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The robustness of the assumption of equilibrium between native and added N during 15N isotope dilution has recently been questioned by Watson et al. (Soil Biol Biochem 32 (2000) 2019-2030). We re-analyzed their raw data using equations that consider the added and native NH4+ and NO3− pools as separate state variables. Gross mineralization rates and first-order rate constants for NH4+ and NO3− consumption were obtained by combining analytical integration of the differential equations with a non-linear fitting procedure. The first-order rate constants for NH4+ consumption and NO3− immobilization for the added NH4+ and NO3− pool were used to estimate gross mineralization rates and first-order rate constants for nitrification of native NH4+. The latter were 2-4 times lower than the first-order rate constants derived from the added N pool. This discrepancy between first-order rate constants for nitrification implies that one or more process rates estimated for the added N pools cannot be applied to the native N pools. Preferential use of the added N resulted in an overestimation of the gross mineralization by 1.5-2.5-fold, emphasizing the need for critical evaluation of the assumption of equilibrium before gross mineralization rates are calculated. 相似文献
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可矿化氮与各有机氮组分的关系 总被引：20，自引：2，他引：20
用通气培养法测定了6种肥力36个不同土层土壤的可矿化氮,用Bremner法测定了各有机氮组分,采用相关分析、多元回归分析和通径分析确定可矿化氮与各有机氮组分之间的关系。结果表明,酸解氮与可矿化氮有较密切的正相关关系。在酸解氮中,酸解未知态氮与可矿化氮不相关;而氨基酸态氮、铵态氮、氨基糖态氮的多少与可矿化氮相互平行,相关系数均较高,似乎对可矿化氮皆有贡献。但多元回归分析表明,氨基糖态氮在方程中不显著;逐步回归分析更肯定了这一结果。通径分析进一步表明氨基酸态氮和铵态氮对可矿化氮有很高的通径系数,表明了它们有着直接重大贡献,而氨基糖态氮直接通径系数甚低。这些结果说明,可矿化氮主要来自酸解氮,特别是氨基酸态氮和铵态氮,后两者是其产生的主要来源。 相似文献
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J. Petersen I. K. Thomsen L. Mattsson E. M. Hansen B. T. Christensen 《Soil Use and Management》2010,26(4):455-464
Organic inputs [e.g. animal manure (AM) and plant residues] contribute directly to the soil organic N pool, whereas mineral N fertilizer contributes indirectly by increasing the return of the crop residues and by microbial immobilization. To evaluate the residual effect of N treatments established in four long‐term (>35 yr) field experiments, we measured the response of barley (grain yield and N offtake at crop maturity) to six rates (0, 30, 60, 90, 120 and 150 kg N/ha) of mineral fertilizer N (Nnew) applied in subplots replacing the customary long‐term plot treatments of fertilizer inputs (Nprev). Rates of Nprev above 50–100 kg N/ha had no consistent effect on the soil N content, but this was up to 20% greater than that in unfertilized treatments. Long‐term unfertilized plots should not be used as control to test the residual value of N in modern agriculture with large production potentials. Although the effect of mineral Nprev on grain yield and N offtake could be substituted by Nnew within a range of previous inputs, the value of Nprev was not eliminated irrespective of Nnew rate. Provided a sufficient supply of plant nutrients other than N, the use‐efficiency of Nnew did not change significantly with previous mineral N fertilizer rate. The residual effect of mineral N fertilizer was negligible compared with the residual effect of N from AM and catch crop residues. 相似文献
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Today, a large share of mineral fertilizer is substituted by biogas digestates. Biogas digestates are known to promote N2O production, compared to mineral fertilizer. In particular, the initial phase following fertilizer application is crucial for the N gas release as N2O and also N2. However, this period impact has been rarely investigated, especially not across various field sites. Thus, undisturbed soil cores from two fertilizer types (biogas digestate vs. mineral fertilizer) at five sites with different site characteristics were investigated in a short‐term laboratory experiment under N2‐free helium–oxygen incubation atmosphere. Across sites, biogas digestate soil cores showed significantly higher absolute N2O fluxes compared to mineral fertilizer soil cores, even though this effect was dominated by samples from one site (Dornburg with the highest biogas digestate fertilization rate). Also relative N2O fluxes showed a similar tendency. On average, absolute and relative N2 