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1.
Exchangeable ammonium and nitrate from different nitrogen fertilizer preparations in polyacrylamide-treated and untreated agricultural soils 总被引:3,自引:0,他引:3
J. L. Kay-Shoemake M. E. Watwood L. Kilpatrick K. Harris 《Biology and Fertility of Soils》2000,31(3-4):245-248
High molecular weight, anionic polyacrylamide (PAM) is currently being used as an irrigation water additive to significantly
reduce soil erosion associated with furrow irrigation. PAM contains amide-N, and PAM application to soils has been correlated
with increased activity of soil enzymes, such as urease and amidase, involved in N cycling. Therefore we investigated potential
impacts of PAM treatment on the rate at which fertilizer N is transformed into NH4
+ and NO3
– in soil. PAM-treated and untreated soil microcosms were amended with a variety of fertilizers, ranging from common rapid-release
forms, such as ammonium sulfate [(NH4)2SO4] and urea, to a variety of slow-release formulations, including polymerized urea and polymer-encapsulated urea. Ammonium
sulfate was also tested together with the nitrification inhibitor dicyandiamide (DCD). The fertilizers were applied at a concentration
of 1.0 mg g–1, which is comparable to 100 lb acre–l, or 112 kg ha–1. Potassium chloride-extractable NH4
+-N and NO3
–-N were quantified periodically during 2–4 week incubations. PAM treatment had no significant effect on NH4
+ release rates for any of the fertilizers tested and did not alter the efficacy of DCD as a nitrification inhibitor. However,
the nitrification rate of urea and encapsulated urea-derived NH4
+-N was slightly accelerated in the PAM-treated soil.
Received: 16 January 1998 相似文献
2.
Nitrification inhibition of soil and applied fertilizer N is desirable as the accumulation of nitrates in soils in excess
of plant needs leads to enhanced N losses and reduced fertilizer N-use efficiency. In a growth chamber experiment, we studied
the effects of two commercial nitrification inhibitors (NIs), 4-amino 1,2,4-triazole (ATC) and dicyandiamide (DCD), and a
commonly available and economical material, encapsulated calcium carbide (CaC2) (ECC) on the nitrification of soil and applied NH4
+-N in a semiarid subtropical Tolewal sandy loam soil under upland [60% water-filled pore space (WFPS)] and flooded conditions
(120% WFPS). Nitrification of the applied 100 mg NH4
+-N kg–1 soil under upland conditions was retarded most effectively (93%) by ECC for up to 10 days of incubation, whereas for longer
periods, ATC was more effective. After 20 days, only 16% of applied NH4
+-N was nitrified with ATC as compared to 37% with DCD and 98% with ECC. Under flooded soil conditions, nitrates resulting
from nitrification quickly disappeared due to denitrification, resulting in a tremendous loss of fertilizer N (up to 70% of
N applied without a NI). Based on four indicators of inhibitor effectiveness, namely, concentration of NH4
+-N and NO3
–-N, percent nitrification inhibition, ratio of NH4
+-N/NO3
–-N, and total mineral N, ECC showed the highest relative efficiency throughout the 20-day incubation under flooded soil conditions.
At the end of the 20-day incubation, 96%, 58% and 38% of applied NH4
+-N was still present in the soil where ECC, ATC and DCD were used, respectively. Consequently, nitrification inhibition of
applied fertilizer N in both arable crops and flooded rice systems could tremendously minimize N losses and help enhance fertilizer
N-use efficiency. These results suggest that for reducing the nitrification rate and resultant N losses in flooded soil systems
(e.g. rice lowlands), ECC is more effective than costly commercial NIs.
Received: 25 May 2000 相似文献
3.
