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1.
Results are presented from a 3-year investigation into nitrate leaching from grassed monolith lysimeters treated with double (15NH415NO3) or single (15NH4NO3) labelled ammonium nitrate at three rates, 250, 500 and 900 kg N ha?1 a?1. Over the 3 years of the experiment, 0.14%, 3.1% and 18.1% of the applied fertilizer was recovered in the leachate at 250, 500 and 900kg N ha?1 respectively. This represented 9%, 39% and 75% of the overall nitrate leaching at the three application rates. A significant proportion of the fertilizer leached as nitrate at the three application rates was derived, via nitrification, from the fertilizer ammonium. Increasing fertilizer applications caused a rise in the leaching of both soil and fertilizer derived nitrogen, although whether the increase reflected a true priming effect was not clear.  相似文献   

2.
Fate of fertilizer nitrogen.   总被引：3，自引：0，他引：3  
Results are presented from a three year lysimeter investigation, employing single (15NH4NO3) and double (15NH415NO3) labelled ammonium nitrate to study the uptake of soil and fertilizer nitrogen by cut ryegrass at 250, 500 and 900 kg N ha?1 a?1. Average annual recoveries of nitrogen were equivalent to 99,76 and 50% of the nitrogen added at 250, 500 and 900 kg N ha?1, respectively. At 250 kg N ha?1 the difference between the overall nitrogen recovery and the fertilizer recovery was almost entirely attributable to pool substitution resulting from mineralization/immobilization turnover (MIT). At 900 kg N ha?1 both the low overall recovery of nitrogen and the low fertilizer recovery reflected the large excess of available nitrogen over crop requirements. No evidence of ‘priming’ was obtained. Analysis of the results from single and double labelled lysimeters using simultaneous equations indicated that at 250 kg N ha?1,～70% of the nitrogen in the crop was derived from the ammonium pool. At 500 kg N ha?1 this dropped to 64%, while at 900 kg N ha?1 the figure was 59%. There was a suggestion that at the lower application rates, preferential uptake of ammonium was occurring but that as N supply exceeded crop requirements, nitrate was the major N source. Despite the preferential exploitation of the ammonium pool, at 250 and 500 kg N ha?1 pool substitution resulting from MIT resulted in lower recoveries of fertilizer ammonium compared with fertilizer nitrate.  相似文献   

3.
The objective of this work was to determine the fate of fertilizer nitrogen (labelled with nitrogen-15) applied to an undisturbed shallow soil overlying Chalk contained in 10 lysimeters (80 cm diameter, 135 cm deep). Measurements are reported of the nitrogen uptake by four spring barley crops and the rate and extent of leaching of nitrate beyond the roots. The crops were fertilized with 0, 80 or 120 kg N ha?1 in each of four years, but only the first application in 1977 was labelled with nitrogen ?15. Rainfall and irrigation approximated to the long-term average, but in two treatments dry or wet spring conditions were imposed for the 10 weeks after sowing the first crop in 1977. The dry matter and grain yields of the spring barley crops varied from year to year in the ranges 8.7–14.0 t ha?1 and 3.5–6.1 t ha?1 respectively. The total nitrogen harvested in the crop approximated to the amount of nitrogen applied in each year with an apparent recovery of fertilizer in the range 38–76%. The recovery of nitrogen derived from fertilizer (labelled with nitrogen-15) was 46–54% in the first crop and after 2 years rapidly declined to below 1%. The total amount of nitrogen-15 labelled fertilizer recovered in four barley crops was 49–57% of that applied. Mean annual nitrate concentrations in water draining from the base of the lysimeters were in the range 11.8–26.7 mg N 1?1 and did not differ significantly between nitrogen fertilizer treatments (0, 80 and 120 kg N ha?1 a?1). In all treatments nitrate concentrations varied considerably within each growing season, with a cycle of peaks and troughs. Annual losses of nitrate were in the range 39–128 kg N ha?1, and the mean annual losses over the 4 years varied between lysimeters from 65 to 83 kg N ha?1. Nitrogen-15 labelled nitrate was detected in the first drainage water collected in autumn following its spring application, 5 months earlier. Recovery of fertilizer-derived nitrogen in drainage water was greatest during the winter following the second barley crop, and was 3.4–3.7% of the nitrogen-15 applied. Over the 4 years of the experiment 6.3–6.6% of labelled fertilizer was accounted for in drainage water, representing 2–3% of the total nitrogen lost by leaching.  相似文献   

