首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
The influence of temperature (T) and water potential (ψ) on the denitrification potential, C and N mineralization and nitrification were studied in organic and mineral horizons of an acid spruce forest soil. The amount of N2O emitted from organic soil was 10 times larger than from the mineral one. The maximum of N2O emission was in both soils at the highest water potential 0 MPa and at 20°C. CO2 production in the organic soil was 2 times higher than in mineral soil. Net ammonification in organic soil was negative for most of the T‒ψ variations, while in mineral soil it was positive. Net nitrification in organic soil was negative only at the maximum water potential and temperature (0 MPa, 28°C). The highest rate was between 0 and −0.3 MPa and between 20 and 28°C. In mineral soil NO3− accumulated at all T‒ψ variations with a maximum at 20oC and −0.3 MPa. We concluded that in organic soil the immobilization of NH4+ is the dominant process in the N‒cycling. Nevertheless, decreasing of total N mineralized at 0 MPa and 20—28oC can be explained by denitrification.  相似文献   

2.
High N fertilizer and flooding irrigation applied to rice in anthropogenic‐alluvial soil often result in N leaching and low use efficiency of applied fertilizer N from the rice field in Ningxia irrigation region in the upper reaches of the Yellow River. Sound N management practices need to be established to improve N use efficiency while sustaining high grain yield levels and minimize fertilizer N loss to the environment. We investigated the effects of Nursery Box Total Fertilization technology (NBTF) on N leaching at different rice growing stages, N use efficiency and rice yield in 2010 and 2011. The four fertilizer N treatments were 300 kg N ha−1 (CU, Conventional treatment of urea at 300 kg N ha−1), 120 kg N ha−1 (NBTF120, NBTF treatment of controlled‐release N fertilizer at 120 kg N ha−1), 80 kgN ha−1 (NBTF80, NBTF treatment of controlled‐release N fertilizer at 80 kg N ha−1) and no N fertilizer application treatment (CK). The results showed that the NBTF120 treatment increased N use efficiency, maintained crop yields and substantially reduced N losses to the environment. Under the CU treatment, the rice yield was 9634 and 7098 kg ha−1, the N use efficiency was 31·6% and 34·8% and the leaching losses of TN were 44·51 and 39·89 kg ha−1; NH4+‐N was 5·26 and 5·49 kg ha−1, and NO3−‐N was 27·94 and 26·22 kg ha−1 during the rice whole growing period in 2010 and 2011, respectively. Compared with CU, NBTF120 significantly increased the N use efficiency and decreased the N losses from the paddy field. Under NBTF120, the N use efficiency was 56·3% and 51·4%, which was 24·7% and 16·6% higher than that of CU, and the conventional fertilizer application rate could be reduced by 60% without lowering the rice yield while decreasing the leaching losses of TN by 16·27 and 14·36 kg ha−1, NH4+‐N by 0·90 and 1·84 kg ha−1, NO3−‐N by 110·6 and 10·14 kg ha−1 in 2010 and 2011, respectively. Our results indicate that the CU treatment resulted in relatively high N leaching losses, and that alternative practice of NBTF which synchronized fertilizer application with crop demand substantially reduced these losses. We therefore suggest the NBTF120 be a fertilizer application alternative which leads to high food production but low environmental impact. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

3.
Field experiments were conducted to determine the effect of nitrogen (N) fertilizer forms and doses on wheat (Triticum aestivum L.) on three soils differing in their ammonium (NH4) fixation capacity [high = 161 mg fixed NH4-N kg?1 soil, medium = 31.5 mg fixed NH4-N kg?1 soil and no = nearly no fixed NH4-N kg?1 soil]. On high NH4+ fixing soil, 80 kg N ha?1 Urea+ ammonium nitrate [NH4NO3] or 240 kg N ha?1 ammonium sulfate [(NH4)2SO4]+(NH4)2SO4, was required to obtain the maximum yield. Urea + NH4NO3 generally showed the highest significance in respect to the agronomic efficiency of N fertilizers. In the non NH4+ fixing soil, 80 kg N ha?1 urea+NH4NO3 was enough to obtain high grain yield. The agronomic efficiency of N fertilizers was generally higher in the non NH4+ fixing soil than in the others. Grain protein was highly affected by NH4+ fixation capacities and N doses. Harvest index was affected by the NH4+ fixation capacity at the 1% significance level.  相似文献   