Nutrient concentrations in the soil and crop uptake from incorporated green manure and urea in flooded rice was studied in
field experiments. Release of plant-available nitrogen (NH4
+-N) from green manure was slightly delayed compared with that from prilled urea (PU) because Sesbania rostrata L. and Aeschynomene afraspera L. released the N gradually after their decomposition, whereas N became available immediately after PU application. Exchangeable
NH4
+-N concentration in soil peaked at 163 mg kg–1 in the transplanted rice (TPR) and 198 mg kg—1 in broadcast-seeded rice (BSR) at 0 and 1 week after PU application. Broadcast-seeded rice depleted NH4
+-N faster than did TPR because of the crop‘s vigorous growth in the former during the early stage. Soil solution NH4
+-N followed a similar trend to that of soil NH4
+-N. Incorporation of S. rostrata and A. afraspera increased the concentration of P, K+, Fe2+ and Mn2+ in soil solution more than did the application of PU. However, zinc concentration decreased in all treatments. Both PU and
green manure increased the N status of the rice plants and enhanced the uptake of P, K, Fe, Mn and Zn by the rice crop. This
suggests that application of green manures improves the uptake of these nutrients by the crop. The highest apparent N recovery
was obtained with PU followed by green manure.
Received: 11 November 1996 相似文献
4.
Simple and rapid chemical indices of soil nitrogen (N)-supplying capacity are necessary for fertilizer recommendations. In
this study, pot experiment involving rice, anaerobic incubation, and chemical analysis were conducted for paddy soils collected
from nine locations in the Taihu Lake region of China. The paddy soils showed large variability in N-supplying capacity as
indicated by the total N uptake (TNU) by rice plants in a pot experiment, which ranged from 639.7 to 1,046.2 mg N pot−1 at maturity stage, representing 5.8% of the total soil N on average. Anaerobic incubation for 3, 14, 28, and 112 days all
resulted in a significant (P < 0.01) correlation between cumulative mineral NH4+-N and TNU, but generally better correlations were obtained with increasing incubation time. Soil organic C, total soil N,
microbial C, and ultraviolet absorbance of NaHCO3 extract at 205 and 260 nm revealed no clear relationship with TNU or cumulative mineral NH4+-N. Soil C/N ratio, acid KMnO4-NH4+-N, alkaline KMnO4-NH4+-N, phosphate–borate buffer extractable NH4+-N (PB-NH4+-N), phosphate–borate buffer hydrolyzable NH4+-N (PBHYDR-NH4+-N) and hot KCl extractable NH4+-N (HKCl−NH4+-N) were all significantly (P < 0.05) related to TNU and cumulative mineral NH4+-N of long-term incubation (>28 days). However, the best chemical index of soil N-supplying capacity was the soil C/N ratio,
which showed the highest correlation with TNU at maturity stage (R = −0.929, P < 0.001) and cumulative mineral NH4+-N (R = −0.971, P < 0.001). Acid KMnO4-NH4+-N plus native soil NH4+-N produced similar, but slightly worse predictions of soil N-supplying capacity than the soil C/N ratio. 相似文献
5.
David Fangueiro Henrique Ribeiro João Coutinho Laura Cardenas Henrique Trindade Cristina Cunha-Queda Ernesto Vasconcelos Fernanda Cabral 《Biology and Fertility of Soils》2010,46(4):383-391
The following six pig slurries obtained after acidification and/or solid/liquid separation were used in the research: original
(S) and acidified (AS) pig slurry, nonacidified (LF) and acidified (ALF) pig slurry liquid fraction, and nonacidified (SF)
and acidified (ASF) pig slurry solid fraction. Laboratory incubations were performed to assess the effect of the application
of these slurries on N mineralization and CO2 and N2O emissions from a sandy soil. Acidification maintained higher NH4
+-N contents in soil particularly in the ALF-treated soil where NH4
+-N contents were two times higher than in LF-treated soil during the 55–171-day interval. At the end of the incubation (171 days),
32.9 and 24.2 mg N kg−1 dry soil were mineralized in the ASF- and SF-treated soils, respectively, but no mineralization occurred in LF- and S-treated
soils, although acidification decreased N immobilization in ALF- (−25.3 mg N kg−1 soil) and AS- (−12.7 mg N kg−1 soil) compared to LF- (−34.4 mg N kg−1 soil) and S-treated (−18.6 mg N kg−1 soil) soils, respectively. Most of the dissolved CO2 was lost during the acidification process. More than 90% of the applied C in the LF-treated soil was lost during the incubation,
indicating a high availability of the added organic compounds. Nitrous oxide emissions occurred only after day 12 and at a
lower rate in soils treated with acidified than nonacidified slurries. However, during the first 61 days of incubation, 1,157 μg N
kg−1 soil was lost as N2O in the AS-treated soil and only 937 in the S-treated soil. 相似文献
6.
