Henri Dinel

Transformations of carbon and nitrogen during composting of animal manure and shredded paper

Abstract Composts produced from animal manures and shredded paper were characterized in terms of their carbon (C) and nitrogen (N) forms and C mineralization. Total, water-soluble, acid-hydrolyzable and non-hydrolyzable C and N contents were determined on composts sampled on days 0, 11, 18, 26, 33, 40 and 59 after composting was initiated. Water-soluble and acid-hydrolyzable C and N decreased during composting, whereas non-hydrolyzable C remained relatively constant, and non-hydrolyzable N greatly increased during composting. The water-soluble forms of N were characterized by a decrease of ammomium (NH4+-N) at the beginning of composting, followed by an increase of nitrate (NO3–-N) towards the end of composting. The mineralization of C in composted materials was generally higher at the beginning than at the end of composting, whereas no differences were observed for mineralization of C in non-hydrolyzable materials. The addition of N inhibited C mineralization in composts except in samples collected on days 40 and 59, while C mineralization was strongly stimulated by adding N to the non-hydrolyzable materials. The data suggest that the N forms in the non-hydrolyzable materials were chemically similar and not readily available to microbes, indicating that the C/N ratios often used to assess the biodegradability of organic matter and to develop compost formulations should be based on biologically available N and C and not on total N and C.

Extractability of trace metals during co-composting of biosolids and municipal solid wastes

Abstract Composts made from biosolids and municipal solid wastes contain heavy metals which may be exported outside soil systems by plants, animals and surface and subsurface waters after the compost has been added to soils. Chemical distributions of Cu, Zn, Cr, Pb, Ni and Co were determined by eight sequential extractions of co-composted materials sampled on days 0, 13, 27 and 41. The concentrations of residual Zn, Cr, Cu and Pb increased by 145, 124, 73.6 and 26.3% during the composting period, respectively, whereas the concentration of residual Ni remained relatively constant and that of Co decreased by 60% over the same period. These results show that co-composting contaminated residues substantially reduces the extractability and exchangeability of four out of six heavy metals, suggesting that the risks of entering the food chain and contaminating crops, animals and water reserves would be equally reduced. Fourier-transform infrared spectra showed that heavy metals in the compost are bonded to COO- groups of the organic matter.

Post-fire soil microbial biomass and nutrient content of a pine forest soil from a dunal Mediterranean environment

Abstract A chronosequence of forest fires (from 1981 to 1992) in a homogeneous Mediterranean pine forest ecosystem was investigated. The effect of fire on soil microbial biomass was evaluated in the 0–5 cm soil layer utilizing the substrate induced respiration (SIR) method (Anderson and Domsch, 1978) and the fumigation extraction (FE) method (Sparling and West, 1988). The C, N and P contents of soil surface layer were greater 1 y after a fire and declined in soils as time since the last fire increased. After 11 y, the soil nutrient content and the size of the microbial biomass were still lower than the neighbouring unburned site suggesting that forest fires have a long-term effect on soil microbiological properties.

Chemical changes during composting of a paper mill sludge–hardwood sawdust mixture

Abstract Recycling of paper mill sludge (PMS) by composting is becoming an acceptable practice for converting these chemically complex materials into useful soil amendments, while eliminating negative environmental impacts. The organic composition of a PMS–hardwood sawdust mixture was investigated during composting to better understand the changes in main chemical components. Pyrolysis-field ionization mass spectrometry (Py-FIMS) and cross polarization-magic angle spinning 13C nuclear magnetic resonance (CP-MAS 13C NMR) were employed to characterize the organic composition of the PMS composted materials. The spectroscopic data revealed that the major components of the PMS were lipids, sterols, lignin, N-compounds, and carbohydrates. By the end of composting (at biomaturity), concentrations of carbohydrates and lignin became more prominent, while those of lipids, sterols and proteinaceous components decreased. Increases in carbohydrates and decreases in paraffinic C, proteinaceous C and C in OCH3 groups appeared to be related to increased microbial activity. Other chemical changes observed during composting were increases in aromatic C, phenolic C, and in aromaticity. While the total C and N contents decreased by about only 12.0%, the compost lost 50% of its initial weight. At biomaturity, the compost consisted primarily of polysaccharide/carbohydrate materials, specifically cellulose and acidic polysaccharides (uronic acids) in combination with smaller quantities of lignin.