fluxes differed between the two fertilizer types, while N2 fluxes were highest at the Dornburg site. A N2O/(N2O+N2) ratio of denitrification below or equal to 0.5 clearly highlighted the importance of N2O reduction to N2 for three of five the biogas digestate soil cores. Soil characteristics like bulk density and water‐filled pore space as proxies for gas diffusivity in soil, as well as N availability ( , ), significantly affected the N2O and N2 fluxes from the biogas digestate soil cores. While this study presents data on short‐term N2O and N2 fluxes, there is a need for further studies in order to investigate the dynamics, the duration of the observed effects and their significance at the field scale. 相似文献
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Muneshwar Singh Samaresh Kundu Ashis K. Biswas Jayanta K. Saha Awadhesh K. Tripathi Chuni L. Acharya 《植物养料与土壤学杂志》2004,167(5):577-583
A computational exercise was undertaken to quantify the percent N derived from atmosphere %Ndfa) in soybean and consequent N benefit from biological N2‐fixation process annually accrued to the soil by the soybean crop using average annual N‐input/‐output balance sheet from a 7 yr old soybean‐wheat continuous rotational experiment on a Typic Haplustert. The experiment was conducted with 16 treatments comprised of combinations of four annual rates of farmyard manure (FYM ? 0, 4, 8, and 16 t ha–1) and four annual rates of fertilizer N (? 0, 72.5, 145, and 230 kg N ha–1) applications. The estimated N contributed through residual biomass of soybean (RBNS) consisting of leaf fall, root, nodules, and rhizodeposition varied in the ranges of 7.02–16.94, 11.65–28.83, 3.31–8.91, and 11.3–23.8 kg N ha–1 yr–1, respectively. A linear relationship was observed between RBNS and harvested biomass N (HBNS) of soybean in the form of RBNS = 0.461 × HBNS – 20.67 (r = 0.989, P < 0.01), indicating that for each 100 kg N assimilated by the harvested biomass of soybean, 25.4 kg N was added to the soil through residual biomass. The Ndfa values ranged between 13% and 81% depending upon the annual rates of application of fertilizer N and FYM. As per the main effects, the %Ndfa declined from 76.4 to 26.0 with the increase in annual fertilizer‐N application from 0 to 230 kg N ha–1, whereas %Ndfa increased from 40.8 to 65.8 with the increase in FYM rates from 0 to 16 t ha–1, respectively. The N benefit from biological N2 fixation accrued to the soil through residual biomass of soybean ranged from 7.6 to 53.7 kg N ha–1 yr–1. The treatments having %Ndfa values higher than 78 showed considerable annual contribution of N from N2 fixation to the soil which were sufficient enough to offset the quantity of N removed from the soil (i.e., native soil N / FYM‐N / fertilizer‐N) with harvested biomass of soybean. 相似文献
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Wolfgang Merbach Joachim Schulze Maja Richert Evan Rrocco Konrad Mengel 《植物养料与土壤学杂志》2000,163(4):375-379
The suitability of three 15N application methods (15NH3 fumigation, split‐root technique, 15N pre‐cultivation) for the estimation of N net rhizodeposition (NRD) of wheat plants into soil has been tested and compared under similar conditions and at the same developmental stage. The results were as follows: 1. The use of the 15N tracer technique allows the detection of the net N release by roots under soil conditions. NRD was considerable and can be estimated to be at least 15 kg N ha−1 a−1. 2. All three methods applied are practicable under non‐sterile experimental conditions. The distribution of applied 15N in the system and NRD can be balanced totally only by using the 15NH3 fumigation and the 15N pre‐cultivation methods. The split‐root technique leads to an overestimation of NRD. 3. The split‐root technique allows a qualitative separation of the NRD under nearly undisturbed conditions. With the 15N precultivation, a higher 15N‐labelling can be achieved for long‐term balance studies. 4. Despite the required high 15N abundance, the 15NH3 fumigation method works best to evaluate the influence of microbes on NRD and to quantify the gaseous 15N release. 相似文献
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Richard K. F. Nair Kendalynn A. Morris Mirco Migliavacca Gerado Moreno Marion Schrumpf 《植物养料与土壤学杂志》2020,183(4):517-529
