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  • 1
    ISSN: 1432-0789
    Keywords: Nitrification inhibitor ; Dicyandiamide ; Soil microbial adaptation ; Zero-order kinetics ; Lag phase ; DCD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The kinetics of dicyandiamide (DCD) decomposition were studied (at 80% water-holding capacity) in pretreated and non-pretreated soils, using model experiments. DCD was added in different concentrations (6.7, 16.7, and 33.3 μg DCD-N g−1 dry soil) and incubated at various temperatures (10°, 20°, and 30°C). Additionally, DCD decomposition was examined in sterile soil (with or without Fe2O3) after inoculation with a DCD-enrichment culture. In the sterile variant, (30°C)the applied dicyandiamide concentration remained constant, even after 36 days. In the sterilized and reinoculated variant, DCD disappeared within 7 days. Addition of Fe2O3 powder to the sterilized soil had no effect on DCD degradation. In the pretreated soils, DCD mineralization started immediately at all temperatures and concentrations without a lag phase. A temperature increase of 10°C doubled the mineralization rate. The mineralization rates were independent of the initial concentrations. In the non-pretreated soils (except at 30°C with 16.7 and 33.3 μg DCD-N g−1 dry soil) DCD decreased only after a short (30°C) or a long (10°C) lag phase. These results suggest that an inducible metabolic degradation occurred, following zeroorder kinetics.
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  • 2
    ISSN: 1432-0789
    Keywords: Microbial biomass N ; Spruce forest ; Acid deposition ; Irrigation ; Liming ; Carbon mineralization ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seasonal effects of liming, irrigation, and acid precipitation on microbial biomass N and some physicochemical properties of different topsoil horizons in a spruce forest (Picea abies L.) were measured throughout one growing season. The highest biomass N was recorded in autumn and spring in the upper soil horizons, while the lowest values were obtained in summer and in deeper horizons. The clearest differences between the different soil treatments were apparent in autumn and in the upper horizons. Liming increased the microbial biomass N from 1.7% of the total N content to 6.8% (Olf1 layer) and from 1% to 2% of the total N content in the Of2 layer. The main inorganic-N fraction in the deeper horizons was NO inf3 sup- . An increase in cation exchange capacity was observed down to the Oh layer, while soil pH was only slightly higher in the Olf1 and Of2 layers after liming. The effects of irrigation were less marked. The microbial biomass N increased from 1.7% of total N to 4.8% in the Olf1 layer and from 1% to 2% of total N in the Of2 layer. In the Olf1 layer an increase in C mineralization was observed. Acid precipitation decreased the microbial biomass N in the upper horizons from 4.8% of total N to 1.8% in the Olf1 layer and from 2% to 0.5% in the Of2 layer. No significant changes in soil pH were observed, but the decrease in cation exchange capacity may result in a decrease in the proton buffering capacity in the near future.
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  • 3
    ISSN: 1432-0789
    Keywords: Acetylene inhibition technique ; Denitrification ; Carbon: nitrate ratio ; Acetylene blockage ; Reliability of AIT ; N2O-reductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In model experiments with a silty loam soil the effect of different C : NO inf3 sup- -N ratios on the reliability of C2H2 (1% v/v) in blocking N2O-reductase activity was examined. The soil was carefully mixed with different amounts of powdered lime leaves (Tilia vulgaris) to obtain organic C contents of about 1.8, 2.3, and 2.8%, and of NO inf3 sup- solution to give C : NO inf3 sup- -N ratios of 84, 107, 130, 156, 200, and 243. The soil samples were incubated in specially modified anaerobic jars (22 days, 25°C, 80% water-holding capacity, He atmosphere) and the atmosphere was analysed for N2, N2O, CO2, and C2H2 by gas chromatography at regular intervals. Destruction jars were used to analyse soil NO inf3 sup- , NH 4 + and C. The results clearly showed that N2O-reductase activity was completely blocked by 1% (v/v) C2H2 only as long as NO inf3 sup- was present. In the presence of C2H2, NO inf3 sup- was apparently entirely converted into N2O. The C2H2 blockage of N2O-reductase activity ceased earlier in soils with a wide C : NO inf3 sup- -N ratio (156, 200, and 243) than in those with closer C : NO inf3 sup- -N ratios (84, 107, and 130). As soon as NO inf3 sup- was exhausted, N2O was reduced to N2 in spite of C2H2. The wider the C : NO inf3 sup- -N ratio, the earlier the production of N2 and the less the reliability of the C2H2 blockage. In the untreated control complete inhibition of N2O-reductase activity by C2H2 lasted for 7–12 days. In the field, estimates of total denitrification losses by the C2H2 inhibition technique should be considered reliable only as long as NO inf3 sup- is present. Consequently, NO inf3 sup- monitoring in the field is essential, particularly in soils supplied with easily decomposable organic matter.