Organic matter quality and structural stability of a Black Chernozemic soil under different manure and tillage practices

Abstract No-tillage (NT) and addition of organic matter can improve soil aggregation and affect soil organic matter (SOM) levels. The effects of short-term (3 years, 1993–1996) conventional tillage (CT), NT, and cattle manure applications on SOM quality and water-stable aggregates (WSA) were investigated on a Melfort silty clay loam (Orthic Black Chernozem) at Melfort (Saskatchewan, Canada). Four methods for managing manure (dry weight basis) within CT and NT were established: fresh manure (FM) was applied at the beginning of the experiment at 23.0 Mg ha−1 and annually at 4.5 Mg ha−1, whereas stockpiled manure (SM) with equal N concentration to FM was applied at the beginning of the study at 23.0 Mg ha−1 and annually at 4.5 Mg ha−1. The control treatment consisted in annual application of 81.0 kg N ha−1 as ammonium nitrate and 9.3 kg P ha−1 as monoammonium phosphate, according to soil test recommendations. Soil samples (0–15 cm) were collected at the end of the 3-year period and lipids were extracted with diethyl ether (DEE) and chloroform (CHCl3) to assess SOM quality. Water-stable aggregates were measured with and without ethanol pretreatment and before and after extraction of unbound lipids. The amounts of C and N was not affected by the treatments. Between NT and CT, the changes in SOM were expressed by an increase of 21% of the amounts of total extractable lipids (TEL) in the CT soils, whereas in the NT soils, the DEE/CHCl3 ratio used to assess the degree of biodegradability of OM increased by 40%. Following the application of FM, the stability of soil aggregates against the dissolution and dispersive actions of water decreased by 13 and 16% in CT and NT soils, respectively; however, this effect was compensated by an equivalent increase in resistance to slaking forces. In contrast, the incorporation of SM did not affect the stability of soil aggregates against the dissolution and dispersive actions of water, but increased by 7% the resistance of aggregates to slaking forces.

Compost Maturity: Extractable Lipids as Indicators of Organic Matter Stability

An organic matter stability test was developed for assessing compost maturity. Lipids extracted sequentially with diethyl ether (DEE) and chloroform (CHCl3) from four composted manure mixes and four commercially produced composts were used to set and test the limits of gravimetrically based indices of maturity. Limits of 0.25 for CHCl3-extractable/total lipid ratios constitute acceptable limits for mature composts. The proposed test for compost maturity is scientifically-sound, relatively inexpensive and universally applicable, and can be performed by workers with low technical skills.

Compost Maturity: Chemical Characteristics of Extractable Lipids

Chemical changes in extractable lipids from four mixtures of farmyard manures were investigated during the composting process. Lipid extractions with diethyl ether (DEE) and chloroform (CHCl3) were sequentially performed on samples collected at seven different times during composting. Amounts of DEE-extractable lipids decreased continuously during composting, while CHCl3-extractable lipids remained relatively constant. 13C NMR and mass spectrometric data indicated that the lipids became chemically more homogeneous during composting and that biologically resistant molecules predominated at the end of composting.