4.
Denitrification loss from a loam under a cut ryegrass sward receiving 0, 250 and 500 kg N ha?1 a?1 in four equal amounts was measured during 14 months using the acetylene-inhibition technique. The rate of denitrification responded rapidly to changes in soil water content as affected by rain. Mean rates of denitrification exceeded 0.2 kg N ha?1 day?1 only when the soil water content was >20% (w/w) and nitrate was >5μ N g?1 in the upper 20 cm of the profile and when soil temperature at 2 cm was >5–8°C. When the soil dried to a water content <20%, denitrification decreased to <0.05 kg N ha?1 day?1. Highest rates (up to 2.0 kg N ha?1 day?1) were observed following application of fertilizer to soil at a water content of about 30% (w/w) in early spring. Denitrification in the control plot during this period was generally about a hundredth of that in plots treated with ammonium nitrate. High rates of N2O loss (up to 0.30 kg N ha?1 day-1) were invariably associated with high rates of denitrification (> 0.2 kg N ha?1 day?1). However, within 2–3 weeks following application of fertilizer to the plot receiving 250 kg N ha?1 a?1 the soil acted as a sink for atmospheric N2O when its water content was >20% and its temperature >5–8°C. Annual N losses arising from denitrification were 1.6, 11.1 and 29.1 kg N ha?1 for the plots receiving 0, 250 and 500 kg N ha?1 a?1, respectively. More than 60% of the annual loss occurred during a period of 8 weeks when fertilizer was applied to soil with a water content >20%.  相似文献   

5.
Pollution of ground water caused by excessive and uncontrolled use of nitrogen fertilizer is worrying. A recent example of such pollution has been observed in an agricultural basin in the province of Nevsehir, Turkey, where up to 900 kg ha?1 nitrogen fertilizer is used for growing potatoes in sandy soils under irrigation. Using nitrogen fertilizer in amounts that guarantee large yields without polluting ground water is essential. We present results of field experiments and numerical simulations involving 15N-labelled nitrogen fertilizer leaching. In the field, we monitored the movement of water and the distributions of nitrogen species within the soil–water–plant continuum. The detailed dynamics of the nitrogen cycle within the system were simulated. Simulations included calibration and validation of the nitrogen version of the LEACHM model (LEACHN, version 3) and long-term applications of the model. The model’s predictions of nitrogen fluxes under long-term use of fertilizer and irrigation were analysed. Nearly half of the applied ammonium-N was converted to nitrate-N during the growing season. With increasing additions of N the rate of plant uptake declined, while leaching increased significantly, and the fraction of nitrogen remaining in the soil profile increased only moderately. In long-term applications, a significant fraction of the applied fertilizer tended to accumulate after the first year in soil as the residual nitrogen not taken up by the crop. Accumulated residual nitrogen is converted to nitrate-N and leached rapidly from the soil profile during the wet season following the harvest. To reduce leaching of the residual nitrate, the rates, frequencies and timings of fertilizer application and irrigation must be scheduled in accordance with the plant growth periods and the hydraulic regime of the soil.  相似文献   

6.
Nitrogen balances and total N and C accumulation in soil were studied in reseeded grazed grassland swards receiving different fertilizer N inputs (100–500 kg N ha?1 year?1) from March 1989 to February 1999, at an experimental site in Northern Ireland. Soil N and C accumulated linearly at rates of 102–152 kg N ha?1 year?1 and 1125–1454 kg C ha?1 year?1, respectively, in the top 15 cm soil during the 10 year period. Fertilizer N had a highly significant effect on the rate of N and C accumulation. In the sward receiving 500 kg fertilizer N ha?1 year?1 the input (wet deposition + fertilizer N applied) minus output (drainflow + animal product) averaged 417 kg N ha?1 year?1. Total N accumulation in the top 15 cm of soil was 152 kg N ha?1 year?1. The predicted range in NH3 emission from this sward was 36–95 kg N ha?1 year?1. Evidence suggested that the remaining large imbalance was either caused by denitrification and/or other unknown loss processes. In the sward receiving 100 kg fertilizer N ha?1 year?1, it was apparent that N accumulation in the top 15 cm soil was greater than the input minus output balance, even before allowing for gaseous emissions. This suggested that there was an additional input source, possibly resulting from a redistribution of N from lower down the soil profile. This is an important factor to take into account in constructing N balances, as not all the N accumulating in the top 15 cm soil may be directly caused by N input. N redistribution within the soil profile would exacerbate the N deficit in budget studies.  相似文献   

