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1.
Charcoal‐based amendments have a potential use in controlling NH3 volatilization from urea fertilization, owing to a high cation‐exchange capacity (CEC) that enhances the retention of NH . An incubation study was conducted to evaluate the potential of oxidized charcoal (OCh) for controlling soil transformations of urea‐N, in comparison to urease inhibition by N‐(n‐butyl) thiophosphoric triamide (NBPT). Four soils, ranging widely in texture and CEC, were incubated aerobically for 0, 1, 3, 7, and 14 d after application of 15N‐labeled urea with or without OCh (150 g kg?1 fertilizer) or NBPT (0.5 g kg?1 fertilizer), and analyses were performed to determine residual urea and 15N recovery as volatilized NH3, mineral N (as exchangeable NH , NO , and NO ), and immobilized organic N. The OCh amendment reduced NH3 volatilization by up to 12% but had no effect on urea hydrolysis, NH and NO concentrations, NO accumulation, or immobilization. In contrast, the use of NBPT to inhibit urea hydrolysis was markedly effective for moderating the accumulation of NH , which reduced immobilization and also controlled NH3 toxicity to nitrifying microorganisms that otherwise caused the accumulation of NO instead of NO . Oxidized charcoal is not a viable alternative to NBPT for increasing the efficiency of urea fertilization.  相似文献   

2.
Remediation of an uranium‐mine soil from Settendorf (East Germany) includes phytoextraction under conditions which make its heavy metals more plant‐available but less leachable. A second way is active inhibition of heavy metal uptake by the plant. In a pot trial with Chinese cabbage (Brassica chinensis L.), planted and unplanted soil samples were daily irrigated with deionized water or aqueous solutions with a total of (g (kg soil)–1) CaCl2 (0.26 Ca), NH4Cl (1.39), casein, sucrose, citric acid (13), and an extract of rape (B. napus L.) shoots (13 DW) in a phytotron for 26 d. Water‐irrigated plants were also treated with a 50 mM citric acid solution (10.5 g (kg soil)–1) 6 and 7 d prior to harvesting. Total elements in plant tissue and soluble elements in aqueous extracts from control and postharvest soils were determined by ICP‐AES. Supplements of NH , and the NH ‐generating casein and rape extract reduced soil pH during nitrification, and increased plant uptake of Cd, Cu, Ni, and Zn. Citric acid at 50 mM adjusted soil to pH 4.5–6.0 and enhanced uptake of all elements. Long‐term application of sucrose and citric acid increased pH and inhibited uptake of Cd, Cr, Cu, Ni, and Zn. Contemporarily, leaching of heavy metals and humic substances was lowest with Ca and NH and highest with sucrose and citric acid amendments. It is concluded that Chinese cabbage grown for chelate‐assisted phytoextraction should be supplied with Ca and NH to obtain a high plant biomass on soil with a low hazard of leaching. Metal uptake should be stimulated by application of chelator 7 d prior to harvesting. Undesired uptake of heavy metals by Chinese cabbage determined as food should be inhibited with carbohydrate amendments. Long‐term application of NH or chelator, which reduces the solubility of certain elements but increases their uptake moderately, is recommended as a tool for continuous phytoextraction technologies.  相似文献   

3.
Oat consumption has been rapidly increased worldwide because its high β‐glucan concentration may lower the level of blood cholesterol. The rates of β‐glucan accumulation in two husk and two nude oats were determined with an interval of 5 d after anthesis in a pot experiment. The results showed that a higher nitrogen level increased oat grain yield per plant, thousand‐grain weight, and concentrations of protein and β‐glucan. β‐glucan concentration generally increased with development of grain after anthesis, whereas the accumulation rate of β‐glucan was greater at the early stage of grain development and reached a maximum around 25 d after anthesis. We also found a larger β‐glucan concentration when plants were grown with NO ‐N as compared to NH ‐N. This study may suggest that the agronomic approaches such as nutrient management by optimizing the time and the level of nitrogen application and a higher ratio of NO ‐N to NH ‐N can play an important role in enhancing β‐glucan concentration in oat grains.  相似文献   

