Papers by Christopher Teh
The development and use of a soil water model to predict the soil water flow and content under oi... more The development and use of a soil water model to predict the soil water flow and content under oil palm would be useful as a tool for more effective oil palm water management. Although many soil water models exist, none of them has been specifically developed, applied, and validated for oil palm. Consequently, the purpose of this study is to develop and validate such a model. Water flow was modelled following a one-dimensional " tipping bucket " system, and the soil profile was divided into several soil layers where the soil water and hydraulic characteristics for each layer were estimated based on the soil carbon content and soil texture. Darcy's law was applied to estimate the various soil water fluxes. The soil water model included algorithms to estimate the root water uptake and water stress response by oil palm. Raw data of measured soil water content for several soil depths (up to 90 cm) from two studies (Moraidi et al., 2015; Nur Farahin, 2013) were obtained, so that the accuracy of the soil water model could be validated by comparing simulations of soil water content with measured values. The model was satisfactorily accurate, showing similar daily trend as that observed for the measured soil water content. Goodness-of-fit indexes further indicated that the model simulations showed little to no overall model bias and with an average absolute prediction error of only 10%. Future work is to increase model accuracy by estimating the daily actual evapotranspiration instead as assumed constant in this study.
American Journal of Agricultural and Biological Sciences, 2009
Problem statement: Intercropping has been shown to have many advantages but it is fallacious to c... more Problem statement: Intercropping has been shown to have many advantages but it is fallacious to conclude it is always a better cropping system. Little is known about a new doublehedgerow intercropping of rubber, banana and pineapple in relation to its effects on growth and yield of the component crops when compared to their monocrops. Simulation modeling offers a cheaper and faster alternative to explore cropping scenarios and estimate their productivity under a wide range of management and environmental conditions. This simulation study was therefore undertaken to evaluate the growth and yield of immature rubber, banana and pineapple intercrop and monocrop scenarios with the aid of an intercrop simulation model named SURHIS, as well as estimating the intercropping advantage. Approach: A FORTRAN computer model (SURHIS) that simulated the daily light interception and utilization by immature-rubber, banana and pineapple intercropping system was used to simulate intercrop and monocrop scenarios to estimate potential Dry Matter Yield (DMY) for all crops as well as fruit yields for banana and pineapple. The results of the model were tested for accuracy by comparing actual field experimental results with the aid of Mean Deviation (MD) and Mean Absolute Error (MAE) statistical analyses. Intercropping advantage was assessed using the Land Equivalent Ratio (LER) analysis. Results: The model was representative or predicted DMY of the crops with sufficient accuracy. The LER analysis showed that the intercropping system had a dry matter yield productivity advantage of 81% more than monocrops of the component crops. The results also showed that the higher the Plant Population Density (PPD), the greater is the dry matter yield. It was also shown that banana and pineapple had no deleterious effect on the growth of rubber. Fruit weight per plant of banana and pineapple was reduced with increase in PPD for the monocrops. Measured average fresh fruit bunch weight for banana was 18 kg plant −1 and the average fresh fruit weight per plant for pineapple was 2.1 kg for the intercropping system. Conclusion: Intercropping of banana and pineapple with immature-rubber is more productive than the component crops grown as monocrops in their respective optimum plant population densities per hectare. The model can be useful for predicting potential productivity, with sufficient accuracy, of the afore-mentioned intercropping system under varying plant density and environment scenarios as well as acting as a guide for plant density experimentation.
Australian Journal of Crop Science, 2014
Irrigation frequency is one of the most important factors in the management of water in the agric... more Irrigation frequency is one of the most important factors in the management of water in the agriculture sector to sustain crop productivity, especially in arid and semi-arid regions of the world. Additionally, fertilizers have to be adequately applied. An experiment was carried out under a rain shelter from July to December 2012 in Malaysia to determine the effects of irrigation frequency and fertilizer sources on the growth and yield of sweet corn planted on a limed sandy clay, Ultisol, using a drip-irrigation system. This experiment was conducted using a split-plot design with four drip-irrigation frequencies (daily, once every 2 days, once every 3 days and once every 4 days) and four sources of fertilizers (NPK, goat manure, poultry manure and control). The drip irrigation was the main plot, while fertilizers were the subplot factors. The results of the study indicated that total dry matter and yield components increased with the increase in drip-irrigation frequency with values of 44% and 32% respectively. The highest growth parameters and shoot dry weight were recorded from daily irrigation intervals with goat manure, while the highest yield components were obtained from daily irrigation frequency with NPK fertilizer and poultry manure. In the light of these results, therefore, for optimum biomass of corn, high irrigation frequency with goat and poultry manure is the most viable option while yield was greatly favoured by a high irrigation frequency with NPK.
Pertanika Journal of Tropical Agricultural Science
Silt pit is one of the recommended soil water conservation practices in oil palm plantations.