Fixation and defixation of ammonium in soils: a review 总被引:2,自引:0,他引:2
Fixed NH4+ (NH4+
f) and fixation and defixation of NH4+ in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences
in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH4+
f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH4+
f does not necessarily reflect the fraction that is truly available to plants. The content of native NH4+
f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the
soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows
that the NH4+
f-N content amounts to 10–90 mg kg−1 in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg−1 in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg−1 in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH4+
f are mainly due to the fact that some investigators distinguished between native and recently fixed NH4+ while others did not. Recently fixed NH4+ is available to plants to a greater degree than the native NH4+
f, and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed
NH4+ suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH4+ defixed during a growing season varied greatly within the groups of silty (20–200 kg NH4+-N ha−1 30 cm−1) as well as clayey (40–188 kg NH4+-N ha−1 30 cm−1) soils. The pool of recently fixed NH4+ may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from
soils. 相似文献
7.
M. D. Serna J. Bañuls A. Quiñones E. Primo-Millo F. Legaz 《Biology and Fertility of Soils》2000,32(1):41-46
The objectives of this work were to evaluate the inhibitory action on nitrification of 3,4-dimethylpyrazole phosphate (DMPP)
added to ammonium sulphate nitrate [(NH4)2SO4 plus NH4NO3; ASN] in a Citrus-cultivated soil, and to study its effect on N uptake. In a greenhouse experiment, 2 g N as ASN either with or without 0.015 g
DMPP (1% DMPP relative to NH4
+-N) was applied 6 times at 20-day intervals to plants grown in 14-l pots filled with soil. Addition of DMPP to ASN resulted
in higher levels of NH4
+-N and lower levels of NO3
–-N in the soil during the whole experimental period. The NO3
–-N concentration in drainage water was lower in the ASN plus DMPP (ASN+DMPP)-treated pots. Also, DMPP supplementation resulted
in greater uptake of the fertilizer-N by citrus plants. In another experiment, 100 g N as ASN, either with or without 0.75 g
DMPP (1% DMPP relative to NH4
+-N) was applied to 6-year-old citrus plants grown individually outdoors in containers. Concentrations of NH4
+-N and NO3
–-N at different soil depths and N distribution in the soil profile after consecutive flood irrigations were monitored. In
the ASN-amended soil, nitrification was faster, whereas the addition of the inhibitor led to the maintenance of relatively
high levels of NH4
+-N and NO3
–-N in soil for longer than when ASN was added alone. At the end of the experiment (120 days) 68.5% and 53.1% of the applied
N was leached below 0.60 m in the ASN and ASN+DMPP treatments, respectively. Also, leaf N levels were higher in plants fertilized
with ASN+DMPP. Collectively, these results indicate that the DMPP nitrification inhibitor improved N fertilizer efficiency
and reduced NO3
– leaching losses by retaining the applied N in the ammoniacal form.
Received: 31 May 1999 相似文献
8.