4.
Nitrogen (N) is taken up by most plant species in the form of nitrate (NO ) or ammonium (NH ). Plant response to continuous NH nutrition is species‐dependent. In this study, we compare the responses of tomato (Solanum lycopersicum L. cv. Rio Grande) plants to N source (NO or NH ). To this end, early plant growth, photosynthesis, chlorophyll, carbohydrate, and N‐compound concentrations as well as the activities of main enzymes involved in N metabolism (nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate dehydrogenase) were analyzed. Early plant growth was remarkably ameliorated under NH ‐ in comparison to NO ‐based nutrition. Concomitantly, photosynthetic activity, total chlorophyll, and carbohydrate concentrations were significantly increased. With increasing external NH concentration, NH accumulated mainly in roots. In addition, root protein concentration was significantly increased, reflecting high NH incorporation into organic nitrogen. Root glutamine synthetase (GS) activity was enhanced by NH for concentrations below 5 mM, whereas root glutamate dehydrogenase (GDH) activity increased in parallel to NH availability. Together with the positive effect of NH on tomato plant cv. Rio Grande growth, these results reveal that GDH could have, in addition to GS, a possible role in NH detoxification and tolerance of NH ‐based nutrition.  相似文献   

5.
Both earthworms and plant growth–promoting rhizobacteria (PGPR) are ubiquitous and important for promoting circulation of plant macronutrients. Two series of laboratory experiments were conducted to investigate the effects of earthworm casts and activities on the growth of PGPR, and the inoculation of earthworms and PGPR on the availability of N, P, and K in soils, respectively. During a short incubation period (0–34 h), the extracts of earthworm (Pheretima guillelmi)‐worked soil significantly (p < 0.05) increased the abundance of the three species of PGPR, including N‐fixing bacteria (NFB) (Azotobacter chroococcum HKN‐5), phosphate‐solubilizing bacteria (PSB) (Bacillus megaterium HKP‐1), and K‐solubilizing bacteria (KSB) (B. mucilaginous HKK‐1), in Luria‐Bertani (LB) broth. There were synergistic effects of dual inoculation of earthworms and PGPR on increasing the concentrations of NH$ _4^+ $ ‐N, (NO$ _3^- $ + NO$ _2^- $ )‐N, NaHCO3‐extractable P, and NH4OAc‐extractable K in the corresponding soils. Bioavailable N (the sum of NH$ _4^+ $ ‐N and [NO$ _3^- $ + NO$ _2^- $ ]‐N) in the dual inoculation was 4 to 24 times those inoculated with earthworms or NFB alone, respectively. The significantly higher concentrations of bioavailable N and P in the dual inoculation of earthworms and NFB or PSB may be due to the higher abundance of PGPR and/or higher activities of urease and acid phosphatase than those of single inoculation of NFB or PSB, respectively. Dual inoculation of earthworms and PGPR would be most effective in reducing the need for chemical fertilizers in agriculture.  相似文献   

6.
Ammonium (NH ) nutrition causes retardation of growth in many plant species. In Arabidopsis grown with NH as the sole N source, growth retardation occurs already at early stages before photosynthesis has come to its full power. In order to describe the peculiarities of these retarded plants, they were compared with nitrate (NO )‐grown plants of the same age of 15 d. Photosynthetic activity as measured by CO2 uptake per unit chlorophyll is half as high in NH ‐grown seedlings as in NO ‐grown ones. This finding is confirmed by the analysis of chlorophyll fluorescence. Chloroplasts of NO ‐grown, but not of NH ‐grown, seedlings show starch deposits after 5 h of illumination with 40 μmol m–2 s–1. Gene‐expression analysis based on cDNA microarray and on Northern blots provide a clue about the biochemical background. After the first 2 weeks of growth, it seems that NO ‐grown seedlings subsist mainly on normal photosynthesis, whereas NH ‐grown seedlings still use lipids from the seeds stored in oleosomes. Corresponding to this observation, the mRNAs for enzymes of β‐oxidation are more strongly expressed in NH ‐grown seedlings. Different carbohydrate sources for sucrose synthesis are indicated by different gene expression. Higher gene expression of fructose bisphosphate aldolase (cytosolic isoform) in NO ‐grown seedlings indicates the dependence on photosynthesis, whereas a higher gene expression of PEP carboxykinase in NH ‐grown seedlings points to a prominent role of β‐oxidation of storage lipids still present.  相似文献   