Background: Nitrogen deposition can cause an ecosystem‐level shift in available N (nitrogen) to P (phosphorus) availability. However, most plant N nutrition is from edaphic sources rather than deposition and in seasonally dry grassland systems, root litter is the predominant nutrient source. Aims: We were interested how litter turnover and altered nutrient recycling from dead biomass can compensate for these shifts in ecosystem stoichiometry. Methods: We studied a Mediterranean savanna amended with N or NP treatments three years prior. We measured root and plant‐available soil N:P stoichiometry in two micro‐habitats: open pasture and beneath oak canopies. 15N‐labelled root litter incubated in topsoils without litterbags was used to trace uptake of litter N by herbaceous strata roots. Results: Since fertilization, NP added sites have become relatively P enriched, resulting in lower N:P ratios in living roots than either when N was added alone or control sites. Total litter‐derived 15N uptake by roots was proportional to root ingrowth response but higher in the NP than N treatment, indicating a higher N demand when N and P were added together. We observed more 15N uptake by plants under tree canopies, indicating a tighter nutrient recycling loop in these micro‐habitats in contrast to treatment level ‘fertility' trends. Conclusions: Root stoichiometry responded to manipulated soil nutrient availability and N uptake was altered as plants attempted to compensate for nutrient availability imbalances, indicating that these ecosystem perturbations have long term effects on nutrient cycling which can propagate to whole system function. This was also related to functional community‐level adaptions between micro‐habitats with under canopy communities more able to take advantage of the litter nutrient source. 相似文献
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High N fertilizer application to irrigated wheat in Northern Mexico for conventionally tilled and permanent raised beds: Effects on N balance and short term N dynamics
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下载免费PDF全文 Kathrin Grahmann Nele Verhulst Klaus Dittert Bram Govaerts Andreas Buerkert 《植物养料与土壤学杂志》2018,181(4):606-620
Nitrogen (N) surpluses from fertilizer application can cause major environmental harm including pollution of surface water, groundwater, and air. To assess such negative externalities, N balances are a complex but useful tool to predict surpluses and to measure effects of nutrient optimization strategies in agriculture. The Yaqui Valley in north‐western Mexico is representative for thousands of square kilometres of intensive, irrigated wheat production under arid conditions worldwide and has been targeted for conservation agriculture in recent years. For these cropping systems, detailed N balances are scarce and often incomplete. To help fill this knowledge gap, data from a long‐term experiment were collected in 2013/14 on a Vertisol to examine the impact of three tillage‐straw management practices (CTB: conventionally tilled beds; PB‐straw: permanent raised beds with residue retention; PB‐burn: permanent raised beds with residue burning) on N dynamics. Tillage had significant effects on soil NO3‐N, NH4‐N, and total N contents across the cropping period. Soil total N content was at all sampling depths lowest in CTB. Soil NO3‐N in the 0–90 cm profile was highest in PB‐burn over the cropping period and ranged from 77 kg ha?1 in the bed before pre‐planting fertilizer application up to 269 kg ha?1 in the furrow after the second fertilizer application. Annual simple N balances were +59 kg N ha?1 in CTB, +39 kg N ha–1 in PB‐straw, and +46 kg N ha?1 in PB‐burn. Residual mineral soil N was significantly affected by tillage‐straw management and lowest for PB‐straw (+205 kg N ha?1) and highest for CTB, and for PB‐burn (+283 kg N ha?1 each) in the 0–90 cm soil profile. Soil NO3‐N moved out of the effective wheat root zone, as indicated by the high residual NO3‐N content at 30–90 cm depth, which is an important pathway of N leaching. Quantifiable N losses through leaching and volatilization averaged 100 kg N ha?1. Our findings suggest that there is potential for substantial reductions in N inputs in all tillage‐straw systems to decrease N losses and to reduce mineral residual soil N, but care should be taken to avoid reducing grain protein content, which in PB straw was already below the quality standard. A knowledge transfer of the European “Nmin” concept is advisable in this region to regulate N fertilizer over‐application. 相似文献