Journal of Food Agriculture and Environment
Application of adequate fertilizers becomes one of the most important agronomic practices to sust... more Application of adequate fertilizers becomes one of the most important agronomic practices to sustain corn production on soils of the tropical regions, which are mostly acidic and poor in nutrients. An experiment under rain shelter was conducted at the Faculty of Agriculture, Universiti Putra Malaysia, Serdang to evaluate the influence of different NPK fertilizer rates on the biomass and yield components of sweet corn. The experiment was carried out using split plot design with four replications. Three drip irrigation frequencies as a main plot: [Once in 2 days (Ir1), once in 3 days (Ir2) and once in 4 days irrigations (Ir3)] and four NPK fertilizer rates as sub-plot [0:, henceforth referred to as F1, F2, F3 and F4, respectively] were tested in this experiment. The results of the study showed that total dry matter significantly (P<0.05) increased with increase in the irrigation frequencies. For Ir1 treatments at F4 fertilizer rate, the shoot dry weight was higher compared to the o...
Journal of Geographic Information System, 2012
Validity of CA-Markov in land use and cover change simulation was investigated at the Langat Basi... more Validity of CA-Markov in land use and cover change simulation was investigated at the Langat Basin, Selangor, Malaysia. CA-Markov validation was performed using validation metrics, allocation disagreement, quantity disagreement, and figure of merit in a three-dimensional space. The figure of merit, quantity error, and allocation error for total landscape simulation using the 1990-1997 calibration data were 5.62%, 3.53%, and 6.13%, respectively. CA-Markov showed a poor performance for land use and cover change simulation due to uncertainties in the source data, the model, and future land use and cover change processes in the study area.
Journal of Water Resource and Protection, 2014
There is still very little information on the sources of water absorbed by oil palm plant. This i... more There is still very little information on the sources of water absorbed by oil palm plant. This information is very important for water management system in oil palm plantation. Thus, this study was carried out to determine current water sources absorbed by the oil palm roots using oxygen (δ 18 O) and deuterium isotopes (δD) techniques. Sketches of oxygen and deuterium isotope were total rainfall, throughfall, runoff, measurement at 5 soil depths (namely: 20 cm, 50 cm, 100 cm, 150 cm, and 200 cm), and oil palm stem. Results of this study showed huge variance in the values of oxygen and deuterium isotope. Based on Least Significant Difference (LSD) test, there was no significant value in the oxygen and deuterium isotope of stem water and others; however, a similar value was obtained at the depths of 0 -20 cm and 20 -50 cm with the stem water. This indicated that oil palm absorbed water from 0 -50 cm depth. This result agreed with the oil palm rooting system, which has verified that the root quarter is the most active root of oil palm.
The main objectives of this study were to determine the physical changes in oil palm empty fruit ... more The main objectives of this study were to determine the physical changes in oil palm empty fruit bunches (EFB) and EFB mat (Ecomat), which were used as soil mulching materials, during their decomposition in the field, as well as to compare the soil water content under these mulches and with bare soil. A field experiment was conducted at an estate using ten-year-old oil palm trees. Experimental design was a Randomized Complete Block with two treatments (EFB and Ecomat) and three replications. EFB was applied at 1000 kg palm-1 as a single layer on the soil surface. Ecomat was applied as a single layer with an area of 4 m2. Physical properties of EFB and Ecomat, measured every two month for six months, were bulk density, water content, water retention, and saturated hydraulic conductivity. Soil water content up to 750 mm depth was further measured on a daily basis. Results showed that EFB was better than Ecomat as a mulching material to conserve soil water. As compared to Ecomat, EFB had a lower bulk density (two times less dense), higher saturated hydraulic conductivity (about two times higher) and higher water content (between 20 to 57% more water). EFB was also found to hold its water more strongly than Ecomat. On average, the soil under EFB mulches had, nearly 27% more water than the soil under Ecomat mulches, and 38% more than bare soil. The soil under Ecomat mulches had only 8% more water than bare soil on average. Based on the model simulations, 5 layers of Ecomat would conserve as much soil water as 1 layer of EFB. Both mulching materials were estimated to fully decompose in the field in about 9 months.
