Compost-treated Soils Research Articles

Evaluation of different pig slurry composts as fertilizer of horticultural crops: Effects on selected chemical and microbial properties

AbstractThe excessive use of mineral fertilizers affects soil quality, gives rise to environmental problems and consumes energy. In contrast, organic amendment may improve soil quality at the same time as providing nutrients to plant. The aim of the work was to study the effects on crop yield and soil microbial activity of the successive addition of mineral fertilizers and fresh pig slurry before each successive crop compared with one sole application of different pig slurry composts (solid fraction of a pig slurry (CSFPS) and fresh pig slurry plus wood shavings (1:1 v/v; CPS+WS) before planting the first crop. Compost-treated soils exhibited higher organic carbon content than inorganically fertilized soils, throughout the experimental period. However, N content in the former soils was lower than in the latter after the second crop. Nevertheless, yields obtained with repeated additions of fresh pig slurry or with a sole application of pig slurry composts were similar to those obtained with repeated mineral fertilization. After the horticultural crops, organically treated soils generally showed higher values of both microbial biomass and metabolic microbial activity (measured as basal respiration and dehydrogenase activity) than the soil receiving mineral fertilization. Subsequently, the organically amended soils showed higher protease, phosphatase and β-glucosidase activities than the inorganically fertilized soil and similar levels of urease activity. From this study it can be concluded that both fresh and composted pig slurry can be used as an alternative for mineral fertilizer in growing horticultural crops and maintaining soil quality.

Community structure and functional diversity of indigenous fluorescent Pseudomonas of long-term swine compost applied maize rhizosphere

The community structure and catabolic functional diversity of indigenous rhizosphere fluorescent pseudomonad isolates recovered from un-amended soil (control treated) and following long-term (6 years) swine compost application (compost treated) were studied. Soils collected for the pot experiments were from a Taiwanese experimental farm established in 1995 to study the long-term effects of crop rotation and organic amendment. In the pot experiments, corn seed was cultured; after the elongation stage, 13 and 32 indigenous rhizosphere fluorescent pseudomonad isolates were collected from compost-treated ( n=13) and control-treated ( n=32) soils. All isolates were classified by 16S rDNA restriction fragment length polymorphism (RFLP) and unweighted pair-group method using arithmetic averages analyses. Most (84.4%) of the control-treated soil isolates belonged to genotype A, which corresponded to Pseudomonas putida based on 16S rDNA sequences analysis. However, only 61.5% of compost-treated soil isolates were from genotype A; 30.7% of the isolates belonged to genotype B, whose 16S rDNA profile corresponded to Stenotrophomonas maltophilia. Differing catabolic potentials of the P. putida isolates from control- and compost-treated soils were evident; isolates from control-treated soils utilized organic acids including citric acid, cis-aconitic acid, and formic acid more actively than compost-treated soil isolates. Moreover, the latter isolates more efficiently utilized carbohydrates of i-erythritol and l-rhamnose than P. putida isolates from control-treated soil, consistent with the alteration in the catabolic functions of indigenous rhizosphere P. putida by long-term compost application.

Traceability of ammonia-oxidizing bacteria in compost-treated soils

Composts are increasingly used as environmentally safe biofertilizers in sustainable agriculture all over the world. Although it is well known that composts may contribute to soil vitality and sustainability, and in the enhancement of various soil microbiological processes, little is known about their direct or indirect effects on a microbial-community or population level. Ammonia oxidation by autotrophic ammonia-oxidizing bacteria (AOB) is a key process in agricultural and natural ecosystems and plays an important role in the global nitrogen cycle. Here, we studied the diversity and community composition of ammonia oxidizers in a long-term crop rotation field experiment (>10 years) where four major types of compost (from organic waste, cattle manure, green waste and sewage sludge) had been applied annually. The methods used ranged from PCR-DGGE (denaturing gradient gel electrophoresis) and cloning of 16S rDNA fragments to quantitative real-time PCR. Cluster analysis of DGGE profiles differentiated between the microbial communities of composts, compost-treated soils and mineral-fertilized soils. The community composition of the composts was not reflected in the community composition of the compost-treated soils. Sequencing of screened clones revealed a characteristic AOB community structure for the representative soil sample and the four composts. All AOB-like sequences grouped within the Nitrosospira cluster 3 and 4 and within the Nitrosomonas cluster 6 and 7. The average AOB abundance in compost-treated soils was two times higher than in mineral-fertilized soils (4.3×10 7 and 1.9×10 7, respectively). Our data suggest that composts do not leave direct microbial imprints in soils after long-term amendment, but an indirect effect on the AOB community was evident.

