Factors controlling the aggregate stability and bulk density in two different degraded soils amended with biosolids (original) (raw)
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Waste Management, 2004
The effect of land application of biosolids on an agricultural soil was studied in a 2-month incubation experiment. The soil microbial biomass and the availability of heavy metals in the soil was monitored after the application of four different composting mixtures of sewage sludge and cotton waste, at different stages of composting. Land application caused an increase of both size and activity of soil microbial biomass that was related to the stabilization degree of the composting mixture. Sewage sludge stabilization through composting reduced the perturbance of the soil microbial biomass. At the end of the experiment, the size and the activity of the soil microbial biomass following the addition of untreated sewage sludge were twice those developed with mature compost. For the mature compost, the soil microbial biomass recovered its original equilibrium status (defined as the specific respiration activity, qCO 2 ) after 18 days of incubation, whereas the soil amended with less stabilized materials did not recover equilibrium even after the two-month incubation period. The stabilization degree of the added materials did not affect the availability of Zn, Ni, Pb, Cu, Cr and Cd in the soil in the low heavy metal content of the sewage sludge studied. Stabilization of organic wastes before soil application is advisable for the lower perturbation of soil equilibria status and the more efficient C mineralization. #
Effects of sewage sludge stabilization on organic-N mineralization in two soils
Sewage sludge is a valuable source of organic matter, N, P and certain micronutrients that have beneficial effects on plant growth and biomass production. However, sanitary regulations often require the stabilization of sewage materials prior to applying them to soils as biosolids. Environmental regulations also demand appropriate management of biosolid-N to avoid groundwater contamination. Because stabilization processes usually make sewage sludge less putrescible, we hypothesized that the mineralization rates of organic-N from stabilized biosolids would be affected. Therefore, this study aimed to evaluate the mineralization of five biosolids in two soils – a sandy Spodosol and a clayey Oxisol. Digested sludge, composted sludge, limed sludge, heat-dried sludge and solar-irradiated sludge were mixed with soil samples at a concentration of 32.6 mg N ⁄ kg soil (1.0 dry t ⁄ ha of digested sludge) and incubated at 25 °C in a humidity chamber for 23 weeks. Results showed that the stabilization processes generally slowed the release of mineral-N in soils relative to the digested sludge from which the biosolids originated. However, increments in the levels of mineral-N were more influenced by soil type than by the type of stabilization process applied to the sewage sludge. Mineralization rates were up to 5-fold higher in the Oxisol than in the Spodosol soil, and as a result, organic-N in biosolids mineralized 10–24% in Spodosol and 23–52% in Oxisol. Any appropriate plan for the management of biosolid-N for plant use should consider the interaction between soil type and biosolid type.
Soil Research, 2014
Recycling of organic wastes via their incorporation in cultivated lands is known to alter soil structural stability. Aggregate stability tests are commonly used to express quantitatively the susceptibility of soil structural stability to deformation. The objective of this study was to investigate the effects of biosolids addition, namely composted manure (MC) and activated sludge (AS), and spiking of the soils with orthophosphate (OP), phytic acid (PA) or humic acid (HA), on soil aggregate stability of semi-arid loamy sand, loam and clay soils before and after subjecting the soils to six rain storms (each 30 mm rain with a break of 3-4 days). Aggregate stability was determined from water-retention curves at high matric potential. The effects of the applied amendments on pre-and post-rain aggregate stability were inconsistent and soildependent. For the pre-rain state, all of the tested amendments improved aggregate stability relative to the control. For the post-rain condition, aggregate stability was lower in the MC, OP and PA treatments and higher in the AS and HA treatments than in the control. The coarse-textured loam and loamy sand soils were more affected by the soil amendments than the clay soil. For the pre-rain state, addition of organic matter significantly improved macro-porosity and hence the stability of apparent macro-aggregate (>250 mm). Our results indicate a possible advantage for separation of aggregates into macroand micro-aggregates for more precise evaluation and understanding of the effects organic amendments might have on aggregate stability.
EFFECT OF ORGANIC AMENDMENTS ON SOIL AGGREGATE STABILITY
Intensive agriculture is known to cause a decline in soil organic matter content and alter soil structure. The objective of this study was to compare the effect of two urban composts (a municipal solid waste com- post, MSW and a biowaste compost, BW) and a farmyard manure (FYM) on aggregate stability in a loamy soil under field condition. Laboratory incubations of calibrated aggregates added of the same organic amendments were realized in controlled conditions (28 and 4 °C) to confirm the effects observed in field conditions. After one application of the MSW and BW composts in the field experiment, aggregate stabi- lity increased compared to the control plot. In lab conditions, MSW and FYM enhanced the aggregate sta- bility, more at 4°C than at 28°C. In both experiments, the aggregate stability were related to the stimula- tion of microbial activity after addition of still highly biodegradable organic amendments, more persistent at 4°C than at 28°C.