Pertanika J. Trop. Agric. Sci., 2016
Hypothetically, leafy vegetables need water and nitrogen (N) simultaneously in their applications... more Hypothetically, leafy vegetables need water and nitrogen (N) simultaneously in their applications for good growth. Therefore, this study was conducted to determine the effects of four watering frequencies (watering once a day, once a week and once in every two weeks and no watering) and five levels of nitrogen (0, 34, 68, 136 and 272 kg N ha-1) on the vegetative and yield parameters of choy sum over a period of four weeks. The choy sum was grown in polyethylene bags under a rain shelter. The experimental design was a split-split plot with four replications. Plant vegetative and yield parameters measured weekly were plant height, leaf number, total leaf area, maximum root length, the various plant part weights and total tissue nitrogen. Water stress detrimentally affected choy sum's leaf growth more than root growth and the effect of water stress was more than nitrogen stress. Higher nitrogen rates in water-stressed condition increasingly reduced the number of leaves and height of the choy sum. Choy sum grown under once-a-day watering and once-a-week treatments did not experience water stress. The optimal soil water content and nitrogen application rate were 0.4 m 3 m-3 and 30 to 40 kg N ha-1 , respectively. The rate of 34 kg N ha-1 and once-a-week watering treatment generally gave the highest values for all the measured vegetative and yield parameters. Under lower and point of sufficient nitrogen rates, nitrogen was used for leaf thickness and weight rather than for intercepting light via leaf area expansion.
Agronomy Journal, 2012
In Malaysia, four soil conservation practices are oft en recommended for non-terraced oil palm (E... more In Malaysia, four soil conservation practices are oft en recommended for non-terraced oil palm (Elaeis guineensis Jacq.) plantations. Th ese practices are oil palm empty fruit bunches (EFB), Ecomat (a compressed EFB mat; ECO), and pruned oil palm fronds. Th ese three oil palm residues are used as organic mulching materials. Th e fourth method is silt pits (SIL) which are soil trenches to collect nutrients from runoff water and later redistribute them back into the soil. Nonetheless, the relative eff ectiveness of these four methods in improving soil and oil palm properties have never been studied. A 3-yr fi eld experiment was consequently conducted to determine their relative eff ects on increasing soil chemical properties (pH, cation exchange capacity, organic C, total N, available P, and exchangeable K, Ca, and Mg) and oil palm nutrition levels (N, P, K, Ca, and Mg). Biomass decomposition rate and nutrients release rate in the fi eld by the three mulching materials were also determined. Results showed that EFB mulching was signifi cantly better than the other three soil conservation practices in improving nearly all of the measured soil and plant parameters. Empty fruit bunches was most eff ective partly because of the combined eff ects of higher amounts of dry matter added and the higher nutrient concentrations in the EFB than in other mulching materials. Silt pitting was found not to be as eff ective as EFB because SIL could only trap and return nutrients back into the soil, whereas EFB could do both: trap nutrients and release additional nutrients into the soil as it decomposes.
Soil and Tillage Research, 2015
Water and Environment Journal, 2012
The impacts of land use/cover changes (LUCC) on a developed basin in Malaysia were evaluated. Thr... more The impacts of land use/cover changes (LUCC) on a developed basin in Malaysia were evaluated. Three storm events in different intensities and durations were required for KINEROS2 (K2) calibration and LUCC impact analysis. K2 validation was performed using three other rainfall events. Calibration results showed excellent and very good fittings for runoff and sediment simulations based on the aggregated measure. Validation results demonstrated that the K2 is reliable for runoff modelling, while K2 application for sediment simulation was only valid for the period 1984-1997. LUCC impacts analysis revealed that direct runoff and sediment discharge increased with the progress of urban development and unmanaged agricultural activities. These observations were supported by the NDVI, landscape and hydrological trend analyses. bs_bs_banner Water and Environment Journal. Print
Hydrological Sciences Journal, 2014
The Hulu Langat basin, a strategic watershed in Malaysia, has in recent decades been exposed to e... more The Hulu Langat basin, a strategic watershed in Malaysia, has in recent decades been exposed to extensive changes in land-use and consequently hydrological conditions. In this work, the impact of Land Use and Cover Change (LUCC) on hydrological conditions (water discharge and sediment load) of the basin were investigated using the Soil and Water Assessment Tool (SWAT). Four land-use scenarios were defined for landuse change impact analysis, i.e. past, present (baseline), future and water conservation planning. The land-use maps, dated 1984, 1990, 1997 and 2002, were defined as the past scenarios for LUCC impact analysis. The present scenario was defined based on the 2006 land-use map. The 2020 land-use map was simulated using a cellular automata-Markov model and defined as the future scenario. Water conservation scenarios were produced based on guidelines published by Malaysia's Department of Town and Country Planning and Department of Environment. Model calibration and uncertainty analysis was performed using the Sequential Uncertainty Fitting (SUFI-2) algorithm. The model robustness for water discharge simulation for the period 1997-2008 was good. However, due to uncertainties, mainly resulting from intense urban development in the basin, its robustness for sediment load simulation was only acceptable for the calibration period 1997-2004. The optimized model was run using different land-use maps over the periods 1997-2008 and 1997-2004 for water discharge and sediment load estimation, respectively. In comparison to the baseline scenario, SWAT simulation using the past and conservative scenarios showed significant reduction in monthly direct runoff and monthly sediment load, while SWAT simulation based on the future scenario showed significant increase in monthly direct runoff, monthly sediment load and groundwater recharge.
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Papers by Christopher Teh