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A significant wastewater source in every household is washed rice water (WRW) because it contains leached nutrients (from washing the rice prior to cooking) that could be used as fertilizer. The paper reviewed the current understanding of the potential use of WRW as a plant nutrient source. WRW was shown to increase vegetables growth, such as water spinach, pak choy, lettuce, mustard, tomato, and eggplant. Different researchers have used various amounts of WRW, and their results followed a similar trend: the higher the amount of WRW, the higher the plant growth. WRW has also been used for other purposes, such as a source of carbon for microbial growth. WRW from brown rice and white rice had nutrients ranging from 40-150, 43-16306, 51-200, 8-3574, 36-1425, 27-212, and 32-560 mg L-1 of N, P, K, Ca, Mg, S, and vitamin B1 (thiamine), respectively. Proper utilization of WRW could reduce chemical fertilizer use and prevent both surface and groundwater contamination and environmental pollution. However, only a few of the studies have compared the use of WRW with the use of conventional NPK fertilizer. The major drawback of WRW studies is that they lack depth and scope, such as determining the initial and (or) final soil physico-chemical properties or plant nutrient contents. Considering the rich nutrient content in WRW, it will impact plant growth and soil fertility when used as both irrigation water and plant nutrient source. Therefore, it is recommended that studies on WRW effect on soil microbial population, plant, and soil nutrient contents to be carried out to ascertain the sustainability of WRW use as a plant nutrient source.

A significant wastewater source in every household is washed rice water (WRW) because it contains leached nutrients (from washing the rice prior to cooking) that could be used as fertilizer. The paper reviewed the current understanding of the potential use of WRW as a plant nutrient source. WRW was shown to increase vegetables growth, such as water spinach, pak choy, lettuce, mustard, tomato, and eggplant. Different researchers have used various amounts of WRW, and their results followed a similar trend: the higher the amount of WRW, the higher the plant growth. WRW has also been used for other purposes, such as a source of carbon for microbial growth. WRW from brown rice and white rice had nutrients ranging from 40-150, 43-16306, 51-200, 8-3574, 36-1425, 27-212, and 32-560 mg L-1 of N, P, K, Ca, Mg, S, and vitamin B1 (thiamine), respectively. Proper utilization of WRW could reduce chemical fertilizer use and prevent both surface and groundwater contamination and environmental pollution. However, only a few of the studies have compared the use of WRW with the use of conventional NPK fertilizer. The major drawback of WRW studies is that they lack depth and scope, such as determining the initial and (or) final soil physico-chemical properties or plant nutrient contents. Considering the rich nutrient content in WRW, it will impact plant growth and soil fertility when used as both irrigation water and plant nutrient source. Therefore, it is recommended that studies on WRW effect on soil microbial population, plant, and soil nutrient contents to be carried out to ascertain the sustainability of WRW use as a plant nutrient source.

The under-utilized legume Mucuna bracteata is a potential biomass resource in Malaysia. A 24-month study was conducted under 10-year-old mature oil palm trees to determine the effects of several harvesting frequencies of M. bracteata on the legume biomass and soil properties. The experimental design was a randomized complete block design (RCBD) for the biomass and a two-factorial RCBD for the soil properties. The treatments were the harvesting frequencies, which were once every two, four, six, and twelve months. The control treatment was without harvest. There were significant effects on the legume’s cumulative biomass, standing biomass, leaf area, nutrient contents, and total nutrient harvested for N, Ca, Mg, and cellulose content. Generally, the more frequent the harvest, the more biomass was obtained, but the more legume standing biomass and leaf area were reduced. Despite the reduction in legume growth and leaf area in the field, harvesting the legume did not affect any of the soil physicochemical properties. The biomass N, Ca, and Mg contents and nutrient harvested were also affected by harvesting. This was due to the production of relatively more young shoots after harvesting, which would remove most of the aboveground plant parts. The cellulose content in the legume also increased for the same reasons. Results showed that harvesting M. bracteata once every six months was an acceptable compromise between collecting large amounts of legume biomass and having a reduced legume growth recovery and leaf area in the field, but yet not detrimentally affecting the soil properties.