Aggregate stability changes in a semiarid soil after treatment with different organic amendments
Arid Soil Research and Rehabilitation, 1996
Structural stability of soils is one of the most important characteristics related to soil degradation in semiarid areas. Organic additions can considerably improve soil structure and prevent soil degradation. In this experiment the effectiveness was compared of four types of organic amendments on the improvement of soil structure. The four treatments are sewage sludge, fresh uncomposted urban refuse, composted urban refuse, and horse manure. The uncomposted urban refuse was the most effective in increasing soil stable aggregates. The higher doses of sewage sludge and compost also improved aggregation of soil particles. Horse manure did not significantly improve soil aggregation. A significant correlation (τ = 0.955, ρ < 0.01) was found between fungal populations and stable aggregates. No significant correlations were found between stable aggregates in soil and the other parameters assessed. The organic treatments increasing soil microbial populations and promoting their activity appear to be very effective in improving soil structure.
Effect of biosolids from municipal sewage sludge composted with rice husk on soil functionality
Biology and Fertility of Soils, 2013
Two different biosolids were obtained composting anaerobic (A) and aerobic (B) municipal sewage sludge (SS) with rice husk. Higher amounts of SS (1:1 v/v) could be used in this composting process than in conventional ones. The two biosolids were characterized by chemical analysis and compared with a conventional green manure plus municipal solid waste and municipal SS compost. The effect of these products on soil functionality was studied in a 14week incubation experiment by their addition to two different soils (silty clay-Ustic Endoaquert-and sandy loam-Aquic Xeropsamment). The total organic C ranged from 20 to 26 % and total N from 1.6 to 2.5 % in the two biosolids. The most relevant difference was due to dissolved organic C that was lower in the anaerobic biosolid (1 mgCkg −1 ) than in the other products (5-6 mgCkg −1 ). The total trace elements (Cd, Cr, Cu, Ni, Pb and Zn) contents were under the limits fixed by the European legislation for soil application of SS (EC Directive 86/278/EEC, 1986). The three biosolids did not show strong negative effects on soil functionality during the incubation experiment, although some significant differences were found. The aerobic biosolid B mainly increased cumulative N release, microbial activity, basal respiration rate, microbial biomass-C-tototal organic C ratio, β-glucosidase, alkaline phosphomonoesterase and aryl-sulphatase activities. The anaerobic one (B) decreased basal respiration rate, microbial biomass-C-to-total organic C ratio and aryl-sulphatase activity. DTPA soil bioavailable heavy metals were not affected by biosolids additions.
Agriculture Ecosystems & Environment
The objective of this study was to compare the effects of repeated field applications of three urban compost amendments and one farmyard manure amendment over a 9-year period on aggregate stability in a silty loam soil initially characterized by low clay and initial organic matter contents and poor aggregate stability. Three different aggregate stability tests with increasing disruptive intensities (fast wetting>mechanical breakdown>slow wetting tests) and different disaggregation mechanisms, were used. All of the amendments, which were applied at approximately 4MgCha−1 every other year, increased the organic carbon content and improved the stability of the aggregates against the disruptive action of water, as determined by each of the stability tests. However, the year-to-year variations in the aggregate stability that related to factors other than the organic inputs were greater than the cumulative increase in aggregate stability relative to the control. The positive effects...
The effect of biosolids application rates on bulk density and total porosity of degraded soils was investigated. The study was conducted on the degraded sites of Amaiyi, Oruruala and Ugwu rubber all in Abia State, Nigeria. Sewage sludge samples were collected from the Enugu State Environmental Protection Agency Sewage dumpsite at Ugwaji Nike Enugu, Nigeria, and composted with wood chips in 60:40 ratios using improvised aerated static piles systems for 21 days. The ameliorating effects of biosolids on degraded soils were carried out in a 4X3 factorial experiment in a randomized complete block design with three replicates. Processed biosolids were incorporated into the degraded soils at the rate of 0t/ha (control), 10t/ha, 20t/ha and 30t/ha. Soil samples 0- 30cm were collected 157 days after incorporation, air dried, crushed and sieved. Bulk density was determined by the method of Blake and Hartage (1986), and total porosity was determined indirectly from the bulk density. Treatment effects of bulk density and total porosity were analyzed using the student’s t- test. Results showed that the mean values of treatment rates 10 t/ha, 20 t/ha and 30/t/ha on bulk density were 1.54gm/cm3, 1.43g/cm3 and 1.31g/cm3 respectively against 1.59g/cm3 recorded at the control, while the mean values for total porosity were 41.9%, 46.1% and 50.6% for 10t/ha, 20t/ha and 30t/ha respectively against 40% of the control. Though there were significant differences between bulk density and total porosity in all the treatment rates, more significant differences (P<0.05) were observed at rate 30 t/ha when compared with the control. As treatment rates increased from 10t/ha to 30t/ha, results revealed an inverse relationship between bulk density and total porosity, as bulk density decreased, total porosity increased; and the higher the treatment rates, the higher the total porosity and the lower the bulk density. Total porosity did not correlate significantly with bulk density for the main effects of biosolids application rates (r= -0.56). Significant negative relationship existed between total porosity and bulk density for the main effects of degraded soil types (r= -0.88). The accelerated soil erosion in all the sites studied was due to decreases in infiltration and total porosity brought about by high bulk density. The use of processed biosolids at moderate rates to improve total porosity and reduce bulk density as a measure to ameliorate degraded state of the study sites was recommended. Keywords: Degraded Soils, Biosolids, Treatment Rates, Bulk Density, and Total Porosity