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1.
To develop a low cost and energy-saving wastewater treatment technique in combination with resource recycling and amenity functions, we constructed a plant bed filter ditch in which useful terrestrial and aquatic plants can be utilized for nitrogen and phosphorus removal from wastewater. Screening studies were conducted to evaluate and compare the effectiveness of 20 kinds of plant species which are economically important or exhibit on aesthetic value, including 13 terrestrial species, for domestic wastewater treatment. Artificial wastewater containing 20 mg L-1 of Nand 3.3 mg L-1 of P, was supplied to the ditch at the rate of about 1.41–2.08 g m-2 d-1 for N and 0.20–0.33 g m-2 d-1 for P. The experiments were performed in a glass house with windows opened from April to November. The ditches showing high Nand P removal rates were planted with plants which exhibited high biomass production rates. In the case of the papyrus ditch, Nand P removal rates exceeded 0.8 g m-2 d-1 for N and 0.15 g m-2 d-1 for P from late spring to autumn, in the case of the kenaf ditch and sorghum ditch, from summer to autumn and in the case of the Italian ryegrass ditch and barley ditch, in early spring. These findings indicated that efficient wastewater treatment can be performed consistently except in the winter season, by cultivating these plants in an appropriate combination in the ditches.  相似文献   

2.
Cultivation of useful terrestrial and aquatic plant species in plant bed filter ditches enables to treat domestic wastewater in addition to resource recycling and amenity functions. We reported previously that a ditch planted with papyrus removed Nand P most effectively from artificial wastewater. We evaluated the effectiveness of plant bed filter ditches in the treatment of eutrophic pond water, which unlike artificial wastewater, contains particulate Nand P. Experimental ditches were planted with papyrus, African marigold, peppermint, and impatience. These plant species were effective in removing N and P from artificial wastewater and could be used by rural communities for the production of handicrafts, cut flowers, and ornamental purposes. The control ditch did not contain plants (plant-free ditch). Pond water was continuously supplied to the ditches at a loading rate of 0.6–0.9 g m-2 d-1 for Nand 0.2–0.35 g m-2 d-1 for P. In the plant-free ditch, particulate Nand P in the influent were removed by passage through the bed filter, unlike NO3-N and PO4-P. A larger amount of PO4-P was dissolved from particulate P in the bed filter. The planted ditches effectively removed NO3-N, PO4-P as well as particulate Nand P. The planted ditches were able to purify eutrophic pond water, resulting in clear water with a concentration below 0.3 mg L-1 for N and 0.02 mg L-1 for P, concentrations at which water bloom does not occur. The average removal rate of pollutants by the planted ditches during the experiment, except for the first 2 weeks, was 0.67 g m-2 d-1 for total N and 0.03 g m-2 d-1 for total P. We recommend that plant bed filter ditches containing papyrus and flowers be used for ornamental purposes and removal of N and P from pond water along with the supply of clear water as ornamental streams.  相似文献   

3.
Abstract

In three field trials in southern Norway, Italian ryegrass (Lolium multiflorum Lam.), white clover (Trifolium repens L.) or subterranean clover (T. subterraneuni L.) was undersown in spring grain at three N fertilizer rates and ploughed under in late October as a green manure for a succeeding spring grain crop. The content of topsoil (0-20 cm) mineral nitrogen was determined during the growth of the grain crop, after grain harvest and after ploughing. In addition, mineralization of nitrogen and carbon was measured in green-manured soil incubated at 15°C and controlled moisture conditions. During grain crop growth, ryegrass tended to reduce soil mineral N compared with the other treatments. After grain harvest, in a small-plot experiment where extra nitrate was added, ryegrass reduced soil nitrate N (0-18 cm) from 4.2 to 0.4 g m?2 within 13 days, while the clovers had negligible effect compared with bare soil. Up to 9.4 g N m?2 was present in above-plus below-ground ryegrass biomass at ploughing. In incubated ryegrass soil, there was a temporary net N immobilization of up to 0.9 g N m?2 as compared with unamended soil. In clover-amended soil, mineral N exceeded that in unamended soil by up to 5 g N m?2.  相似文献   

