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Ingrid C Burke - One of the best experts on this subject based on the ideXlab platform.
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potential Nitrogen Immobilization in grassland soils across a soil organic matter gradient
Soil Biology & Biochemistry, 2000Co-Authors: John E Barrett, Ingrid C BurkeAbstract:Nitrogen additions to grasslands have increased historically and are likely to continue increasing given the current and projected land use patterns, urbanization and fossil fuel use. Nitrogen retention in both grassland and forest soils is often limited by organic substrate availability, but few studies have explicitly tested the relationship between soil carbon content and Nitrogen retention. We initiated a laboratory study to directly assess the influence of soil organic matter content on potential Nitrogen Immobilization and turnover for soils collected from across a temperature gradient in the Great Plains region of the U.S. We measured soil organic carbon, total Nitrogen and carbon‐Nitrogen ratios and estimated carbon mineralization and net Nitrogen mineralization over 5- and 30-day laboratory incubations. We used the 15 N pool dilution assay to estimate gross Nitrogen Immobilization and Nitrogen turnover for 5 day laboratory incubations. Soil organic carbon concentration and soil carbon‐ Nitrogen ratios were negatively correlated with mean annual temperature in a linear regression model that accounted for 46‐ 56% of the variability, respectively. Regional patterns in soil organic carbon content and small scale variability in substrate availability imposed by discontinuous plant cover together strongly influenced potential Nitrogen Immobilization. Potential carbon mineralization and Nitrogen Immobilization increased with increasing soil organic matter content. Soil organic carbon content accounted for 58% of the variation in potential rates of N Immobilization. A strong correlation between Nitrogen Immobilization and carbon mineralization further suggests that rapid stabilization of Nitrogen is facilitated by an active microbial community and the availability of a readily mineralizable organic substrate. 7 2000 Elsevier Science Ltd. All rights reserved.
Eric A Davidson - One of the best experts on this subject based on the ideXlab platform.
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short term soil respiration and Nitrogen Immobilization response to Nitrogen applications in control and Nitrogen enriched temperate forests
Forest Ecology and Management, 2004Co-Authors: Patricia Micks, John D Aber, Richard D Boone, Eric A DavidsonAbstract:Forest stands at the Harvard Forest, Petersham, MA, receiving experimentally elevated N inputs have shown greatly increased N leaching loss yet still retain over 70% of the added N in soils, presumably in organic form. Whether microbial or abiotic mechanisms are responsible for the high N retention is not well understood. We monitored soil respiration and extractable NH4N and NO3-N following monthly applications of NH4NO3 to a hardwood forest and a pine plantation during the fifth year of chronic fertilizer applications (15 g N as NH4NO3 m � 2 per year). We hypothesized that individual N applications would increase short-term soil respiration (within 1 month) in previously unamended and N-limited soil, but that little or no increase would occur following N applications to chronically N-amended soils, assumed to be carbon-limited to some degree after 5 years of N additions. Short-term soil respiration did not increase after N additions in either the chronically amended or previously untreated soils except for one instance in the latter. However, extractable N levels in both previously unamended plots returned to preapplication levels within 2 weeks of the N addition. This rapid disappearance of the applied N suggests microbial Immobilization, but in all but one instance there was no accompanying CO2 efflux increase indicating increased microbial biomass growth. A model of N Immobilization through microbial biomass production, driven by the observed apparent net N Immobilization, predicted soil CO2 efflux 4‐17 times greater than measured rates. Microbial biomass production does not appear to be the mechanism by which the fertilizer N Immobilization occurred, according to our assumptions about microbial C:N ratios and carbon use efficiency. Hardwood stand average soil respiration rates over the study period were significantly higher in the previously unamended plot than in the control, and the control and chronically N-treated plot respiration rates were similar. Soil respiration rates for all pine stand treatments were similar. These results are insufficient to support our hypotheses concerning carbon versus Nitrogen limitation in these soils. Our results, along with evidence from other studies, suggest that abiotic mechanisms play a role in the high retention of long-term N additions in these soils. # 2004 Elsevier B.V. All rights reserved.