7.
Nitrogen (N) is taken up by most plant species in the form of nitrate (NO ) or ammonium (NH ). The plant response to continuous ammonium nutrition is species‐dependent. In this study, the effects of the source of N nutrition (NO , NH , or the mixture of NO and NH ) on the response of clover (Trifolium subterraneum L. cv. 45C) plants to prolonged root hypoxia was studied. Under aerobic conditions, plant growth was strongly depressed by NH , compared to NO or mixed N nutrition, as indicated by the significant decrease in root and shoot‐dry‐matter production (DW), root and shoot water contents (WC), leaf chlorophyll concentration, and chlorophyll fluorescence parameters (F0, Fv/Fm). However, the N source had no effect on chlorophyll a–to–chlorophyll b ratio. Under hypoxic conditions, the negative effects of root hypoxia on plant‐growth parameters (DW and WC), leaf chlorophyll concentration, and chlorophyll fluorescence parameters were alleviated by NH rather than NO supply. Concomitantly, shoot DW–to–root DW ratio, and root and leaf NH concentrations were significantly decreased, whereas root and leaf carbohydrate concentrations, glutamine synthetase activities, and protein concentrations were remarkably increased. The present data reveal that the N source (NO or NH ) is a major factor affecting clover responses to hypoxic stress, with plants being more tolerant when NH is the N form used. The different sensitivity is discussed in terms of a competition for energy between nitrogen assimilation and plant growth.  相似文献   

8.
We have synthesized a novel ambipolar membrane for the simple, rapid, and simultaneous extraction of key nutrients from soil. The membrane was made by adding an anion‐ and a cation‐exchange resin to a polyvinyl alcohol hydrogel in the presence of glutaraldehyde as a cross‐linking agent. The synthetic membrane was efficient in adsorbing (extracting) NO , PO , K+, Ca2+, and Mg2+ ions from soil simultaneously. The ion‐adsorption capacity of the membrane was related to the soil nutrient status, duration of membrane–soil contact, and soil water content. The importance of these factors followed the order: soil nutrient status > contact time > soil water content. Adsorption by the membrane of NO and Mg2+ ions from soil leveled off after 48 h of membrane–soil contact but uptake of Ca2+, PO , and K+ ions required a longer contact time for equilibrium to be established. When the soil water content exceeds 55% w/w, this factor ceased to influence ion adsorption by the ambipolar‐resin membrane. The synthetic membrane is potentially useful for the in situ assessment of the nutrient requirement of certain crops at a given point in time.  相似文献   

9.
The objective of this laboratory study with six loess soils (three Eutric CambisoIs and three Haplic Phaeozems) incubated under flooded conditions was to examine the effect of a wide range of NO doses under anaerobic conditions on soil redox potential and N2O emission or absorption. Due to the fact that loess soils are usually well‐drained and are expected to be absorbers during prevailing part of the season, the study aimed at determination of the conditions decisive for the transition from emission to absorption process. On the basis of the response to soil nitrate level, the two groups of soils were distinguished with high and low denitrification capacity. The soil denitrification activity showed Michaelis‐Menten kinetics with respect to soil nitrate content with KM in the range 50–100 mg NO ‐N kg–1. Percentage of nitrates converted to N2O increased linearly with nitrate concentration in the range from 25 to 100 mg NO ‐N kg–1 up to 43% and decreased linearly at higher concentrations reaching practically zero at concentrations about 600 mg NO ‐N kg–1. No denitrification was observed below 25 mg NO ‐N kg–1. Nitrous oxide absorption in soil occurred only at nitrate concentrations to 100 mg NO ‐N kg–1 and in this concentration range was proportional to the denitrification rate. Nitrous oxide was formed at redox potentials below +200 mV and started to disappear at negative Eh values.  相似文献   