Crop residues and fertilizer nitrogen influence residue decomposition and nitrous oxide emission from a Vertisol 总被引:2,自引:0,他引:2
Wisal Muhammad Sarah M. Vaughan Ram C. Dalal Neal W. Menzies 《Biology and Fertility of Soils》2011,47(1):15-23
Crop residues with high C/N ratio immobilize N released during decomposition in soil, thus reducing N losses through leaching,
denitrification, and nitrous oxide (N2O) emission. A laboratory incubation experiment was conducted for 84 days under controlled conditions (24°C and moisture content
55% of water-holding capacity) to study the influence of sugarcane, maize, sorghum, cotton and lucerne residues, and mineral
N addition, on N mineralization–immobilization and N2O emission. Residues were added at the rate of 3 t C ha−1 to soil with, and without, 150 kg urea N ha−1. The addition of sugarcane, maize, and sorghum residues without N fertilizer resulted in a significant immobilization of
soil N. Amended soil had significantly (P < 0.05) lower NO3−–N, which reached minimum values of 2.8 mg N kg−1 for sugarcane (at day 28), 10.3 mg N kg−1 for maize (day 7), and 5.9 mg N kg−1 for sorghum (day 7), compared to 22.7 mg N kg−1 for the unamended soil (day 7). During 84 days of incubation, the total mineral N in the residues + N treatments were decreased
by 45 mg N kg−1 in sugarcane, 34 mg kg−1 in maize, 29 mg kg−1 in sorghum, and 16 mg kg−1 in cotton amended soil compared to soil + N fertilizer, although soil NO3−–N increased by 7 mg kg−1 in lucerne amended soil. The addition of residues also significantly increased amended soil microbial biomass C and N. Maximum
emissions of N2O from crop residue amended soils occurred in the first 4–5 days of incubation. Overall, after 84 days of incubation, the
cumulative N2O emission was 25% lower with cotton + N fertilizer, compared to soil + N fertilizer. The cumulative N2O emission was significantly and positively correlated with NO3−–N (r = 0.92, P < 0.01) and total mineral N (r = 0.93, P < 0.01) after 84 days of incubation, and had a weak but significant positive correlation with cumulative CO2 in the first 3 and 5 days of incubation (r = 0.59, P < 0.05). 相似文献
9.
Nitrogen uptake and growth of two citrus rootstock seedlings in a sandy soil receiving different controlled-release fertilizer sources 总被引:4,自引:0,他引:4
Understanding the fate of different forms of nitrogen (N) fertilizers applied to soils is an important step in enhancing
N use efficiency and minimizing N losses. The growth and N uptake of two citrus rootstocks, Swingle citrumelo (SC), and Cleopatra
mandarin (CM), seedlings were evaluated in a pot experiment using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments)
without N application or with 400 mg N kg–1 applied as urea or controlled-release fertilizers (CRF; either as Meister, Osmocote, or Poly-S). Meister and Osmocote are
polyolefin resin-coated urea with longevity of N release for 270 days (at 25°C). Poly-S is a polymer and sulfur-coated urea
with release duration considerably shorter than that of either Meister or Osmocote. The concentrations of 2 M KCl extractable
nitrate nitrogen (NO3
–-N) and ammonium nitrogen (NH4
+-N) in the soil sampled 180 days and 300 days after planting were greater in the soil with SC than with CM rootstock seedlings.
In most cases, the extractable NH4
+ and NO3
– concentrations were greater for the Osmocote treatment compared to the other N sources. For the SC rootstock seedlings, dry
weight was greater with Meister or Poly-S compared with either Osmocote or urea. At the end of the experiment, ranking of
the various N sources, with respect to total N uptake by the seedlings, was: Meister = Osmocote > Poly-S > Urea > no N for
CM rootstock, and Meister = Poly-S = Osmocote > Urea > no N for SC rootstock. The study demonstrated that for a given rate
of N application the total N uptake by seedlings was greater for the CRF compared to urea treatment. This suggests that various
N losses were lower from the CRF source as compared to those from soluble fertilizers.
Received: 11 April 1997 相似文献
10.
