The response of choy sum (Brassica chinensis var. parachinensis) to water and nitrogen (N) stress is still uncertain and no growth and yield model exists specifically for this crop. Consequently, this study conducted a field experiment to determine the growth and yield of choy sum grown under several watering frequencies and N application rates. Measured crop parameters were then used to aid in the crop model development and in model validation. Choy sum growing under the once-a-day and once-a-week watering treatments did not experience water stress unlike the water-stressed choy sum grown under the once-every-two-weeks watering treatment. The optimal volumetric soil water content level and N application rate for maximum yield were determined to be 40% and between 30 to 40 kg N ha-1, respectively. Model validation showed that the choy sum model had an overall mean estimation error of 7.3% for leaves dry weight, 28.9% for stem dry weight, 28.9% for roots dry weight, 41.7% for leaf area index, and -0.8% for plant height. The model errors could be due to the assumption of an open-field energy balance growing environment and the lack of accuracy on the leaf area index estimation.
Keywords: Brassica, choy sum, drought, model, nitrogen fertilizer, water stress
Richards' equation was approximated by finite-difference solution and implemented in FORTRAN to simulate water infiltration profile of yolo light clay. The simulation was successfully validated by published data of Philip's semi-analytical solution. Global sensitivity analysis using Sobol' variance-based method was also coded in FORTRAN and implemented to study the effect of parameter uncertainty on model output variability. Sobol' sequences were used to generate quasi-random numbers to study the effect of every possible combination of different input parameters' values, based on each parameter's uncertainty range on model outputs. First order sensitivity index (Si) and total effect index (STi) were estimated based on quasi-Monte Carlo estimators. Various statistical parameters, coded in FORTRAN, such as kurtosis, skewness, 95% confident intervals, etc. were used to provide a better understanding and description of the model outputs. Results found parameter constants (β, B) and saturated volumetric water content (θs) of Haverkamp constitutive functions to be dominant parameters with a combined 93% of model variability which could be explained by these parameters. The total effect index for every parameter was found to be greater than the first order effect index. In addition, global sensitivity analysis tool was able to generate informative sensitivity indicators and a good statistical description compared to the local sensitivity tool.
Keywords: First order index, global sensitivity analysis, Haverkamp constitutive functions, Richards' equation, Sobol' variance-based method, total effect index, uncertainty analysis
The geochemistry of ophiolite related serpentinite soils has been one of the most challenging concerns among soil scientists and ecologists for several decades. Despite increasing global knowledge about the specificity of serpentinites, they have received limited attention in Malaysia. Considering the role of climate in the chemical composition of the derived soils, this study focused on tropical serpentinite soils in Malaysia. A total of 27 soil samples was collected from five serpentinite outcrops in Peninsular Malaysia and Sabah and analysed elementally. Based on their major oxide contents, the soils were divided into two groups of ‘rich in Fe’ and ‘rich in Mg’ which represent mature and immature soils, respectively. However, the most striking result that emerged from this study was the anomalous concentration of three trace metals of chromium, nickel and cobalt in the studied serpentinite soils in comparison with those of the adjacent sedimentary soils (soils of Crocker). The observed elemental ranges were Cr 2,427-27,863, Ni 850-4,753 and Co 35-167 (in µg g-1), while the ranges for these elements for the soils of Crocker formation were Cr 67-182, Ni 33-270 and Co 11-23 (in µg g-1). It is obvious that the amounts of Cr, Ni and Co in the studied serpentinites soils were 105, 15 and 6 times higher, respectively, than those in Crocker soils comparing with the Dutch List standard and Great London Council guidelines, serpentinite soils of Malaysia can be considered to be heavily contaminated with Cr, Ni and Co.
Keywords: Chromium, nickel, cobalt, geochemistry, serpentinite soils
Land use can have an impact on the physical and chemical properties of soils. The aim of this study was to identify and determine changes in soil physics-chemical properties of Andisols under three different land use profiles in the Mt. Sinabung area. These were: natural forest, perennial cropland with low-intensity cultivation, and annual cropland (horticulture) with high-intensity cultivation. Our findings show that differing land use profiles did not change soil classification, solum thickness, and effective depth of the Andisols of Mt. Sinabung. However, intensive cultivation of the Andisols resulted in the top soil having a more intense red colour and increased pH0 and Al-humus complex.
Keywords: Annual cropland, natural forest, perennial cropland, soil classification, volcanic ash
The radioactivity of environmental samples from sites and suspected of contamination must be analyzed before free access is given to the public. Towards this end, plant and corresponding soil samples were collected from two different locations of North- western parts of Dhaka (Savar and Manikganj) and the activity concentrations of natural radionuclides 226Ra (238U-chain), 228Ra (232Th-chain) and non-chained 40K were measured using gamma ray spectrometry. Soils of Savar contained more radioactive 40K than Manikganj whereas soils of Manikganj contained more 226Ra and 228Ra than Savar. The influence of certain soil properties on the activity concentrations and transfer factors (TF) of natural radionuclides were investigated by correlating the observed data with those of soil properties. The activity concentrations of 40K were much higher than those of 226Ra and 228Ra in plants for both locations due to higher uptake from soils. The transfer factors for 226Ra, 228Ra and 40K were found to range from 0.082 to 0.926, 0.153 to 0.563 and 1.274 to 3.741 at Savar and 0.087 to 0.455, 0.061 to 0.806 and 0.738 to 1.949 at Manikganj, respectively. The soil to plant transfer factors for 40K was found to be much higher in plants, which might be due to the essentiality of this element in plants. Our study showed that activity concentrations of these radionuclides in plants and their plant transfer factors seem to depend on the activity concentrations of the same radionuclides in soil.