4.
Abstract

Multi-soil-layering (MSL) system was designed for purifying domestic wastewater and for treating polluted river water. MSL system is typically comprised of layers of soil mixture blocks alternating with permeable layers. The permeable layer has roles of preventing clogging and to increasing the efficiency of infiltration of wastewater through the soil mixture blocks. In this study, the comparative efficiency of five MSL systems as a function of five permeable layer materials (zeolite, zeolitized perlite, perlite, gravel, and charcoal) was investigated. The MSL systems were constructed in 15 × 50 × 100 cm boxes where the soil mixture blocks contained sandy clay soil, kenaf + corncob, and iron scraps at a ratio of 6 : 1 : 1 by weight, respectively, and filled up in alternation with the permeable layer. The results indicated that all the MSL systems at loading rates of 96–346 L m?2 d?1 under nonaerated conditions were able to reduce the levels of COD (342–1,231 mg L?1), BOD5 (201–802 mg L?1), and soluble reactive phosphorus (SRP) (3.5–10.1 mg P L?1) at percentages of 79.0–98.1, 80.0–99.6, and 97.1–100%, respectively. The zeolite and the charcoal-based MSL systems under a 96–346 L m?2 d?1 loading rate effectively reduced the level of TN (41.4–65.5 mg N L?1) at percentages of 79.0–92.1 and 30.7–88.9%, respectively. In terms of prevention of clogging, the charcoal-based MSL system was the most effective, followed by the gravel and zeolite-based MSL. The apparent efficiency of pollutant removal, for zeolitized perlite, perlite, and gravel-based MSL systems was low. With an on-off aeration operation, the efficiency of the MSL systems in the reduction of the levels of COD, BOD5 , and SRP (hereafter reference to as “removal”) was significantly enhanced. Overall, the zeolite-based MSL system seemed to be more effective than the other MSL systems. However, if optimum aeration could be obtained, the removal efficiency of charcoal-based MSL system might be improved. Aeration at a rate of 64,000 L m?3 d?1 for 1 week alternating with 2 weeks of nonaeration enhanced the removal of COD, BOD5 , and SRP but not that of TN.  相似文献   

5.
A 3-year field study was conducted to determine the influence of nitrogen (N) application timing on the growth and quality of a turfgrass mixture consisting of perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), creeping red fescue (Festuca rubra var. rubra L.), and chewings fescue (Festuca rubra var. commutata Gaud.) under irrigated conditions. Nitrogen was applied annually at the rate of 30 g m?2 year?1, with six application regimes: control (no N), single spring (30 g m?2), single fall (30 g m?2), spring + fall (15 + 15 g m?2), spring + summer + fall (10 + 10 + 10 g m?2), and monthly from April through September (5 g m?2).

Color, turf quality, clipping weights, and shoot density were correlated with fertilizer rates and application timing in this study. Fertilization monthly or every 2 months resulted in more uniform color and turf quality and less clipping weights than with comparable heavy spring and fall fertilizations. Heavy N applications in the fall did not cause winter injury and produced significantly darker color and more uniform appearance in early spring than other N applications. All N-fertilization regimes increased shoot density, but spring fertilization stimulated density the most. Nitrogen applied monthly or every 2 months was enough to enhance the color, turf quality, and shoot density of the turf during the growing season but did not greatly affect the growth rate.  相似文献   

6.
Biological processes can achieve nitrate removal from groundwater. The sulfur/limestone autotrophic denitrification by Thiobacillus denitrificans was evaluated with three laboratory-scale column reactors. The optimum sulfur/limestone ratio was determined to be 2:1 (mass/mass). Different hydraulic retention times were used during the column tests to examine nitrate removal efficiencies. Under an HRTs of 13 h, nitrate concentration of 60 mgNO3 --N L-1 was reduced to less than 5 mg NO3 --N L-1. On a higher HRT of 26 h the nitrate removal efficiency was close to 100% for all nitrate-nitrogen loading rates. Different initial nitrate-nitrogen concentrations (30, 60, and 90 mg NO3 --N L-1) were used in the study. Column tests showed that the nitrate-nitrogen loading rate in this study was between 50 to 100 g NO3 --N m-3 d-1 to obtain a removal efficiency of 80–100%. It was found that approximately 6 mg SO4 2- was produced for 1 mg NO3 --N removed. Nitrite-nitrogen in all cases was less than the maximum allowable concentration of 1 mg NO2 --N L-1. Effluent pH was stable in the range of 7 to 8; the effluent dissolved oxygen was less than 0.15 mg L-1 and the oxidation-reduction potential in all columns was in the range of –110 to –250 mV.  相似文献   

