Variations of soil structure and microbial population in a compost amended soil

Changes in soil structure and in microbial population were recorded in a long term field experiment over the growing season of maize (June–November). Determinations were made on samples from plots which had received, for two years, the following treatments: mineral fertilizers, farmyard manure and three rates of compost. Seasonal variations were observed for the stability of soil aggregates, total porosity, pore size distribution, mycorrhizal infection and aerobic cellulolytic microorganisms. The stability of the soil aggregates changed in a similar way to that found for both mycorrhizal infection and the number of aerobic cellulolytic microorganisms. Physical characteristics were not affected in any instance by the organic dressings and microbiological populations were generally influenced only by the higher doses of compost.     

Growth-limiting phosphate nutrition suppresses nitrate accumulation in greenhouse lettuce

Lettuce was grown in aerated nutrient solutions containing all necessary plant nutrients except phosphate. Phosphate was supplied at four different exponentially increasing rates of daily dosage. In addition, two levels of light and atmospheric CO2 were imposed. The four phosphate addition treatments resulted in different, fairly constant relative growth rates, whereas little effect was observed from light or CO2 levels. Growth reduction associated with limiting phosphate nutrition resulted in increases in root/shoot ratio, dry matter content and concentrations of sugars and organic acids. By contrast, the concentrations of nitrate in the shoots was decreased. The concentrations of nitrate and the sum of sugars and organic acids in the shoot showed a strong negative correlation. Two opposing mechanistic models concerning the effects of environmental conditions on nitrate accumulation in plants are discussed in the light of these results.     

Chemical properties of soils amended with compost of urban waste

The influence of urban waste compost on soil fertility was tested by an experiment performed under laboratory conditions in which two soils treated with compost were incubated at a constant moisture for 12 months at 25°C and 35°C. Separately, some soil-compost samples were treated with atrazine at the rate of 40 ppm. Analyses of total and available elements and the characteristics of extracted humus were carried out during the experiment. The initial increase of most of the analytical parameters tested, caused by the addition of compost, was maintained till the end of the experiment. Negligible differences were noted between soils incubated with and without atrazine.     

Denitrification in lucerne nodules and bacteroids supplied with nitrate

Nodulated lucerne plants ( Medicago sativa L. cv. Aragón) were supplied with 20 m M nitrate. Anaerobically isolated bacteroids of Rhizobium meliloti from these plants were able to denitrify after 48 h treatment. R. meliloti bacteroids behave as total denitrifiers, reducing nitrate to dinitrogen: when acetylene was omitted from the assay medium very little nitrous oxide was recovered. The onset of denitrification activity was coincident with the induction of nitrite reductase activity (EC 1.7.99.3) whereas nitrate reductase activity (EC 1.7.99.4) was constitutive. Whole nodules from plants receiving several doses of nitrate were assayed, in a nitrate-free medium, to monitor denitrification activity dependent on nitrate within the nodules. Denitrification activity was detected after 2 days of 20 m M nitrate supply or after 3 days in the presence of 10 or 5 m M nitrate. These results are discussed in relation to current controversy about nitrate entry into the infection region of nodules. It is concluded that this process occurs more rapidly than suggested in recent research.     

Bacterial community diversity assessment in municipal solid waste compost amended soil using DGGE and ARISA fingerprinting methods

Bacterial community structure and diversity of Tunisian agricultural soil treated with different amounts of municipal solid waste compost (MSWC) and other fertilizers were studied using DGGE and ARISA fingerprinting methods. Sequence analysis of dominant DGGE bands revealed the presence of three major clusters, Cytophaga/Flexibacter/Bacteroides (CFB) group, Proteobacteria and Acidobacteria group. Using ARISA profiles, dominant populations were assigned to low and high GC Gram positive bacteria, Cyanobacteria, Spirochetes and Cytophagales. The two methods revealed the absence of significant bacterial community shifts related to the different MSWC applications. Moreover, indigenous bacterial population of the used loam-clayey soil was observed to limit proliferation and survival of Proteobacteria, initially dominant in MSWC and farmyard manure. Effectiveness of the two methods for soil bacterial community studying was shown. While DGGE was more accurate for bacterial identification, ARISA was more practical for handling and rapid estimation of dominant bacteria.     

