Much of the present coastal plains in the Malay Peninsula were inundated by seawater some 6,000 years ago. That was the time when pyrite is believed to have been mineralized in the sediments of the seawater. This paper attempts to explain the process of pyrite mineralization in the coastal sediments during the Holocene as well as to show how pyrite oxidation affects plants and aquatic life in their vicinity. At that point in time, the sea level was 3-5 meters above the present level. Under reduced conditions, Fe3+ ions existing in the sediments were reduced to Fe2+ ions, while SO42- anions from seawater were reduced to S2- ions. These reactions were promoted by microorganisms feeding on the organic matter provided by native vegetation. Finally, the ferrous and polysulfide ions reacted to form pyrite (FeS2). Over the years, this pyrite accumulated in the sediments, occurring at varying depths. In some sediment of the coastal plains of the Malay Peninsula, there are considerable amounts of pyrite; however, they are environment-friendly. When the areas are developed for agriculture or otherwise, this pyrite is exposed to atmospheric conditions, resulting in its oxidation which in turn leads to acidity and the formation of yellowish jarosite [KFe3(SO4)2(OH)6]. Toxic amounts of Al and Fe are usually present in the soils and water in the area, affecting crop growth and aquatic life.
Keywords: Acid sulfate soil, aluminum, Holocene, jarosite, Malay Peninsula, pyritization
This study aimed to characterize, classify and evaluate the agricultural potentials of soils formed from the beach ridge sands parent material in the Niger Delta area of Akwa Ibom State, Nigeria. Three toposequences were used as study sites. Along with each toposequence, three profile pits were studied – one at the crest, middle slope and valley bottom. Results of laboratory analysis and fertility capability classification (FCC) showed that the soils were predominantly sandy in texture, strongly acidic (pH 3.3-4.3) and low in the following fertility parameters – organic matter content (1.00-1.28%), total nitrogen (N) (0.043-0.057%), effective cation exchange capacity (ECEC) (2.38-6.02 cmolc kg-1), base saturation (56-71%), exchangeable K (0.038-0.090 cmolc kg-1) and available phosphorus (P) (4.60-13.12 mg kg-1). Based on Soil Taxonomy, soils in the area belonged to two soil orders – Entisols (44.4%) and Inceptisols (55.6%). Also, results of land suitability evaluation (LSE) revealed the land to be marginally suitable (S3) for oil palm, rubber and upland rice cultivation, moderately suitable (S2) for cocoa and cashew and highly suitable (S1) for coconut cultivation. Major crop production constraints were soil physical characteristics (texture/structure) and fertility. To raise land productivity, management techniques should include application of organic fertilizers to enhance nutrient holding capacity of the soils and supply deficient basic cations. Regular soil testing for proper fertilizer application to ensure a balance nutrient application is also recommended.
Keywords: Agricultural potential, beach ridge sands, Niger Delta, Nigeria, soil characteristics
The effect of different soil management practices on soil structure was studied in a vineyard. In 2006, an experiment of the different management practices in a productive vineyard (Leptosol) was established in Nitra-Dražovce (Slovakia). The following treatments were established: 1. control (grass without fertilization), 2. T (tillage), 3. T+FM (tillage+farmyard manure), 4. G+NPK3 (grass+NPK 120-55-195 kg ha-1), 5. G+NPK1 (grass+NPK 80-35-135 kg ha-1). The results showed that the highest value of the critical level of soil organic matter was seen in the G+NPK3 treatment. In the tilled treatment (T), the highest vulnerability of the soil structure was observed. The application of nutrients in G+NPK1 had a negative influence on the content of water-stable micro-aggregates. However, higher doses of fertilization (NPK 120-55-195 kg ha-1) had a positive effect on the decrease in water-stable micro-aggregates. Overall, G+NPK3 (NPK 120-55-195 kg ha-1) gave the best improvement in the structure of the soil.
Keywords: Crusting index, Leptosol, soil management, soil structure, vineyard
Ecological factors, which are the basis for the calculation of soil erosion, are included in the simulation model. Social aspects, such as the attitude of farmers towards practising environmentally sustainable land use techniques, are difficult to analyse because of lack of data and the level of difficulty inherent in connecting natural, economic, and social data together. At the level of the river basin, the use of an IntErO model allowed the quantification of the environmental effects of erosion and the land use planning measures. Maximal outflow (incidence of 100 years) from the river basin Qmax, is 240 m3/s suggests the possibility of a large flood. The strength of the erosion process was medium, and the erosion type was mixed erosion. The predicted soil losses were 645 m3/km2 per year. To support the faster renewal of the vegetation and slow down the erosion processes, biological protection measures need to be applied, together with technical ones, notably by using shoulders and ditches to partition water fluxes at the land surface. These would reduce runoff velocity and further support reforestation and the renewal of grass, shrubs and trees.
