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1.
Effects of ammonium and nitrate on mineralization of nitrogen from leguminous residues 总被引:2,自引:0,他引:2
A laboratory incubation experiment was conducted to compare the effects of NH
inf4
sup+
and NO
inf3
sup-
on mineralization of N from 15N-labelled vetch (Vicia villosa Rotn) in an Illinois Mollisol, and to determine the effect of a nitrification inhibitor (nitrapyrin) on mineralization of vetch N when used with NH
inf4
sup+
. The addition of either NH
inf4
sup+
or NO
inf3
sup-
(100 and 200 mg N kg-1 soil) significantly increased mineralization of vetch N during incubation for 40 days. The effect was greater with NH
inf4
sup+
than with NO
inf3
sup-
, and a further increase occurred in the presence of nitrapyrin (10 mg kg-1 soil). The addition of NO
inf3
sup-
retarded the nitrification of NH
inf4
sup+
-N derived from vetch. 相似文献
2.
The effects of wheat straw and different forms of N on denitrification and N immobilization were studied in an anaerobic water-sediment system. The water-sediment system was supplemented with various combinations of wheat straw and 15N-labelled and unlabelled (NH4)2SO4 or KNO3, and incubated anaerobically at 30°C for 10 days. 15N-labelled and unlabelled NO
inf3
sup-
, NO
inf2
sup-
, NH
inf4
sup+
, and organic N were determined in the water-sediment system. The gases evolved (N2, CO2, N2O, and CH4) were analyzed by gas chromatography at regular intervals. Larger quantities of 15N2–N and organic 15N were formed in wheat straw-amended systems than in non-amended systems. Trends in CO2 production were similar to those of N2–N evolution. The evolution of N2O and CH4 was negligible. Denitrification processes accounted for about 22 and 71% of the added 15NO
inf3
sup-
–N in the absence and presence of wheat straw, respectively. The corresponding denitrification rates were 3.4 and 12.4 g 15Ng-1 dry sediment day-1. In systems amended with 15NO
inf3
sup-
–N and 15NO
inf3
sup-
+NH
inf4
sup+
–N without wheat straw, 1.82 and 1.58%, respectively, of the added 15NH
inf3
sup-
–N was immobilized. The corresponding figures for the same systems supplemented with wheat straw were 5.08 and 4.10%, respectively. Immobilization of 15NO
inf4
sup+
–N was higher than that of 15NO
inf3
sup-
–N. The presence of NO
inf3
sup-
–N did not stimulate NH
inf4
sup+
–N immobilization. 相似文献
3.
Summary Gross rates of N mineralization, assimilation, nitrification, and NO
in3
sup-
reduction were determined in soil from a wet riparian fen by 1-day incubations of soil cores and slurries with 15N-labelled substrates. N mineralization transformed 0.1% of the total organic N pool daily in the soil cores, of which 25% was oxidized through autotrophic nitrification and 53%–70% was incorporated into microorganisms. N mineralization and nitrification were markedly inhibited below 5 cm in soil depth. At least 80% of the NO
in3
sup-
reduction in aerated cores occurred through dissimilatory processes. Dissimilatory reduction to NH
in4
sup+
(DNRA) occurred only below 5 cm in depth. The results show that NH
in4
sup+
oxidation was limited by available substrate and was itself a strong regulator of NO
in3
sup-
-reducing activity. NO
in3
sup-
reduction was significantly increased when the soil was suspended under anaerobiosis; adding glucose to the soil slurries increased NO
in3
sup-
reduction by 2.4–3.7 times. Between 3% and 9% (net) of the added NO
in3
sup-
was reduced through DNRA in the soil slurries. The highest percentage was observed in soil samples from deeper layers that were pre-incubated anaerobically. 相似文献
4.