Soil fumigation and compost amendment alter soil microbial community composition but do not improve tree growth or yield in an apple replant site

Apple replant disease (ARD) is a disease complex that reduces survival, growth and yield of replanted trees, and is often encountered in establishing new orchards on old sites. Methyl bromide (MB) has been the fumigant used most widely to control ARD, but alternatives to MB and cultural methods of control are needed. In this experiment, we evaluated the response of soil microbial communities and tree growth and yield to three pre-plant soil treatments (compost amendment, soil treatment with a broad-spectrum fumigant, and untreated controls), and use of five clonal rootstock genotypes (M.7, M.26, CG.6210, G.30 and G.16), in an apple replant site in Ithaca, New York. Polymerase chain reaction (PCR)—denaturing gradient gel electrophoresis (DGGE) analysis was used to assess changes in the community composition of bacteria and fungi in the bulk soil 8, 10, 18 and 22 months after trees were replanted. PCR-DGGE was also used to compare the community composition of bacteria, fungi and pseudomonads in untreated rhizosphere soil of the five rootstock genotypes 31 months after planting. Tree caliper and extension growth were measured annually in November from 2002 to 2004. Apple yield data were recorded in 2004, the first fruiting year after planting. Trees on CG.6210 rootstocks had the most growth and highest yield, while trees on M.26 rootstocks had the least growth and lowest yield. Tree growth and yield were not affected by pre-plant soil treatment except for lateral extension growth, which was longer in trees growing in compost-treated soil in 2003 as compared to those in the fumigation treatment. Bulk soil bacterial PCR-DGGE fingerprints differed strongly among the different soil treatments 1 year after their application, with the fingerprints derived from each pre-plant soil treatment clustering separately in a hierarchical cluster analysis. However, the differences in bacterial communities between the soil treatments diminished during the second year after planting. Soil fungal communities converged more rapidly than bacterial communities, with no discernable pattern related to pre-plant soil treatments 10 months after replanting. Changes in bulk soil bacterial and fungal communities in response to soil treatments had no obvious correlation with tree performance. On the other hand, rootstock genotypes modified their rhizosphere environments which differed significantly in their bacterial, pseudomonad, fungal and oomycete communities. Cluster analysis of PCR-DGGE fingerprints of fungal and pseudomonad rhizosphere community DNA revealed two distinct clusters. For both analyses, soil sampled from the rhizosphere of the two higher yielding rootstock genotypes clustered together, while the lower yielding rootstock genotypes also clustered together. These results suggest that the fungal and pseudomonad communities that have developed in the rhizosphere of the different rootstock genotypes may be one factor influencing tree growth and yield at this apple replant site.

Analysis of carbon and nitrogen forms in soil fractions after the addition of 15N-compost by 13C and 15N nuclear magnetic resonance.

A quantitative laboratory assessment of the different C and N forms in soil humus fractions was carried out by incubation of a mineral substrate after the addition of (15)N-labeled compost. The experimental design included (i) preparation of the (15)N-labeled organic matter (city refuse compost, 640 g kg(-1) wheat straw and K(15)NO(3) composted for 80 days), (ii) a further 80 day incubation of a mixture of the labeled compost with a mineral soil (32 g kg(-1)), (iii) measurement of stable isotope ratios, and (iv) isolation and structural comparison by (13)C and (15)N cross-polarization, magic-angle spinning nuclear magnetic resonance (NMR) of different organic fractions, i.e., soluble, colloidal (humic and fulvic type), and particulate (free organic matter and humin), from both the compost and the compost-treated soil. The results showed that the amide forms dominated in all of the newly formed N compounds, but an increased amount of alkali insoluble organic fractions was observed after incubation of the soil. The analysis of the insoluble, particulate fractions shows that nonextractable amides constitute the major pool of newly formed N compounds. The particulate soil fraction isolated by flotation in CHBr(3)-MeOH contained 16.8% of the total soil N and 26% of the (15)N. The (13)C NMR spectra showed that the fulvic acid-like fraction (7.6% of the soil N, 8.8% of (15)N) consisted almost completely of a C=O-containing carbohydrate material, whereas the humic acid-like fraction (20.3% of the total soil N, 8.6% of (15)N) resembled an oxidized lignoproteic fraction containing the most significant aromatic domain. The water soluble fraction was, in both soil and compost, the one with the highest isotopic abundance of (15)N (96%), but the (15)N NMR spectrum revealed minor amounts of soluble mineral N in this fraction and the remainder consisting of amide compounds.