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The effects of various measures introduced to increase nitrogen (N)‐use efficiency and reduce N losses to water in a 6‐yr crop rotation (winter wheat, spring barley, green manure, winter wheat, spring barley, spring oilseed rape) were examined with respect to N leaching, soil mineral N (SMN) accumulation and grain yield. An N‐use efficient system (NUE) with delayed tillage until late autumn and spring, direct drilling of winter wheat, earlier sowing of winter and spring crops and use of a catch crop in winter wheat was compared with a conventional system (CON) in a field experiment with six separately tile‐drained plots in south‐western Sweden during the period 1999–2011 (two crop rotation cycles). Total leaching of NO3‐N from the NUE system was significantly 46 and 33% lower than in the CON system during the first and second crop rotation cycle, respectively, with the most pronounced differences apparently related to management strategies for winter wheat. Differences in NO3‐N leaching largely reflected differences in SMN during autumn and winter. There was a tendency for lower yields in the NUE system, probably due to problems with couch grass. Overall, the measures for conserving N, when frequently used within a crop rotation, effectively reduced NO3 concentrations in drainage water and NO3‐N leaching losses, without severely affecting yield. 相似文献
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化肥氮对冬小麦氮素吸收的贡献和土壤氮库的补偿 总被引：4，自引：1，他引：3
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《European Journal of Soil Biology》2006,42(1):43-50
Trachypogon savannas in Venezuela are mainly used for extensive cattle raising. These savannas are currently affected with man-made or natural fires. During fires, 24% of the nitrogen (N) necessary for primary production is lost through volatilisation. More is lost by leaching and/or erosion. Since those losses are not compensated for by N input through precipitation, N balance in these savannas depends on biological mechanisms. In this study we explore the possible forms of biological N fixation, in particular the cyanobacterial activity from soil microbial crusts, and the contribution of grass rhizosphere microorganisms. Determinations were made by using, in situ, the method of acetylene reduction as an estimate of nitrogenase activity (NA). N2 fixation due to NA in the soil–plant system is 13.7 and 7.8 kg ha–1 year–1 for the burned and protected plots, respectively. Even considering the lowest fixation values by microbial crusts, they could provide 6% of the N needed for annual production of the vegetation of the savanna under fire, and 9% in the protected savanna. These amounts of N2 sustained the productivity of the vegetation experiencing periodical fires. 相似文献
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Availability of N from Casuarina residues and inorganic N to maize, using 15N isotope techniques 总被引：1，自引：0，他引：1
The contribution of N from Casuarina equisetifolia (casuarina) residues to maize with inorganic N (ammonium sulphate) supplementation was studied in a pot experiment using
15N labelling techniques. A single rate of N application of 100 mg N kg–1 soil was applied as N-ammonium sulphate in combination with casuarina residues in the proportions 100 : 0; 75 : 25; 50 : 50;
25 : 75 and 0 : 100, respectively. The directly 15N-labelled casuarina residue and indirect labelling (unlabelled casuarina + 15N soil) were compared to estimate the proportion and amount of N derived from the residue and fertilizer. The application
of ammonium sulphate at a high rate significantly affected shoot dry matter (P<0.05) and likewise reduced the contribution of soil-derived N compared to residues. Total recoveries by maize of residue
N and applied fertilizer N averaged 11% and 24%, respectively. Residue and fertilizer use efficiencies were not influenced
by the addition of different rates of fertilizer or residue. The estimation of the contribution of N from different sources
showed that direct measurement of the 15N-labelled organic source was more reliable.