A pot experiment was conducted to compare the uptake and dry matter production potential of NH
inf4
sup+
and NO
inf3
sup-
and to study the effect of Baythroid, a contact poison for several insect pests of agricultural crops, on growth and N uptake of maize (Zea mays L.). Nitrogen was applied as (15NH4)2SO4, K15NO3, or 15NH4NO3 and in one treatment Baythroid was combined with 15NH4NO3. Source of N had, in general, a nonsignificant effect on dry matter and N yield, but uptake of NO
inf3
sup-
was significantly higher than that of NH
inf4
sup+
when both N sources were applied together. Substantial loss of N occurred from both the sources, with NH
inf4
sup+
showing greater losses. Baythroid was found to have a significant positive effect on dry matter yield of both root and shoot; N yield also increased significantly. Uptake of N from both the applied and native sources increased significantly in the presence of Baythroid and a substantial added nitrogen interaction (ANI) was determined. The positive effect of Baythroid was attributed to: (1) a prolonged availability of NH
inf4
sup+
due to inhibition of nitrification, (2) an increased availability of native soil N through enhanced mineralization, and (3) an enhanced root proliferation. 相似文献
5.
We measured the growth, nutrition, and N assimilation of arbuscular-mycorrhizal and non-mycorrhizal lettuce (Lactuca sativa L.) as affected by forms of N and drought. Moisture was maintained at 80% water-holding capacity, and N was applied as NO
inf3
sup-
, NH
inf4
sup+
, or NO
inf3
sup-
/NH
inf4
sup+
(3:1, 1:1, or 1:3). The growth of Glomus fasciculatum-colonized plants was comparable to that of uncolonized P-supplemented plants when N was provided as NH
inf4
sup+
or combined NO
inf3
sup-
/NH
inf4
sup+
. When N was supplied solely as NO
inf3
sup-
, G. fasciculatum-colonized plants produced a higher yield than P-fertilized plants, suggesting that the uptake and/or assimilation of NO
inf3
sup-
was particularly affected by mycorrhizal status in this water-limited situation. Nutrient availability, except Ca, was less limited for mycorrhizal plants than for P-fertilized plants. P fertilization increased the growth, glutamine synthetase activity, and protein content of lettuce to the same extent that G. fasciculatum colonization did when N was applied as NH
inf4
sup+
. With NO
inf3
sup-
-fertilization, G. fasciculatum-colonized plants showed increased growth, nitrate reductase activity, and protein content compared to P-fertilizer treatment. Plants colonized by G. mosseae showed increased photosynthetic activity and proline acumulation, and these mechanisms may be important in adaptation by the plant to drought conditions. The present results confirmed that under drought conditions, the uptake or metabolism of N forms is particularly affected in mycorrhizal fungi-colonized plants, depending on the mycorrhizal endophyte and the N source added. Thus the significance of arbuscular-mycorrhizal fungus selection for plant growth in drought conditions is a consideration for management strategy. 相似文献
6.
Temperature dependence of nitrification,denitrification, and turnover of nitric oxide in different soils 总被引:2,自引:0,他引:2
Summary The temperature dependence of the NO production rate and the NO consumption rate constant was measured in an Egyptian soil, a soil from the Bavarian Forest, and a soil from the Donau valley, together with the temperature dependence of the potential rates of ammonium oxidation, nitrite oxidation, and denitrification, and the temperature dependence of the growth of NH
inf4
sup+
-oxidizing, NO
inf2
sup-
-oxidizing, and NO
inf3
sup-
-reducing bacteria in most probable number assays. In the acidic Bavarian Forest soil, NO production was only stimulated by the addition of NO
inf3
sup-
but not NH
inf4
sup+
. However, NO production showed no temperature optimum, indicating that it was due to chemical processes. Most probable numbers and potential activities of nitrifiers were very low. NO consumption, in contrast, showed a temperature optimum at 25°C, demonstrating that consumption and production of NO were regulated individually by the soil temperature. In the neutral, subtropical Egyptian soil, NO production was stimulated only by the addition of NH
inf4
sup+
but not NO
inf3
sup-
. All activities and most probable numbers showed a temperature optimum at 25° or 30°C and exhibited apparent activation energies between 61 and 202 kJ mol-1. However, a few nitrifiers and denitrifiers were also able to grow at 8° or 50°C. Similar temperature characteristics were observed in the Donau valley soil, although it originated from a temperate region. In this soil NO production was stimulated by the addition of NH
inf4
sup+
or of NO
inf3
sup-
. Both NO production and consumption were stimulated by drying and rewetting. 相似文献
7.