Influence of N and non-N salts on atmospheric methane oxidation by upland boreal forest and tundra soils 总被引:10,自引:0,他引:10
S. C. Whalen 《Biology and Fertility of Soils》2000,31(3-4):279-287
The short-term (24 h) and medium-term (30 day) influence of N salts (NH4Cl, NaNO3 and NaNO2) and a non-N salt (NaCl) on first-order rate constants, k (h–1) and thresholds (CTh) for atmospheric CH4 oxidation by homogenized composites of upland boreal forest and tundra soils was assessed at salt additions ranging to 20 μmol
g–1 dry weight (dw) soil. Additions of NH4Cl, NaNO3 and NaCl to 0.5 μmol g–1 dw soil did not significantly decrease k relative to watered controls in the short term. Higher concentrations significantly reduced k, with the degree of inhibition increasing with increasing dose. Similar doses of NH4Cl and NaCl gave comparable decreases in k relative to controls and both soils showed low native concentrations of NH4
+-N (≤1 μmol g–1dw soil), suggesting that the reduction in k was due primarily to a salt influence rather than competitive inhibition of CH4 oxidation by exogenous NH4
+-N or NH4
+-N released through cation exchange. The decrease in k was consistently less for NaNO3 than for NH4Cl and NaCl at similar doses, pointing to a strong inhibitory effect of the Cl– counter-anion. Thresholds for CH4 oxidation were less sensitive to salt addition than k for these three salts, as significant increases in CTh relative to controls were only observed at concentrations ≥1.0 μmol g–1 dw soil. Both soils were more sensitive to NaNO2 than to other salts in the short term, showing a significant decrease in k at an addition of 0.25 μmol NaNO2 g–1 dw soil that was clearly attributable to NO2
–. Soils showed no recovery from NaCl, NH4
+-N or NaNO3 addition with respect to atmospheric CH4 oxidation after 30 days. However, soils amended with NaNO2 to 1.0 μmol NaNO2 g–1 dw showed values of k that were not significantly different from controls. Recovery of CH4-oxidizing ability was due to complete oxidation of NO2
–-N to NO3
–-N. Analysis of soil concentrations of N salts necessary to inhibit atmospheric CH4 oxidation and regional rates of N deposition suggest that N deposition will not decrease the future sink strength of upland
high-latitude soils in the atmospheric CH4 budget.
Received: 30 April 1999 相似文献
11.
U. Kumar M. C. Jain H. Pathak S. Kumar D. Majumdar 《Biology and Fertility of Soils》2000,32(6):474-478
N2O emissions from a transplanted irrigated rice grown on a Typic Ustochrept soil at New Delhi, India, were studied to evaluate
the effect of N fertilizers, i.e. urea and (NH4)2SO4, alone and in combination with the nitrification inhibitors dicyandiamide (DCD) and thiosulphate. The addition of urea and
(NH4)2SO4 increased N2O emissions considerably when compared to no fertilizer N application (control). N2O measurement in the field was done by a closed-chamber method for a period of 98 days. The application of urea with DCD and
thiosulphate reduced N2O fluxes considerably. The highest total N2O-N emission (235 g N2O-N ha–1) was from the (NH4)2SO4 treatment, which was significantly higher than the total N2O-N emission from the urea treatment (160 g N2O-N ha–1). DCD reduced N2O-N emissions by 11% and 26% when applied with urea and(NH4)2SO4, respectively, whereas thiosulphate in combination with urea reduced N2O-N emissions by 9%. Total N2O-N emissions were found to range from 0.08% to 0.14% of applied N. N2O emissions were low during submergence and increased substantially during drainage of standing water.
Received: 20 October 1999 相似文献
12.
Nitrogen fertilizers promote denitrification 总被引:8,自引:0,他引:8
A laboratory study was conducted to compare the effects of different N fertilizers on emission of N2 and N2O during denitrification of NO3
– in waterlogged soil. Field-moist samples of Drummer silty clay loam soil (fine-silty, mixed, mesic Typic Haplaquoll) were
incubated under aerobic conditions for 0, 2, 4, 7, 14, 21, or 42 days with or without addition of unlabelled (NH4)2SO4, urea, NH4H2PO4, (NH4)2HPO4, NH4NO3 (200 or 1000 mg N kg–1 soil), or liquid anhydrous NH3 (1000 mg N kg–1 soil). The incubated soil samples were then treated with 15N-labelled KNO3 (250 mg N kg–1 soil, 73.7 atom% 15N), and incubation was carried out under waterlogged conditions for 5 days, followed by collection of atmospheric samples
for 15N analyses to determine labelled N2 and N2O. Compared to samples incubated without addition of unlabelled N, all of the fertilizers promoted denitrification of 15NO3
–. Emission of labelled N2 and N2O decreased in the order: Anhydrous NH3>urea<$>\gg<$> (NH4)2HPO4>(NH4)2SO4≃NH4NO3≃NH4H2PO4. The highest emissions observed with anhydrous NH3 or urea coincided with the presence of NO2
–, and 15N analyses indicated that these emissions originated from NO2
– rather than NO3
–. Emissions of labelled N2 and N2O were significantly correlated with fertilizer effects on soil pH and water-soluble organic C.