Bram Govaerts - One of the best experts on this subject based on the ideXlab platform.
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crop residue management and soil health a systems analysis
Agricultural Systems, 2015Co-Authors: Mariesoleil Turmel, Frédéric Baudron, Alicia B Speratti, Nele Verhulst, Bram GovaertsAbstract:Abstract Due to the scarcity of alternative organic amendments, the retention of crop residue in fields can be considered key in promoting physical, chemical, and biological attributes of soil health in agricultural systems of developing countries. However, due to multiple other uses, small landholders in these countries are faced with trade-offs in managing crop residues. This article reviews crop residue management practices, mainly surface retention, incorporation or removal, describing their advantages and limitations in cereal-based agroecosystems in developing countries. The benefits of residue retention are regionally variable and depend on both agroclimatic and socioeconomic factors. Most studies from developing countries in Asia, Latin America, and Africa show positive effects of retaining crop residues on soil quality, soil organic matter and carbon storage, soil moisture retention, enhanced nutrient cycling, and decreased soil loss, among other environmental and soil health benefits. Variation was observed in the effect of surface retention vs. incorporation on various soil properties indicating the importance of taking into account abiotic factors such as climate, soil texture, study duration, sampling methods, and agronomic practices when assessing the impact of these practices. Negative effects of residue retention on crop performance attributed to Nitrogen Immobilization, waterlogging and decreased soil temperature have also been reported in some environments. Residue trade-offs in mixed crop-livestock systems in developing countries can limit the amount of residue retained. However, interventions such as intensification, partial retention, improved return of nutrients from manures, and the provision of substitutes to the current functions of livestock (e.g. mechanization, insurance) could reduce these residue trade-offs in favour of promoting long-term soil health.
Jason P Kaye - One of the best experts on this subject based on the ideXlab platform.
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nitrate transformation and Immobilization in particulate organic matter incubations influence of redox iron and a biotic conditions
PLOS ONE, 2019Co-Authors: Fiona R Kizewski, Jason P Kaye, Carmen MartinezAbstract:Nitrate can be reduced to other N inorganic species via denitrification and incorporated into organic matter by Immobilization; however, the effect of biotic/abiotic and redox condition on Immobilization and denitrification processes from a single system are not well documented. We hypothesize nitrate (NO3-) transformation pathways leading to the formation of dissolved- and solid-phase organic N are predominantly controlled by abiotic reactions, but the formation of soluble inorganic N species is controlled by redox condition. In this study, organic matter in the form of leaf compost (LC) was spiked with 15NO3- and incubated under oxic/anoxic and biotic/abiotic conditions at pH 6.5. We seek to understand how variations in environmental conditions impact NO3- transformation pathways through laboratory incubations. We find production of NH4+ is predominantly controlled by redox whereas NO3- conversion to dissolved organic Nitrogen (DON) and Immobilization in solid-phase N are predominantly controlled by abiotic processes. Twenty % of added 15N-NO3- was incorporated into DON under oxic conditions, with abiotic processes accounting for 85% of the overall incorporation. Nitrogen Immobilization processes resulted in N concentrations of 4.1–6.6 μg N (g leaf compost)-1, with abiotic processes accounting for 100% and 66% of the overall (biotic+abiotic) N Immobilization under anoxic and oxic conditions, respectively. 15N-NMR spectroscopy suggests 15NO3- was immobilized into amide/aminoquinones and nitro/oxime under anoxic conditions. A fraction of the NH4+ was produced abiotically under anoxic conditions (~10% of the total NH4+ production) although biotic organic N mineralization contributed to most of NH4+ production. Our results also indicate Fe(II) did not act as an electron source in biotic-oxic incubations; however, Fe(II) provided electrons for NO3- reduction in biotic-anoxic incubations although it was not the sole electron source. It is clear that, under the experimental conditions of this investigation, abiotic and redox processes play important roles in NO3- transformations. As climatic conditions change (e.g., frequency/intensity of rainfall), abiotic reactions that shift transformation pathways and N species concentrations from those controlled by biota might become more prevalent.