The under-utilized legume Mucuna bracteata is a potential biomass resource in Malaysia. A 24-month study was conducted under 10-year-old mature oil palm trees to determine the effects of several harvesting frequencies of M. bracteata on the legume biomass and soil properties. The experimental design was a randomized complete block design (RCBD) for the biomass and a two-factorial RCBD for the soil properties. The treatments were the harvesting frequencies, which were once every two, four, six, and twelve months. The control treatment was without harvest. There were significant effects on the legume’s cumulative biomass, standing biomass, leaf area, nutrient contents, and total nutrient harvested for N, Ca, Mg, and cellulose content. Generally, the more frequent the harvest, the more biomass was obtained, but the more legume standing biomass and leaf area were reduced. Despite the reduction in legume growth and leaf area in the field, harvesting the legume did not affect any of the soil physicochemical properties. The biomass N, Ca, and Mg contents and nutrient harvested were also affected by harvesting. This was due to the production of relatively more young shoots after harvesting, which would remove most of the aboveground plant parts. The cellulose content in the legume also increased for the same reasons. Results showed that harvesting M. bracteata once every six months was an acceptable compromise between collecting large amounts of legume biomass and having a reduced legume growth recovery and leaf area in the field, but yet not detrimentally affecting the soil properties.

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.

Many net rainfall models have been developed, but they are often complex, data demanding and usable only for a specific vegetation type. The focus of this study was to develop and validate two simple equations (a two- and a three-coefficient equation) for nearly full canopies of oil palm, rubber and pine trees. Throughfall and stemflow data from seven past studies were used to determine the best-fit coefficients for the two equations. The three-coefficient equation was Pn = Pg x exp [- {0.3443 – (Pg / (58.9748 + Pg)} x 0.1639)] and the two-coefficient equation was Pn = 0.7724 x Pg – 0.5845 (R2 = 0.91), where Pn and Pg are the net and gross rainfall, respectively. To validate these two equations, field data collections were started. Thirteen rain gauges fit with data loggers were used for rainfall measurement. Three sampled trees were selected randomly for stemflow measurement and one rain gauge was installed at a nearby open area. Two error indices were used as a goodness-of-fit measure for equation accuracy: index of agreement and normalised mean absolute error. The results showed that the two- and three-equation equations performed nearly equally well. They predicted the net rainfall with an error of between 12 to 23% (ranked as "Fair" to "Good" in terms of overall equation accuracy) and with an index of agreement of more than 90%. The results showed that these two equations can be used fairly accurately to estimate throughfall and net rainfall, and, to a lesser degree, stemflow. Estimation errors occurred most probably because canopy and rainfall characteristics were not taken into account in the two equations.

Rubber seedlings raised in the soil-polybag system experience root coiling and restriction and the overhead sprinkler results in much water wastage. The objective of the study was to determine the influence of root trainers and three irrigation systems on rubber seedlings grown in a peat-based medium. The irrigation systems were the overhead sprinkler (SPR), drip (DRP) and capillary wick (WCK). The fourth treatment was the control (CTRL), which required growing rubber seedlings in conventional soil-polybags that were then irrigated using the wick system. The treatments were compared with one another in terms of their influence on nutrient loss, crop water productivity and water use efficiency, plant growth parameters and plant nutrient content of the rubber seedlings. A field experiment was carried out in a rain shelter for eight months, and data collection was carried out once per month. The experimental layout was the completely randomised block design. The results showed that WCK had the lowest cumulative leachate volume and the least cumulative nutrients leached. Both DRP and WCK had the highest plant growth parameters such as total fresh and dry weight, total leaf area and girth size, water productivity and leaf nutrient content. WCK was the best irrigation system together with the peat-based growing medium for raising rubber nursery seedlings.

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.

Many net rainfall models have been developed, but they are often complex, data demanding and usable only for a specific vegetation type. The focus of this study was to develop and validate two simple equations (a two- and a three-coefficient equation) for nearly full canopies of oil palm, rubber and pine trees. Throughfall and stemflow data from seven past studies were used to determine the best-fit coefficients for the two equations. The three-coefficient equation was Pn = Pg x exp [- {0.3443 – (Pg / (58.9748 + Pg)} x 0.1639)] and the two-coefficient equation was Pn = 0.7724 x Pg – 0.5845 (R2 = 0.91), where Pn and Pg are the net and gross rainfall, respectively. To validate these two equations, field data collections were started. Thirteen rain gauges fit with data loggers were used for rainfall measurement. Three sampled trees were selected randomly for stemflow measurement and one rain gauge was installed at a nearby open area. Two error indices were used as a goodness-of-fit measure for equation accuracy: index of agreement and normalised mean absolute error. The results showed that the two- and three-equation equations performed nearly equally well. They predicted the net rainfall with an error of between 12 to 23% (ranked as "Fair" to "Good" in terms of overall equation accuracy) and with an index of agreement of more than 90%. The results showed that these two equations can be used fairly accurately to estimate throughfall and net rainfall, and, to a lesser degree, stemflow. Estimation errors occurred most probably because canopy and rainfall characteristics were not taken into account in the two equations.