Received: 17 January 1996 相似文献
13.
Methane oxidation in arable soil as inhibited by ammonium, nitrite, and organic manure with respect to soil pH 总被引:12,自引:0,他引:12
B. W. Hütsch 《Biology and Fertility of Soils》1998,28(1):27-35
The effects of inorganic N and organic manure, applied to a loamy arable soil, on CH4 oxidation were investigated in laboratory incubation experiments. Applications (40 mg N kg–1) of NH4Cl, (NH4)2SO4, and urea caused strong instantaneous inhibition of CH4 oxidation by 96%, 80%, and 84%, respectively. After nitrification of the added N the inhibitory effect was not fully reversible,
resulting in an residual inhibition of 21%, 16%, and 25% in the NH4Cl, (NH4)2SO4, and urea treatments, respectively. With large NH4
+ applications [240 mg N kg–1 as (NH4)2SO4] the residual inhibition was as high as 64%. Exogenous NO2
– (40 mg NO2
–-N kg–1) initially inhibited CH4 oxidation by 84%, decreasing to 41% after its oxidation. Therefore, applied NO2
– was a more effective inhibitor of CH4 consumption than NH4
+. Temporary accumulation of NO2
– during nitrification of added N was small (maximum: 1.9 mg NO2
–-N kg–1) and thus of minor importance with respect to the persistent inhibition after NH4
+ or urea application. CH4 oxidation after NaNO3 (40 mg N kg–1) and NaCl addition did not differ to that of the untreated soil. The effect of organic manures on CH4 oxidation depended on their C/N ratio: fresh sugar beet leaves enhanced mineralization, which caused an instantaneous 20%
inhibition, whereas after wheat straw application available soil N was rapidly immobilized and no effect on CH4 oxidation was found. The 28% increase in CH4 oxidation after biowaste compost application was not related to its C/N ratio and was probably the result of an inoculation
with methanotrophic bacteria. Only with high NH4
+ application rates (240 mg N kg–1) could the persistent inhibitory effect partly be attributed to a pH decrease during nitrification. The exact reason for
the observed persistent inhibition after a single, moderate NH4
+ or urea application is still unknown and merits further study.
Received: 31 October 1997 相似文献
14.
灌溉施用氮肥后氮素在土壤中的转化及淋失状况: 土柱模拟研究 总被引:4,自引:0,他引:4
A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH4+-N + NO3--N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH4+-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4+-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4+-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4+-N fixation or volatilization in the soil during the fertigation process. 相似文献
15.
We hypothesized that the integration of trees and shrubs in agricultural landscapes can reduce NO3
– leaching and increase utilization of subsoil N. A field survey was conducted on 14 farms on acid soils in the subhumid highlands
of Kenya, where there is little use of fertilizers, to determine the effect of vegetation types (VT) on soil NH4
+ and NO3
– to 4 m depth. The VT included maize (Zea mays) with poor growth and good growth, Markhamia lutea trees scattered in maize, natural weed fallow, banana (Musa spp.), hedgerow, and eucalyptus woodlot. The effect of VT on NH4
+ was small (<1 mg N kg–1). NO3
– within a VT was about constant with depth below 0.25 m, but subsoil NO3
– varied greatly among VT. Mean NO3
–-N concentrations at 0.5–4 m depth were low beneath hedgerow and woodlot (<0.2 mg kg–1), intermediate beneath weed fallow (0.2–0.7 mg kg–1), banana (0.5–1.0 mg kg–1) and markhamia (0.5–1.6 mg kg–1), and high beneath both poor (1.0–2.1 mg kg–1) and good (1.9–3.1 mg kg–1) maize. Subsoil NO3
– (0.5–4 m) was agronomically significant after maize harvest with 37 kg N ha–1 m–1 depth of subsoil beneath good maize and 27 kg N ha–1 m–1 depth beneath poor maize. In contrast, subsoil NO3
– was only 2 kg N ha–1 m–1 depth beneath woodlot and hedgerow. These results demonstrate that the integration of perennial vegetation and the rotation
of annual and perennial crops can tighten N cycling in agricultural landscapes.
