Organic Matter Amended Soils Research Articles

Alternate wetting and drying decreases arsenic content and increases yield of rice grown in organic matter amended soil

Organic matter (OM) shows a critical role in mobilization and uptake of arsenic (As) by rice, and water management practice can mitigate this problem. However, very few research highlighted the impact of management of water on rice as influenced by OM amendment. Therefore, this study has evaluated the changes in As mobilization in paddy soil under different OM amendment and water management practices. Here, rice was grown to maturity in a two-factorial pot experiment comprising two different water management practices [continuous flooding (CF) and alternate wetting drying (AWD)] and eight combinations of As and OM amendment [comprising two As treatments (0 and 20 ppm) and four OM amendments (0, 0.25%, 0.5% and 5.0% w/w)]. Application of OM in As contaminated soil caused a significant increase in As accumulation in rice, and exhibited decreased growth and yield of rice. However, the results showed that rice growth and yield was significantly higher under AWD practice compared to CF. Arsenic concentration in rice was the lowest in As and OM control pots (44.67 µg/kg in AWD and 62.13 µg/kg in CF), and higher in As treated pots. Moreover, As concentration in rice grain increased with increasing levels of OM amendment. The As concentration in rice grain (168.44 µg/kg in AWD and 183.85 µg/kg in CF) was significantly higher in As treated pots with 0.5% OM amendment compared to other treatment combinations. Application of 5% OM in As contaminated soil did not produce any grains due to extreme toxicity. Thus, As accumulation in rice can be decreased by AWD water management technique without compromising yield. The findings suggest that applying OM in paddy soils with high soil As content should be done with caution.

Assessing equilibria of organo-arsenic complexes and predicting uptake of arsenic by wheat grain from organic matter amended soils

In view of limited information, a laboratory experiment was conducted to study the stability of organo-arsenic complexes as affected by competing anions i.e. phosphate, nitrate and sulphate. For this purpose, humic acid (HA) and fulvic acid (FA) were extracted from farmyard manure (FYM), vermicompost (VC), sugarcane bagasse (SB) and soil. A pot experiment was also conducted with 4 levels each of arsenic (As) (10, 20, 30 and 40 mg kg−1) and amendments (no amendment, FYM, VC and SB at the rate of 10 t ha−1 each). Results indicate that stability of FA extracted from sugarcane bagasse have the highest stability constant (log K) as 9.77 and the corresponding mole ratio (x) value of 1.51. The phosphate was the most effective in replacing As from organo-As complexes followed by sulphate and nitrate. Under pot culture study, As content in wheat grain was the lowest in sugarcane bagasse amended soil followed by FYM and VC at all levels of As application. Solubility-free ion activity model was most effective in predicting As uptake by wheat grain based on Olsen extractable As, pH and Walkley & Black organic C. Efficacy of organic amendments in reducing health hazard for intake of As through consumption of wheat grain grown on contaminated soil was also reflected in the values of hazard quotient (HQ).

Solubility of arsenic and its uptake by ryegrass from polluted soils amended with organic matter

The study focused on suitability of ryegrass (Lolium perenne) for phytostabilization of As-polluted soils as well as on the effects of soil amendment with organic matter on the solubility of As. Four soil samples, containing 505–6500mg·kg−1 As, were collected from the areas of historical ore mining and processing in Złoty Stok and Radzimowice (Poland). Soils were amended with different organic materials, i.e. cattle manure (M), three kinds of variously treated sewage sludge (fresh SS1, digested and limed SS2, and composted SS3), and two kinds of forest litter (representative of pine and alder stands FL1, FL2). In a three-month incubation experiment, the changes of As concentrations in water extracts and As extractability with 0.01M CaCl2 were measured. After that time, a pot experiment with ryegrass was established. Soil amendment with all organic materials caused an initial increase in As solubility and extractability that decreased during incubation, but in most cases remained higher compared to untreated samples. Plant growth and As concentrations in plant roots and shoots depended both on soil properties and on the kind of amendment. Sewage sludge SS2 and forest litters caused adverse effects on plant growth, except for the least polluted soil 4, while application of M, SS1 and SS3 posed beneficial effects. Unlike As extractability, its uptake by ryegrass was reduced in organic matter-amended soils, particularly those treated with SS2 and SS3, which was reflected by an amendment factor AF. In spite of that fact, the concentrations of As in shoots of ryegrass grown in soils 1 and 2 were assessed as relatively high and often exceeded 50mg·kg−1. The effects of soil treatment with organic amendments on As phytoavailability to ryegrass turned out difficult to predict and therefore should be experimentally determined in each case of remediation.