Received: 10 September 1997 相似文献
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A new 15N tracing model was developed to analyse nitrogen (N) transformations in old grassland soil. There was a need to develop a new model because existing models such as FLUAZ were not able to simulate the observed N dynamics. The new features of the model are: (a) simulation of heterotrophic nitrification, (b) simulation of dissimilatory nitrate (NO3−) reduction to ammonium (NH4+) (DNRA), (c) release of adsorbed or stored fertiliser N into the available mineral N pools and (d) immobilisation of NH4+ and NO3− into two separate organic N pools with different re-mineralisation characteristics. The tracing model contains six N pools and nine simultaneous N transformations either at zero- or first-order kinetics. The model is set up in the modelling software ModelMaker which contains non-linear optimisation routines based on the Marquardt-Levenberg algorithm. The model is able to simulate data obtained from triple labelling studies where either the NH4+, the NO3− or both pools were labelled with 15N. The flexible modelling environment allows the user to develop the model further. 相似文献
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黑垆土有机氮组分对可矿化氮的关系 总被引：4，自引：0，他引：4
Mineralizable N and organic N components in different layers (0-15, 15-30, 30-45, 45-60, 60-80 and 80-100 cm) of six soils with different fertilities sampled from Yongshou County, Shaanxi Province, China,were determined by the aerobic incubation method and the Bremner procedure, respectively. Correlation,multiple regression and path analyses were performed to study the relation of minerallzable N to organic N components. Results of correlation and regression analyses showed that the amounts of the N mineralized were parallel to, and significantly correlated with, the total acid hydrolyzahle N, but was not so with the acid-insoluble N. Of the hydrolyzable N, the amino acid N and the ammonia N had a highly consistent significant correlation with the mineralized N, and their partial regression coefficients were significant in the regression equations, showing their importance in contribution to the mineralizable N. The amino sugar N, on the other hand, had a relatively high correlation with the mineralized N, but their partial regression coefficients were not significant in the regression equations. In contrast, the hydrolyzable unknown N had no such relations.Path analysis further indicated that the amino acid N and ammonia N made great direct contributions to the mineralized N, but the contributions of the amino sugar N were very low. These strongly suggested tha tthe mineralized N in the soils tested was mainly from the hydrolyzable N, particularly the amino acid N and ammonia N which are the major sources for its production. 相似文献
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《European Journal of Soil Biology》2006,42(2):89-98
Heavy metals such as arsenic (As), lead (Pb), copper (Cu) and zinc (Zn) can be found in large concentrations in mine spills in Mexico. Interest in contamination by these heavy metals has increased recently as they can change the functioning of soil ecosystems qualitatively and quantitatively. They disturb the activities of soil fauna and contaminate drinking water in large parts of the world, which severely affects human health. Little, however, is known how heavy metals might affect the biological functioning of a soil. Soil was sampled from eight locations along a gradient of heavy-metal contamination with distance from a mine in San Luis Potosí (Mexico) active since about 1800 AD. Microbial biomass was determined with the original chloroform fumigation incubation (CFI) as well as extraction (CFE) techniques and the substrate induced respiration (SIR) technique while C and N mineralization were measured. Total concentrations of As in the top 0–10 cm soil layer ranged from 8 to 22992 mg kg–1, from 31 to 1845 mg kg–1 for Pb, from 27 to 1620 mg kg–1 for Cu and from 81 to 4218 mg kg–1 for Zn. There was a significant negative correlation (P < 0.0001) between microbial biomass, soil organic carbon, total N and C mineralization and the heavy metal content of the soil. The microbial biomass C to organic C ratio, which varied from 0.4 to 1.9%, specific respiratory activity (qCO2), and oxidation of NO2– were not affected by heavy metals. It was found that long-term contamination of soil with heavy metals had an adverse effect on the amount of soil microorganisms as evidenced by a marked decrease in microbial biomass C, but not some of their characteristics. According to principal components analysis (PCA), the correlation matrix showed three distinct factors explaining 71% of the variance. A first factor including heavy metals (As, Pb, Cu and Zn) with a negative loading and total N, organic C, soil microbial biomass with a positive loading characterized the soil organic matter and contamination status. Loam and sand combined for the second factor characterizing the textural classification while the third factor was loaded by CEC and clay content. 相似文献
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Three 15N labelling strategies for estimating below-ground N in Sesbania rostrata grown in pots under flooded conditions were examined. The estimated proportions of total plant N resident below-ground were 13% (stem injection), 42% (leaf immersion) and 56% (adventitious root feeding). The average estimate based on leaf and root immersion (49%) was considered to be realistic on the basis of published literature with other foliar labelled legumes, while root and root-derived N appeared to be underestimated by stem injection. 相似文献
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Highlights
- We review the inherent connections between the soil N cycle, plant N preference and climate.
- Nitrification plays a central role in regulating the NO3? to NH4+ ratio in soil and soil solution.
- Soil N transformations regulate the composition of hydrological N export.
- Plant N uptake can be optimized if soil N cycle is well matched with plant N preference.