Acid sulfate soils are widespread along the coastal plains of theMalay Peninsula, with some being cultivated with rice. Following farmers’ practices, rice yields are very low due to low pH and prevailing adverse condition such as Al and/or Fe toxicity. A study was conducted in a glasshouse to determine the effect of lime and fertilizer application in combination with water management on rice cultivated on an acid sulfate soil, using MR 219 rice variety as the test crop. The soil used was Typic Sulfosaprists. The results showed that soil pH increased from 4.27 to 4.93 by applying 4 t GML/ha, thereby reducing Al and/or Fe toxicity. In this treatment, exchangeable Ca increased from 1.28 to 3.13 cmolc/kg soil, which is above the rice Ca requirement. The increase in exchangeable Ca also reduced Al toxicity. Fertliser or fertiliser in combination with lime affected rice production significantly. Rice yield was negatively correlated with acid-extractable Fe. Additionally, rice yield increased with increasing pH and Ca. The best yield of 14.15 t/ha was obtained for treatment with 4 t/ha lime together with 120 kg N/ha + 16 kg P/ha +120 kg K/ha. This shows that liming together with prudent fertilizer management improves rice production on an acid sulfate soil.
Keywords: Rice, ground magnesium limestone, acid sulfate soil, aluminum, iron
Humic acids are commonly used to improve the aggregate stability of soils; however, it is not popular in this region. In this paper, low grade coal from Mukah was used as the source of nitrohumic acids and the effects of the nitrohumic acids on the aggregate stability of loamy sand (83.5% sand, 16.4% clay) and clay loam (31% sand, 37% clay) were investigated. Nitrohumic acids were prepared with nitric acid pretreatment and extracted with acid base fractionation. On loamy sand and clay loam, six application rates of nitrohumic acids (0.00, 0.05, 0.10, 0.50, 1.00 and 10.00 g/kg) and 5 wetting and drying cycles were used to assess the changes in the aggregate stability. Results showed that the aggregates stability of loamy sand was improved with nitrohumic acids amendment. For a clay loam sample, the aggregate stability was instead reduced. Nevertheless, there was an upper limit (0.10 g/kg) where the aggregate stability was improved or alleviated. In conclusion, the effect of nitrohumic acids on aggregate stability is dependent on soil type.
Keywords: Nitrohumic acids, low grade coal, aggregate stability, loamy sand, clay loam
The Malaysian cocoa industry is facingmany problems due to cocoa being grown on marginal soils, such as Ultisols and Oxisols. These soils are generally acidic, low in basic cations and also low in soil cation exchange capacity. A field study was undertaken to investigate the effect of organic- based and foliar fertilisers on soil fertility improvement, the growth of matured trees, yield and quality of cocoa grown on an Oxisol in Malaysia . The treatments (with four replications) consisted of T1: NPK (fertiliser) (control), T2: organic-based fertiliser + NPK. T3: foliar + NPK, T4: foliar + Ca-foliar + NPK and T5: organic-based fertiliser + foliar + Ca-foliar + NPK applied on approximately 5-year-old cocoa plants located at the Malaysian Cocoa Board Experimental Station, Jengka, Pahang. The results showed that the combination of these fertilisers gave negative response on the growth, yield and quality of cocoa. For clone PBC 130, T2 (organic-based fertiliser + NPK) gave greater pod weight compared to other treatments. Manganese toxicity is possibly the most limiting factor observed in this study.
Keywords: Organic based fertiliser, foliar fertiliser, cocoa yield, bean quality, Mn toxicity
Phosphorus (P) mobility in three P-fixing (laterite, red and sandy) sweetpotato soils in relation to inoculation with arbuscular mycorrhizal (AM) fungi Glomus microcarpum has been studied through a pot culture trial for two seasons. In all the inoculated soils, irrespective of season, the sweetpotato plants had a comparatively high rate of colonisation. However, increased P level in the soil tended to decrease colonisation. Percentage root colonisation increased with days after planting (DAP) while, the spore density in the root-zone soil decreased with DAP. Soil P availability varied between inoculated and uninoculated treatments and different soil types. In general, inoculated treatments showed a low soil P availability but the rate of removal of P from soil to plant tissue was more in mycorrhiza inoculated treatments in both the seasons and at different DAP. The rate of removal of P by mycorrhizal plants was maximum in laterite and sandy soils at all DAP. Mycorrhizal inoculation did not give any added benefit on soil P release and fixation in the soil types studied.