4.
This study determined N uptake by serrano chilli pepper for two years and evaluated the effects of biochar amendment or organic N (org-N) fertilizer on N use under a Mediterranean climate. A field experiment was conducted using microplots from 2016 to 2017 in California, USA. Treatments included biochar amendment rates [0 (control), 10, 30 and 50 tons (t) ha−1] biochar, all with 100% inorganic N fertilizer (165 kg N ha−1), and org-N fertilizer applications at 50%, 75% and 100% of the total available N supply. Pepper yield, vegetative biomass, N uptake, ammonia (NH3) volatilization and changes in soil organic carbon (SOC), and nitrate were determined. Pepper yield was highest in the 50% org-N and lowest in the 50 t ha−1 biochar treatment during the first year. There were no differences in fruit yield among the organic treatments during the second year, and all were higher than that from the control. The 100% org-N treatment had less NH3 volatilization than all other treatments during the first year. The two-year results showed that chilli pepper plants sequestered 4.6‒6.1 kg N to produce one ton fresh pepper fruits. During the first year, the 50% org-N treatment resulted in the highest N productivity or yield with lowest projected N fertilizer application requirements as compared to other treatments although there were no differences among all treatments in the second year. Thus, a combination of inorganic and org-N fertilizers can be an effective strategy to improve soil N productivity in long-term management.  相似文献   

5.
In 1994, the 14 hectare plateau of a coal refuse bank in Landsweiler‐Reden (Southwest‐Germany) was covered with a mixture consisting of 80% (v/v) refuse materials, 10% (v/v) composted wood and 10% (v/v) of sewage sludge as part of a reclamation project. The amount of sludge dry matter applied was approximately 450 Mg ha−1 to a depth of 2 m. The approximate amount of nitrogen (N) applied with the substrate was 20 Mg ha−1 (total N). From April 1996 until November 1997, contents of mineral nitrogen and nitrogen mineralization were monitored down to a depth of 2 m. Nitrogen mineralization was monitored by means of a modified buried bag procedure using a retrievable cylindrical receptacle. The contents of NH4+‐ and NO3−‐N were largest at the beginning of the observation period, reaching a peak value of 650 kg ha−1 in May 1996. Then, mineral N stabilized in 1997 at a level of 200 kg N ha−1, with the soil profile below 150 cm contributing about 75% to this amount. Net nitrogen mineralization was characterized by the same depth distribution. Other than in surface horizons, mineralization activity at the bottom of the profile continued into 1997 with the same intensity as in 1996. Variability among replicate buried bag incubations was high (CV > 100% on several occasions). Nitrogen loss through leaching was estimated at 630 kg N ha−1 over the observation period, averaging at 360 kg N ha−1 a−1. The reclamation procedure used in this study may have the potential to contaminate ground water in hydrologically sensitive areas.  相似文献   

6.
The effect of acidic deposition on the soil under red pine forest in Chunchon, Korea was investigated. Precipitation, stream water, and soil solution chemistry were monitored at the watershed from 1997 to 1998. Acidity of the open-bulk precipitation was often neutralized by large amounts of ammonia (NH3) that might have originated from livestock farming and fertilization. Estimated elemental budget at the watershed showed a positive correlation between loss of base cations and proton (H+) production due to nitrogen transformation in soil (ΔH+ NT: ([NH4 +]in-[NH4 +]out)- ([NO3 ?]in-[NO3 ?]out)). When ΔH+ NT increased, concentrations of nitrate in soil solutions also increased. Consequently, pH values of soil solutions decreased, although ion exchange with base cations contributed to buffer reaction. Since acid buffering capacity of the red pine forest soil was small, it was concluded that the input of ammonium nitrogen enhanced nitrification in soil thus causing soil acidification represented by loss of base cations from the watershed.  相似文献   