Received: 8 July 1999 相似文献
16.
Xu Zhao 《Soil biology & biochemistry》2009,41(12):2584-2587
The effects on nitrification and acidification in three subtropical soils to which (NH4)2SO4 or urea had been added at rate of 250 mg N kg−1 was studied using laboratory-based incubations. The results indicated that NH4+ input did not stimulate nitrification in a red forest soil, nor was there any soil acidification. Unlike red forest soil, (NH4)2SO4 enhanced nitrification of an upland soil, whilst urea was more effective in stimulating nitrification, and here the soil was slightly acidified. For another upland soil, NH4+ input greatly enhanced nitrification and as a result, this soil was significantly acidified. We conclude that the effects of NH4+ addition on nitrification and acidification in cultivated soils would be quite different from in forest soils. During the incubation, N isotope fractionation was closely related to the nitrifying capacity of the soils. 相似文献
17.
A laboratory experiment was conducted to investigate the relative mobility of dicyandiamide (DCD) and jointly applied ammoniacal salts or urea in three different soils of lower Egypt, and to determine the extent to which DCD separates from N-fertilizer in unsaturated soil undergoing leaching. The experimental results suggest that, under conditions of water flow, DCD is readily separated from NH4+ but parts from urea to a far lesser extent. The large difference in mobility between DCD and NH4+ should severely limit the effectiveness of DCD as a nitrification inhibitor in the three soils considered when applied in conjunction with ammoniacal salts. In two out of three cases, the situation is similarly unfavorable in the case of joint DCD and urea application. However, the observation that DCD, in a low CEC sandy loam, moves within the soil solution at a slightly lower rate than urea suggests that joint application with urea would keep at least part of the DCD in contact with the NH4+ ions and, therefore, would preserve some of the effectiveness of DCD under leaching conditions in this soil. 相似文献
18.
Chemical and biological characteristics of alkaline saline soils from the former Lake Texcoco as affected by artificial drainage 总被引:3,自引:0,他引:3
M. L. Luna-Guido R. I. Beltrán-Hernández N.A. Solís-Ceballos N. Hernández-Chávez F. Mercado-García J. A. Catt V. Olalde-Portugal L. Dendooven 《Biology and Fertility of Soils》2000,32(2):102-108
Soils from the former Lake Texcoco are alkaline saline and were artificially drained and irrigated with sewage effluents
since the late 1980s. Undrained soil and soil drained for 1, 5 and 8 years were sampled, characterized and incubated aerobically
for 90 days at 22±1 °C while production of CO2, available P and concentrations of NH4
+, NO2
– and NO3
– were monitored. Artificial drainage decreased pHH2O, water holding capacity, organic C, total N, and Na+, K+, Mg2+, B, Cl– and SO4
2– concentrations, increased inorganic C and Ca2+ concentrations more than 5-fold while total P was not affected. Microbial biomass C decreased with increased length of drainage
but bacteria, actinomycetes, denitrifiers and cellulose-utilizing bacteria tended to show opposite trends. CO2 production was less in soils drained ≥5 years compared to undrained soil but more than in soils drained for 1 year. Emission
of NH3 was negligible and concentrations of NH4
+ remained constant over time in each soil. Nitrification, as witnessed by increases in NO3
– concentrations, occurred in soil drained for 8 years. NO2
– concentrations decreased in soils drained ≤1 year in the first 7 days of the incubation and remained constant thereafter.