Nitrogen mineralization, N 2 O production and soil microbiological properties as affected by long-term applications of sewage sludge composts

A field study was conducted to investigate the long-term effect of surface application of sewage sludge composts vs chemical N fertilizer on total N, total C, soluble organic C, pH, EC, microbial biomass C and N, protease activity, deaminase activity, urease activity, gross and net rates of N mineralization and nitrification, CO2 evolution, and N2O production. Soil samples were taken from five depths (0–15, 15–20, 20–30, 30–40, and 40–50 cm) of a long-term experiment at the University of Tokyo, Japan. Three fields have been receiving sewage sludge composted with rice husk (RH), sawdust (SD), or mixed chemical fertilizer NPK (CF), applied at the rate of 240 kg N ha−1 each in split applications in summer and autumn since 1978. Significantly higher amounts of total N and C and soluble organic C were found in the compost than in the CF treatments up to the 40-cm soil depth, indicating improved soil quality in the former. In the CF treatment, soil pH values were significantly lower and electrical conductivity values were significantly higher than those of compost-treated soils of up to 50 cm depth. Soil microbial biomass C and N, CO2 evolution, protease, deaminase, and urease activities were significantly higher in the compost than in the CF treatments due to greater availability of organic substrates that stimulated microbial activity. Gross N mineralization rates determined by 15N dilution technique were eight and five times higher in the SD and RH treatments than in the CF treatment, respectively, probably due to high levels of microbial and enzyme activities. Net N mineralization rates were also significantly higher in the compost treatments and were negative in the CF treatment indicating immobilization. Net nitrification rates were higher in compost treatments and negative in the CF treatment. Nitrous oxide productions from compost treatments were higher than the CF treatment due to the greater availability of mineral N as a result of higher mineralization and nitrification rates and soluble organic C in the former. Most of the measured parameters were highest in the surface soil (0–15 cm) and were significantly higher in the SD treatment than in the RH treatment.

Analysis of total inositol phosphates in municipal solid waste compost-treated soils by two extraction methods

Humic substances are the most dynamic component of agricultural soils. In this study, humic substances were extracted from soils based on standard acid/base solubility and by gel filtration using Sephadex G25. Organic P is a component of humic substances, and inositol phosphates are considered to have high prominence in organic P. The objectives of the study were to determine the effects of municipal solid waste (MSW) compost on the amount of inositol phosphates (IP) present in soils, and compare methods of extracting humic substances from soils. Total IP (IPT) in soil extracts was determined following separation using a AG-1× 8 anion exchange resin, acid digestion and ICAP analysis for P. The percentage of IP (%IP) of the total P in the soil was also determined by colorimetric analysis. The soils were part of an experiment to study the effects of three rates of MSW compost and fertilizers on three crops grown in a Pugwash sandy loam (Humo-Ferric Podzol). The data were compared using ANOVA atP≤0.05; extraction methods, fractions [humic/fulvic, high/low molecular (MW)], and five treatments (three different rates of compost, fertilizer, and untreated soil) were compared. The gel filtration method extracted significantly more IPT and %IP than the solubility method. In the solubility method, humic and fulvic acids contained the same amounts of IPT and %IP, while the high MW fraction always contained more IPT and %IP than the low MW fraction in the gel filtration method. Fulvic acids and the low MW fraction contained similar amounts of IPT and %IP. There were differences in %IP between compost-treated soils and the non-compost-treated soils, although there were no differences in IPT due to rate of compost addition.