7.
Five poinsettia (Euphorbia pulcherrima Willd.), ‘Freedom Red’, ‘Angelika Red’, ‘Nutcracker Red’, ‘Maren’, and ‘Red Splendor’ received the following treatments of a commercial fertilizer based on nitrogen (N) concentrations of: 75 mg L‐1 to anthesis; 75 mg L‐1 first 4 weeks then 125 mg L‐1 to anthesis; 125 mg L‐1 first 4 weeks then 200 mg L‐1 to anthesis; and 200 mg L‐1 to anthesis. Plants were fertigated to appearance of leachate from the bottom of the pot. Treatment concentrations greater than 125/200 and 200 mg.L‐1 significantly increased plant width of ‘Red Splendor’, height of ‘Nutcracker Red’ and dry weight of ‘Angelika Red’, ‘Nutcracker Red’, and ‘Maren’. Tissue concentrations of N, phosphorus (P), magnesium (Mg), and sulfur (S) increased as fertilizer treatment concentration increased for some cultivars. Significant differences between elemental concentrations of poinsettia cultivars occurred, specifically ‘Nutcracker Red’. Although tissue nutrient concentrations were at or below the critical level, general observations of each cultivar indicated that all plants were of commercial quality and almost indistinguishable between treatments. Poinsettia stem strength was not significantly affected by any fertilizer treatment used in this study.  相似文献   

8.
In recent years, applying humic acid (HA) has been common in turfgrass management. A series of experiments were conducted to evaluate the effect of HA on qualitative and quantitative characteristics of “Speedygreen” perennial ryegrass (Lolium perenne L.). Different concentrations of HA (0, 100, 400, and 1000 mg L?1) were applied monthly as foliar application. Results showed that leaf phosphorus (P), potassium (K), and zinc (Zn) content, fresh and dry weight, chlorophyll content, and root fresh weights were not affected by HA. Meanwhile, HA improved the root and shoot development, except for root fresh weight. While just 100 mg L?1 improved height, visual quality, nitrogen (N) content, roots length, and surface of roots, all of HA concentrations were effective on iron content. These results suggest that HA foliar application might be of benefit to enhance some nutrients uptake and root development of ryegrass possibly leading to improved drought resistance.  相似文献   

9.
The decomposition of 15N-labelled catch-crop materials (rape, radish and rye), obtained from field experiments, was studied in a chalky Champagne soil during a 60-week incubation at 28°C. Mineralized N was assumed to come from either labile or recalcitrant fractions of plant residues. The labile fraction represented about one-third of the catch-crop N; its mineralization rate constant varied from 0.06 to 0.12 d?1. The decomposition rate of the recalcitrant N fraction ranged from 0.03 × 10?2 to 0.06 × 10?2 d?1. Catch-crop species and rate of incorporation had no effect on N residue mineralized at the end of incubation. The decomposition of labelled rye was monitored in the same soil during a 5-month pot experiment to determine the N availability to an Italian ryegrass crop and the effect of plants on the decomposition processes. The 15N-rye decomposed rapidly both in the presence or absence of Italian ryegrass, but the amounts of N mineralized were influenced by the presence of living roots: 42% of the 15N in labelled rye was present as inorganic N in the pots without plants after 5 months, compared with only 32% in the ryegrass crop. Comparison of microbial-biomass dynamics in both treatments suggested that there had been preferential utilization by soil micro-organisms of materials released from the living roots than the labelled plant residues.  相似文献   