10.
In recent years, interest has grown in cultivating Allium species with enhanced health benefits and/or distinct flavor. Concentrations of phytochemicals determining these desired characteristics may be influenced by nitrogen forms (ammonium or nitrate) and arbuscular mycorrhizal (AM) fungi. We examined these relations with the test plant bunching onion (Allium fistulosum L.). Three different ammonium‐to‐nitrate (NH : NO ) ratios were supplied in combination with or without inoculation with an AM fungus (Glomus mosseae). The plants were evaluated for dry weight, leaf number, and content of nutrients (N, NO , P, S), sugars (glucose, fructose, and sucrose), and organosulfur compounds (measured as pyruvic acid). The experiment was carried out under controlled conditions in a greenhouse. Plants were grown on perlite amended twice a day with nutrient solution. In nonmycorrhizal plants, the application of nutrient solution with predominant NO or NH4NO3 as N source supported adequate growth of Allium fistulosum while predominant NH supply resulted in decreased growth and occurrence of wilting symptoms. Mycorrhizal inoculation significantly increased dry weight and leaf number of predominantly NH ‐fed or NH4NO3‐fed plants. While shoot P concentration increased with higher NH supply, shoot N concentration increased in predominantly NH ‐fed plants only. Nitrogen form and AM colonization had little effect on shoot S or sugar concentrations. The total content in organosulfur compounds was significantly affected by both, N form and AM colonization. The optimal growth condition for a high formation of organosulfur compounds in this experiment was a nutrient solution with predominant NO supply, but when supported by AM fungi, Allium fistulosum produced similar amounts of pyruvic acid in NH4NO3‐fed plants.  相似文献   

11.
Changes of EUF‐extractable nitrogen (N) (nitrate, ammonium, organic N) in 20 arable bare soils, subsequently planted with ryegrass (Lolium multiflorum L.) and cutting three times were investigated in pot experiments. All 20 soils responded qualitatively in the same way. During the period of bare soil, there was a significant increase of EUF‐extractable nitrate (EUF NO ), while extractable ammonium (EUF NH ) remained on the same level and organic N (EUF Norg) decreased. This decrease, however, was not significant. From sowing until the first cutting of the grass, EUF‐NO concentration decreased to almost zero. This low EUF‐NO level was maintained throughout the subsequent experimental period (three cuttings of grass). During the growth of the first cutting, EUF Norg decreased while EUF NH remained constant, however, on a low level. EUF NH fell during the growth of the second and third cutting. In this period, however, the N supply of the grass was insufficient. EUF Norg decreased during the growth of the second cutting, but increased during the growth of the third cutting. This shows that the EUF‐Norg fraction represents a transient pool, which gains and loses N. EUF NO , EUF NH , and EUF Norg correlated with the N uptake of the grass. Strongest correlation for EUF NO was found for the first cutting (p < 0.001), and for EUF NH and EUF Norg for the second and third cutting (p < 0.001). Total soil N was not correlated with the N uptake of the grass. EUF Norg was only about 2% of the total N. This relatively small EUF‐Norg fraction, however, is relevant for the mineralization of organic soil N, and the N quantity indicated by EUF Norg is in the range of the N amount mineralized in arable soils within a growing season.  相似文献   

12.
Nitrate (NO$ _3^ - $ ) and ammonium (NH$ _4^+ $ ) are the predominant forms of nitrogen (N) available to plants in agricultural soils. Nitrate concentrations are generally ten times higher than those of NH$ _4^+ $ and this ratio is consistent across a wide range of soil types. The possible contribution of these small concentrations of NH$ _4^+ $ to the overall N budget of crop plants is often overlooked. In this study the importance of this for the growth and nitrogen budget of maize (Zea mays L.) was investigated, using agriculturally relevant concentrations of NH$ _4^+ $ . Maize inbred line B73 was grown hydroponically for 30 d at low (0.5 mM) and sufficient (2.5 mM) levels of NO$ _3^ - $ . Ammonium was added at 0.05 mM and 0.25 mM to both levels of NO$ _3^ - $ . At low NO$ _3^ - $ levels, addition of NH$ _4^+ $ was found to improve the growth of maize plants. This increased plant growth was accompanied by an increase in total N uptake, as well as total phosphorus, sulphur and other micronutrients in the shoot. Ammonium influx was higher than NO$ _3^ - $ influx for all the plants and decreased as the total N in the nutrient medium increased. This study shows that agriculturally relevant proportions of NH$ _4^+ $ supplied in addition to NO$ _3^ - $ can increase growth of maize.  相似文献   