Microbial Community Responses to Increased Water and Organic Matter in the Arid Soils of the McMurdo Dry Valleys, Antarctica.

The soils of the McMurdo Dry Valleys, Antarctica are an extreme polar desert, inhabited exclusively by microscopic taxa. This region is on the threshold of anticipated climate change, with glacial melt, permafrost thaw, and the melting of massive buried ice increasing liquid water availability and mobilizing soil nutrients. Experimental water and organic matter (OM) amendments were applied to investigate how these climate change effects may impact the soil communities. To identify active taxa and their functions, total community RNA transcripts were sequenced and annotated, and amended soils were compared with unamended control soils using differential abundance and expression analyses. Overall, taxonomic diversity declined with amendments of water and OM. The domain Bacteria increased with both amendments while Eukaryota declined from 38% of all taxa in control soils to 8 and 11% in water and OM amended soils, respectively. Among bacterial phyla, Actinobacteria (59%) dominated water-amended soils and Firmicutes (45%) dominated OM amended soils. Three bacterial phyla (Actinobacteria, Proteobacteria, and Firmicutes) were primarily responsible for the observed positive functional responses, while eukaryotic taxa experienced the majority (27 of 34) of significant transcript losses. These results indicated that as climate changes in this region, a replacement of endemic taxa adapted to dry, oligotrophic conditions by generalist, copiotrophic taxa is likely.

Effects of γ-irradiation of original and organic matter-amended soils on the sorption of triclosan and diuron from aqueous solutions

Soil γ-irradiation is a well-known method of inhibiting microbial activity in studies of the soil sorption of organic compounds. However, few studies have addressed the possible effect of γ-irradiation on the sorptive ability of soils enriched with different types of organic matter (OM). The objective of this study was to probe the effect of soil γ-irradiation on organic compound–soil interactions in two different situations representing adding OM to soils through land disposal of (a) OM-rich sewage sludge-originating biosolids and (b) olive mill wastewater (OMW). Both situations describe frequent environmental and agricultural scenarios. Comparisons of aqueous sorption on cobalt-60 γ-irradiated and non-irradiated soil sorbents were carried out for (a) triclosan (in a series of three soils and their lab-incubated mixtures with three different types of biosolids), and (b) the pesticide diuron (in two different untreated and OMW-affected soils). In each case, sodium azide was used as a biocide. Soil γ-irradiation affected the sorption of organic compounds by a factor generally not exceeding 2–3. Specifically, for triclosan, the sorbed concentration ratio between irradiated and non-irradiated soils when averaged over all the soil samples was 0.94. No significant effects of γ-irradiation on soil organic carbon or total nitrogen contents were observed. The effect of γ-irradiation on a soil sorbent may be less important when a rough estimate of a soil sorption coefficient of an organic compound is needed. However, it may need to be taken into account in mechanistic sorption studies, specifically, when the shape of sorption isotherms is of interest.