Keywords: Activity concentrations, plants, soil, soil parameters, transfer factors
As plants grown in high pH soils usually suffer from nutrient deficiency, the present study was carried out to determine the influence of elemental sulphur as a soil acidulate on soil chemical properties and maize performance in a high pH soil of Malaysia. After 0, 20 and 40 days of soil incubation with different amounts of elemental sulphur (0, 0.5, 1 and 2 g S kg-1 of soil), maize plants were grown for 45 days under glasshouse conditions. Application of elemental sulphur at a rate of 0.5 g S kg-1 soil decreased soil pH value from the background level of 7.03 to 6.29 but significantly increased availability of Mn and Zn by 0.38% and 0.91%, respectively. This resulted in a 45.06% increase in total dry weight of maize. Further pH reduction due to the acidifying character of elemental sulphur at addition rates of 1 and 2 g kg-1 soil increased Mn and Zn availability, but significantly decreased maize performance. Overall, it can be concluded that when used in appropriate amounts, elemental sulphur can efficiently enhance soil fertility and maize performance by providing micronutrients for balanced fertilization.
Keywords: Mn and Zn, nutrient release, soil acidification
Rice yield grown on acid sulfate soils is very low because of Al3+ and/or Fe2+ toxicity. A study was conducted to determine the effects of applying ground basalt with or without organic fertilizer on the growth of rice. Results showed clear benefits of ground basalt as an amendment for acid sulfate soil infertility. The ameliorative effects were comparable with that of applying 4 t ground magnesium limestone (GML) ha-1; however, basalt had an additional advantage over GML as it contained K and P besides Ca and Mg. But as basalt needs time to disintegrate and dissolve completely in the acid sulfate soil under submerged conditions, the best option is to apply ground basalt in combination with organic fertilizers a few months ahead of transplanting rice in the field. The organic fertilizers would then be able to partly reduce Al and/or Fe in the soil via the chelation process.
Keywords: Acid sulfate soil, aluminum toxicity, basalt, iron toxicity, organic fertilizer, rice production
The vermicompost industry in Malaysia has grown rapidly in recent years. However, there is a lack of documentation on the quality of commercially available vermicomposts; moreover, there are no guidelines for the production of quality vermicomposts. Therefore, a trial was conducted in Universiti Putra Malaysia to convert sago pith waste into a value-added organic fertilizer through vermicomposting using cow, goat and horse dung manure as co-composting materials. Two types of sago pith waste vermicomposts were produced in Universiti Putra Malaysia and compared with fifteen different vermicomposts available in the market. The chemical characteristics of these vermicomposts were determined. Results showed that pH of the vermicomposts ranged from 4.5-6.5 indicating significant difference between the different feedstock. The macronutrients of the different vermicomposts varied greatly, that is, total N, total P and total K were 1.5-2.16, 0.54-1.89 and 0.39-1.73%, respectively. Humic acid concentration in the vermicomposts ranged from 16.7- 24%. Study results indicate that the chemical properties of the vermicomposts varied according to the type of initial feedstock and earthworms used and the vermicomposting procedure adopted.
Keywords: Agricultural waste, earthworms, vermicompost
Ultisols require greater amounts of fertilizer application compared to other soils. Unfortunately, the price of synthetic fertilizers has increased over time during the years, making them unaffordable for most Indonesian farmers. Over the last century, efforts to reduce reliance on synthetic agro-chemicals have recently focused on Tithonia diversifolia as a green manure alternative. Generally known by its common name of tree marigold or Mexican sunflower, this plant has attracted considerable attention for its prolific production of green biomass, rich in nitrogen, phosphorous and potassium (NPK). This outstanding feature and the plant’s capacity to solubilize soil P have recently been capitalized for improving the fertility of highly leached soils in Africa and particularly in Kenya. As microorganisms are expected to play an important role in biomass production and high nutrient uptake of this plant, this issue of importance was pursued further in the following investigation. The aim of this study was to determine the type of bacteria suitable for Tithonia cultivation as hedgerow plants in Ultisols which have higher biomass production and nutrient content. The field experiment was conducted with 5 treatments in a randomized block design (RBD) using 3 replications. The treatments were: without microorganisms inoculation or control (K); phosphate solubilizing bacteria (PSB) (L); Azospirillium (M); PSB + Azospirillium (N); and PSB + Azospirillium + Azotobacter (O). The bacterial substrates were inoculated into the Tithonia rhizosphere in the nursery. The young Tithoniaplants were then planted as hedgerow on Ultisols in the experimental field for 8 months, and pruned once every 2 months. The differences between treatments were statistically significant by HSD test at the 95% level of probability. Treatment L (phosphate solubilizing bacteria) was found to be the most effective, followed by treatment N (PSB +Azospirillum).
Keywords: Azospirillium, azotobacter, green manure, PSB, Tithonia hedgerow plants