A laboratory incubation experiment was conducted to study the effect of indigenous inorganic N on the immobilization of applied N and on the occurrence of an added N interaction (ANI). Samples of six Mollisols from Illinois were incubated with 15N-labelled (NH4)2SO4 (100 or 200 mg N kg-1 soil), with or without the use of 0.01 M CaCl2 to extract inorganic N (mainly NO
inf3
sup-
) before incubation. From 6 to 49% of the N applied was immobilized, higher percentages being obtained with unextracted soils than with the extracted soils and with the higher rate of N addition. Net mineralization of native N occurred in both the unextracted and extracted soils, but was more extensive in the unextracted soil and increased with the addition of N. The increases were accompanied by a positive ANI, which usually exceeded the amount of applied N immobilized and increased with the rate of addition. The ANI values observed with extracted soils were attributed to increased mineralization of native organic N. 相似文献
8.
Hyphal transport by a vesicular-arbuscular mycorrhizal fungus of N applied to the soil as ammonium or nitrate 总被引:6,自引:0,他引:6
Summary Transport of N by hyphae of a vesicular-arbuscular mycorrhizal fungus was studied under controlled experimental conditions. The N source was applied to the soil as 15NH
inf4
sup+
or 15NO
inf3
sup-
. Cucumis sativus was grown for 25 days, either alone or in symbiosis with Glomus intraradices, in containers with a hyphal compartment separated from the root compartment by a fine nylon mesh. Mineral N was then applied to the hyphal compartment as 15NH
inf4
sup+
or 15NO
inf3
sup-
at 5 cm distance from the root compartment. Soil samples were taken from the hyphal compartment at 1, 3 and 5 cm distance from the root compartment at 7 and 12 days after labelling, and the concentration of mineral N in the samples was measured from 2 M KCl extracts. Mycorrhizal colonization did not affect plant dry weight. The recovery of 15N in mycorrhizal plants was 38 or 40%, respectively, when 15NH
inf4
sup+
or 15NO
inf3
sup-
was applied. The corresponding values for non-mycorrhizal plants were 7 and 16%. The higher 15N recovery observed in mycorrhizal plants than in non-mycorrhizal plants suggests that hyphal transport of N from the applied 15N sources towards the host plant had occurred. The concentration of mineral N in the soil of hyphal compartments was considerably less in mycorrhizal treatments than in controls, indicating that the hyphae were able to deplete the soil for mineral N. 相似文献
9.
Erythrina poeppigiana, a woody tropical plant, was inoculated with vesicular-arbuscular mycorrhizal (VAM) fungiGlomus etunicatum Becker and Gerdeman,G. mosseae Nicol. and Gerd. Gerdeman and Trappe, orG. intraradices Schenk and Smith. Growth, N uptake, and nutrition were evaluated in VAM-inoculated plants and controls fertilized with two levels (3 or 6 mM) of either NH
inf4
sup+
-N or NO
inf3
sup-
-N. The response by the mycorrhizal plants to N fertilization, according to N source and/or level differed significantly from that of the control plants. In general, the growth of the mycorrhizal plants was similar to that of the non-mycorrhizal plants when N was provided as NH
inf4
sup+
. When the N source was NO
inf3
sup-
the control plants grew significantly less than the VAM plants. Inoculation with VAM fungi gave yield increases of 255 and 268% forG. etunicatum-colonized plants, 201 and 164% forG. mosseae-colonized plants and 286 and 218% forG. intraradices-colonized plants fertilized with 3 and 6 mM NO
inf3
sup-
-N, respectively. The increased growth and acquisition of nutrients by plants fertilized with NO
inf3
sup-
-N and inoculated with VAM shows that VAM mycelium has a capacity for NO
inf3
sup-
absorption. The results also showed thatE. poeppigiana seedlings preferred NH
inf4
sup+
as an N source.G. etunicatum was the most effective endophyte, not only increasing N, P, Ca, Mg, and Zn uptake in the presence of NO
inf3
sup-
fertilizer but also P and Mg in the presence of NH
inf4
sup+
applications. From these results we conclude that VAM symbiosis affects N metabolism inE. poeppigiana plants and that this species can overcome limitations on the use of NO
inf3
sup-
-N by the mediation of VAM fungi. 相似文献
10.