7.
To simulate a future ion input reduction scenario in forests, a large scale field experiment was set up in a (1999) 66‒year‒old Norway spruce plantation at Solling, central Germany. Throughfall input of H+, SO42—, and N‒compounds is artificially reduced by means of a permanent roof construction below the canopy and a de‒ionizing equipment since 1991. Here we present long term soil solution records for SO42—, NO3—, Al3+ and the pH of the 10 cm mineral soil sampling depth. A significant decrease in ion concentrations since the start of the treatment is observed, but no change of the soil solution pH. Even in the fourth year pH values remained well within the aluminium buffer range (pH < 4.2). Three years after the start of the experiment (July 1994) it was examined whether microbial biomass (Cmic), specific activity (heat production per unit biomass), and the percentage of Cmic in organic C material indicated any changes. Furthermore chemical standard parameters (CEC, base saturation, pH) were analyzed for all soil samples. Results indicate that despite of drastic decreases of soil solution ion concentrations in the upper soil horizons microbial parameters were not affected and that the soil solid phase is not deacidified by the treatment until now.  相似文献   

8.
Dairy manure (DM) rates of [0 (DM0), 30 (DM30)), 60 (DM60) Mg ha?1] and three nitrogen (N) rates [0 (N0), 125 (N125), 250 (N250) kg ha?1] were tested in a sandy clay loam, to evaluate their effects on growth and yield of wheat crop (Triticum aestivum L.), residual nitrate nitrogen (NO3-N) and phosphorus (P) concentrations in the surface soil, and selected soil physical measurements [saturated hydraulic conductivity (Ksat), and bulk density (BD)]. Increasing N and DM rates gave higher wheat yields, increased concentrations of residual NO3-N and P in the surface soil and improved Ksat and BD. Highest grain yield of 3.8 Mg ha?1 (70.3% more than the control) was observed in DM60 × N250 treatment. Residual accumulation of N-NO3 and P in the surface soil at high N and/or DM application rates suggests the need to carefully manage N and DM inputs on farm fields to avoid environmental contamination.  相似文献   

9.
Nitrate leaching from intensively and extensively grazed grassland measured with suction cup samplers and sampling of soil mineral‐N I Influence of pasture management Leaching of nitrate (NO3—) from two differently managed cattle pastures was determined over four winters between 1993 and 1997 using ceramic suction cup samplers (with min. 34 cups ha—1); additionally, vertical soil mineral‐N content in 0—0.9 m (Nmin) was measured at the beginning and end of two winters (with min. 70 different sample cores ha—1). The experimental site in the highlands north‐east of Cologne, Germany, is characterized by high annual precipitation (av. 1,362 mm between 1993 and 1996). An intensive continuous grazing management (1.3 ha, fertilized with 250 kg N ha—1 yr—1, average stocking density 4.9 LU ha—1, = [I]) was tested against an extensive continuous grazing system (2.2 ha, av. 2.9 LU ha—1; no N‐fertilizer but an estimated proportion of Trifolium repens up to 15 % of total dry matter in the final year, = [E]). The results can be summarized as follows: (1) Mean leaching losses of NO3‐N, estimated from suction cup sampling and balance of drainage volume, were 85 kg NO3‐N ha—1 [I] and 15 kg NO3‐N ha—1 [E] during three wet winters with drainage volumes between 399 and 890 mm; in a dry winter with 105 mm calculated percolation, nitrate leaching decreased by a factor of 5 for both grazing treatments. (2) Although the amount of mineral N in soil (Nmin) sampled in late autumn showed differences between intensive and extensive grazing, the Nmin method permits no certain indication of the risk of NO3 leaching. For example, during the winter period 1994/95 a reduction of mineral N in the soil (0—0.9 m) in both grazing treatments was found (—33 [I] / —8 [E] kg NO3‐N ha—1 and —26 [I] / —21 [E] kg NH4‐N ha—1) whereas during the winter 1996/97 an increase in almost all mean mineral N values occurred (+10 [I] / +2 [E] kg NO3‐N ha—1 and +10 [I] / —10 [E] kg NH4‐N ha—1). (3) In spite of the differences between both methods, the experiment shows that NO3‐N leaching under extensive grazing could be reduced almost to levels close to those under mown grassland.  相似文献   