10.
The effects of humic acids extracted from two commercially‐available products (CP‐A prepared from peat and CP‐B prepared from leonardite) on the growth and mineral nutrition of tomato plants (Lycopersicon esculentum L.) in hydroponics culture were tested at concentrations of 20 and 50 mg L‐1. Both the humic acids tested stimulated plants growth. The CP‐A stimulated only root growth, especially at 20 mg L‐1 [23% and 22% increase over the control, on fresh weight basis (f.w.b.), and dry weight basis (d.w.b.), respectively]. In contrast, CP‐B showed a positive effect on both shoots and roots, especially at 50 mg L‐1 (shoots: 8% and 9% increase over the control; roots: 18% and 16% increase over the control, on f.w.b. and d.w.b., respectively). Total ion uptake by the plants was affected by the two products. In particular, CP‐A showed an increase in the uptake of nitrogen (N), phosphorus (P), iron (Fe), and copper (Cu), whereas, CP‐B showed positive effects for N, P, and Fe uptake. The change in the Fe content was the most appreciable effect on mineral nutrition (CP‐A: 41% and 33% increase over the control for 20 mg L‐1 and 50 mg L‐1 respectively; CP‐B: 31% and 46% increase over the control for 20 mg L‐1 and 50 mg L‐1, respectively). Increases in Fe concentration in the plant roots were especially pronounced (CP‐A: 113% and 123% increases with respect to controls for the 20 mg L‐1 and 50 mg L‐1 treatments; CP‐B: 135% and 161% increases with respect to the control for 20 mg L‐1 and 50 mg L‐1 treatments). On the basis of the current experiments and from evidence in the literature, reduction of Fe3+ to Fe2+ by humic acid is considered as a possibility to explain a higher Fe availability for the plants.  相似文献   

11.
Silver nanoparticles (AgNPs) are widely used antimicrobial compounds;however,they may pose a threat to non-targeted bacteria in the environment.In this study high-throughput sequencing was used to investigate the effects of different concentrations of AgNPs (10,50,and 100 mg kg-1) on soil microbial community structure during short-term (7 d) exposure.The amounts of Acidobacteria,Actinobacteria,Cyanobacteria,and Nitrospirac significantly decreased with increasing AgNP concentration;meanwhile,several other phyla (e.g.,Proteobacteria and Planctomycetes) increased and dominated.Nitrosomonas europaea,a well-characterized ammoniaoxidizing bacterium,was used to study the sensitivity of bacteria to AgNPs and ionic silver (Ag+).Flow cytometry was used to monitor the toxicity of low (1 mg L-1),middle (10 mg L-1),and high concentrations (20 mg L-1) of AgNPs,as well as Ag+ (1 mg L-1) released into the medium from 20 mg L-1 concentration of AgNPs,towards N.europaea.After 12 h of exposure,the survival rate of N.europaea treated with 1 mg L-1 Ag+ was significantly lower than those treated with low (1 mg L-1) and middle concentrations (10 mg L-1) of AgNPs,but the survival rate in the treatment with high concentration (20 mg L-1) of AgNPs was much lower.Additionally,necrosis rates were higher in the treatment with 20 mg L-1 AgNPs.Electron microscopy showed that Ag+ caused serious damage to the cell wall of N.europaea,disintegrated the nucleoids,and condensed next to the cell membrane;however,dissolved Ag+ is only one of the antibacterial mechanisms of AgNPs.  相似文献   

12.
The effects of ammonium chloride on survival and feeding energetics of the freshwater fish Oreochromis mossambicus were studied. At a concentration of 600 mg L-1 ammonium chloride, 100% mortality was observed within 24 h; no mortality occurred at 400 mg L-1 within 96 h; Concentration of 450 mg L-1 ammonium chloride was found as median lethal concentration at 96 h exposure. Rearing the fish in increasing sublethal concentrations of ammonium chloride, it was found that the feeding rate decreased from 20.309 ± 0.506 mg g live fish-1 day-1 (mg g-1 d-1 (control) to 11.594 ± 0.479 mg g-1 d-1 at the highest sublethal concentration (100 mg L-1. Growth rate was drastically reduced.  相似文献   

13.
Hu  Zhaoyang  Wang  Yufeng  Fang  Zhigang  Shi  Gaoling  Lou  Laiqing  Ren  Kaidi  Cai  Qingsheng 《Journal of Soils and Sediments》2020,20(2):874-882
Purpose

Growing energy plants in Cd-contaminated soil to produce bioenergy feedstock and remove excess Cd in the soil is a promising approach to the production of sustainable bioenergy feedstock and safe food. Rice, an important staple food for human beings, is a major source of Cd intake in human beings. Italian ryegrass (Lolium multiflorum Lam) is a potential bioenergy plant with high biomass productivity and high biofuel conversion efficiency.