7.
The objective was to estimate the potential risk of N leaching into the groundwater under various types of agriculture by using lysimeter experiments on the nitrogen(N)‐cycle of various soil types. Results were obtained with 12 weighable, monolithic lysimeters with a surface area of 1 m2, a total depth of 3 m, and free drainage. Mean annual N‐leaching losses of 5 to 44 kg ha—1 and nitrate concentrations of the seepage water (leachate) between 80 and 200 mg l—1 were measured during the period of intensive agricultural use. On fallow land with a well‐established grass vegetation, some nitrate was removed by the plants. As a result, the nitrate concentrations in the leachate were reduced significantly. Ecological farming measures generally reduced N leaching losses and kept the N‐concentration in the leachate below the German threshold value for drinking water with 50 mg l—1 nitrate. However, ploughing in of clover or leguminous vegetation and the application of farmyard manure in autumn caused the nitrate concentration in the leachate to rise significantly above the mentioned threshold value.<?show $6#>  相似文献   

8.
The leaching of nitrate-N under autumn-sown arable crops was measured using hydro-logically isolated plots, about 0.24 ha in area, from 1984–1988. Fluxes of water and nitrate moving over the soil surface (surface runoff), at the interface between topsoil and subsoil (interflow), and in the subsoil (drainflow) were monitored in plots with mole-and-pipe drain systems (drained plots); surface runoff and interflow only were monitored in ‘undrained’ plots. Half the drained and undrained plots were direct-drilled, and on the other half seedbeds were prepared by tillage to 200 mm. Tillage increased the total leaching loss of nitrate by 21 % compared with direct drilling in drained plots. About 95% or the nitrate moving from the soil was present in the water intercepted by the subsoil drains in these plots. In undrained plots less water and nitrate were collected in total; more of the nitrate was present in interflow on ploughed plots and in surface runoff in direct-drilled land. Losses of nitrate for the whole experiment from 1978-1988 were analysed. This showed that, between the harvest of one crop and the spring application of fertilizer to the next, loss of nitrate-N from ploughed land (Lp) was approximated by Lp=22+Fkg N ha?1, where F was the autumn fertilizer-N applied. After fertilizer was applied in spring, loss of nitrate-N depended on rainfall such that for 100 mm rainfall about 30% of the fertilizer-N was lost by leaching. About 18% more nitrate-N was lost from direct-drilled land than from ploughed land in spring, but the total loss was generally small compared to that over winter. The apparent net mineralization of organic-N was measured in 1988. In autumn and winter there was little effect of tillage treatment (26 and 31 kg N ha?1 on direct drilled and tilled plots respectively). However, over the year 83 kg N ha?1 were mineralized in tilled plots, and 67 kg N ha?1 in direct-drilled plots. Five factors governing the leaching of nitrate are assessed and this identified that fertilizer nitrogen application to the seedbed of winter sown crops and the mineralization of nitrogen from the residues of the previous crop are the most significant factors for nitrogen leaching in the UK.  相似文献   

9.
Four successive spring barley crops were grown in monoliths of a shallow soil overlying Chalk, contained in lysimeters. After harvest of the fourth crop, 25% of the nitrogen-15 labelled fertilizer applied 4 years earlier was found remaining in the roots and soil. Of this, 73% was present in the upper 30cm of the profile. From the amounts of fertilizer derived nitrogen that remained at the beginning of each cropping season we estimate that 5–6% of the residual nitrogen-15 turned over each year, representing a net release of 20% of the labelled nitrogen contained in the microbial biomass. Mineralization of the total biomass at the same fractional rate would release 120 kg N ha?1 a?1. This estimate is supported by the difference between input and outputs of total nitrogen during the experiment of 76–94 kg N ha?1 a?1 in fertilized lysimeters and 129kg N ha?1 a?1 in unfertilized control lysimeters. The total recovery of the applied labelled nitrogen was 81–87%. The nitrogen not accounted for was taken to be lost by denitrification of nitrate to dinitrogen, as no nitrous oxide emissions were detected during the experiment. Laboratory studies in aerobic and anaerobic conditions in presence of acetylene confirmed that 10–20% of the applied nitrogen-15 could have been transformed to dinitrogen.  相似文献   