Metal accumulation and growth performance of Phaseolus vulgaris grown in fly ash amended soil

Phytoextraction of heavy metals from fly ash (FA) contaminated soil was evaluated using Phaseolus vulgaris var. T55. The results showed that electrical conductivity (EC), cation exchange capacity (CEC), organic carbon (OC) and organic matter (OM) of different amendments decreased with the addition of FA in the soil. The level of diethylene triaminepenta acetic acid (DTPA) extractable metals increased with increase in FA amendments up to 25%. However, Cr was found below detection limit in both the amendments. The metal accumulation in the plant tissues was found in the order of Fe>Zn>Mn>Co>Ni>Pb>Cu>Cd at 25% FA. Accumulation of Fe, Mn, Ni, Cu and Co was found more in the roots while Zn, Pb and Cd were more in the aerial parts.     

Absorption and accumulation of nitrate in plants: influence of environmental factors

Plants adopt various strategies to fulfill their nitrogen nutrition requirement, the most important being the uptake of nitrate from the soil and its subsequent assimilation in to amino acids. The uptake of nitrate is energy dependent and is an active process involving high affinity and low affinity transport systems. The net uptake of the anion depends upon both influx as well as on its passive efflux. When the uptake far exceeds over its assimilation in the plant, there is considerable accumulation of nitrate in the plant parts making them unfit for human and cattle consumption. Various environmental factors affect the uptake and accumulation of nitrate, which along with the genetic component of the plant affecting the net uptake and accumulation of the nitrate, need to be considered and carefully manipulated for effective nitrogen management in the plant, soil and aquatic environment.     

Sulfide persistence in oil field waters amended with nitrate and acetate

Nitrate amendment is normally an effective method for sulfide control in oil field-produced waters. However, this approach has occasionally failed to prevent sulfide accumulation, despite the presence of active nitrate-reducing bacterial populations. Here, we report our study of bulk chemical transformations in microcosms of oil field waters containing nitrate-reducing, sulfide-oxidizing bacteria, but lacking denitrifying heterotrophs. Amendment with combinations of nitrate, acetate, and phosphate altered the microbial sulfur and nitrogen transformations. Elemental sulfur produced by chemotrophic nitrate-reducing bacteria was re-reduced heterotrophically to sulfide. Ammonification, rather than denitrification, was the predominant pathway for nitrate reduction. The application of nitrite led to transient sulfide depletion, possibly due to higher rates of nitrite reduction. The addition of molybdate suppressed both the accumulation of sulfide and the heterotrophic reduction of nitrate. Therefore, sulfidogenesis was likely due to elemental sulfur-reducing heterotrophic bacteria, and the nitrate-reducing microbial community consisted mainly of facultatively chemotrophic microbes. This study describes one set of conditions for continued sulfidogenesis during nitrate reduction, with important implications for nitrate control of sulfide production in oil fields.     

农田土壤硝酸盐积累与淋失研究进展

农田土壤硝酸盐淋失是导致地下水硝酸盐污染的主要原因。影响农田土壤中硝酸盐积累的淋失的因素很多。主要有施肥、降水、灌溉、土壤性质以及耕种制度等,过量施用氮肥,不论是单独施用无机肥、有机肥还是有机、无机混施都能造成硝酸盐在土体中大量积累;耕作和种植制度均能影响硝酸盐在土体中的积累和迁移;降水和灌溉带来的下渗水流是累积在土壤中的硝酸盐向下迁移直至淋失的必要条件,也是运载工具,而土壤中的大孔隙则是下渗水流的主要通道,农田土壤硝酸盐的积累与淋失是多种因素综合作用的结果,模型是研究和预测硝酸盐淋失的理想工具,近年来发展很快,并且得到了很好的应用。     

Growth of bedding plants in commercial potting substrate amended with vermicompost

Vermicompost has been promoted as a viable alternative container media component for the horticulture industry. The purpose of this research was to investigate the use of vermicompost at different points in the production cycle of tomato, marigold, pepper, and cornflower. The incorporation of vermicompost of pig manure origin into germination media up to 20% v/v enhanced shoot and root weight, leaf area, and shoot:root ratios of both tomato and French marigold seedlings; however amendment with vermicompost had little influence on pepper and cornflower seedling growth. Moreover there was no effect on the germination of seed of any species. When seedlings of tomato, French marigold, and cornflower were transplanted into 6-cell packs there was greater plant growth in media amended with vermicompost compared to the control media, and the greatest growth when vermicompost was amended into both the germination and transplant media. This effect was increased when seedlings in the transplant media were irrigated with water containing fertilizer.     