Materials and methods

An Italian ryegrass and rice crop rotation system would be beneficial for the harvest of bioenergy and phytoremediation. An Italian ryegrass–rice rotation system was established in a moderately Cd-contaminated paddy field. The yield of biomass, amount of Cd removal, and transfer factors for three cropping systems (winter fallow, non-cutting, and cutting) were evaluated over 3 consecutive years of field experiments.

Results and discussion

The total biomass production of the Italian ryegrass–rice rotation system was significantly higher than that of the traditional cropping system. Biomass growth was further promoted by cutting during March. No significant differences were found in yield or Cd concentration of brown rice among the different cropping systems. Total Cd accumulation in rice and Italian ryegrass straw in the rotation cropping system was significantly higher than that in the winter fallow cropping system. Cd was mainly accumulated in the roots, and the ability of Italian ryegrass to transport Cd to the leaves was higher than that of rice.

Conclusions

The Italian ryegrass–rice rotation system is a potential cropping system for Cd-contaminated paddy fields. The average annual yield of biomass was 1656.6 kg km?2, and the average annual amount of Cd removal was more than 9.8 g Cd km?2.

  相似文献   

14.
A two-year irrigated field study was conducted to determine the effects of plant growth-promoting rhizobacteria (PGPR; Bacillus subtilis OSU-142 and Bacillus megaterium M3) as biofertilizer, and in combination with a chemical nitrogen (N) fertilizer, on turf color and clipping yield, and interaction of biofertilizer and chemical N fertilizers in perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea L. Schreb.), and Kentucky bluegrass (Poa pratensis L.). The three turf species were tested separately in split-plot design experiments with three replications. Three fertilizer sources (ammonium nitrate only, ammonium nitrate + B. megaterium M3, and ammonium nitrate + B. subtilis OSU-142) were the main plots. N applications with monthly applications of 0.0, 2.5, 5.0, and 7.5 g N/m2 were the subplots. Color ratings and clipping yields increased with increasing chemical N fertilizers in all species. Both Bacillus sp. significantly increased color ratings and clipping yields in perennial ryegrass and tall fescue. However, there were no significant differences among the three fertilizer sources in color and clipping yield of Kentucky bluegrass. The experiments showed that there is a small but significant benefit from applying biofertilizers for turf color, and that N fertilization may be reduced in some turf species when biofertilization are made for this purpose.  相似文献   

15.
Development of Appalachian coal mining regions of the USA has been severely hampered by lack of domestic waste disposal technologies suited to fills. The suitability of on-site wastewater treatment and disposal systems (OSWTDS) in fill material is uncertain due to the effects of surface mining on soil physical properties. This research was conducted to evaluate the potential for renovation of N and P present in domestic wastewater by fills produced from mining operations. Nitrogen and P were chosen because of their potential adverse environmental impacts. Soil-fill (a mixture of Jefferson, fine-loamy, siliceous, mesic Typic Hapludult and Muskingom, fine-loamy, mixed, mesic Typic Dystrochrept soils) and minespoil (spoil)-fill (blasted rock material associated with the Taggart Marker and Low Splint Bench coal seams of the Upper Middle Wise Formation) were used in this study. Septic tank effluent (STE) and sand filter effluent (SFE) were applied to spoil-fill columns at four loading rates (0, 5.4, 10.8, and 21.6 L m-2d-1) and spoil-fill columns at one loading rate (21.6 L m-2d-1) for a period of 20 wk. Renovation of wastewater was assessed by determining the concentration of N and P present in column leachate. Reduction of inorganic N (NO3 - + NH4 +), based on N/Cl ratios, ranged from 14.9 to 32.1% after the varying application rates of STE and SFE passed through the soil columns. However, leachate NO3 --N concentrations were still above the 10 mg-1 drinking water standard. The quantity of P emerging from the spoil-fill columns (3.0 mg P L-1) was higher than anticipated and may be related to the indigenous P present in the minespoil. Sorption of P in the soil-fill column decreased with increased STE and SFE application (reductions ranged from 99.1 to 74.4%). Results from this study indicate that there is potential for renovating wastewater in OSWTDS in selected soil-fill areas in reclaimed minelands.  相似文献   