10.
Abstract

Hydrogen (H+) and hydroxyl ion (OH‐) production by the tropical grass, Brachiaria humidicola, is quantified using a method in which the plants are grown in soil then transferred to agar gel for 24 h. The amount of H+ and OH‐produced was calculated from the pH of the melted gel and the gels’ buffer curve. Values were obtained for plants of different ages and with nitrogen (N) supplied in the gel as nitrate (NC3 ‐), ammonium (NH4 +), or ammonium nitrate (NH4NO3) and compared with data calculated using the sum of H+ changes in differently colored zones of the gel. Daily H+ and OH‐ production increased with plant age and total dry matter for the NH4 +‐ and NO3 ‐‐fed plants, respectively. By integrating the data over time, a value of 0.33 mmol H+ plant‐1 was obtained for the total H+ production over 62 d. The proposed method was sufficiently rapid and versatile to allow the comparison between plant species or genotypes, which were grown using a variety of nutrient supplies. This procedure may indicate how acid production affects plant nutrient acquisition and aid the prediction of soil acidification by different plant species or cultivars.  相似文献   

11.
Improved understanding of the seasonal dynamics of C and N cycling in soils, and the main controls on these fluctuations, is needed to improve management strategies and to better match soil N supply to crop N demand. Although the C and N cycles in soil are usually considered to be closely linked, few data exist where both C and N pools and gross N fluxes have been measured seasonally. Here we present measurements of inorganic N, extracted soluble organic N, microbial biomass C and N, gross N fluxes and CO2 production from soil collected under wheat in a ley‐arable and continuous arable rotation within a long‐term experiment. The amounts of inorganic N and extracted soluble organic N were similar (range 5–35 kg N ha−1; 0–23 cm) but had different seasonal patterns: whilst inorganic N declined during wheat growth, extracted soluble organic N peaked after cultivation and also during maximal stem elongation. The microbial biomass was significantly larger in the ley‐arable (964 kg C ha−1; 0–23 cm) than the continuous arable rotation (518 kg C ha−1; 0–23 cm) but with no clear seasonal pattern. In contrast, CO2 produced from soil and gross N mineralization showed strong seasonality linked to soil temperature and moisture content. Normalization of soil CO2 production and gross N mineralization with respect to these environmental regulators enabled us to study the underlying influence of the incorporation of fresh plant material into soil on these processes. The average normalized gross rates of N mineralized during the growing season were 1.74 and 2.55 kg N ha−1 nday−1 in continuous arable and ley‐arable rotations respectively. Production rates (gross N mineralization, gross nitrification) were similar in both land uses and matched rates of NH4+ and NO3− consumption, resulting in periods of net N mineralization and immobilization. There was no simple relationship between soil CO2 production and gross N mineralization, which we attributed to changes in the C : N ratio of the mineralizing pool(s).  相似文献   

12.
The mineralization and nutrient evolution of an organic fertilizer compost of flour, meat, and crop residues was evaluated in two vineyard soils. A lysimetric testing, using 2.2-L Büchner funnels, was carried out to study the evolution of pH, electrical conductivity, and nutrients during the 400-day experiment. The net mineralization for two different doses of the fertilizer mixed with the soils was compared with an unfertilized control. The pH value of the acidic soil decreased to values less than 4.5 because of the yield of hydrogen (H+) in the organic fertilizer mineralization, whereas the soluble aluminium (Al3+) increased quickly in the leachates. The mineralization process was quicker in the alkaline soil (with a maximum mineralization rate of 0.83 mg nitrogen (N) kg?1 day?1 for the 8 Mg ha?1 dose and 0.43 mg N kg?1 day?1 for the 4 Mg ha?1 dose) in comparison with the acidic soil, which reduced these rates up to 50%. The N-nitrate (NO3) amounts yielded in a year were 150 and 79 kg N ha?1 for the 8 and 4 Mg ha?1 doses respectively in the alkaline soil, enough to cover the vineyard N demand. These values were reduced to 50% and 60% of N-NO3 for the acidic soil, indicating the important effect of pH in the mineralization.  相似文献   