Bioremediation of Hydrocarbon Contaminated Soil Using Selected Organic Wastes

Traditionally soil remediation has been known to be among the most expensive treatments in the world. Thus, various strategies have been opted to investigate the most cost-effective solution to deal with contaminated sites. Among the highly potential approach is bioremediation since many studies have reported of its effectiveness in removing numerous pollutants from many contaminated sites. It mainly involved biostimulation where organic or inorganic components were introduced to enhance indigenous microbial growth that directly degrades the contaminants. This paper aims to identify potential organic wastes in enhancing the biodegradation of used lubricating oil in contaminated soil. To achieve the objective, sewage sludge and cow dung were selected as the organic components to be added individually into the 10% (w/w) used lubricant oil-contaminated soil. Each set up with 1.5kg of used lubricant oil-contaminated soil were added with 10% of the organic matter (sewage sludge or cow dung) and left for degradation for 98 days in plastic vessels. Periodic sampling of soil from each vessel was carried out at 14 days interval for total petroleum hydrocarbon analysis, and isolation and enumeration of bacteria. Results indicated that after 98 days of exposure to the organic matters, biodegradation of used lubricant in the soil were much higher than that of the control set-ups. Cow dung amended set-ups showed 94% biodegradation while sewage sludge amendment gave 82%, as compared to the control set-up (56%). This probably was due to the presence of additional nutrient in the organic matter amended soil which enhanced the indigenous microbes’ degradation capabilities. As for the performance, the biodegradation rate of the two organic matters differed due to the differences in the nutrient content, particularly of available N and P. In addition, cow dung amended-soil was found to have improved soil physiochemical characteristics that enabled speedy adaption by the microbes to the contaminated soil. Statistical analysis indicated a significant difference at P<0.05. Based on the first order kinetics model, cow dung amended soil gave the highest biodegradation rate of 0.2086/day with used-lubricant half-life of 3.32 day. On the other hand, sewage sludge amended soil has a biodegradation rate of 0.149/day with used-lubricant half-life of 4.65 days. These biodegradation rates were significantly higher than that of the control soil (0.0915/day) and autoclaved soil (0.0309/day). As for the microbial counts, cow dung amended soil recorded (69–122) ×107 CFU/g while sewage sludge amended soil recorded (63–96) × 107 CFU/g. On the other hand the control soil recorded (52–73) ×107 CFU/g. Again, the presence of available nutrients required by the microbes could be the contributing factor to the high distribution of microbes in the organic matter amended soil as compared to the control soil. In conclusion, cow dung and sewage sludge can be an effective organic amendment for the biodegradation of used lubricant contaminated soil. Both organic matters proved to enhance the multiplication of indigenous microbes thus enabling rapid biodegradation of the contaminant in the soil.

Reclamation of calcareous saline sodic soil with different amendments (II): Impact on nitrogen, phosphorous and potassium redistribution and on microbial respiration

Macronutrients deficiency is one of the most important limitations of saline sodic soils. This study is focused on redistribution of nitrogen (N), phosphorous (P) and potassium (K) as well as microbial respiration in ameliorating process of a calcareous saline sodic soil. The experimental work was performed with five soil treatments: cattle manure, pistachio residue, gypsum, manure+gypsum and pistachio residue+gypsum, plus the control. One water treatment (with sulfuric acid) plus the control and three replications were applied. After one month of incubation, four intermittent irrigation events with a monthly frequency were applied. The results indicated that concentrations of N and K increased with soil depth while, the highest P concentration was observed in surface soil. The organic matter-amended soils showed the highest concentrations of N. It was found that P availability increased due to the application of amendments except for gypsum which showed an antagonism influence. Application of organic matters increased the absorbable K, but part of its concentration came from their chemical composition. Compared to the untreated water, sulfuric acid had positive impacts on P and K availability, however its influence on N concentration was negligible. Measurement of microbial respiration showed that cattle manure had the highest rates of carbon mineralization. The application of gypsum as well as sulfuric acid had no significant effects on microbial respiration. Results showed that pistachio residue is an efficient amendment to reclaim saline sodic soils, and to improve availability of macronutrients.