16.
Iron(III)(hydr)oxides can dissolve under reducing soil conditions. Simultaneously, oxide-associated inorganic phosphate is released to the soil solution. In this study, the effect of reducing soil conditions on phosphate leaching from transient waterlogging clayey soil is evaluated. We applied glucose solutions (either 100 or 1000 mg glucose-C L-1) at a steady flow rate of 0.63 mm h-1 to a saturated intact column of structured Alfisol (diam. 0.5 m, height 1.0 m). Effluent concentrations of iron(II) and reactive orthophosphate (Pi) increased slightly during 5 d of low glucose application, reaching values of 2.5 mg Fe L-1, and 0.02 mg PO4-P L-1, respectively. During 10 d of high glucose application, the iron(II) concentration increased to 14 mg Fe L-1 and fluctuations in the Pi-concentration between 0.002 and 0.1 mg PO4-P L-1 were observed. The fluctuations in Pi-concentration are ascribed to interactions between progression of the glucose front, and Pi-mobilization/resorption processes at the walls of macropores. The daily P-losses during low and high glucose applications averaged 0.3 mg PO4-P m-2 d-1, and 0.5 mg PO4-P m-2 d-1, respectively. Comparisons with a parallel topsoil study suggest that subsoil exerts a strong control on leaching – probably via resorption – of Pi mobilized in the topsoil.  相似文献   

17.
Perennial ryegrass growing in monolith lysimeters and treated with 400 kg N ha-1 as calcium nitrate labelled with nitrogen-15 (10.5 atoms per cent), during one growing season recovered between 43 and 54 per cent of the fertilizer nitrogen. In the following year without further nitrogen additions 4.6–9.5 per cent was taken up, whilst in the fifth year the recovery was less than 1 per cent. The contribution of non-fertilizer sources of nitrogen to the total nitrogen taken up by the plants during the season that nitrogen was applied was estimated using tracer methods to be about 13–14 g N m-2 year-1. The estimate from measuring the nitrogen content of an unfertilized sward was 7 g N m-2 year-1. The residual effects of a fertilizer application are likely to be detectable for a period of between 6 and 9 years. Losses of nitrogen to drainage in the winter after application represented 2–5 per cent of the fertilizer applied, whilst in subsequent years the amounts did not exceed 0.1 per cent. Mean concentrations of nitrate ranged between 4 and 16 mg N I-1. Fertilizer contributed about 60–70 per cent of the total nitrogen lost in the first winter after nitrogen application and 45–60 per cent averaged over three winters.  相似文献   

18.
ABSTRACT

Annual ryegrass (Lolium multiflorum Lam.) provides livestock feed and captures nutrients from fields receiving manure application. The objective of this study was to determine relationships among maturity and yield, mineral uptake, and mineral concentration. Primary spring growth of ‘Marshall’ ryegrass was harvested every 7 d to 56 d maturity and was fertilized with swine effluent containing 254 and 161 kg nitrogen (N) and 42 and 26 kg phosphorus (P) ha?1 for two years. Yield increased linearly to a maximum of 13.6 mg ha?1 after 49 d in 2001 and 8.0 mg ha?1 after 56 d in 2002. Mineral uptake was highly correlated (r > 0.95) with yield and attained a maximum single harvest of 192 kg N ha?1 and 32 kg P ha?1 (mean of two years). Concentration of all minerals except calcium (Ca) declined as ryegrass matured. Low magnesium (Mg) concentration (< 2 g kg?1 dry matter) increases the risk of hypomagnesemic grass tetany.  相似文献   