It was found that artificial drainage of soils from the former Lake Texcoco profoundly affected soil characteristics. Decreases
in pH and Na+, K+, Cl– and SO4
2– concentrations made conditions more favourable for plant growth, although low concentrations of inorganic N and available
P might be limiting factors.
Received: 1 December 1999 相似文献
19.
In less populated rural areas constructed wetlands with a groundfilter made out of the local soil mixed with peat and planted
with common reed (Phragmites australis) are increasingly used to purify waste water. Particularly in the rhizosphere of the reed, nitrification and denitrification
processes take place varying locally and temporally, and the question arises to what extent this type of waste-water treatment
plant may contribute to the release of N2O. In situ N2O measurements were carried out in the two reed beds of the Friedelhausen dairy farm, Hesse, Germany, irrigated with the waste
water from a cheese dairy and 70 local inhabitants (12 m3 waste water or 6 kg BOD5 or 11 kg chemical O2 demand (CODMn) day–1). During November 1995 to March 1996, the release of N2O was measured weekly at 1 m distances using eight open chambers and molecular-sieve traps to collect and absorb the emitted
N2O. Simultanously, the N2O trapped in the soil, the soil temperature, as well as the concentrations of NH4
+-N, NO3
–-N, NO2
–-N, water-soluble C and the pH were determined at depths of 0–20, 20–40 and 40–60 cm. In the waste water from the in- and
outflow the concentrations of CODMn, BOD5, NH4
+-N, NO3
–-N, NO2
–-N, as well as the pH, were determined weekly. Highly varying amounts of N2O were emitted at all measuring dates during the winter. Even at soil temperatures of –1.5 °C in 10 cm depth of soil or 2 °C
at a depth of 50 cm, N2O was released. The highest organic matter and N transformation rates were recorded in the upper 20 cm of soil and in the
region closest to the outflow of the constructed wetland. Not until a freezing period of several weeks did the N2O emissions drop drastically. During the period of decreasing temperatures less NO3
–-N was formed in the soil, but the NH4
+-N concentrations increased. On average the constructed wetlands of Friedelhausen emitted about 15 mg N2O-N inhabitant equivalent–1 day–1 during the winter period. Nitrification-denitrification processes rather than heterotrophic denitrification are assumed to
be responsible for the N2O production.
Received: 28 October 1998 相似文献
20.
Impact of land-use types on soil nitrogen net mineralization in the sandstorm and water source area of Beijing,China 总被引:1,自引:0,他引:1
Changes of land-use type (LUT) can affect soil nutrient pools and cycling processes that relate long-term sustainability of ecosystem, and can also affect atmospheric CO2 concentrations and global warming through soil respiration. We conducted a comparative study to determine NH4+ and NO3− concentrations in soil profiles (0–200 cm) and examined the net nitrogen (N) mineralization and net nitrification in soil surface (0–20 cm) of adjacent naturally regenerated secondary forests (NSF), man-made forests (MMF), grasslands and cropland soils from the windy arid and semi-arid Hebei plateau, the sandstorm and water source area of Beijing, China. Cropland and grassland soils showed significantly higher inorganic N concentrations than forest soils. NO3−-N accounted for 50–90% of inorganic N in cropland and grassland soils, while NH4+-N was the main form of inorganic N in NSF and MMF soils. Average net N-mineralization rates (mg kg−1 d−1) were much higher in native ecosystems (1.51 for NSF soils and 1.24 for grassland soils) than in human disturbed LUT (0.15 for cropland soils and 0.85 for MMF soils). Net ammonification was low in all the LUT while net nitrification was the major process of net N mineralization. For more insight in urea transformation, the increase in NH4+ and, NO3− concentrations as well as C mineralization after urea addition was analyzed on whole soils. Urea application stimulated the net soil C mineralization and urea transformation pattern was consistent with net soil N mineralization, except that the rate was slightly slower. Land-use conversion from NSF to MMF, or from grassland to cropland decreased soil net N mineralization, but increased net nitrification after 40 years or 70 years, respectively. The observed higher rates of net nitrification suggested that land-use conversions in the Hebei plateau might lead to N losses in the form of nitrate. 相似文献