Thiosulfate and CS2 inhibit nitrification. The effect of the addition of thiosulfate on the turnover of inorganic N compounds was tested in an Egyptian and a German arable soil under nitrifying and denitrifying conditions. For nitrification, the soils were amended with NH
inf4
sup+
and incubated under aerobic conditions. For denitrification, the soils were amended with NO
inf3
sup-
and incubated under anaerobic conditions. In both cases, the thiosulfate decreased with time while tetrathionate accumulated to an intermediate extent. Both compounds disappeared completely after <25 days. Production of CS2 was not observed. Carbonyl sulfide was produced only in the Egyptian soil, but production decreased with increasing amounts of added thiosulfate. Under nitrifying conditions, the addition of increasing amounts of thiosulfate (25, 50, and 100 g S g-1 dry weight) resulted in decreasing rates of NH
inf4
sup+
oxidation to NO
inf3
sup-
; it also resulted in an increasing intermediate accumulation of NO
inf2
sup-
and NO, and in an increasing production of N2O. Under denitrifying conditions, the addition of increasing amounts of thiosulfate did not significantly affect the rate of NO
inf3
sup-
reduction, and resulted in an increasing intermediate accumulation of NO
inf2
sup-
and of NO only in the German soil in which the production of N2O was slightly inhibited by thiosulfate. These results demonstrate that the nitrification of NH
inf4
sup+
and NO
inf2
sup-
was inhibited by increasing concentrations of thiosulfate and/or tetrathionate without involving the formation of volatile S compounds as potential nitrification inhibitors. Denitrification was not affected by the addition of thiosulfate. 相似文献
11.
We observed that soil cores collected in the field containing relatively high NH
inf4
sup+
and C substrate levels produced relatively large quantities of N2O. A series of laboratory experiments confirmed that the addition of NH
inf4
sup+
and glucose to soil increase N2O production under aerobic conditions. Denitrifying enzyme activity was also increased by the addition of NH
inf4
sup+
and glucose. Furthermore, NH
inf4
sup+
and glocose additions increased the production of N2O in the presence of C2H2. Therefore, we concluded that denitrification was the most likely source of N2O production. Denitrification was not, however, directly affected by NH
inf4
sup+
in anaerobic soil slurries, although the use of C substrate increased. In the presence of a high substrate C concentration, N2O production by denitrifiers may be affected by NO
inf3
sup-
supplied from NH
inf4
sup+
through nitrification. Alternatively, N2O may be produced during mixotrophic and heterotrophic growth of nitrifiers. The results indicated that the NH
inf4
sup+
concentration, in addition to NO
inf3
sup-
, C substrate, and O2 concentrations, is important for predicting N2O production and denitrification under field conditions. 相似文献
12.