旱地土壤铵态氮和硝态氮累积特征及其与小麦产量的关系

在陕西永寿和河南洛阳分别进行了11处和7处小麦大田试验,设对照(不施氮)和施氮(150 kg N·hm^-2)2个处理,测定了小麦生物量、籽粒产量及不同土层(0～20、20～40、40～60、60～80、80～100 cm)土壤铵态氮、硝态氮浓度.结果表明: 两地土壤铵态氮浓度均很低,而硝态氮浓度较高,其中硝态氮数量占铵态氮、硝态氮总量的91%,在反映土壤供氮特性方面与两者之和有完全一致趋势.不施氮情况下,永寿0～40、0～60、0～80和0～100 cm土层累积的硝态氮与小麦生物量和产量显著相关;而洛阳无显著相关关系.施氮后,永寿不同深度土层累积的硝态氮与小麦生物量和产量的相关关系显著下降,而洛阳出现负相关;两地小麦产量增量与0～80 和0～100 cm土层累积的硝态氮显著或极显著相关.小麦苗期主要依赖0～20 cm土层硝态氮;返青期、拔节期分别利用0～40 cm和0～60 cm土层硝态氮,成熟期则能利用0～100 cm土层累积硝态氮.小麦收获后对照土壤的铵态氮浓度与播前起始值无明显差异,而硝态氮大幅下降.     

Effect of isobutanol on toluene biodegradation in nitrate amended, sulfate amended and methanogenic enrichment microcosms

Isobutanol is an alternate fuel additive that is being considered because of economic and lower emission benefits. However, future gasoline spills could result in co-contamination of isobutanol with gasoline components such as benzene, toluene, ethyl-benzene and xylene. Hence, isobutanol could affect the degradability of gasoline components thereby having an effect on contaminant plume length and half-life. In this study, the effect of isobutanol on the biodegradation of a model gasoline component (toluene) was examined in laboratory microcosms. For this, toluene and isobutanol were added to six different toluene degrading laboratory microcosms under sulfate amended, nitrate amended or methanogenic conditions. While toluene biodegradation was not greatly affected in the presence of isobutanol in five out of the six different experimental sets, toluene degradation was completely inhibited in one set of microcosms. This inhibition occurred in sulfate amended microcosms constructed with inocula from wastewater treatment plant activated sludge. Our data suggest that toluene degrading consortia are affected differently by isobutanol addition. These results indicate that, if co-contamination occurs, in some cases the in situ half-life of toluene could be significantly extended.     

Potential nitrification in alum-treated soil slurries amended with poultry manure

Alum is used to reduce environmental pollutants in poultry production. Alum decreases NH3 volatilization and increases total N and NH4+-N compared to untreated poultry manure. Nitrification in poultry wastes could therefore be stimulated due to higher NH4+ concentrations or could be inhibited because the soil environment is acidified. A 10-day laboratory study was conducted to study potential nitrification rates in soil slurries (20 g soil in 150 ml water) amended with 2.0 g alum-treated poultry manure. Fecal bacteria, NH4+, NO2-, NO3-, orthophosphate, pH, and NH3 were measured at 2-day intervals. Alum significantly reduced fecal bacteria concentrations through day 6. Water-soluble P was reduced 82% by day 10. Alum-treated manure had significantly increased NH4+ concentrations by day 8 and 10, and significantly decreased NO2- and NO3- concentrations by days 6-10. Alum's effect on potential nitrification was inhibitory in the soil environment. Slurries with alum-treated poultry manure had reduced nitrification rates, fecal bacteria, and soluble P. Therefore, in addition to reducing P loss, alum could temporarily reduce the risk for environmental pollution from land-applied manures in terms of both NO3- and fecal bacteria loss.     

Heavy-metal accumulation in crops grown on sewage sludge amended with metal salts

Poplar (Populus euramericana Robusta), oats (Avena sativa L. Leander), maize (Zea mays L. Ona 36), English ryegrass (Lolium perenne L.), butter head lettuce (Lactuca sativa L. Reskia), spinach (Spinacia oleracea L. Subito) and French beans (Phaseolus vulgaris Prelude), were grown in pots with pure sewage sludge (pH 6.7), amended with Cd, Cr, Cu, Ni, Pb and Zn acetates, either added singly or in combination, to study metal effects on plant growth and metal uptake. Phytotoxic metal doses varied with metal and plant species, increasing in the order Cd<Ni<Cu<Zn<Cr and Pb. The threshold dose of toxic metals applied in combination was generally lower than that of metals given singly. Addition of Cd, Ni and Zn was clearly reflected in the respective plant concentrations. This was much less so for Cu, whereas Cr and Pb concentrations were not affected in most plant species. Critical plant (leaf) metal concentrations were lower for metals applied in combination than for single metals. Because of such phenomena the use of critical levels as a diagnostic tool for determining potential multiple metal toxicity is limited.     

