Mineralogy and physico-chemical properties of pyritic soils from three sites along the coastal plains of Kelantan, Peninsular Malaysia were studied. The aim of the study was to identify the variability and principal components of soil properties in this area. Soil sampling was conducted at three sites, stretching from North (Bachok) to south (Pasir Puteh) of the plains. Soil samples were taken from different depths at each site based on the presence of pyritic evidence. Soil physico-chemical properties were determined using standard laboratory methods while X-ray diffraction and SEM-EDX were carried out to determine the shape and stages of pyrite disintegration. Soils with sulfidic materials were found to be sporadically distributed throughout the plains, exhibiting different properties and distribution with depth. The soils with a sulfidic materials layer close to the soil surface had pH values below 3.5. Based on principal component analysis (PCA), the variables of all sites could be classified into three components, namely, soil pH, soil nutrients and organic matter content, which accounted for 83% of the site variability. The different dominant controlling factors in soil variables among the studied sites suggest that acid sulfate soils occurring in the area may have embraced many distinctive features even if they occur close to each other. This is a result of the multiple complex reactions after the sea level rose 3–5 m above the present level many thousands of years ago. Generally, the productivity of the soils in the area is low due to the occurrence of excessive acidity and the presence of toxic amounts of Al in the soils.
Keywords: Acid sulfate soils, principal component analysis, pyrite, acidity, soil productivity
Sweet potato is the most important food crop after wheat, rice, maize and cassava. Soil compaction degrades soil by altering its structure and aggregate, thereby causing poor plant-water relationship. This study aimed to determine the effect of soil compaction on some soil physical properties and eco-physiological characteristics of sweet potato. Prior to planting and after harvest, soil bulk density and moisture content were determined. For the eco-physiological measurements, the treatments tested were assembled in a factorial combination of three levels of soil compaction as main plots and three varieties in the sub-plots. The treatments were arranged in a split plot design and replicated four times. Gas exchange parameters, leaf area index and chlorophyll content were subsequently determined. The results showed that soil compaction significantly decreased plant chlorophyll content, leaf area index and gas exchange parameters. On tropical sandy loam soils, tilling the soil once was sufficient for optimum emergence and establishment of a sweet potato. Gendut proved to be a tolerant variety, suitable to be planted in environments prone to compaction stress.
Keywords: Bulk density, compaction, physiology, soil and sweet potato
This study was conducted to determine the mobility and availability of Cd, Zn and P to oil palm seedlings and their soil phase association (water soluble, exchangeable, carbonate, Fe-Mn oxide, organic and residual fractions) after the soil was applied with a phosphate rock fertiliser and amended with palm oil mill effluent (POME) or lime. The potential of these amendments in reducing Cd uptake by oil palm seedlings from phosphate rock fertiliser application was also investigated. Four rates of POME (0, 5, 10 and 20 t/ha) and lime (0, 2, 4 and 8 t/ha) were applied on a Jawa Series soil (Sulfic Endoaquepts) planted with 3-month-old oil palm seedlings until the 9th month. In lime amended soil, 65% of Cd in the soil was in the immobile phase and Cd content in the root decreased with increasing rates of lime application. Meanwhile, application of POME sludge amendment resulted in 44% of Cd being in the mobile fraction and 56% in the immobile phase. The mobile fractions, which comprised the exchangeable and water soluble fractions, were found to increase with increasing POME sludge rates. However, there was no influence on the Cd content in plant parts. Application of POME sludge also increased Zn content in roots and leaves as exchangeable Zn fraction also increased with increasing application rates. As for P, the content increased in all plant parts as a result of POME sludge application. Cadmium in the soil was dominant in the mobile fraction (exchangeable), while Zn and P were dominant in the immobile fractions (residual and organic, respectively) after being amended with POME and lime. Thus, lime was found to be a better amendment in reducing Cd uptake from PR fertiliser application in comparison to POME.
Keywords: Sequential fractionation study, potential acid sulfate soil, phosphate rock fertiliser, heavy metals, alkaline mineral and biosolid amendments
Briquette compost (BC) was made from water mimosa (Neptunia prostrate Lam.) which grows in the swampland rice fields. Factorial Randomised Block Design (FRBD) was used with the placement of BC as the first factor and BC dosage as the second factor. The placement of compost was one BC at 1 dosage for 1 plant clump with the BC being placed inside soil and rice seedling planted above it (BC1) and the second placement was one BC applied at the middle of four plant clumps, so 4 dosages were combined into one BC because this was for 4 clumps as (BC2). The second factor was application of BC at rates of 0, 10, 20 and 30 ton ha-1 for both treatments. Regression analysis showed that placement and dose of BC significantly correlated with absorbed N, tillers, productive tillers and rice yield. Placement of BC under plant roots gave better results than placement of BC in the middle of four plant clumps. The best combination was between BC1 and a dosage of 20 ton ha-1 which produced a rice yield of 1,014 g m-2 (or 10.14 ton ha-1). This yield was 175% higher compared with the control plot (586.73 g m-2 or 5.867 ton ha-1). The higher rice yield in BC1 compared to BC2 was due to plants being better able to absorb nutrients from BC straight away compared to BC2 where the plant roots needed a longer time to elongate and reach the BC placed in the middle of the four plant clumps. Meanwhile, nitrogen could have been lost before the roots reached the location where the BC was placed. Our study suggests that it is better to form the compost into a BC and insert it into the soil under a plant clump for direct absorption by the roots.