Rubber seedlings raised in the soil-polybag system experience root coiling and restriction and the overhead sprinkler results in much water wastage. The objective of the study was to determine the influence of root trainers and three irrigation systems on rubber seedlings grown in a peat-based medium. The irrigation systems were the overhead sprinkler (SPR), drip (DRP) and capillary wick (WCK). The fourth treatment was the control (CTRL), which required growing rubber seedlings in conventional soil-polybags that were then irrigated using the wick system. The treatments were compared with one another in terms of their influence on nutrient loss, crop water productivity and water use efficiency, plant growth parameters and plant nutrient content of the rubber seedlings. A field experiment was carried out in a rain shelter for eight months, and data collection was carried out once per month. The experimental layout was the completely randomised block design. The results showed that WCK had the lowest cumulative leachate volume and the least cumulative nutrients leached. Both DRP and WCK had the highest plant growth parameters such as total fresh and dry weight, total leaf area and girth size, water productivity and leaf nutrient content. WCK was the best irrigation system together with the peat-based growing medium for raising rubber nursery seedlings.

Build a complete and working soil water model in either Python or Microsoft Excel. With this book, you will: understand how and why water flows in the soil and what factors affect its flow; how the soil water flow can be described as a set of mathematical equations; and how these equations can be implemented into a computer program in Python language and in Excel to simulate the vertical soil water flow. Fair knowledge in either Python or Excel is required to build the model (but knowledge in Visual Basic for Applications is not needed). Several scenarios are presented to describe how the model can be applied, and the simulation results for each scenario are discussed.

Build a complete and working soil water model in either Python or Microsoft Excel. With this book, you will: understand how and why water flows in the soil and what factors affect its flow; how the soil water flow can be described as a set of mathematical equations; and how these equations can be implemented into a computer program in Python language and in Excel to simulate the vertical soil water flow. Fair knowledge in either Python or Excel is required to build the model (but knowledge in Visual Basic for Applications is not needed). Several scenarios are presented to describe how the model can be applied, and the simulation results for each scenario are discussed.

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 sumfs 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 m3 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.

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 sumfs 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 m3 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.

Silt pit is one of the recommended soil water conservation practices in oil palm plantations. It is commonly regarded that the larger and deeper the silt pit, the more effective the pit would be to conserve soil water. This hypothesis was tested in this paper, where the effectiveness of four silt pit dimensions on conserving soil water in the oil palm active rooting zone was simulated using the HYDRUS 2D model. These silt pits had different sizes and total wet wall-to-floor area ratio (W:F): H1 silt pit (1x1x1 m of width, length, and depth, respectively, and W:F ratio of 4.0), H2 (1.5x1x1 and W:F of 2.5), H3 (2x1x0.5 and W:F of 1.5) and H4 (2×1×2 and W:F of 1.5). Simulations showed that silt pits with larger W:F ratios could store water for longer periods and feed water to a farther horizontal distance within the soil compared to silt pits with smaller W:F ratios. H1 took the longest to dry out, whereby it took 14 to 19 hours longer to dry out compared to than H2, H3 and H4. H1 and H3 could feed water as far as 80 cm away from the pit more than H2 and H4 (60 and 50 cm, respectively). This is because silt pits with larger W:F ratios had larger horizontal water flow than the vertical water flow. Meanwhile, the depth of a silt pit should not be below the oil palm active rooting depth, which water would flow out of reach by the roots. This study is a preliminary work to a field experiment where simulations from this paper would be validated against measurements obtained in the field before recommending the use of silt pits and their size to be constructed in oil palm plantations.