10.
Abstract. Large nitrogen (N) inputs to outdoor pig farms in the UK can lead to high nitrate leaching losses and accumulation of surplus N in soil. We investigated the residual effects of three contrasting outdoor pig systems as compared to an arable control on nitrate leaching and soil N supply for subsequent spring cereal crops grown on a sandy loam soil during 1997/98 and 1998/99 harvest seasons. Previously, the pig systems had been stocked for 2 years from October 1995 and were designated current commercial practice (CCP, 25 sows ha?1 on stubble), improved management practice (IMP, 18 sows ha?1 on undersown stubble) and best management practice (BMP, 12 sows ha?1 on established grass). Estimated soil N surpluses by the end of stocking in September 1997 were 576, 398, 265 and 27 kg ha?1 N for the CCP, IMP, BMP and continuous arable control, respectively. Nitrate leaching losses in the first winter were 235, 198, 137 and 38 kg ha?1 N from the former CCP, IMP and BMP systems and the arable control, respectively. These losses from the former pig systems were equivalent to 41–52% of the estimated soil N surpluses. Leaching losses were much smaller in the second winter at 21, 14, 23 and 19 kg ha?1 N, respectively. Cultivation timing had no effect (P>0.05) on leaching losses in year 1, but cultivation in October compared with December increased nitrate leaching by a mean of 14 kg ha?1 N across all treatments in year 2. Leaching losses over the two winters were correlated (P<0.001) with autumn soil mineral N (SMN) contents. In both seasons, spring SMN, grain yields and N offtakes at harvest were similar (P>0.05) for the three previous pig systems and the arable control, and cultivation timing had no effect (P>0.05) on grain yields and crop N offtake. This systems study has shown that nitrate leaching losses during the first winter after outdoor pig farming can be large, with no residual available N benefits to following cereal crops unless that first winter is much drier than average.  相似文献   

11.
A 3-year study was conducted to determine the effects of broiler litter relative to inorganic fertilizer on soil nutrient content and quality in an upland Loring silt loam soil. Treatments included annual broiler litter rates of 0, 2.2, 4.5, 5.6, 6.7, 10.1, and 13.4 Mg ha?1 y?1 and commercial fertilizer rates of 34, 68, 90, 112, 134, and 168 kg nitrogen (N) ha?1 y?1. Broiler litter application linearly increased soil total carbon (C), microbial biomass C, extractable soil phosphorus (P), potassium (K), soil cation exchange capacity (CEC), and the stability of soil aggregate. At the highest broiler litter rate, the stability of soil aggregate was 34% greater than inorganic fertilizer. Application of broiler litter or fertilizer N at rate greater than 6.7 Mg ha?1 or 90 kg N ha?1, respectively, exceeded plant N utilization potential as evidenced by higher end-of-season soil residual nitrate (NO3)-N. Broiler litter is more effective in improving soil physical, chemical, and biological components than conventional fertilizer.  相似文献   

12.
(pp. 825–831)

This study was carried out to clarify the effects of soil nitrate before cultivation and amounts of basal-dressed nitrogen on additional N application rate and yields of semi-forced tomato for three years from 1998 to 2000. The amounts and timing of additional N dressing were determined based on diagnosis of petiole sap nitrate. The top-dressing was carried out with a liquid fertilizer when the nitrate concentration of a leaflet's petiole sap of leaf beneath fruit which is 2–4 cm declined below 2000 mg L?1.