13.
Nitrate leaching depending on N fertilization and different crop rotations was studied at two sites with sandy soils in N Germany between 1995 and 2000. The leaching of NO was calculated by using a numerical soil‐water and N model and regularly measured Nmin values as input data. Also the variability of Nmin values on the sandy soils was determined along transects. They reveal the high variability of the Nmin values and show that it is not possible to confirm a significant Nmin difference between fertilizer treatments using the normal Nmin‐sampling intensity. Nitrate‐leaching calculations of five leaching periods showed that even strongly reduced N‐fertilizer applications did not result in a substantially lower NO leaching into the groundwater. Strong yield reductions of even more than 50%, however, were immediately measured. Mean NO concentrations in the groundwater recharge are >50 mg L–1 and are mainly due to mineralization from soil organic matter. Obviously, the adjustment of the N cycle in the soil to a new equilibrium and a reduced NO ‐leaching rate as a consequence of lower N inputs need a much longer time span. Catch crops are the most efficient way to reduce the NO concentrations in the groundwater recharge of sandy soils. Their success, however, strongly depends on the site‐specific development possibilities of the catch crop. Even with all possible measures implemented, it will be almost impossible to reach NO concentrations <50 mg L–1 in sandy soils. The only way to realize this goal on a regional scale could be by increasing areas with lower nitrate concentrations in the groundwater recharge like grassland and forests.  相似文献   

14.
In most plant species, nutrient uptake is facilitated upon root association with symbiotic arbuscular mycorrhizal (AM) fungi. The aim of the present experiment was to test how the form in which nitrogen (N) is supplied to the growth medium affects substrate pH, AM development, and contribution of the symbiosis to phosphorus (P) uptake from sparingly available or soluble resources. Cowpea (Vigna unguiculata L. Walp) plants inoculated or noninoculated with AM fungi (Glomus sp.) were grown in pots with a sand substrate supplied with nutrient solution. The nutrient solution was prepared either with a high or a low concentration of soluble P, and NO ‐N : NH ‐N ratios of 9:1 or 5:5. The substrate supplied with low‐P nutrient solution was either or not additionally amended with ground rock phosphate. Despite a high level of root colonization, AM fungi used in the present study did not appear to increase plant availability of rock phosphate. It cannot be excluded that the ability of AM root systems to acquire P from sparingly available resources differs depending on the plant and fungal genotypes or environmental conditions. The absence from the growth substrate of P‐solubilizing microorganisms able to associate with AM mycelia might also have been a reason for this observation in our study. Increased supply of NH relative to NO improved plant P availability from rock phosphate, but also had a negative effect on the extent of AM‐fungal root colonization, irrespective of the plant P‐nutritional status. Whether increasing levels of NH can also negatively affect the functioning of the AM symbiosis in terms of plant element uptake, pathogen protection or soil‐structure stabilization deserves further investigation.  相似文献   

15.
Recent studies suggest an important role of thermophilic bacterial communities of the Phylum Firmicutes on soil C, N and S cycling, and a positive effect on crop productivity through the production of sulfate (SO $ _4^{2 - } $ ) and ammonium (NH $ _4^+ $ ), essential plant nutrients. Copper (Cu) is commonly supplemented to soils as a fungicide in phytosanitary treatments although its consequences to the bacterial communities is frequently overlooked. Herein, we report on the influence of temperature and Cu on the microbial communities, namely those of the Phylum Firmicutes, from a soil collected at an olive orchard in S Portugal. Community fingerprints and band identification through sequencing was combined with measurement of SO $ _4^{2 - } $ and NH $ _4^+ $ production at different supplemented amounts of Cu and at moderate and high temperatures (30°C and 50°C, respectively). Both temperature and Cu induced changes in these communities, selecting for specific bacteria. Temperature induced the dominance of Brevibacillus, and Cu addition to soil caused a reduction of SO $ _4^{2 - } $ release by soil bacteria. Ammonium production during bacterial growth at moderate and high temperatures was not affected by Cu addition. A Cu‐tolerant thermophilic isolate, belonging to the Bacillus genus, showed significant inhibition by high Cu concentrations and a reduction of NH $ _4^+ $ release during growth; genera Brevibacillus and Bacillus have been previously reported as high NH $ _4^+ $ and SO $ _4^{2 - } $ producers of the Firmicutes phylum. Results indicate that Cu treatments select specific tolerant bacterial strains which could influence natural soil fertilization in Cu‐treated orchards.  相似文献   