Effect of Organic Matter Amendment on Hydraulic and Pore Characteristics of a Clay Loam Soil

The objective of this study was to examine the effect of compost, rice straw and sawdust amendment on hydraulic and pore characteristics of a clay loam soil. Amendments were applied at an application rate of0.2 m3/m3 (apparent soil volume) in three rectangular plots each comprising an area of3.0 m2. Water retention characteristics were measured by hanging water column and centrifuge method. Hydraulic conductivity was measured by disc permeameter at -15.0, -6.0, -3.0 and0 cmof water pressure heads. Volumetric water content increased in all amended soils, compared with the control. Unsaturated hydraulic conductivity was almost identical for straw and sawdust at all pressure heads, although that for compost amended soils were much higher. Field saturated hydraulic conductivity (Kfs) was higher in organic matter amended soils as were number of macropores (14.7% - 29.2%). Contribution of each pore class to the total saturated flux was evaluated from the hydraulic conductivity and water retention measurement. A new alternative weighed factor (We) was proposed to estimate the actual contribution of macro- and mesopores to the total saturated water flux. The Wg was found to be more representative for calculating pores contribution to saturated water flux than that of hydraulic conductivity measurement. Although there is only a small fraction of the total porosity, amendment increased effective macro- and meso-porosity (qe). Pores in the amended soils were hydraulically active and water movement was dominated by gravity. Collectively, our results demonstrated that organic matter generated as agricultural by-product could effectively be used to improve soil quality

Application of different organic wastes in a soil polluted by cadmium: Effects on soil biological properties

The effects of adding a poultry manure (PM), a crushed cotton gin compost (CC), a sewage sludge (SS) and an organic municipal solid waste by-product (MSW) on the biological properties of a soil artificially polluted with cadmium (Cd) were studied. Soil samples were mixed with PM at a rate of 10%, CC at a rate of 17.2%, SS at a rate of 23.1% and MSW at a rate of 13.1% in order to apply the same amount of organic matter to soil. Soil enzymatic activities, nematodes abundance, earthworm weight, Cd concentration in earthworm tissues and Cd extractable in soils were measured at two different incubation times (3 and 90 days) in soils containing 0, 100, 250, 500 and 1000 mg Cd kg − 1 and in the same soils amended with PM, CC, SS and MSW. An unamended soil was used as the control. For non-amended polluted soils, the highest decrease of soil biological properties appeared at the highest rates of Cd at the end of the incubation period. For organic amended polluted soils, the inhibition percentage of soil enzyme activities and Cd concentration in earthworm tissues were lower than in non-organic amended soils, and nematodes abundance, earthworm weight increased than in non-organic amended soils. However, the inhibition percentage of soil enzymatic activities and nematodes abundance, earthworm weight, Cd concentration in earthworm tissues differed between organic matter amended soils. In this respect, at 1000 mg Cd kg − 1 soil and at the end of the incubation period, the Cd concentration in earthworm tissues, the enzymatic activities inhibition were lower in soils amended with MSW followed by SS, PM and CC, respectively, than in the non-amended soils. Also, the nematodes abundance and earthworm weight were higher in soils amended with CC followed by PM, SS and MSW, respectively, than in the non-amended soils. Since the adsorption capacity of Cd was higher in CC than the PM, SS and MSW-amended soils, the addition of organic wastes with higher humic acid concentration is more beneficial for remediation of soils polluted with cadmium.

Biodynamics of microbial biomass nitrogen and sulfur in organic matter amended soil

Biodynamics of microbial biomass nitrogen and sulfur in organic matter amended soil

Population dynamics of rhizosphere microflora of mycorrhizal and non-mycorrhizal barley (Hordeum vulgare) in organic amended soils

A pot experiment was conducted to study the response of barley (Hordeum vulgare) to inoculation with Glomus fasciculatum in unsterilised organic matter amended soils on the colonization of barley roots by (V)-Arbuscular mycorrhizal (AM) fungi and other rhizosphere microflora. The populations of bacteria, fungi and actinomycetes were higher in amended than in control soils. Paddy straw compost (PSC) stimulated all three groups of organisms (bacteria, fungi and actinomycetes) more than city compost (CC). The fungal and actinomycetes populations decreased with increasing plant age. The effect was more pronounced in the rhizosphere of paddy straw-amended soils. The mycorrhizal spore count and the colonization of barley roots by (V)-AM were more pronounced in soils amended with PSC than in those amended with CC.