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  • 4
    ISSN: 1432-0789
    Keywords: Green manuring ; Sesbania rostrata ; Aeschynomene afraspera ; Wetland soils ; Rice yield ; Urea ; Nitrogen accumulation ; Exchangeable ammonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Organic-N fertilizers in the form of flood-tolerant, leguminous, stem-nodulating Sesbania rostrata and Aeschynomene afraspera may be useful alternatives to resource-poor rice farmers if applied as green manure. Therefore, the accumulation of N by these green manure species and their effect on the performance and yield of wetland rice (IR 64) was examined at four different sites in Luzon, Philippines. Soils deficient in N, P, and K were selected and compared with the fertile Maahas clay of the International Rice Research Institute (IRRI) at Los Baños. The green manure plants were grown under flooded conditions for 49 days in the wet season of 1987, chopped, and then ploughed in before transplanting rice seedlings. In a second experiment, the effect of S. rostrata green manure was studied under rainfed conditions. All green manure treatments were compared to an urea treatment (60 kg N ha−1) and an untreated control. Both legumes developed well, even on the marginally productive soils. S. rostrata accumulated up to 190 kg N ha−1 and A. afraspera even accumulated 196 kg N ha−1 in the shoots. In all treatments, green manure increased grain yield significantly (P=0.05) over the untreated control, by 1.3–1.7 Mg ha−1. The yields were comparable to those obtained with 60 kg N ha−1 of urea fertilizer. S. rostrata caused the highest grain yield, of 6.5 Mg ha−1 on the Maahas clay soil of IRRI. The apparent release of exchangeable NH 4 + -N in the soils after green manuring and the rice grain yield response showed that both green manure species may provide sufficient available N throughout the development of IR 64 in the wet season. In the rainfed marginal soil site, green manure with S. rostrata produced even higher rice grain yields than urea. Green manure therefore seems particularly attractive for poor farmers on marginally productive soils, at least as a temporary strategy to improve yield and yield sustainability.
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  • 5
    ISSN: 1432-0789
    Keywords: Key words Constructed wetlands ; Waste-water treatment ; Reed ; Phragmites australis ; Released and retained nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In less populated rural areas constructed wetlands with a groundfilter made out of the local soil mixed with peat and planted with common reed (Phragmites australis) are increasingly used to purify waste water. Particularly in the rhizosphere of the reed, nitrification and denitrification processes take place varying locally and temporally, and the question arises to what extent this type of waste-water treatment plant may contribute to the release of N2O. In situ N2O measurements were carried out in the two reed beds of the Friedelhausen dairy farm, Hesse, Germany, irrigated with the waste water from a cheese dairy and 70 local inhabitants (12 m3 waste water or 6 kg BOD5 or 11 kg chemical O2 demand (CODMn) day–1). During November 1995 to March 1996, the release of N2O was measured weekly at 1 m distances using eight open chambers and molecular-sieve traps to collect and absorb the emitted N2O. Simultanously, the N2O trapped in the soil, the soil temperature, as well as the concentrations of NH4 +-N, NO3 –-N, NO2 –-N, water-soluble C and the pH were determined at depths of 0–20, 20–40 and 40–60 cm. In the waste water from the in- and outflow the concentrations of CODMn, BOD5, NH4 +-N, NO3 –-N, NO2 –-N, as well as the pH, were determined weekly. Highly varying amounts of N2O were emitted at all measuring dates during the winter. Even at soil temperatures of –1.5  °C in 10 cm depth of soil or 2  °C at a depth of 50 cm, N2O was released. The highest organic matter and N transformation rates were recorded in the upper 20 cm of soil and in the region closest to the outflow of the constructed wetland. Not until a freezing period of several weeks did the N2O emissions drop drastically. During the period of decreasing temperatures less NO3 –-N was formed in the soil, but the NH4 +-N concentrations increased. On average the constructed wetlands of Friedelhausen emitted about 15 mg N2O-N inhabitant equivalent–1 day–1 during the winter period. Nitrification-denitrification processes rather than heterotrophic denitrification are assumed to be responsible for the N2O production.