19.
Outwintering beef cattle on woodchip corrals offers stock management, economic and welfare benefits when compared with overwintering in open fields or indoors. A trial was set up on a loamy sand over sand soil to evaluate the pollution risks from corrals and the effect of design features (size and depth of woodchips, stocking density, and feeding on or off the corral). Plastic‐lined drainage trenches at 9–10 m spacing under the woodchips allowed sampling of the leachate. Sampling of the soil to 3.6 m below the corral allowed evaluation of pollutant mitigation during vadose zone transport. Mean corral leachate pollutant concentrations were 443–1056 mg NH4‐N L?1, 372–1078 mg dissolved organic carbon (DOC) L?1, 3–13 mg NO3‐N L?1, 8 × 104–1.0 × 106Escherichia coli 100 mL?1 and 2.8 × 102–1.4 × 103 faecal enterococci 100 mL?1. Little influence of design features could be observed. DOC, NH4 and (in most cases) E. coli and faecal enterococci concentrations decreased 102–103 fold when compared with corral leachate during transport to 3.6 m but there were some cores where faecal enterococci concentrations remained high throughout the profile. Travel times of pollutants (39–113 days) were estimated assuming vertical percolation, piston displacement at field moisture content and no adsorption. This allowed decay/die‐off kinetics in the soil to be estimated (0.009–0.044 day?1 for DOC, 0.014–0.045 day?1 for E. coli and 0–0.022 day?1 for faecal enterococci). The mean [NO3‐N] in pore water from the soil cores (n = 3 per corral) ranged from 114 ± 52 to 404 ± 54 mg NO3‐N L?1, when compared with 59 ± 15 mg NO3‐N L?1 from a field overwintering area and 47 ± 40 mg NO3‐N L?1 under a permanent feeding area. However, modelling suggested that denitrification losses in the soil profile increased with stocking density so nitrate leaching losses per animal may be smaller under corrals than for other overwintering methods. Nitrous oxide, carbon dioxide and methane fluxes (measured on one occasion from one corral) were 5–110 g N ha?1 day?1, 3–23 kg C ha?1 day?1, and 5–340 g C ha?1 day?1 respectively. Ammonia content of air extracted from above the woodchips was 0.7–3.5 mg NH4‐N m?3.  相似文献   

20.
The effects of an intercrop catch crop (Italian ryegrass) on (i) the amounts and concentrations of nitrate leached during the autumn and winter intercrop period, and (ii) the following crop, were examined in a lysimeter experiment and compared with that from a bare fallow treatment. The catch crop was grown in a winter wheat/maize rotation, after harvest of the wheat, and incorporated into the soil before sowing the maize. A calcium and potassium nitrate fertilizer labelled with 15N (200 kg N ha?1; 9.35 atom per cent excess) was applied to the winter wheat in spring. Total N uptake by the winter wheat was 154 kg ha?1 and the recovery of fertilizer-derived N (labelled with 15N) was 60%. The catch crop (grown without further addition of N) yielded 3.8t ha?1 herbage dry matter, containing 43 kg N ha?1, of which 4.1 % was derived from the 15N-labelled fertilizer. Two-hundred kg unlabelled N ha?1 was applied to the maize crop. During the intercrop period the nitrate concentration in water draining from the bare fallow lysimeters reached 68 mg N1?1, with an average of 40 mg N1?1. With the catch crop, it declined rapidly, from 41 mg N I?1 to 0.25 mg N I?1, at the end of ryegrass growth. Over this period, 110 kg N ha?1 was leached under bare fallow, compared with 40 kg N ha?1 under the catch crop. 15N-labelled nitrate was detected in the first drainage water collected in autumn, 5 months after the spring application. The quantity of fertilizer-N that was leached during this winter period was greater under bare fallow (18.7% of applied N) than when a catch crop was grown (7.1 %). In both treatments, labelled fertilizer-N contributed about 34% of the total N lost during this period. With the ryegrass catch crop incorporated at the time of seedbed preparation in spring, the subsequent maize grain-yield was lowered by an average of 13%. Total N-uptake by the maize sown following bare fallow was 224 kg N ha?1, compared with 180 kg ha?1 with prior incorporation of ryegrass; the corresponding values for uptake of residual labelled N were 3% (bare fallow) and 2% (ryegrass) of the initial application. Following the maize harvest, where ryegrass was incorporated, 22.7% of the previous year's labelled fertilizer addition was present in an organic form on the top 30 cm of lysimeter soil. This compares with 15.7% for the bare fallow intercropping treatment. Tracer analyses showed overall recoveries of labelled N of 91.7% for the winter wheat/ ryegrass/maize rotation and 97% for the winter wheat/bare fallow/maize rotation. The study clearly demonstrated the ecological importance of a catch crop in reducing N-leaching as well as its efficient use of fertilizer in the plant-soil system from this particular rotation. However, the fate of the organic N in the ploughed-down catch crop is uncertain and problems were encountered in establishing the next crop of maize.  相似文献   

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