Keywords: AM fungi, G. microcarpum, P-fixing soil, P mobility, sweetpotato
The accumulation of Fe, Zn, Cu, Mn, Co md Pb in vegetables was investigated in two farmlands, Siburan and Beratok at Kuching,Sarawak. Leafy and fruit vegetable samples were collected and analysed for metal content using the acid wet digestion method. Topsoil samples (0-30 cm) were characterised for pH, organic matter, particle size, nitrogen content, phosphorus content and heavy metals. Leafy vegetables accumulated higher amount of metals compared to fruit vegetables. Metals were determined at the highest concentrations in leaves of kale at Beratok compared to other plant parts. No clear pattern of metal uptake in different parts was observed for green mustard and white mustard. Essential metals, Fe, Zn and Cu, were generally high in the vegetables. Pb levels in the vegetables analysed (dry weight basis) exceeded slightly the level recommended by the Malaysian food Act 1983. Atmospheric deposition and gas emissions from traffic were the contributing factors for Pb contamination since Pb displayed a tendency to accumulate in leaves compared to other parts of the vegetables. Element concentration in the soils differed between sampling sites. Correlation analysis yielded a significant relationship between Zn concentrations in soils and vegetables (n = 15, r = 0.86, P = 0.001) and moderate correlation for Cu (r =0.55, P < 005) and Pb (r = 0.65, P < 0.05).
Keywords: Metals, vegetables, soil, correlation
Tannery industries create serious environmental problems especially in terms of polluting organic effluent and hazardous solid waste as a result of hides and skin processing. It is very important that tannery waste in the form of sludge is managed in an environmentally sound manner. This study focuses on the characterisation of tannery sludge and its development as a composting material. The results show that electrolytic conductivity (EC) of the compost was 2.0 mS cm-1, pH 6.6 and C/N ratio of 16. Total concentrations of chromium, zinc, copper, lead, and cadmium in dry compost were reduced and complied with the standards of the Canadian limits, thus classifying them excellent for making the compost suitable for use as a fertiliser and soil conditioner. The compost characteristics indicated that it was mature, and the germination index for Chinese cabbage was 82.5%, which may suggest absence of phytotoxic compounds.
Keywords: Composting, tannery, sludge, pathogens, heavy metals, germination
Soil fractionation studies of heavy metals can provide insight into their solubility and chemical reactivity in terms of labile and non-labile pools of these metals. The fractionation of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) in domestic sewage sludge, soil, soil applied with (NH4)2SO4 and soil applied with sewage sludge was studied after the first and third maize cycles. The second cycle did not give significant yield results because of the dry period during this cycle. The correlation between different forms of heavy metals in the soil and content in maize grain was also investigated. Fractionation of heavy metals in sewage sludge showed that most soil metals were associated with the less soluble or non-labile soil moieties (carbonate, Fe-Mn oxides, organic and residual fraction). The dominant form of all heavy metals was the residual form (non-phytoavailable form) except for Cu. Leaving the residual fraction aside, Cd and Pb were dominant in exchangeable (labile pool) form, Ni in carbonate form and Zn in Fe-Mn oxide form. For the untreated and treated soils, the residual fraction was also the dominant fraction except for Cd and Pb. The organic form is the dominant form for Cu in sludge treated soil. In general, the percentage of water soluble content was less than 5%. Also, in general, there was no significant difference between the different metal fractions of the inorganic fertiliser treatment compared to the control, except for exchangeable Pb and Zn associated with Fe-Mn oxide fraction. The addition of sewage sludge tended to shift the solid phase forms of the metals away from the residual to the Fe-Mn oxide form. Significant correlations were only obtained between Cd content in maize grain and the organic forms in soil (n = 30, r = 0.378, and p < 0.05), Ni content in grain with total metal in the soil (n = 30, r = 0.406, p < 0.05) and between Cu content in maize grain and the carbonate. Fe-Mn oxide and organic forms in soils (n = 30, r = 0.475, p < 001; n = 30. r = 0.539, p < 0.01; and, n = 30, r = 0.545, p < 0.01, respectively).
Keywords: Sewage sludge, fractionation study, geochemical forms, labile and non-labile pool, correlation study