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Inorganic Nitrogen Immobilization in live and sterile soil of old-growth conifer and hardwood forests: implications for ecosystem Nitrogen retention
Biogeochemistry, 2012Co-Authors: David Bruce Lewis, Jason P KayeAbstract:Rapid Immobilization of inorganic Nitrogen (N) in soil contributes to ecosystem N accumulation, even in old-growth and chronically-fertilized forests once thought to have poor N retention capacity. In old-growth conifer and hardwood stands in Pennsylvania, we tested the hypotheses that biotic and abiotic N Immobilization are regulated by N form and forest type. We added ^15NH_4 ^+, ^15NO_2 ^−, and ^15NO_3 ^− to sterile (γ-irradiated) and live organic-horizon soil and define N Immobilization as the mass of added ^15N remaining in soil following extractions conducted 15 min, 24 h, and 21 days later. Immobilization of NO_2 ^− (19–25% of added N) occurred in sterile soils within 15 min and was little changed thereafter. Tracer NO_3 ^− Immobilization was not observed, although soils had been pretreated (refrigerated) so as to quantify the lower limit of Immobilization potential. Immobilization of NH_4 ^+ (27%) occurred in live conifer soils by 21 days but not in other treatments. In 21-day incubations, tracer N Immobilization was greater in NO_3 ^−-poor and humic-rich soils. Immobilization was greater in sterile than in live soil, perhaps owing to artifacts of sterilization. Conifer stands exhibited more massive O-horizons, so NO_2 ^− Immobilization per unit area was greater in conifer (1.46 mg N m^−2) than hardwood (0.43 mg N m^−2) stands, possibly accounting for lower N leaching from conifer forests. Areal Immobilization rates appear to be fast enough to retain all N transformed to NO_2 ^−, so NO_2 ^− production may be a limiting step in soil N retention in old-growth ecosystems.
Lihong Gao - One of the best experts on this subject based on the ideXlab platform.
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effects of summer catch crop residue management soil temperature and water on the succeeding cucumber rhizosphere Nitrogen mineralization in intensive production systems
Nutrient Cycling in Agroecosystems, 2010Co-Authors: Yongqiang Tian, Jun Liu, Xueyan Zhang, Lihong GaoAbstract:Nitrogen nutrient management is crucially important in shallow-rooted vegetable production systems characterized by high input and high environmental risk. To investigate the effects of summer catch crop (sweet corn, common bean, garland chrysanthemum and edible amaranth), residue management, and soil temperature and water on the succeeding cucumber rhizosphere Nitrogen mineralization in intensive production systems, we determined the rates of net Nitrogen mineralization and nitrification in a 4-year field experiment on greenhouse cucumber double-cropping systems. Summer catch crop and its residue significantly increased the succeeding cucumber rhizosphere mineral Nitrogen contents, when compared to conventional practices. In general, summer catch crop and its residue significantly increased the rates of both net Nitrogen mineralization and net Nitrogen nitrification at 4 or 40°C, and increased the rates of net Nitrogen Immobilization (negative mineralization) and net Nitrogen nitrification at 15 or 28°C, in succeeding cucumber rhizosphere after four-year treatment. Soil temperature and water had more influence than catch crops and residue management on N mineralization. The effect of carbon on Nitrogen mineralization was more pronounced than that of Nitrogen, and the effect of microbial carbon on the different forms of inorganic N was more pronounced than that of organic carbon. When the effects of soil temperature and water content were eliminated, cumulative net Nitrogen mineralization and nitrification in catch crop and residue management plots were 296–784 and 57–84% higher, respectively, than conventional practices plots. Catch crops and residue management influenced change of ammonium-N more significantly than that of nitrate-N. Additionally, there were complex relationships between fruit yield and soil N mineralization in catch crop- and residue management-induced systems.