渭北旱塬苹果园土壤深层干燥化与硝酸盐累积

以渭北旱塬的苹果园为研究对象,对5～34龄苹果园土壤剖面水分含量分布与硝酸盐累积状况进行研究．结果发现,旱地苹果园的高投入与高产出经营方式不但导致了土壤深层干燥化,而且土壤深层累积了大量的硝态氮,累积层在40～260cm土层,最高含量达403．4mg·kg^-1．由于连续施氮肥,这些氮素被再利用的可能性很小,存在土体中的硝态氮会造成潜在的环境问题．由于土壤深层水对干旱的调节作用减弱或丧失,导致苹果产量受控于当季节降水．因此,应当控制苹果园施氮量,避免氮素的大量累积,并采取措施改善果园水分状况。     

双氰胺单次配施和连续配施的土壤氮素形态和蔬菜硝酸盐累积变化

采用田间试验研究了双氰胺(dicyandiamide,缩写DCD)单次配施和连续配施的土壤氮素形态和蔬菜硝酸盐累积变化。结果表明,与单施化肥相比,DCD单次配施的长期叶菜甘蓝生长过程中土壤铵态氮含量增幅为21.3%—339.4%,土壤硝态氮和菜体硝酸盐含量降幅分别为5.4%—80.2%和4.4%—58.3%;短期叶菜空心菜收获时土壤铵态氮含量增加了299.4%,土壤硝态氮和菜体硝酸盐含量分别降低了26.2%和31.7%。DCD连续配施的"甘蓝-菠菜-空心菜-萝卜-大白菜"种植体系中,土壤铵态氮、硝态氮和菜体硝酸盐含量均呈累积的趋势,配施DCD的土壤铵态氮含量从略高于化肥处理(44.0%)发展到极显著高于化肥处理(392.5%,P<0.01),土壤硝态氮含量从极显著低于化肥处理(-68.2%,P<0.01)发展到显著高于化肥处理(146.6%,P<0.05),菜体硝酸盐含量从显著低于化肥处理(-30.2%,P<0.05)发展到极显著高于化肥处理(40.4%,P<0.01)。由此可见,DCD单次配施可显著降低菜体硝酸盐含量,而连续配施DCD的土壤能维持一定量的铵态氮水平,这些盈余的铵态氮会进一步转化为硝态氮残留在土壤中,并可能产生蔬菜硝酸盐累积的风险。     

Changes in microbial biomass and P fractions in biogenic household waste compost amended with inorganic P fertilizers

The present study was conducted to evaluate the changes in microbial biomass indices (C, N, and especially P) and in P fractions in compost amended with inorganic P fertilizers. In the non-amended control, the average contents of microbial biomass C, N, and P were 1744, 193, and 63 microg g(-1) compost, respectively. On average, 1.3% of total P was stored as microbial biomass P. The addition of KH(2)PO(4) and TSP (triple super phosphate) led to immediate significant increases in microbial biomass C, N, and P. Approximately, 4.6% of the added TSP and 5.8% of the added KH(2)PO(4) were incorporated on average into the microbial biomass throughout the incubation. Approximately, 4.7% of the 1mg and 5.8% of the 2mg addition rate were incorporated on average into the microbial biomass. In the amendment treatments, the average contents of microbial biomass C, N, and P declined by 44%, 64%, and 49%, respectively. Initially, the average size of the P fractions in the non-amended compost increased in the order (% of total P in brackets) resin P (0.7%)相似文献   

Denitrification of nitrate and nitric acid with methanol as carbon source

Summary A methanol/nitrate-medium and anaerobic conditions yielded an enrichment culture which consisted ofHyphomicrobium andParacoccus. This mixed culture proved to be very effective in denitrification of solutions containing high concentrations of nitrate and free nitric acid when grown in a chemostat (D=0.04 h^-1). With 0.1 mol/l nitric acid solution as feed medium the pH in the culture vessel adjusted itself to 5.8. For the reduction of 1 g NO₃–N 2.6 g methanol were consumed and 0.56 g cells were produced.