly higher in 2X recommended application rate of 14 C-carbofuran as compared to 1X recommended application rate, in both Bungor and riverine alluvial soils.
Mineral elemental uptake by Colocasia esculenta growing in swamp agroecosystem was studied following 14, 18 or 28 months of field spraying (MAT, months after treatment) with herbicide Gramoxone ® (paraquat). In overall, Al (68226.67 + 24066.56 μg/g dw) was the major element in riverine alluvial swamp soil, followed by micronutrient Fe (22280.00 + 6328.87 μg/g dw).
Concentration of macronutrient K (20733.33 + 7371.82 μg/g dw) was the highest in swamp taro leaf followed by macronutrient Ca (7050.00 + 3767.26 μg/g dw). In overall, the order of importance of the average mineral concentration in swamp taro leaf was K > Ca > Mn > Al > Na > Fe > Zn > Br > Co. However at 14 MAT, the order of importance of mineral content concentration in swamp taro leaf was K > Ca > Al > Na > Mn > Fe > Zn > Br > Co. At 18 MAT, the order of importance of mineral content concentration in swamp taro leaf was K > Ca > Mn > Al > Fe > Na > Zn > Br > Co. At 28 MAT, the order of importance of mineral content concentration in swamp taro leaf was K > Ca > Mn > Fe > Al > Zn > Na > Br > Co. In overall, the average order of importance of mineral elemental uptake or the soil plant transfer coefficient was Mn > K > Na > Zn > Co > Fe > Al; similar with the order at 28 MAT. However, at 14 MAT the order of importance of the soil plant transfer coefficient was different at Mn > K > Na > Co > Zn > Al > Fe.
The adsorption equilibrium time and effects of pH and concentration of ¹⁴C-labeled chlorpyrifos
O,O-diethyl O-(3, 5, 6 trichloro-2-pyridyl)-phosphorothiote in soil were investigated. Two types of Malaysian soil under oil palm were used in this study; namely clay loam and clay soil obtained from the Sungai Sedu and Kuala Lumpur International Airport (KLIA) Estates, respectively. Equilibrium studies of chlorpyrifos between the agricultural soil and the pesticide solution were conducted. Adsorption equilibrium time was achieved within 6 and 24 hours for clay loam and clay soil, respectively. It was found that chlorpyrifos adsorbed by the soil samples was characterized by an initial rapid adsorption after which adsorption remained approximately constant. The percentage of ¹⁴C-labeled chlorpyrifos adsorption on soil was found to be higher in clay loam than in clay soils. Results of the study demonstrated that pH affected the adsorption of chlorpyrifos on both clay loam and clay soils. The adsorption of chlorpyrifos on both types of soil was higher at low pH with the adsorption reduced as the pH increased. Results also suggest that chlorpyrifos sorption by soil is concentration dependent.
The purpose of this study was to determine the adsorption coefficient (Koc) of chlorpyrifos in clay soil by measuring the Freundlich adsorption coefficient (Kads(f)) and desorption coefficient (1/n value) of chlorpyrifos. It was found that the Freundlich adsorption coefficient (Kads(f)) and the linear regression (r 2 ) of the Freundlich adsorption isotherm for chlorpyrifos in the clay soil were 52.6 L/kg and 0.5344, respectively. Adsoprtion equilibrium time was achieved within 24 hours for clay soil. This adsoprtion equilibrium time was used to determine the effect of concentration on adsorption. The adsorption coefficient (Koc) of clay soil was found to be 2783 L/kg with an initial concentration solution of 1 µg/g, soil-solution ratio (1:5) at 30 o C when the equilibrium between the soil matrix and solution was 24 hours. The Kdes decreased over four repetitions of the desorption process. The chlorpyrifos residues may be strongly adsorbed onto the surface of clay.
Effects of cultural practice under different habitats, of well-managed monoculture plantation and growing wild under rubber trees, were studied in Aquilaria malaccensis (Karas) leaves. This study was carried out on Karas growing in these two habitats each from Lipis, Pahang and Sepang, Selangor areas in Malaysia; under the control and induced treatments. The parameters studied include wet and dry weight of 50 matured leaves, iron and zinc elemental contents in leaf, iron and zinc uptakes from soil, and leaf and soil moisture contents. Iron and zinc were analysed in Karas leaves and soil by using Instrumental Neutron Activation Analysis (INAA) technique.
A study to determine the influence of soil water status on the physiology of rice plant Oryza sativa var. MR220 after panicle initiation stage was carried out at Ladang Merdeka Mulong Lating in the Kemubu Agricultural Development Authority (KADA) area, Kelantan. Five water management treatments imposed on direct seeded rice were; T1. Continuous flooding, T2. Early flooding up to panicle initiation stage followed by saturated (F55-saturated), T3. Early flooding for the first month followed by saturated (F-30 saturated), T4. Continuous saturated, and T5. Continuous field capacity condition throughout the growth stage. The treatments were arranged in Randomized Complete Block Design (RCBD) with four replicates. In-situ stomatal conductance measurement was carried out at 68 DAS (days after seeding) and the elemental analysis of soil and plant samples was carried out using the Instrumental Neutron Activation Analysis (INAA). Results from this study showed significant differences between treatments for soil moisture content and plant moisture content, but no significance different in leaf stomatal conductance. Rice plant moisture, soil moisture and leaf stomatal conductance showed no interaction. Early flooding up to panicle initiation stage followed by saturated (T2: F55-saturated) resulted in higher plant moisture content. Soil plant transfer coefficient was highest in continuous saturated (T4) for nitrogen, early flooding for the first month followed by saturated (T3: F-30 saturated) for potassium, continuous field capacity condition throughout the growth stage (T5) for magnesium, and continuous flooding (T1) for sodium.
Six varieties of Ficus deltoidea Jack (Moraceae) showed leaf morphological variations through quantitative measurement on different plant parts. There were significant differences among six varieties studied by plant parts. The varieties studied include var. deltoidea Corner, var. angustifolia (Miq.) Corner, var. trengganuensis Corner, var. bilobata Corner, var. intermedia Corner, and var. kunstleri (King) Corner. The upper, middle and lower plant parts showed morphological variations in terms of leaf length, leaf width, leaf area and petiole length. Qualitative parameters also showed trends in morphological variations in terms of leaf shape, leaf base, leaf apex and leaf attachment. However, some qualitative parameters were not the recommended parameters to differentiate among varieties. On the other hand, leaf heterophylly has occurred in F. deltoidea because foliage of the young plant was different from the mature plant. Leaf heterophylly was observed in leaf shape and leaf apex parameters, whereby leaves from the lower plant parts were different from the upper and middle parts. The heterophylly in leaf shape was detected in varieties angustifolia, bilobata, intermedia and trengganuensis, whilst six varieties of F. deltoidea showed leaf apex heterophylly
The mobility of (14)C-chlorpyrifos using soil TLC was investigated in this study. It was found that chlorpyrifos was not mobile in clay, clay loam and peat soil. The mobility of (14)C-chlorpyrifos and non-labelled chlorpyrifos was also tested with silica gel TLC using three types of developing solvent hexane (100%), hexane:ethyl acetate (95:5, v/v); and hexane:ethyl acetate (98:2, v/v). The study showed that both the (14)C-labelled and non-labelled chlorpyrifos have the same Retardation Factor (Rf) for different developing solvent systems. From the soil column study on mobility of chlorpyrifos, it was observed that no chlorpyrifos residue was found below 5 cm depth in three types of soil at simulation rainfall of 20, 50 and 100 mm. Therefore, the soil column and TLC studies have shown similar findings in the mobility of chlorpyrifos.