13.
Effects of stabilized urea fertilizers [Alzon 46 (A) and UREAstabil (US)] on soil microbiological and chemical parameters and also on grain yield, 1000-grain weight, and oil content were tested in a precise field study on Luvisol in 2010–2012. Winter rapeseed (Brassica napus L. cv. Californium) was fertilized both in autumn [45 kg nitrogen (N) ha?1] and in spring (155 kg N ha?1) with A [urea with DCD (dicyandiamide) plus pyrrodiazole (1,2,4-1H-triazole)], US {urea with NBPT [N-(n-butyl)-thiophosphoric acid triamide]}, and conventional N fertilizers (pure urea, calcium ammonium nitrate). Eleven parameters were used to evaluate the soil status: microbial biomass carbon (C; microwave method [MW]), dehydrogenase activity, arylsulfatase activity, available organic carbon, electroconductivity, Corg (MW method), and pH (in water, H2O). None of the 11 parameters demonstrated significant difference between control, conventional N fertilizers, and stabilized urea fertilizers. The greatest yield significantly different from the control (zero kg N ha?1; 2598 ± 881 kg ha?1) was found for both stabilized urea fertilizers: A (200 kg N ha?1; 3772 ± 759 kg ha?1) and US (200 kg N ha?1; 3764 ± 625 kg ha?1). The control achieved the greatest oil content (46.0 ± 1.2%), which was significantly different from all N-fertilized variants, and also the greatest 1000-grain weight (5.62 ± 0.62 g).  相似文献   

14.
The responses of nitrogen transformations and nitrate (NO_3 -) leaching to experimentally increased N deposition were studied in forested sub-catchments (1500 m2) with Gleysols in Central Switzerland. The aim was toinvestigate whether the increase in NO3 - leaching,due to elevated N deposition, was hydrologically driven orresulted from N saturation of the forest ecosystem.Three years of continuous N addition at a rate of 30 kgNH4NO3-N ha-1 yr-1 had no effects on bulksoil N, on microbial biomass N, on K2SO4-extractableN concentrations in the soil, and on net nitrification rates.In contrast, N losses from the ecosystem through denitrification and NO3 - leaching increased significantly. Nitrate leaching was 4 kg N ha-1yr-1at an ambient N deposition of 18 kg N ha-1 yr-1.Leaching of NO3 - at elevated N deposition was 8 kg Nha-1 yr-1. Highest NO3 - leaching occurredduring snowmelt. Ammonium was effectively retained within theuppermost centimetres of the soil as shown by the absence ofNH4 + in the soil solution collected with microsuction cups. Quantifying the N fluxes indicated that 80% ofthe added N were retained in the forest ecosystem.Discharge and NO3 - concentrations of the outflow from the sub-catchments responded to rainfall within 30 min. The water chemistry of the sub-catchment outflow showed thatduring storms, a large part of the runoff from this Gleysol derived from precipitation and from water which had interactedonly with the topsoil. This suggests a dominance of near-surface flow and/or preferential transport through this soil. The contact time of the water with the soil matrix wassufficient to retain NH4 +, but insufficient for a complete retention of NO3 -. At this site with soilsclose to water saturation, the increase in NO3 - leaching by 4 kg N ha-1 yr-1 through elevated N inputsappeared to be due to the bypassing of the soil and the rootsystem rather than to a soil-internal N surplus.  相似文献   