Effects of carbohydrate application on diazotroph populations and nitrogen availability in grass swards established in garden waste compost

The potential of using free-living nitrogen fixing bacteria (diazotrophs) as a source of nitrogen nutrition for crops has not been realised in most parts of the world, largely because of the inability of the organisms to multiply effectively in temperate agricultural soils. In recent papers (Keeling et al., 1994, 1996) we showed how populations of diazotrophs in green waste compost-treated soil can be stimulated to increase by soil glucose treatment after sward development, and measured an associated increase in grass sward yield of 36% over a 12 month period. Here, we describe in detail the changes in bacterial populations over a 12 month period and relate them to grass growth patterns and nitrogen uptake, for compost amended-soil treated with both glucose and soluble starch. It was found that diazotrophic populations were enhanced 300% over the long term, and nitrogen uptake by plants increased by over 100% in the first 2 months post 15 gl −1 glucose treatment in compost-grown swards, while soluble starch-treated sward growth was inhibited. Further, a typical field soil similarly treated with glucose failed to respond to the treatment; rather, a nitrogen immobilizing effect was observed. It was concluded that significant nitrogen fixation and plant N availability was stimulated by the glucose treatment of compost, but the mechanisms of these processes require more extensive investigation.

Heavy metal contents of vegetable crops treated with refuse compost and sewage sludge

Refuse compost and sewage sludge were mixed with a loamy sand at various rates in pots and sown withBrassica chinensis, Daucus carota andLycopersicon esculentum in a glasshouse. A commercial fertilizer was also applied to the same soil for comparison. Dry matter production of the three crops and contents of Cd, Cu, Mn, Pb and Zn in the harvested tissues were determined at the end of the experiment. In general, crop yield in refuse compost treatment was improved over that in sandy soil alone, but was less than that in the sludge and fertilizer treatments. Despite the relatively high heavy metal contents of refuse compost, crops grown on compost-treated soils accumulated lower levels of metal than those grown on sludge-treated soils. This is probably due to the high pH and organic matter content of the composted refuse. Higher levels of heavy metals were found in the roots than in the aerial parts ofB. chinensis andL. esculentum, but the reverse was found inD. carota. In the edible tissue of the three crops,L. esculentum accumulated metals to a lesser extent than the other two.

Uptake and speciation of mercury and selenium in vegetable crops grown on compost-treated soil

The uptake and speciation of Hg and Se were assessed for the edible portion of 16 different vegetable crops grown on a garden plot which had been exclusively treated with residential compost for 6 yr. This study was conducted under actual field conditions typical of residential gardening and utilized organic gardening techniques. Crops had methylmercury levels averaging 12.8 % of the total edible tissue Hg content, divalent inorganic Hg being the only other element form identified. An average of 20.0% of the total Se content was present as hexavalent Se, the remainder being divalent and tetravalent Se forms. In terms of plant/soil concentration factors, Se was more readily assimilated by crops than Hg.

Application of refuse compost: Yield and metal uptake of three different food crops

The effect of refuse compost on the yield and metal uptake of three vegetable crops ( Brassica chinensis , Daucus carota , Lycopersicon esculentum ) was studied in a greenhouse experiment. Refuse compost was mixed with a loamy sand at the rates equivalent to 25, 50, 75, 100, 125 and 150 tonnes ha −1 in plastic pots. A chemical fertiliser (NPK = 15-9-15) at the rate of 2 tonnes ha −1 was also applied to the soil for comparison. The compost used was slightly alkaline (pH 8) and contained 28% organic carbon, 2.3% Ca and 0.8% Na. It had a C/N ratio of 17, and the amount of plant nutrients was lower than that of chemical fertilisers. The refuse compost also possessed high levels of heavy metals such as Cd, Cu, Mn, Pb and Zn. Results of the pot trial showed that, in general, crop productivity was in the ascending order of sandy soil alone < refuse compost < chemical fertiliser. As for the compost-treated soils, the highest yields were obtained in the treatment with 120 tonnes ha −1 for B chinensis and L . esculentum , and 50 tonnes ha −1 for D . carota . Heavy metal concentrations were distributed differently in different species: in B . chinensis , the root had higher concentrations than the shoot; in D . carota , the aerial part contained higher concentrations than the edible roots; in L . esculentum , the fruit contained lower concentrations than any other part of the plant. When considering edible portions only, B . chinensis and D . carota were the greatest accumulators of heavy metal, whilst L . esculentum accumulated these metals to a lesser extent.