Silt pit is one of the recommended soil water conservation practices in oil palm plantations. It is commonly regarded that the larger and deeper the silt pit, the more effective the pit would be to conserve soil water. This hypothesis was tested in this paper, where the effectiveness of four silt pit dimensions on conserving soil water in the oil palm active rooting zone was simulated using the HYDRUS 2D model. These silt pits had different sizes and total wet wall-to-floor area ratio (W:F): H1 silt pit (1x1x1 m of width, length, and depth, respectively, and W:F ratio of 4.0), H2 (1.5x1x1 and W:F of 2.5), H3 (2x1x0.5 and W:F of 1.5) and H4 (2×1×2 and W:F of 1.5). Simulations showed that silt pits with larger W:F ratios could store water for longer periods and feed water to a farther horizontal distance within the soil compared to silt pits with smaller W:F ratios. H1 took the longest to dry out, whereby it took 14 to 19 hours longer to dry out compared to than H2, H3 and H4. H1 and H3 could feed water as far as 80 cm away from the pit more than H2 and H4 (60 and 50 cm, respectively). This is because silt pits with larger W:F ratios had larger horizontal water flow than the vertical water flow. Meanwhile, the depth of a silt pit should not be below the oil palm active rooting depth, which water would flow out of reach by the roots. This study is a preliminary work to a field experiment where simulations from this paper would be validated against measurements obtained in the field before recommending the use of silt pits and their size to be constructed in oil palm plantations.

Several existing aggregate stability indices are commonly used to represent aggregate stability of soil. Consequently, there is a need to determine how well these common indices characterize or represent aggregate stability. The main objective of this study was to use a multivariate statistical method called factor analysis to determine the effectiveness of eight common indices in measuring aggregate stability. Eighty soil samples (Oxisols and Ultisols) were taken from soil depth of 0-150 mm and from different land uses, such as oil palm, coffee, tea, rubber, pine, fallow, vegetables, and grassland. Aggregate stability of these soils were determined by wet-sieving and water dispersion of the primary particles. Eight aggregate stability indices were used: AIA (average fraction of intact aggregates), WSA >0.3 and >0.5 (water-stable aggregates larger than size 0.3 and 0.5 mm, respectively), MWD (mean weight diameter), CR (clay ratio), WDC (water-dispersible clay), WDCS (water-dispersible clay plus silt), and TP (turbidity percentage). The factor analysis showed that all the aggregate stability indices were related to two common factors, namely, aggregate breakdown resistance and dispersion. By determining how well an aggregate stability index is correlated to either one or both these common factors, the factor analysis ranked the effectiveness of the indices as follows: WSA >0.3 = WDCS > AIA > MWD > WDC > CR. Due to the fact that WSA >0.5 is correlated very strongly with WSA >0.3, both the indices ought to be as effective as the other. The TP index, however, had a questionable efficacy as an aggregate stability index. Based on the findings of this study, it was therefore concluded that only two indices, WSA >0.3 (or WSA >0.5) and WDCS, were sufficient to represent the whole soil aggregate stability.

x-library is a C++ object-oriented framework for modelling the partitioning of captured solar radiation and evapotranspiration in intercropping systems. The design and analysis of the x-library are done to ensure that the soil-plant-atmosphere system is categorised into classes, such as weather, microclimate, intercrop, crop, canopy, leaf, roots, soil, heat, and radiation. Meanwhile, x-library implements two kinds of solar radiation models; namely, one-dimensional (1-D), and two-dimensional (2-D) model, where irradiance varies in one dimension (vertical) and in two dimensions (vertical and horizontal), respectively. Radiation partitioning is based on weighting criteria so that a crop having the larger leaf area index and extinction coefficient would have greater share of captured radiation. Evapotranspiration partitioning is calculated using the Shuttleworth- Wallace equation. Model comparisons with a field experiment showed an overall good agreement between the simulated and measured solar radiation and transpiration values. A graphical user interface front-end for the x-library known as the x-model was also developed, primarily for non-modellers and non-programmers.

This study was carried out to determine the distribution of organic matter and its constituents, as well asother soil properties, in various aggregate size fractions for four soil types in Malaysia, and to investigate therelationship and relative importance of these soil properties on aggregate stability. The four soil series withcontrasting particle size distributions used were Munchong (Typic Hapludox), Melaka (Xanthic Hapludox),Rengam (Typic Paleudult), and Bungor (Typic Paleudult). The top soil, i.e. 0-15 cm of the soils of the four soilseries was sampled and analyzed for their particle size distribution, aggregation, aggregate stability, organicmatter, humic acids (HA), fulvic acids (FA), polysaccharides, functional groups of HA and FA (carboxylic,COOH, and phenolic-OH), and free Fe and Al oxides. Multiple linear regression revealed that silt, followedby free Fe oxides, fine sand, FA-OH, and HA-COOH, were the most important soil constituents to explainthe observed differences in the aggregate stability between the four soil types. Generally, as the aggregatesize decreased, the amount of clay, silt, OM, and free Fe oxides would also increase, while the aggregationand the amount of sand would decrease. As for the Rengam and Bungor series, the aggregate stability wouldgenerally increase with the decreasing aggregate size. Meanwhile, the observed differences in the amountsof HA, FA, and polysaccharides were mainly due to the differences in the soil types.