Keywords: Briquette compost, nitrogen, dosage, rice, swampland
Chromobacterium violaceum is a pathogenic soil bacterium that produces violacein and several types of antibiotics which are active against amoebae, trypanosomes, and Gram-positive and Gram-negative bacteria. The production of antibiotics is controlled by a quorum sensing system with a signal molecule called homoserine lactone (C6-HSL). In both methods (interaction and non-interaction), C. violaceum which reached quorum level produced antibiotics and killed all the selected PGPR (Azospirillum brasilense Sp7, Rhizobium UPMR1102 and Bacillus sphaericus UPMB10) but did not kill the selected PGPR in concentration below their quorum level. This study indicates that quorum sensing is involved in the effect of C. violaceum on selected PGPR and has the potential to threaten the use of PGPR in agriculture.
Keywords: Chromobacterium violaceum, Plant Growth-Promoting Rhizobacteria (PGPR), quorum sensing
Increasing mercury (Hg) accumulation in soil deteriorates cultivated soils, decreases growth and yield of plants, and contaminates the food chain. Therefore, the main objective of this study was to evaluate the effects of three Hg levels (0, 75 and 150 mg l-1) in a saline soil with and without Pseudomonas putida (PTCC 1696) on the growth parameters of the turnip plant. Pots were filled with 3 kg of saline soil (EC: 8.65 dS m-1) and inoculated with Pseudomonas putida. Turnip (Brassica rapa L.) seeds were sown in all the pots. After 10 days, the soils were treated with either 0, 75 or 150 mg l-1 of Hg until the final Hg concentrations in soil were either 0, 75 or 150 mg/kg. The pots were arranged in a completely randomised design in a greenhouse. After 60 days of planting, soluble sugars, chlorophyll a (Chla), chlorophyll b (Chlb) and catalase enzymes (CAT) in leaf samples were determined while fresh and dry weights of roots and shoots and Hg concentrations in turnip were determined 70 days after sowing. The results showed that inoculated soils produced plants with higher soluble sugars, Chla, Chlb; (are Chla and Chlb the same as Chla and Chlb) fresh and dry weights of roots and shoots were also significantly higher perhaps due to improved nutrients uptake from the stressed soil. At the same time, CAT and total Hg concentrations in the roots and shoots were reduced probably due to efficient nutrient uptake even when Hg was present. The addition of Pseudomonas putida to saline soil contaminated with Hg alleviated salinity and Hg toxicity stress of the turnip plants. In conclusion, Hg polluted saline soil inoculated with Pseudomonas putida (PTCC 1696) was efficient in increasing the quality and quantity of turnip plants and improving soil health compared to the non-inoculated soil.
Keywords: Mercury, salinity, plant photosynthetic pigments, bacterium inoculation
Wheat is the major cereal crops in Pakistan and inoculation of beneficial microbes plays a major role in crop growth enhancement. This study was conducted to evaluate bacteria with potential to contribute to enhanced plant nutrient uptake and wheat growth. A total of 10 bacterial strains, isolated from the wheat crop, were characterised. The results showed that selected isolates were able to produce Indole-3-acetic acid (IAA) and biofilm, fix atmospheric nitrogen and solubilise inorganic phosphate. However, NIA-2 and NIA-5 were the most efficient among the isolated bacteria in regard to N2-fixation, biofilm production, P-solubilisation (57.32 and 45.38%) and IAA production (4.28 and 3.49 mg L-1). A pot study was conducted on wheat crop to investigate the effect of NIA-2 and NIA-5 isolates with full NP fertilisers (120 kg N ha-1 in the form of urea, 90 kg P2O5 ha-1 in the form of DAP) and at half rates of NP fertilizers (60 kg N ha-1 in the form of urea, 45 kg P2O5 ha-1 in the form of DAP). The highest plant height (34.49 cm) and root length (10.38 cm) were observed in half NP fertiliser application inoculated with NIA-5 inoculated treatments. Similarly, the highest plant dry biomass (1.270 g plant-1) was recorded in half fertiliser application inoculated with NIA-5. All bacterial inoculated treatments showed the existence of microbes in the soil after 45 days of sowing. Nevertheless, the highest bacterial population was recorded in half NP fertiliser with NIA-05 (5.560 log CFU g-1 soil). Significantly highest plant nitrogen (1.344%), phosphorus (0.697%) and potassium uptake (0.310%) were observed in half NP fertiliser with NIA-05. Overall, the half rate of the NP fertiliser inoculated with bacterial isolate NIA-5 improved nutrient uptake and growth of the wheat crop. Thus, this study suggests that these bacterial isolates might be used as an inoculum for enhancing plant growth by supplying plant nutrient and phytohormones.