For standard yield by the method of fertilizer application based on this condition, no basal-dressed nitrogen was required when soil nitrate before cultivation was 150 mg kg?1 dry soil or higher in the 0–30 cm layer; 38 kg ha?1 of basal-dressed nitrogen, which corresponds to 25% of the standard rate of fertilizer application of Chiba Prefecture, was optimum when soil nitrate before cultivation was 100150 mg kg?1 dry soil; 75 kg ha?1 of basal-dressed nitrogen, which corresponds to 50% of the standard, was optimum when soil nitrate before cultivation was under 100 mg kg?1 dry soil. A standard yield was secured and the rate of nitrogen fertilizer application decreased by 49–76% of the standard by keeping the nitrate concentration of tomato petiole sap between 1000–2000 mg L?1 from early harvest time to topping time under these conditions.  相似文献   

13.
Drained and undrained grassland lysimeter plots were established in 1982 on a clay loam of the Hallsworth series at a long-term experimental site in south-west England. The plots were continuously grazed by beef cattle, and received fertilizer at either 200 or 400 kg N ha-1 per annum to the existing permanent sward, or at 400 kg N ha-1 to a new sward, reseeded to perennial ryegrass following cultivation. Drainage water was monitored at V-notch weirs and sampled daily for the analysis of nitrate-N. Seven years of data are presented (five years for the reseeded swards). On the drained plots a large proportion of the rainfall was routed preferentially down large pores to the mole drains, whilst on the undrained plots, drainage was mainly by surface runoff. The average quantities of nitrate N leached per year were 38.5, 133.8 and 55.7 kg ha-1 from the old sward that received 200 and 400 kg N ha-1, and from the reseed that received 400 kg N ha-1 fertilizer, respectively. Ploughing and reseeding resulted in a two-fold reduction in leaching, except during the first winter after ploughing, and twice as much leaching occurred after a hot, dry summer as after a cool, wet one. Nitrate concentrations in drainage from either drained or undrained plots were rather insensitive to rainfall intensity, such that concentration was a good predictor of nitrate load for a given drainage volume. The drainage volume determined the proportion of the leachable N that remained in the soil after the winter drainage period. Initial (peak) concentrations of nitrate N ranged, on average, from 55 mg dm-3 for the drained old sward that received 400 kg N ha-1 fertilizer, to 12 mg dm-3 for the undrained sward at 200 kg N ha-1 fertilizer input. Concentrations of nitrate N in drainage from similar, unfertilized plots rarely exceeded 1 mg dm-3. The results suggest that manipulating the nitrate supply can lessen leaching and that the route of water through soil to the watercourse determines the maximum nitrate concentration for a given load.  相似文献   

14.
In grassland farming, especially on coarse‐textured soils, K can be a critical element. On these soils, the actual K management as well as fertilizer history to a large extent determine the leaching of K. The effects of four fertilizer regimes on the nutrient balances and leaching of K from grassland grown on a sandy soil were investigated. The swards differed in the source and level of N input and K fertilizer: no fertilizer N + 166 kg K ha?1 year?1 (Control), 320 kg inorganic N ha?1 + 300 kg K ha?1 year?1 (MIN 320), 320 kg N + 425 kg K ha?1 year?1 in form of cattle slurry (SLR 320) and a grass–clover sward + 166 kg K ha?1 year?1 (WCL 0) without any inorganic N input. In a second experimental phase, cores from these swards were used in a mini‐lysimeter study on the fate of K from urine patches. On cut grassland after 6 years K input minus removal in herbage resulted in average K surpluses per year of 47, 39, 56 and 159 kg K ha?1 for the Control, MIN 320, WCL 0 and SLR 320, respectively. Related leaching losses per year averaged 7.5, 5, 15 and 25 kg K ha?1. Losses of urinary‐K through leaching were 2.2–4.5 and 5.7–8.4% of the K supplied in summer and autumn applications, respectively. Plant and soil were the major sinks for K from fertilizer or urine. High levels of exchangeable K in the soil and/or large and late fertilizer or urine applications stimulated leaching of K.  相似文献   

15.
With regard to the low cation-exchange capacity and large saturated hydraulic conductivity of sandy soils, a field experiment was carried out in 2006–2007 to determine the impact of zeolite on nitrogen leaching and canola production. Four nitrogen (N) rates (0, 90, 180, and 270 kg ha–1) and three zeolite amounts (3, 6 and 9 t ha?1) were included as treatments. The results demonstrated that the highest growth parameters and seed yield were attained with 270 kg N ha?1 and 9 t zeolite ha?1. However, the highest and the lowest seed protein percentage and oil content were obtained with 270 kg N ha?1 accompanied by 9 t zeolite ha?1, respectively. Nitrate concentration in drained water was affected by nitrogen and zeolite. The lowest and highest leached nitrate values were found in control without N and zeolite (N0Z0) and in treatments with the highest N supply without zeolite (N270Z0), respectively. In general, nitrogen-use efficiency decreased with an increase in N supply. Application of 9 t zeolite ha?1 showed higher nitrogen use efficiency than other zeolite amounts. Also, application of more N fertilizer in soil reduced nitrogen uptake efficiency. In total, application of 270 kg N ha?1 and 9 t zeolite ha?1 could be suggested as superior treatment.  相似文献   