15.
《Applied soil ecology》2007,35(2):423-431
This study investigated how two different N sources used as fertilizer (NO3− or NH4+) interact with an inoculated arbuscular mycorrhizal (AM) fungus (Glomus etunicatum) in an Andisol from southern Chile. The effect of NO3− or NH4+ on mycorrhizal and non-mycorrhizal wheat plants was measured on key root–soil interface activities: pH, acid phosphatase (P-ase) activity and P availability. Root AM colonization, extraradical mycelium length and spore number were also examined at three stages of AM symbiosis development (120, 150 and 240 days after sowing, DAS). The effect of N-source on AM propagule formation was used as an index of the quality and vigor of AM colonization. Mycorrhizal root length was greater with NO3− than with NH4+ at all times. The NO3− source also improved extraradical mycelium density, which reached its maximum at 150 DAS. At each harvest the spore number in the rhizosphere soil was also greater with NO3− fertilization. This NO3− effect on spore formation ranged from 20% at a 120 DAS to 287% at a 240 DAS increase, compared with NH4+. Extraradical mycelium and AM efficiency for P acquisition appeared to be related. The particular fungus/plant metabolism as affected by N sources (NO3− or NH4+) applied did not result in differential plant growth or in changes in N plant acquisition, but affected AM development and activity. Differences in soil pH, available P or P-ase activity in soil seems not to be responsible for the improved physiological status of mycorrhizal development in NO3− fed plants. Mycorrhizal propagule formation in this soil and the high persistence of extraradical mycelium are important factors which may have a strong influence on the next crop, and thus, this aspects should be considered when a cropping system is designed. The influence of N sources on AM performance is of ecological and practical interest in volcanic soils when conventional management is used.  相似文献   

16.
Mineral N accumulates in autumn under pastures in southeastern Australia and is at risk of leaching as nitrate during winter. Nitrate leaching loss and soil mineral N concentrations were measured under pastures grazed by sheep on a duplex (texture contrast) soil in southern New South Wales from 1994 to 1996. Legume (Trifolium subterraneum)‐based pastures contained either annual grass (Lolium rigidum) or perennial grasses (Phalaris aquatica and Dactylis glomerata), and had a control (soil pH 4.1 in 0.01 m CaCl2) or lime treatment (pH 5.5). One of the four replicates was monitored for surface runoff and subsurface flow (the top of the B horizon), and solution NO3– concentrations. The soil contained more mineral N in autumn (64–133 kg N ha?1 to 120 cm) than in spring (51–96 kg N ha?1), with NO3– comprising 70–77%. No NO3– leached in 1994 (475 mm rainfall). In 1995 (697 mm rainfall) and 1996 (666 mm rainfall), the solution at 20 cm depth and subsurface flow contained 20–50 mg N l?1 as NO3– initially but < 1 mg N l?1 by spring. Nitrate‐N concentrations at 120 cm ranged between 2 and 22 mg N l?1 during winter. Losses of NO3– were small in surface runoff (0–2 kg N ha?1 year?1). In 1995, 9–19 kg N ha?1 was lost in subsurface flow. Deep drainage losses were 3–12 kg N ha?1 in 1995 and 4–10 kg N ha?1 in 1996, with the most loss occurring under limed annual pasture. Averaged over 3 years, N losses were 9 and 15 kg N ha?1 year?1 under control and limed annual pastures, respectively, and 6 and 8 kg N ha?1 year?1 under control and limed perennial pastures. Nitrate losses in the wet year of 1995 were 22, 33, 13 and 19 kg N ha?1 under the four respective pastures. The increased loss of N caused by liming was of a similar amount to the decreased N loss by maintaining perennial pasture as distinct from an annual pasture.  相似文献   

17.
Three years of N application to a Cambic arenosol (Typic Udorthent) in two lysimeter series, one with and one without young saplings of Pinus sylvestris L. have produced significant changes in soil solution and leachate chemistry. An application of 30 kg N/ha*yr?1 significantly increased NO3 ? leaching from the soil. This N load was also sufficient to significantly increase the mobility of the phyto-toxic elements Al3+ and Mn2+, likewise to increase leaching of the important plant nutrients Ca2+, Mg2+ and K+. At a N load of 90 kg N/ha*yr?1 significant increase in NH4 + leaching was observed, but total leaching of NH4 + was still very low compared to NO3 ? leaching. No significant treatment effects were found for SO4 2?, Fe2+ and Cl? in the leachate. Trees grown in the lysimeters buffered the acidifying effect of N application and increased the leachate pH by 0.2 pH units compared to lysimeters without trees.  相似文献   