16.
There has been a partial shift away from conventional flood irrigation (FI) practices for rice (Oryza stativa L.) production in water‐scarce northern China. Drip irrigation with plastic film mulch (DI‐PFM) can maintain high rice yields with significant water savings. However, rice seedlings often develop chlorosis when grown with DI‐PFM on calcareous soil. Bicarbonate is a concern with regard to chlorosis in calcareous soil. The objective of this simulation experiment was to determine the effect of irrigation method and irrigation water HCO $ _3^ - $ concentration on (1) soil pH and DTPA‐Fe concentration, (2) chlorophyll, total Fe, and active Fe concentrations of rice leaves, and (3) rice root and shoot biomass. The experiment consisted of four treatments: FI with water containing either 2 or 10 mM HCO $ _3^ - $ (referred to as FI‐2 and FI‐10, respectively) and DI‐PFM with water containing 2 or 10 mM HCO $ _3^ - $ (referred to as DI‐2 and DI‐10, respectively). The results show that the HCO $ _3^ - $ concentrations of the soil solution were greater under FI than under DI‐PFM, because more irrigation water was applied in the FI system. Soil pH increased as the HCO $ _3^ - $ concentration of the irrigation water increased. The increase in soil pH was greater in DI‐PFM than in FI. Soil DTPA‐Fe concentration, leaf SPAD values, leaf total Fe concentration, leaf active Fe concentration, shoot biomass, and root biomass decreased as the HCO $ _3^ - $ concentration of the irrigation water increased. The decreases were less under DI‐PFM than under FI. Overall, the results indicate that rice plants are more sensitive to the HCO $ _3^ - $ concentration of irrigation water under FI than under DI‐PFM.  相似文献   

17.
An incubation and a pot experiment were conducted to evaluate the dissolution and agronomic effectiveness of a less reactive phosphate rock, Busumbu soft ore (BPR), in an Oxisol in Kenya. Resin (anion and anion + cation)‐extractable P and sequentially extracted P with 0.5 M NaHCO3, 0.1 M NaOH, and 1 M HCl were analyzed. Dissolution was determined from the increase in anion resin (AER)–, NaHCO3‐, and NaOH‐extractable P in soil amended with PR compared with the control soil. Where P was applied, resin P significantly increased above the no‐P treatment. Busumbu‐PR solubility was low and did not increase significantly in 16 weeks. Anion + cation (ACER)‐extractable P was generally greater than AER‐P. The difference was greater for PR than for triple superphosphate (TSP). The ACER extraction may be a better estimate of plant P availability, particularly when poorly soluble P sources are used. Addition of P fertilizers alone or in combination with Tithonia diversifolia (TSP, BPR, TSP + Tithonia, and BPR + Tithonia) increased the concentration of labile inorganic P pools (NaHCO3‐ and NaOH‐Pi). Cumulative evolved CO2 was significantly correlated with cumulative N mineralized from Tithonia (r, 0.51, p < 0.05). Decrease in pH caused NH ‐N accumulation while NO ‐N remained low where Tithonia was incorporated at all sampling times. However, when pH was increased, NH ‐N declined with a corresponding rise in NO ‐N. Tithonia significantly depressed soil exchangeable acidity relative to control with time. A significant increase (p < 0.05) was observed for P uptake but not dry‐mass production in maize where BPR was applied. The variations in yield and P uptake due to source and rates of application were statistically significant. At any given P rate, highest yields were obtained with Tithonia alone. Combination of Busumbu PR with TSP or Tithonia did not enhance the effectiveness of the PR. The poor dissolution and plant P uptake of BPR may be related to the high Fe content in the PR material.  相似文献   