16.
 Rapid nitrate leaching losses due to current agricultural N management practices under the humid tropical environmental conditions of the Pacific island of Guam may contaminate fresh and salt water resources. Potential environmental contamination of the Northern Guam aquifer, which is overlain by shallow limestone-derived soils, is a major public concern because the aquifer is the sole underground source of fresh water for the island. The objectives of this study were to examine the use of waste office paper as a possible management alternative for reducing nitrate leaching due to N fertilizer applications in northern Guam while also providing sufficient N for crop growth. In a laboratory study, increasing rates of waste paper application reduced NO3 –-N leaching up to approximately 200 days after incorporation of N fertilizer and paper treatments. Subsequent mineralization of immobilized N from paper applications was also observed, although cumulative NO3 –-N leaching at the highest rate of paper addition was lower than the control after 394 days of incubation. The effect of waste paper on N availability and NO3 –-N leaching after application of N fertilizer at rates up to 500 kg N ha–1 was also evaluated in two field experiments planted with sweet corn (Zea mays var. rugosa Bonaf.) during consecutive dry and wet periods. Leaching losses of NO3 –-N were higher during the wet cropping season, leading to lower crop yields and crop N uptake. Combining paper with N fertilizer reduced NO3 –-N leaching losses but also decreased crop ear yields up to N fertilizer application rates of 250 kg N ha–1 during the dry cropping season and up to rates of 100 kg N ha–1 during the wet period. Although combining waste paper with N fertilizer reduced NO3 –-N leaching losses, no improvements in fertilizer N recovery were observed during the field experiments. This lack of crop response may be due to the importance of early season N availability for the short-season horticultural crops grown on Guam. We suggest that the application of waste paper may be a useful management practice to reduce NO3 –-N leaching losses when high soil NO3 –-N levels remain after cropping due either to crop failure or to over-application of N fertilizer. Received: 11 May 1999  相似文献   

17.
A two-year field experiment (2001 and 2003) was carried out in a Mediterranean environment to study the effects of municipal solid waste (MSW) compost application compared with mineral nitrogen (N) fertilization on the agronomic performance and N utilization of a tomato crop, in rotation with durum wheat. The research was conducted in the south of Italy where five N treatments and two soil tillage depths (40-45 cm and 10-15 cm) were compared. The N treatments were: MSW compost at 140 kg ha?1 (Ncom); mineral N fertilizer at 140 kg ha?1 (Nmin); MSW compost combined with mineral N fertilizer (Nmix) (70 kg ha?1 as organic N plus 70 kg ha?1 as mineral N); mineral N fertilizer at 70 kg ha?1 combined with two applications of foliar fertilizer (Nfito) (3 kg ha?1 as hydrolyzed proteins), and an untreated control (Contr). During cropping cycles, growth parameters and plant N status (SPAD readings and petiole nitrate content) were determined; at harvest the marketable, overripe, green fruit, total yield, yield components, quality performance, total and fruit N uptake, and N efficiency were recorded. In addition, at the beginning and at the end of the two-year experiment, soil chemical characteristics and mineral N was measured, allowing for the calculation of the mineral N deficit in the soil. The results of this research indicate that the application of MSW compost to tomato plants can serve as a N source in Mediterranean conditions, especially when MSW compost is combined with mineral N fertilizer and deeper soil tillage is applied. In fact, deeper soil tillage increased total yield 7.0 t ha?1 compared to surface tillage, whereas soil amended with MSW compost increased total yield compared to the untreated control by approximately 6.4% when used alone and 11.1% when combined with mineral N fertilizer. Nitrogen utilization parameters and Harvest Index varied significantly across years and N treatments. Petiole nitrate content and SPAD readings did not vary between Nmin and Nmix treatments, but they were significantly different from the untreated control. This indicates that plant N status was an effective tool to monitor N supply. After the two-year experiment, the Nmix treatment was statistically not significant in total yield (86.1 and 88.2 t ha?1, respectively), marketable yield (66.9 and 67.7 t ha?1) and quality compared to the Nmin treatment. Furthermore, the Nmix treatment ensured the least N deficit in the soil, indicating that MSW applications were effectively used as alternative organic supplements. Finally, the results indicated a positive effect of MSW application on organic carbon content in the soil and did not show any significant increase of the heavy metals at the end of the two-year experiment.  相似文献   