Keywords: Bacterial population, inoculation, plant uptake, potential, wheat growth inoculation
Arbuscular mycorrhizal fungi are a fundamental contributor to soil carbon mineralisation and nutrient cycling in saline soils. This study aimed to evaluate the interactions between arbuscular mycorrhizal fungi (Glomus mosseae) (G), tea residue (T), macroalgae biomass (M) and its subsequent effects on carbon mineralisation, actinomycetes counts,nutrients content, chlorophyll content, and corn growth (Zea Mays L.).T wenty four pots with eight treatments, control (C), macroalgae (M), tea residue (T), Glomus mosseae (G), Glomus mosseae + macroalgae (G+M), Glomus mosseae + tea residue (G+T), macroalgae+ tea residue (M+T) and Glomus mosseae + tea residue+ macroalgae (G+T+M) were randomly distributed in the field using randomised complete design (RCD). Results showed that only treatment T had the highest value of carbon mineralisation (0.216 mg C g-1 soil day), while it was lower (0.177 mg C g-1 soil day) in the G+T treatments. Additionally, the highest values of actinomycetes, chlorophyll, phosphorous content and roots weight were 4.2 10-6 CFU g-1, 35 SPAD, 0.4% and 55 g, respectively in G+T treatments. In contrast, the addition of T, M and G alone did not increase phosphorous content as compared to the control. In conclusion,the combination of tea residue and macroalgae biomass with Glomous mossea affected carbon decomposition and increased the number of actinomycetesas as well as nutrients content. This can be beneficial to ecosystems through facilitating carbon conservation and microbial diversity in arid saline soils.
Keywords: Mycorrhizae, carbon mineralisation, actinomycetes, roots, chlorophyll content, nutrients content
Bio fertilisers are relatively safer, environmentally friendly and a cost-effective approach to chemical fertiliser usage. The selection of bacterial strains with multiple beneficial characteristics is important to maximise their effectiveness on the host plant. In the present study, four native and indigenous rhizobial strains (VM-2, VM-8, VM-9 and VM-15) were isolated from root nodules of blackgram (Vignamungo) cultivated in fallow rice soils of Andhra Pradesh, India. All the four strains were screened in vitro for their plant growth-promoting (PGP) characteristics viz. production of indole acetic acid (IAA), exopolysaccharide (EPS), hydrogen cyanide (HCN) and phosphate solubilisation. The results indicated that the rhizobial strains varied in their plant growth promoting activities. All the four strains produced IAA, EPS and also solubilised the insoluble phosphate. The amount of IAA produced varied from strain to strain and relatively high amounts were recorded in VM-8 (43.4 µg/ml) followed by VM-15 with 43.1 µg/ml. Maximum EPS production was recorded in VM-9 (527 mg/ml) followed by VM-8 (483 mg/ml). The phosphate solubilisation efficiency of Rhizobium strains on solid media ranged between 16% and 17%. In liquid medium, strain VM-2 recorded maximum solubilisation (799 µg/ml) followed by VM-8 (372 µg/ml). All the strains except strain VM-8 were HCN producers. Among these three strains, VM-2 and VM-15 showed strong HCN production. These isolates were identified as Rhizobium sp. strain VM-2 (KJ 704783), Brady rhizobium sp. strain VM-8 (KJ 704784), Brady rhizobium sp. strain VM-9 (KJ 704785) and Achromobacter sp. strain VM-15 (KJ501696) after 16S rRNA sequencing. The pot culture experiment showed that VM-8, VM-9 and VM-15 inoculated plants had good results both in inoculated sterilised and inoculated unsterilised soils than the plants grown in sterilised uninoculated soils and control soils. The VM-2 strain showed moderate results under plant inoculation test. This study suggests that these four native rhizobial strains of PGP can be used as bio fertilisers as well as a bio control agent for enhancing the yield of blackgram in rice fallows.
Keywords: Rice fallows, black gram, plant growth promoting characteristics
As an alternative to the application of commercial synthetic fertilizers on land, composted organic wastes can be applied as organic fertilizer for crop production. This is a more viable waste-management system based on ‘resource recovery’ strategy. We compared applications of 0, 30, 60 and 90 tons (dry weight) per acre of composted organic waste with application of commercial inorganic fertilizers containing equivalent amounts of nitrogen over three growing seasons in northern Guam soils. In season 1 (dry season), the yield from plots receiving compost (compost plots) was not significantly higher (p = 0.05) than the plots receiving synthetic fertilizer (fertilizer plots). In season 2, when no compost was applied (for residual effect) but inorganic fertilizer application was continued, the 60- and 90-ton per acre compost applied plots showed a significantly higher yield than control (0-ton compost) plots. However, fertilizer plots performed better than compost plots overall. During season 3 (rainy season), on the other hand, compost was reapplied, as was the inorganic fertilizer. The 90-ton compost plots showed higher yields than equivalent fertilizer plots. Soil organic matter contents of all compost plots were also statistically higher than those of fertilizer plots throughout the study.
Keywords: Calcareous soils, maize, compost, soil organic matter, soils of Guam