Effects of straw, vegetable oil and whey on physical and microbiological properties of a chernozem

A soil microcosm study was carried out to compare the effects of straw, vegetable oil or whey additions on physical and microbiological properties of a chernozem after 18 weeks of incubation. The application rates of the different organic materials were based on the addition of carbon at a concentration equivalent to 1% of soil dry mass. Straw, vegetable oil and whey additions to soil increased dry aggregate size distribution during incubation. All organic treatments had significantly higher mean weight diameter (MWD) of dry aggregates than the untreated control. The ability of whey, straw and oil to increase MWD did not differ significantly. Only straw addition significantly increased soil maximum water-holding capacity after 126 days of incubation. In comparison with the untreated control, straw tended to reduce the resistance of aggregates to abrasion, while addition of whey and vegetable oil seemed to have a positive effect on this property. Aggregates of organic matter amended soil materials had higher resistance to the dispersive action of water than those of the untreated control. Whey and straw additions sustained higher soil biomass-C contents and C mic/ C org ratios than vegetable oil. Biomass development was most favored by whey addition. Fungal contributions to biomass-C dominated over bacterial contributions in whey and straw-amended soil. The opposite was observed for the oil treatment. Increases in MWD of dry aggregates seem to be related to the synthesis of biomass and soil binding metabolites in whey and straw-treated soil. Among the organic treatments, oil-amended soil had the highest respiratory activity and the lowest biomass content. Stabilizing agents derived from the microbial metabolism using oily substrate are discussed.

Adsorption of mecoprop and dichlorprop on calcareous and organic matter amended soils: Comparative adsorption of racemic and pure enantiomeric forms

The adsorption isotherms of mecoprop [R,S‐2‐(4‐chloro‐2‐ methylphenoxy) propanoic acid] and dichlorprop [R,S‐2‐(2,4‐dichlorophenoxy)propanoic acid] on twelve calcareous soils were studied. All the isotherms fit the Freundlich equation. The distribution coefficients (Kf) were low and were only significantly related with the organic matter content of the soils. The main adsorption mechanism at the pH of these soils was found to be by cation bridging between the anionic forms of the two herbicides, and the external surfaces of the organic matter and/or negatively charged clay. The Koc values for mecoprop (R,S‐ MCPP) and dichlorprop (R,S‐ DCPP) adsorption predicted a high mobility of these herbicides in the soils. Their corresponding enantiomeric forms, R (biologically active) and S (biologically inactive) were adsorbed at the same ratio on these soils. The organic matter amended soils showed a significant increase on the retention capacity of both molecules.

Factors inhibiting parathion hydrolysis in organic matter-amended soil under flooded conditions

A water-extractable factor that developed in a flooded soil amended with 0.5% glucose or rice straw inhibited the biological hydrolysis of parathion. In glucose-amended flooded soil, the factor was removed by filtration of the standing water through a Millipore filter. Apparently, glucose application enhanced the proliferation of micro-organisms detrimental to parathionhydrolyzing agents. On the other hand, the toxic factor formed in rice straw-amended soil under flooded conditions passed through a Millipore membrane and was not inactivated by steam treatment. The toxicity developed within 36 h after flooding of rice straw-amended soil and persisted for 90 days or more under continued flooding. These studies indicated that a heat-resistant and stable factor with ability to block the hydrolysis of parathion developed in rice straw-amended soil under flooded conditions.