18.
Soil moisture affects the degradation of organic fertilizers in soils considerably, but less is known about the importance of rainfall pattern on the turnover of C and N. The objective of this study was to determine the effects of different rainfall patterns on C and N dynamics in soil amended with either biogas slurry (BS) or composted cattle manure (CM). Undisturbed soil cores without (control) or with BS or CM, which were incorporated at a rate of 100 kg N ha–1, were incubated for 140 d at 13.5°C. Irrigation treatments were (1) continuous irrigation (cont_irr; 3 mm d–1); (2) partial drying and stronger irrigation (part_dry; no irrigation for 3 weeks, 1 week with 13.5 mm d–1), and (3) periodic heavy rainfall (hvy_rain; 24 mm d–1 every 3 weeks for 1 d and 2 mm d–1 for the other days). The average irrigation was 3 mm d–1 in each treatment. Cumulative emissions of CO2 and N2O from soils amended with BS were 92.8 g CO2‐C m–2 and 162.4 mg N2O‐N m–2, respectively, whereas emissions from soils amended with CM were 87.8 g CO2‐C m–2 and only 38.9 mg N2O‐N m–2. While both organic fertilizers significantly increased CO2 production compared to the control, N2O emissions were only significantly increased in the BS‐amended soil. Under the conditions of the experiment, the rainfall pattern affected the temporal production of CO2 and N2O, but not the cumulative emissions. Cumulative NO leaching was highest in the BS‐amended soils (9.2 g NO ‐N m–2) followed by the CM‐amended soil (6.1 g NO ‐N m–2) and lowest in the control (4.7 g NO ‐N m–2). Nitrate leaching was also independent of the rainfall pattern. Our study shows that rainfall pattern may not affect CO2 and N2O emissions and NO leaching markedly provided that the soil does not completely dry out.  相似文献   

19.
Species‐specific uptake and allocation mechanisms for N are scarce, in particular when trees are cultivated in potted soil under more natural conditions than in hydroponic culture. The objective of this study was to compare specific N‐uptake rates for economically and ecologically important tree species in Central European forests: pine (Pinus sylvestris), spruce (Picea abies), oak (Quercus petraea), beech (Fagus sylvatica), lime (Tilia cordata), and ash (Fraxinus excelsior) when they grow in mineral soil from an old fallow site with a pH of 6. We used an 15N‐labeling method to measure tree seedling 15N uptake in potted soils (Humic Cambisol) when both N forms NH$ _4^+ $ and NO$ _3^- $ were simultaneously present in the soil solution for interspecies comparison and assessment of relationships between specific 15N‐uptake rates and amino acid–accumulation rates or relative growth rates (RGR). The results demonstrate that tree species varied significantly in their capacity to take up NH$ _4^+ $ or NO$ _3^- $ into roots, stems, or leaves, but indicate only marginal differences in their preference for NH$ _4^+ $ or NO$ _3^- $ when they grow in mineral soil. The ranking of specific 15N‐uptake rates for NH$ _4^+ $ and NO$ _3^- $ was oak < beech < spruce < pine < lime < ash. Fine roots of all species had the highest specific 15N‐uptake rates for both N forms, followed by total roots, leaves/needles, and stems. As regards tree seedling species, we found negative relationships between glutamine (Gln)‐accumulation rates in leaves/needles and total 15N‐uptake rates in fine roots. Noteworthy was the fact that, at high Gln‐accumulation rates, the N‐uptake system in fine roots of ash was probably lower under feedback inhibition by the amino acid.  相似文献   

20.
Microbiological and biochemical characterization of agricultural soils Part. I. Determination of a soil microbiological index The intensity of soil microbial activity was determined by measuring the total microbial biomass, the activity of cellfree hydrolases (saccharase, protease and alkaline phosphatase) as well as mainly cellbound reductases (dehydrogenase and catalase). Testing 33 mixed samples of 11 different or differently treated, agricultural soils in Bavaria, a highly significant correlation (r = 0.77–0.99) between all individual microbiological soil properties was found. No correlations could be found with the additionally determined plate counts of bacteria or with nitrifications tests. This close relation between the tested biomass and enzyme activities could be used for calculating an over-all index (Bodenmikrobiologische Kennzahl) of soil microbial activity by transforming and combining the individual analytical soil properties according to the following equation:   相似文献   

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