18.
Abstract

A field experiment was conducted on Maury silt loam soil (Typic Paleudalf) during 2 years to determine the effects of rate of nitrapyrin and source of N fertilizer on soil pH and response of burley tobacco (Nicotiana tabacum L.cv.xKy‐14'). All sources of N were applied at the rate of 280 kg N ha‐1. The information was needed to increase the efficiency of N fertilizer use and improve the growth and safety of tobacco.

Results indicated that application of a NO3 ‐source of N fertilizer or low rates of nitrapyrin (0.56 to 2.24 kg ha‐1) decreased surface soil acidification and the concentration of plant Mn, while plant dry weight early in the growing season was increased. The early growth benefits noted for .nitrapyrin did not lead to increased cured leaf yields or value. Cured leaf yield and value were highest in plots receiving Ca(NO3)2, followed by KH4NO3, then urea.

Concentration of protein N, total alkaloids, and total volatile nitrogenous bases of cured leaves increased and NO3 ‐‐N decreased as rate of nitrapyrin increased. Total N concentration of cured leaf, however, was not significantly affected by nitrapyrin application, indicating that the proportion of absorbed N as NH4 +increased as nitrapyrin rate increased.  相似文献   

19.
Alongside nitrate, dissolved organic nitrogen (DON) represents a significant N loss pathway in many agroecosystems. To better understand the factors controlling DON leaching in soil we followed the vertical movement of 15N-labeled NO3−, NH4+, alanine and trialanine in packed soil columns in response to a simulated rainfall event. We show that in autoclaved (sterile) soil where sorption is assumed to be the dominant regulating factor, leaching followed the series NO3− > trialanine > alanine > NH4+. In the non-sterile packed soil columns, the rapid rate of NO3− leaching was unaffected whilst the movement of the amino acid, peptide and NH4+ was almost completely prevented due to microbial immobilization. Our results support the view that (1) DON loss from agricultural soils occurs mainly in the form of recalcitrant compounds (e.g. humic DON) rather than in the form of labile low MW DON (e.g. oligopeptides and amino acids), and (2) that although nitrate was bioavailable, it was not a preferred N form for the C-limited microbial biomass.  相似文献   

20.
The main aim of this study was to compare the N leaching from grass fertilized with 220 kg N ha−1 and grass‐clover pastures receiving no fertilization during three grazing years and a renewal year, in a 4‐year ley rotation. The other aim was to compare the herbage and milk production of these pastures. The study was conducted on a lysimeter field; five lysimeters (size 10 × 10 m) were assigned to each treatment. Automated drinking water outlets for the cows were located on one of the lysimeters on each treatment. The amount of leachate was recorded and composite samples were analysed for total N, NO3‐N, NH4‐N and soluble organic N (SON). The number of grazing cows was adjusted according to the herbage mass production. The amount of milk was measured. The total input of N to the area was 290 and 215 kg N ha−1 year−1 for grass and grass‐clover treatments, respectively. The total N leaching during grazing years was 17 and 9 kg N ha−1 from grass and grass‐clover treatments, respectively. Renewal of the sward increased N leaching in both treatments, up to 60 and 40 kg total N ha−1 in grass and grass‐clover treatments, respectively. During the grazing years 96% of the leached N was in the form of NO3‐N, but during the renewal year the proportion of NO3‐N was lowered to 89% and the rest was in the form of SON. The total amount of N in the surface runoff was 3–5 kg ha−1 year−1. As high N fertilizer rates per application are a common practice in Finland, short‐term grass‐clover pastures can be considered environmentally beneficial when compared with intensively fertilized grass pastures in comparable circumstances.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号