Keywords: IntErO model, land use, runoff, soil erosion, watershed
Industrial wastes and mining related activity are main sources of zinc contamination in soils and groundwater. The quality of soil, crop and water will also be affected by high concentrations of heavy metals. The adsorption behaviour of clinoptilolite (natural Iranian zeolite) and clinoptilolite-tridymite (Chinese zeolite) at different pHs has been studied in order to find out its applicability in agriculture as soil amendment. To elucidate zinc adsorption, batch experiment at constant pH was used. The mineralogical composition, specific surface area and CEC, were investigated by X-ray diffraction (XRD), BET-N2 sorption analysis and Na-acetate method, respectively. The data indicate that Iranian and Chinese zeolites contained 93.21%, 58.83% Clinoptilolite-Na, respectively, but high amount of tridymite (28.04%) was also present in the Chinese zeolite. The Zn sorption isotherm data for both Iranian zeolite and Chinese zeolite were fitted to the Langmuir and Freundlich models. The sorption results at different pH showed that sorption at constant pH=5 and 7 can best be fitted to the Langmuir equation. It was found that qmax of Iranian zeolite was higher than Chinese zeolite at both pHs. According to the findings, the binding strength of Zn adsorption in Chinese Zeolite was 0.01, 0.03 (L mg-1) at pH 5 and pH 7 whereas KL for the Iranian zeolite was 0.02 (L mg-1) at both pHs. It is revealed that the affinity of Chinese zeolite for zinc adsorption was higher at pH=7. The results indicate that the zinc desorption percent at highest loading rates for Iranian zeolite were 36.1%, 41.5%, while for Chinese zeolite were 45.81%, 36.3% at pH value 5 and 7, respectively.
Keywords: Zeolites, soil amendment, zinc, pH study
The transformation of biochar on tropical peat is yet to be studied as all previous studies have been conducted on mineral or forest soils. The objectives of this study were to investigate the physical and chemical changes experienced by pineapple stump biochar (PSB) in tropical peat and to determine the short-term decomposition model of PSB in a C-rich environment. Elemental composition was determined using CHNS-O analyzer and surface area with Brunauer-Emmett-Teller (BET) method. Surface chemistry and structural study were conducted with Fourier Transform Infrared (FTIR) spectroscopy and 13C solid state Nuclear Magnetic Resonance (NMR) spectroscopy, respectively. The PSB short-term decomposition was conducted with a litter bag study and best fitted into the hyperbolic decay model compared to exponential decay model because no significant mass loss was detected after 4 months. The stagnant phase was probably due to interaction with metals from peat. Redox reaction was prominent on the surface and structural chemistry. Surface oxidation of PSB produced more O-functionalities (hydroxyl, carboxylic and phenolic) and achieved chemical recalcitrance after 12 months. The carbon structure was reduced or saturated causing a decrease in electronegativity. Further PSB decomposition probably depends on biotic decomposition.
Keywords: FTIR, hyperbolic decay model, litter bag study, NMR, organic C
Copper (Cu) plays a key role in plant physiological and biochemical function but is harmful to plants when in excess. Copper availability is influenced by the mineralogical and chemical properties of soils. High Cu concentration is prominent in soils where vegetables are grown intensively with routine application of fertilizers and pesticides. A factorial pot experiment was carried out to determine Cu critical concentration and toxicity threshold for Brassica rapa as well as its soil phase association in Oxisol, Inceptisol and Histosol. Copper sulphate was applied at rates of 0, 5, 10, 15, 20, 30 and 60 mg Cu kg-1 soil. The soil Cu critical level in Oxisol, Inceptisol and Histosol was 5.42, 4.67 and 7.79 mg kg-1, respectively; and threshold toxicity level was 12.69, 13.00 and 21.33 mg kg-1, respectively. Height of plants decreased by 50% at a rate of 15 mg Cu kg-1 soil for Oxisol and Inceptisol, and at 30 mg kg-1 for Histosol. The SPAD value of plant leaves also decreased as the Cu application rate increased starting at 15 mg kg-1 in Oxisol and 20 mg kg-1 in Inceptisol. The amount of Cu in different soil fractions for both Oxisol and Inceptisol applied with Cu at a rate of 60 mg kg-1 was in the order of organic > residual > Fe/Mn oxides > carbonates > exchangeable > water soluble. This study indicated that at 60 mg Cu kg-1, Oxisol had a higher ability to retain Cu in the carbonate, Fe/Mn oxides and organic-bound fractions whereas in Inceptisol, the highest Cu amount was in the residual fraction.
Keywords: Brassica rapa, copper, critical level, phase association, toxicity level, tropical soils
Most studies on biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) evaluate the degradation potential of indigenous microorganisms in either liquid or solid media. There are limited studies on evaluation of the same microorganisms in degrading PAHs under non-indigenous condition in both liquid or solid media. This study investigated the potential of the bacteria, Corynebacterium urealyticum isolated from municipal sludge in degrading phenanthrene in both liquid and solid media. The study also evaluated the performance of the strain when subjected to low and high initial concentration of PAHs. Batch experiments were conducted over 20 days in reactors containing artificially contaminated phenanthrene minimal media and sand slurry inoculated with a bacterial culture. Phenanthrene degradation in liquid culture and sand slurry were found to be 82.15% and 27.71%, respectively. The degradation activity of bacteria in liquid culture remained active throughout the duration of the experiment, but this was not the case in the sand slurry. A significant difference was observed in the amount of phenanthrene remaining in the sand slurry when the bacteria was inoculated into the low and high phenanthrene concentrations. Percentages of phenanthrene remaining for both initial concentrations in liquid culture were not significant. From the bacteria growth curve plotted through viable count analysis, it was observed that the bacteria could immediately adapt to PAH-contaminated sand and had better capability to degrade phenanthrene in liquid culture compared to sand slurry.
Keywords: Biodegradation, Corynebacterium urealyticum, liquid cultures, phenanthrene, sand slurry