Mineralization of carbon and nitrogen,and nitrification in Scots pine forest soil treated with fast- and slow-release nitrogen fertilizers 总被引:5,自引:0,他引:5
We studied the effects of fast- and slow-release organic N fertilizers (urea and urea-formaldehyde, Nitroform) on mineralization, nitrification, and N leaching in an acid, poor forest soil. We also studied the effects of a nitrification inhibitor (dicyandiamide) applied together with urea. Net nitrification, mineralization of N and C were determined by aerobic laboratory incubation of soil samples taken one and three growing seasons after N application. Numbers of autotrophic nitrifiers were estimated by a most probable number method three growing seasons after the treatment. Urea increased the CO2 production immediately after application, but after three growing seasons, CO2 production was the lowest in the urea-treated soils. In the nitroform-treated soils, the concentration of exchangeable NH
inf4
sup+
after the first and third growing seasons was of the same magnitude, in contrast to the urea-treated soils, where hydrolysis took place immediately. Three growing seasons after application, the highest amount of NH
inf4
sup+
accumulated during the laboratory incubation was in the nitro-form-treated soils. Unlike urea, nitroform did not increase the production of NO
inf3
sup-
or the number of NH
inf4
sup+
oxidizers. In the urea+dicyandiamide-treated soils there was less NO
inf3
sup-
and a lower number of nitrifiers than in the urea-treated soils. The results showed that a slow-release N fertilizer, such as nitroform, increases the availability of mineral N in acid forest soils without increasing nitrification and hence the risk of NO
inf3
sup-
leaching. 相似文献
13.
Organic N solubilized by NH3(aq) was extracted from 15N-labelled or unlabelled soil, concentrated and added to non-extracted soil, which was incubated under aerobic conditions at 27±1°C. Gross N mineralization, gross N immobilization, and nitrification in soils with or without addition of unlabelled soluble organic N were estimated by models based on the dilution of the NH
4
+
or NO
inf3
sup-
pools, which were labelled with 15N at the beginning of incubation. Mineralization of labelled organic N was measured by the appearance of label in the mineral N pool. Although gross N mineralization and gross N immobilization were increased in two soils between day 0 and day 7 following addition of unlabelled organic N solubilized by NH3(aq), there was no increase in net N mineralization. Solubilization of 15N-labelled organic N increased and the 15N enrichment of the soluble organic N decereased as the concentration of NH3(aq) added increased. A constant proportion of approximately one-quarter of the labelled organic N added at different rates to non-extracted soil was recovered in the mineral N pool after an incubation period of 14 days, and the availability ratios calculated from net N mineralization data were 1.1:1 and 2.1:1 for 111 and 186 mg added organic-N kg-1 soil, respectively, indicating that the mineralization of organic N was increased by solubilization. 相似文献
14.
Summary Recent developments in biotechnology industries produce increasing amounts of byproducts with potential uses in agriculture. The present research focused on the nitrification of NH
inf4
sup+
-N in biotechnology byproducts added to soils, and on the effects of 29 naturally occurring organic acids (19 aliphatic and 10 aromatic) on nitrification in soils. A 10-g soil sample was incubated for 10 days at 30°C with 2.0 mg NH
inf4
sup+
-N in a byproduct or with 10 or 50 mol organic acid and 2.0 mg reagent-grade NH
inf4
sup+
-N. In condensed molasses-fermentation solubles, produced during the microbial fermentation of sugar derived from corn (Zea mays L.) and molasses derived from beets (Beta sp.), in the production of lysine as a supplement in animal food, the nitrification of NH
inf4
sup+
-N was similar to that of byproduct or reagent-grade (NH4)2SO4. Nitrite accumulated when either of these materials was added to a calcareous Canisteo soil. The NH
inf4
sup+
-N in slops (produced during microbial fermentation processes occurring in the production of citric acid) was not nitrified in soils. Some organic acids inhibited, whereas others activated, nitrification in soils. Formic, acetic, and fumaric acids enhanced the production of NO
inf2
sup-
-N in a calcareous Canisteo soil, whereas all other aliphatic and aromatic acids studied decreased the accumulation of NO
inf2
sup-
-N. It is concluded that the addition or production of organic acids in soils affects the microbial dynamics, leading to significant changes in rates of nitrification and possibly in other N-transformation processes in soils. 相似文献
15.