Several existing aggregate stability indices are commonly used to represent aggregate stability of soil. Consequently, there is a need to determine how well these common indices characterize or represent aggregate stability. The main objective of this study was to use a multivariate statistical method called factor analysis to determine the effectiveness of eight common indices in measuring aggregate stability. Eighty soil samples (Oxisols and Ultisols) were taken from soil depth of 0-150 mm and from different land uses, such as oil palm, coffee, tea, rubber, pine, fallow, vegetables, and grassland. Aggregate stability of these soils were determined by wet-sieving and water dispersion of the primary particles. Eight aggregate stability indices were used: AIA (average fraction of intact aggregates), WSA >0.3 and >0.5 (water-stable aggregates larger than size 0.3 and 0.5 mm, respectively), MWD (mean weight diameter), CR (clay ratio), WDC (water-dispersible clay), WDCS (water-dispersible clay plus silt), and TP (turbidity percentage). The factor analysis showed that all the aggregate stability indices were related to two common factors, namely, aggregate breakdown resistance and dispersion. By determining how well an aggregate stability index is correlated to either one or both these common factors, the factor analysis ranked the effectiveness of the indices as follows: WSA >0.3 = WDCS > AIA > MWD > WDC > CR. Due to the fact that WSA >0.5 is correlated very strongly with WSA >0.3, both the indices ought to be as effective as the other. The TP index, however, had a questionable efficacy as an aggregate stability index. Based on the findings of this study, it was therefore concluded that only two indices, WSA >0.3 (or WSA >0.5) and WDCS, were sufficient to represent the whole soil aggregate stability.

x-library is a C++ object-oriented framework for modelling the partitioning of captured solar radiation and evapotranspiration in intercropping systems. The design and analysis of the x-library are done to ensure that the soil-plant-atmosphere system is categorised into classes, such as weather, microclimate, intercrop, crop, canopy, leaf, roots, soil, heat, and radiation. Meanwhile, x-library implements two kinds of solar radiation models; namely, one-dimensional (1-D), and two-dimensional (2-D) model, where irradiance varies in one dimension (vertical) and in two dimensions (vertical and horizontal), respectively. Radiation partitioning is based on weighting criteria so that a crop having the larger leaf area index and extinction coefficient would have greater share of captured radiation. Evapotranspiration partitioning is calculated using the Shuttleworth- Wallace equation. Model comparisons with a field experiment showed an overall good agreement between the simulated and measured solar radiation and transpiration values. A graphical user interface front-end for the x-library known as the x-model was also developed, primarily for non-modellers and non-programmers.

This study was carried out to determine the distribution of organic matter and its constituents, as well asother soil properties, in various aggregate size fractions for four soil types in Malaysia, and to investigate therelationship and relative importance of these soil properties on aggregate stability. The four soil series withcontrasting particle size distributions used were Munchong (Typic Hapludox), Melaka (Xanthic Hapludox),Rengam (Typic Paleudult), and Bungor (Typic Paleudult). The top soil, i.e. 0-15 cm of the soils of the four soilseries was sampled and analyzed for their particle size distribution, aggregation, aggregate stability, organicmatter, humic acids (HA), fulvic acids (FA), polysaccharides, functional groups of HA and FA (carboxylic,COOH, and phenolic-OH), and free Fe and Al oxides. Multiple linear regression revealed that silt, followedby free Fe oxides, fine sand, FA-OH, and HA-COOH, were the most important soil constituents to explainthe observed differences in the aggregate stability between the four soil types. Generally, as the aggregatesize decreased, the amount of clay, silt, OM, and free Fe oxides would also increase, while the aggregationand the amount of sand would decrease. As for the Rengam and Bungor series, the aggregate stability wouldgenerally increase with the decreasing aggregate size. Meanwhile, the observed differences in the amountsof HA, FA, and polysaccharides were mainly due to the differences in the soil types.