Extractable Soil Lipids and Microbial Activity as Affected by Bt and Non Bt Maize Grown on a Silty Clay Loam Soil

Pyrolysis‐gas (Py‐GC) chromatography was used to characterize extractable lipids from Bt and non‐Bt maize shoots and soils collected at time of harvesting. Py‐GC‐MS (mass spectrometry) showed that the concentrations of total alkenes identified in non‐Bt shoots and soils were 47.9 and 21.3% higher than in Bt maize shoots and soils, respectively. N‐alkanes identified were of similar orders of magnitude in Bt and non‐Bt maize shoots, but were 28.6% higher in Bt than in non‐Bt soils. Bt maize shoots contained 29.7% more n‐fatty acids than non‐Bt maize shoots, whereas the concentrations of n‐fatty acids in Bt soils were twice as high as those in non‐Bt soils. Concentrations of unsaturated fatty acids in Bt maize shoots were 22.1% higher than those in non‐Bt maize shoots, while concentrations of unsaturated fatty acids were 22.5% higher in non‐Bt than in Bt soils. The cumulative CO2–C evolved from soils under Bt and non‐Bt crops was 30.5% lower under Bt as compared to non‐Bt crops, whereas when maize shoots were added to Bt and non‐Bt soils, the decrease in CO2–C evolved were 16.5 and 23.6%, respectively. Our data showed that the cultivation of Bt maize significantly increased the saturated to unsaturated lipid ratios in soils which appeared to negatively affect microbial activity.

The distribution of pollutant heavy metals and their effect on soil respiration and acid phosphatase activity in mineral soils of the Rouyn-Noranda region, Québec

Abstract The distribution of pollutant heavy metals (Cu, Zn, Ni, Cd and Pb) from a CuZn smelter near Rouyn-Noranda, Quebec and their effect on soil respiration and phosphatase activity were studied in mineral soils along two transects oriented in the direction of prevailing winds. The LFH horizon was the more contaminated soil layer having retained the larger part of the atmospheric pollution. The 0–15 cm layers also showed high levels of heavy metals in the vicinity of the smelter. The log-concentration of pollutant heavy metals decreased progressively with the log-distance from the emitting point, and did not accumulate into the 15–30 cm layer significantly. Cd and Pb appeared to have less mobility than Cu and Zn. Soil respiration was a better indicator in assessing the effect of heavy metal pollutants on soil microbial populations than was acid phosphatase activity in these mineral soils with different organic contents.

Growth substrates made from duck excreta enriched wood shavings and source-separated municipal solid waste compost and separates: physical and chemical characteristics.

Production and use of compost is an effective means to reduce wastes, and offers a large potential as growth substrates and source of nutrients. The objective of this study was to determine the physical and chemical characteristics of duck excreta enriched wood shavings (DMC) and source-separated municipal solid waste (MSW) composts and separates, and to assess the physical characteristics of growth substrates made from these two composts and selected substrates. MSW compost separates were the following sizes: F1 > 4 mm diameter, 2 mm < F2 < 4 mm, 1 mm < F3 < 2 mm and F4 < 1 mm. Growth substrates were prepared by mixing DMC and F2 and F3 MSW separates (M/M ratios). Growth substrates A-E consisted exclusively of 10-60% DMC and 20-60% of MSW separates F2 and F3. Growth substrates F-J, and K-O were the same as substrates A E, with 15% M/M brick fragments or shredded plastic added as porosity agents, respectively. Growth substrates (BE/S) made of black earth (BE) and sandy loam soil (Ls) in a 1:4 (M/M) ratio, commercially available peat substrate (Pr) and an in-house sphagnum peat-based substrate (Gs) were used for comparison. Principal component analysis (PCA) showed that DMC was a better material than MSW with respect to porosity and water field capacity. MSW compost and separates differed by their relatively high levels of water-soluble and HCl-hydrolyzable N and increased advantageous water retention capacity. PCA also showed that substrates A-E exhibited porosity and water field capacity similar to those of Pr. Substrates F-J had porosity and water field capacity similar to those of BE/S, whereas substrates K O were more similar to Pr and to substrates A and B. The presented data indicate that DMC and MSW separates were complementary in providing good physical and chemical characteristics to the growth substrates.