To estimate the availability of nonexchangeable NH
inf4
sup+
–N for soil microorganisms four incubation experiments were conducted under controlled conditions. The following results were obtained: Incorporating glucose as a source of readily oxidizable organic material favored the release of nonexchangeable NH
inf4
sup+
–N. Mobilization of NH
inf4
sup+
from the interlayers of the clay minerals was decreased by the application of K++, while Ca2+, which is supposed to expand the lattice of the clay minerals, had no influence on the release of NH
inf4
sup+
. Soil temperature had no effect on microbiological mobilization of NH
inf4
sup+
. It is assumed that, generally, the influence of nitrifying bacteria on the mobilization of nonexchangeable NH
inf4
sup+
–N is negligible. However, in soils with abundant amounts of available carbon promoting the activity of heterotrophic soil microorganisms, the release of NH
inf4
sup+
from clay minerals is favored under fallow conditions. 相似文献
16.
Summary The turnover of interlayer NH
inf4
sup+
in a loess-derived agricultural soil from the Shaanxi Province in China was studied. The concentration of 15N-labeled interlayer NH
inf4
sup+
and total interlayer NH
inf4
sup+
(labeled + unlabeled) in a soil grown with winter wheat was significantly higher at the beginning of the season (March) than when the crop was mature (June). In a further experiment with winter wheat it was shown that under field conditions the concentration of interlayer NH
inf4
sup+
decreased significantly in the two upper soil layers (0–20 and 20–55 cm) during March and in the deeper soil layer (55–75 cm) during April. When the heading stage of wheat was reached, about 200 kg N ha-1 of interlayer NH
inf4
sup+
had been released. During the following growth period (heading until flowering of wheat) the concentration of interlayer NH
inf4
sup+
increased significantly in the upper soil layers. Fertilizer application in the form of 70 kg N ha-1 as urea led to a considerable increase in the nitrate concentration in the upper soil layer but had no influence on the level of interlayer NH
inf4
sup+
concentration. It is concluded that interlayer NH
inf4
sup+
takes part in the N cycle of the soil and that it contributes to the N nutrition of the crop. NH
inf4
sup+
originating from the mineralization of soil organic N may be rapidly incorporated into the interlayer of clay minerals and later released, when the N demand of the crop is high. 相似文献
17.
Summary Denitrification (using the acetylene block method) was determined in earthworm casts and soils from permanent, drained or undrained pasture plots fertilized with 0 or 200 kg N ha-1 year-1 as ammonium nitrate. Rates of N2O production from soil cores were about three times higher from the fertilized than from the unfertilized plots while drainage had a relatively small effect. Denitrification rates from casts were 3–5 times higher than those from soil irrespective of the drainage treatment. Casts generally had higher NO
inf3
sup-
, NH
inf4
sup+
, and moisture contents, and higher microbial respiration rates than soil. Rates of N2O production were determined primarily by NO
inf3
sup-
supply, secondarily by moisture; available C did not appear to limit denitrification in these pastures. Estimates of the potential contribution of casts to denitrification ranges from 10.1% of 29.3 kg ha-1 year-1 from the unfertilized, drained plot to 22% of 82.5 kg ha-1 year-1 from the fertilized undrained plot. 相似文献
18.