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  • 6
    ISSN: 1432-0789
    Keywords: Key words Microbial biomass ; Fumigation extraction method ; Flooded soil ; Lowland rice ; Microbial C : N ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  A chloroform-fumigation extraction method with fumigation at atmospheric pressure (CFAP, without vacuum) was developed for measuring microbial biomass C (CBIO) and N (NBIO) in water-saturated rice soils. The method was tested in a series of laboratory experiments and compared with the standard chloroform-fumigation extraction (CFE, with vacuum). For both methods, there was little interference from living rice roots or changing soil water content (0.44–0.55 kg kg–1 wet soil). A comparison of the two techniques showed a highly significant correlation for both CBIO and NBIO (P〈0.001) suggesting that the simple and rapid CFAP is a reliable alternative to the CFE. It appeared, however, that a small and relatively constant fraction of well-protected microbial biomass may only be lysed during fumigation under vacuum. Determinations of microbial C and N were highly reproducible for both methods, but neither fumigation technique generated NBIO values which were positively correlated with CBIO. The range of observed microbial C:N ratios of 4–15 was unexpectedly wide for anaerobic soil conditions. Evidence that this was related to inconsistencies in the release, degradation, and extractability of NBIO rather than CBIO came from the observation that increasing the fumigation time from 4 h to 48 h significantly increased NBIO but not CBIO. The release pattern of CBIO indicated that the standard fumigation time of 24 h is applicable to water-saturated rice soils. To correct for the incomplete recovery of CBIO, we suggest applying the k C factor of 2.64, commonly used for aerobic soils (Vance et al. 1987), but caution is required when correcting NBIO data. Until differences in fumigation efficiencies among CFE and CFAP are confirmed for a wider range of rice soils, we suggest applying the same correction factor for both methods.
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  • 7
    ISSN: 1432-0789
    Keywords: Sesbania rostrata ; Green manure ; Biofertilizer ; Nitrogen fixation ; Stem nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ratooning and stem cutting were compared with seeding in order to reduce the amount of seeds of Sesbania rostrata for green-manure growth. Both methods increased the biofertilizer yield highly significantly within a 6-week growth period.
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  • 8
    Electronic Resource
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    Springer
    Biology and fertility of soils 1 (1985), S. 59-59 
    ISSN: 1432-0789
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 9
    ISSN: 1432-0789
    Keywords: Denitrification ; Acetylene inhibition technique ; Grassland ; Lolium perenne ; Animal slurry ; Dicyandiamide ; Nitrification inhibition ; Ammonium nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a field experiment, the effect of animal slurry, (with and without the nitrification inhibitor dicyandiamide on total denitrification losses estimated by the C2H2 inhibition technique was measured over 2 years (1989–1990). During this period, four different plots (each with four replicates) were fertilized six times with 150 kg N ha-1 in the form of cattle-pig slurry or NH4NO3. Soil samples (0–20 cm) were analysed at regular intervals for NH inf4 sup+ and NO inf3 sup− concentrations. The soil water content was determined gravimetrically. During the first year (1989) total denitrification losses from unfertilized, mineral-fertilized, and animal slurry-amended plots (with or without dicyandiamide) were estimated as 0.2, 3.1, 0.7, and 0.6 kg N ha-1, respectively. During the second year (1990) the denitrification losses were 0.4, 1.3, 0.7, and 0.7 kg N ha-1, respectively. There was a clear relationship between the NO inf3 sup− concentration or soil water content and the denitrification rate. The results are siteund experiment-specific and cannot be generalized so far.
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  • 10
    ISSN: 1420-9071
    Keywords: N2O release ; activated sludge ; nitrification ; denitrification ; ozone destruction ; greenhouse effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Waste water purification is characterized by intensive mineralization and nitrification processes. Because of the high O2 demand, temporarily anaerobic conditions may be produced, and denitrification by nitrifying organisms as well as heterotropic denitrification may contribute to N2O release. In situ measurements (1993–1994) suggest that N2O is released from activated sludge in a domestic waste water treatment plant at an average rate of 1040 μg m−2h−1 with a range between zero and 6198 μg m−2h−1. The production of N2O seems to be related to the concentration of NO 2 − and NO 3 − as well as to the pH. In the waste water about 75–200 μg N2O l−1 is dissolved. This N2O is released after discharge into the receiving waters. The N2O is produced essentially by nitrification rather than by heterotropic denitrification. On a long-term scale the increasing use of mechanical-biological waste water purification plants world-wide may add increasingly to the anthropogenic production of N2O, although the present amount of N2O produced is negligible compared to its global terrestrial production.
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