The effectiveness of mulching materials, empty fruit bunches (EFB) and EFB mat (Ecomat) and the construction of soil trenches (silt pits) as soil water and nutrient conservation methods, have yet to be compared against one another in any single study. Moreover, as compared to the EFB studies, much less has been studied on the effectiveness of Ecomat and silt pit to improve soil properties and conserve water. Thus, this study was undertaken to compare the effects of the EFB, Ecomat, silt pit, and control (stacked pruned oil palm fronds) on several soil properties at soil depths of 0-150 and 150-300 mm, over a period of six months, at an oil palm estate with a hill slope of 6°. This study found that in just a period of six months, there were significant effects of the four treatments on the soil chemical and physical properties. Overall, the EFB was found to be the best treatment to improve the chemical properties of soil in both depths (CEC, Ca, Mg, K, P, C, and pH). However, both the EFB and Ecomat gave similar values for the soil available water content and aggregate stability. The mean daily total soil water content (up to 1 m depth) for the EFB, Ecomat, and control were found to be insignificantly different from one another, but silt pit had the statistically lowest total soil water content. The soil water distribution under the Ecomat mulches was rather uniform throughout the soil depths (up to 1 m), whereas in the EFB and silt pit treatments, the soil water tended to be concentrated at the upper soil layers until 0.6 m depth, with the concentration of water restricted to a shallower depth for silt pit as compared to the EFB. As for the control, water concentrated mostly below 0.5 m depth. This study is on-going, but the results have so far indicated that the EFB, followed by Ecomat, is the best soil and water conservation method, particularly to improving the chemical properties of soil. Ecomat, due to its lower nutrient content than EFB, generally did not impr

The effectiveness of mulching materials, empty fruit bunches (EFB) and EFB mat (Ecomat) and the construction of soil trenches (silt pits) as soil water and nutrient conservation methods, have yet to be compared against one another in any single study. Moreover, as compared to the EFB studies, much less has been studied on the effectiveness of Ecomat and silt pit to improve soil properties and conserve water. Thus, this study was undertaken to compare the effects of the EFB, Ecomat, silt pit, and control (stacked pruned oil palm fronds) on several soil properties at soil depths of 0-150 and 150-300 mm, over a period of six months, at an oil palm estate with a hill slope of 6°. This study found that in just a period of six months, there were significant effects of the four treatments on the soil chemical and physical properties. Overall, the EFB was found to be the best treatment to improve the chemical properties of soil in both depths (CEC, Ca, Mg, K, P, C, and pH). However, both the EFB and Ecomat gave similar values for the soil available water content and aggregate stability. The mean daily total soil water content (up to 1 m depth) for the EFB, Ecomat, and control were found to be insignificantly different from one another, but silt pit had the statistically lowest total soil water content. The soil water distribution under the Ecomat mulches was rather uniform throughout the soil depths (up to 1 m), whereas in the EFB and silt pit treatments, the soil water tended to be concentrated at the upper soil layers until 0.6 m depth, with the concentration of water restricted to a shallower depth for silt pit as compared to the EFB. As for the control, water concentrated mostly below 0.5 m depth. This study is on-going, but the results have so far indicated that the EFB, followed by Ecomat, is the best soil and water conservation method, particularly to improving the chemical properties of soil. Ecomat, due to its lower nutrient content than EFB, generally did not impr

The purpose of this study was to determine the accuracy of the Saxton-Rawls method in estimating the soil water characteristics of a wide range of mineral soils of Malaysia. This study found that it was necessary to calibrate the Saxton-Rawls method for the soils of Malaysia. The developed equation for calibration was Pti = a $ Pi ]1 - Pig, where Pi and Pi t are the uncalibrated and calibrated estimated values, respectively, for the soil sample no. i, and the parameter values of a were 2.225, 1.605, and 1.528 (for saturation, field capacity, and permanent wilting point) respectively. The calibrated method was validated against three independent soil data sets. The validation tests showed that the calibrated method remained stable and was more accurate than that without any calibration, by an average between 8 to 49%.

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.

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.

The purpose of this study was to determine the accuracy of the Saxton-Rawls method in estimating the soil water characteristics of a wide range of mineral soils of Malaysia. This study found that it was necessary to calibrate the Saxton-Rawls method for the soils of Malaysia. The developed equation for calibration was Pti = a $ Pi ]1 - Pig, where Pi and Pi t are the uncalibrated and calibrated estimated values, respectively, for the soil sample no. i, and the parameter values of a were 2.225, 1.605, and 1.528 (for saturation, field capacity, and permanent wilting point) respectively. The calibrated method was validated against three independent soil data sets. The validation tests showed that the calibrated method remained stable and was more accurate than that without any calibration, by an average between 8 to 49%.