Preservation of nitrifying capacity and nitrate availability in waterlogged soils by radial oxygen loss from roots of wetland plants 总被引:4,自引:0,他引:4
W. M. H. G. Engelaar J. C. Symens H. J. Laanbroek C. W. P. M. Blom 《Biology and Fertility of Soils》1995,20(4):243-248
The effects of radial O2 loss from roots on nitrification and NO
inf3
sup-
availability were studied. Plants of the flooding-resistant species Rumex palustris and the flooding-sensitive species Rumex thyrsiflorus were grown on drained and waterlogged soils with an initially high nitrifying capacity. Nitrate reductase activity in the plant leaves was used as an indicator of NO
inf3
sup-
availability to the plants. In a separate experiment these species were shown to have higher levels of nitrate reductase activity when NO
inf3
sup-
was added to the soils compared to when only NH
inf4
sup+
was provided. In drained soils nitrification was maintained and both plant species showed relatively high nitrate reductase activities in their leaves. In the water-logged series planted with R. thyrsiflorus, nitrification was inhibited, NH
inf4
sup+
accumulated, and the plants grew less well compared to those on drained soils. In contrast, waterlogged soils planted with R. palustris had a redox potential high enough for O2 to be continuously replenished. Furthermore, the nitrifying capacity of these latter soils was maintained at a high level. R. palustris grew well and NO
inf3
sup-
must have been available to the plant, since a high level of nitrate reductase activity was observed in the leaves. 相似文献
19.
S. J. González-Prieto A. Cabaneiro M. C. Villar T. Carballas M. Carballas 《Biology and Fertility of Soils》1996,22(3):252-260
N mineralization capacity and its main controlling factors were studied in a large variety (n=112) of native (forest, bush) and agricultural (pasture, cultivated) soils from several climatic zones in Spain. The available inorganic N content, net N mineralization, and net N mineralization rate were determined after 6 weeks of aerobic incubation. NH
inf4
sup+
–N largely predominated over NO
inf3
sup-
-N (ratio near 10:1) except in some agricultural soils. Net N mineralization predominated (83% of soils) over net N immobilization, which was more frequent in agricultural soils (25%) than in native soils (9%). In forest soils, both net N mineralization and the net N mineralization rate were significantly higher than in the other soil groups. The net N mineralization rate of pasture and cultivated soils was similar to that of bush soils, but available inorganic N was lower. The net N mineralization rate decreased in the order: soils over acid rocks>soils over sediments>soils over basic rocks or limestone; moreover, the highest net N mineralization and available inorganic N were found in soils over acid rocks. The highest N mineralization was found in soils with low C and N contents, particularly in the native soils, in which N mineralization increased as the C:N ratio increased. N mineralization was higher in soils with a low pH and base saturation than in soils with high pH and base saturation values, which sometimes favoured N immobilization. Soils with an Al gel content of >1% showed lower net N mineralization rates than soils with Al gel contents of <1%, although net N mineralization and available inorganic N did not differ between these groups. The net N mineralization rate in silty soils was significantly lower than in sandy and clayey soils, although soil texture only explained a low proportion of the differences in N mineralization between soils. 相似文献
20.
Potential variation of nitrogen transformations in pinyon-juniper ecosystems resulting from burning 总被引:3,自引:0,他引:3
Summary Forest floor litter, duff, and underlying soils were assembled in laboratory microcosms representing pinyon, juniper, and interspace field conditions. Burning removed more than 95% of both N and C from the litter, with losses from the duff dependent on soil moisture conditions. No significant changes in total N or C were noted in the soil. Immediate increases were observed in soil NH
inf4
sup+
, decreasing with depth and related to soil heating. The greatest increases were noted in both the pinyon and juniper soils that were dry at the time of the burn, with interspace soils exhibiting the least changes. Soil NH
inf4
sup+
closely approximated the controls on day 90 after the burns in all treatments. Ninety days after the burn microbial biomass N was highest in the controls, followed by the wet and then the dry-burned soils, in both the pinyon and juniper microcosms. This was inversely related to the levels of accumulated NO
inf3
sup-
. Nitrifying bacteria populations were indirectly correlated to soil temperatures during the burn. Population levels 90 days after the burn showed increases in both the wet- and the dry-burn treatments, with those in the pinyon treatments exceeding those found in the nitial controls of pinyon soils.The use of trade and company names in this paper is for the benefit of the reader; such use does not constitute an official endorsement or approval of any service or product by the U.S. Department of Agriculture to the exclusion of others that may be suitable 相似文献