18.
Abstract. Nitrate leaching was measured over the eight drainage seasons spanning the nine years from 1990–1998 on the 157‐year old Broadbalk Experiment at Rothamsted, UK. The weather pattern of two dry, three wet and three dry years was the dominant factor controlling nitrogen (N) loss. Both the concentration of nitrate in the drainage waters and the amount of N leached increased with the amount of N applied, mostly because of long‐term, differential increases in soil organic matter and mineralization. On average, losses of N by leaching were 30 kg ha?1yr?1 when no more than the optimum N application was applied and were typical of amounts leached from arable land in the UK. Losses increased significantly in both amounts and as the percentage of N applied for supra‐optimal applications of N and from autumn‐applied farmyard manure (FYM). Extra spring‐applied fertilizer was very effective at increasing yields on plots given FYM in the autumn but at the expense of leaching losses three times those from optimum fertilizer N applications. Losses increased after potatoes because they left significant amounts of mineral N in the soil, and decreased after forage maize because it used applied N more effectively. Losses measured 120 years ago from identical treatments were 74% greater than current losses because of today's larger yields and more efficient varieties and management practices. Average concentrations of nitrate in drainage waters did not exceed the EU limit of 11.3 mg NO3‐N l?1 until supra‐optimal amounts of N fertilizer (>150–200 kg ha?1yr?1) were applied in spring or FYM was applied in autumn. However some drainage waters from all plots, even those that have not received fertilizer for >150 years, exceeded the limit when rain followed a dry summer and autumn. Nitrate leaching into waters will remain a problem for profitable arable farming in the drier parts of Eastern England and Europe despite increased N use efficiency.  相似文献   

19.
Leaching of nutrients, particularly in sandy soil with low nutrient and water holding capacity (WHC), is a major threat to marine and fresh water pollution. Addition of clay soil to sandy soil could be an option to increase water and nutrient holding capacity of sandy soils, but the effect of clay soil addition may depend on the form in which the clay soil is added and the addition rate. Clay soil was added to sandy soil at rate of 10 or 20% (w/w) finely ground (<2 mm) or 2 and 5 mm peds with and without nitrogen (N) and phosphorus (P) fertilizer equivalent to 60 kg N ha?1 and 15 kg P ha?1. The clay sand mixture for each treatment was weighed (30 g) in cores with nylon mesh at the bottom. The soils were incubated at 80% WHC for 7 weeks. To obtain leachate, 20 mL reverse osmosis (RO) water was added every week to each core. Leachate was analysed for inorganic N, P, and pH. Soil was analyzed for N, P, and pH before and after the leaching. Clay addition significantly reduced the leaching of N and P compared to sandy soil alone, with greatest reduction by finely ground clay soil and least with 5 mm peds. Compared to sandy soil alone, 83% more N was retained in clay-amended soil and P retention was doubled. This study showed that addition of finely ground clay soil can substantially reduce N and P leaching and thereby increase fertilizer retention compared to sandy soil alone.  相似文献   

20.
Traditional irrigation and nitrogen (N) fertilization in North China may elevate water drainage and nitrate concentrations in soil and groundwater. A field experiment was conducted in an intensively irrigated vegetable (cauliflower, amaranth, and spinach) field for three consecutive years (1999–2002). The main objective was to test to what extent an improved water and fertilizer management, based on the maintenance of field capacity a defined range of the water content in the 0–50 cm soil layer and an N expert system, could reduce drainage and nitrate leaching without impairing vegetable yield. Rates of water drainage and related nitrate leaching were calculated based on measurements of soil water potential and soil‐water nitrate concentrations. Soil water potential was monitored with tensiometers at depths of 75 cm and 105 cm. Nitrate concentrations were analyzed in soil leachates collected at 90 cm soil depth using ceramic suction cups. The results revealed that the average annual drainage related to the cultivation season for cauliflower, amaranth, and spinach was reduced from 275 mm in the traditional system to 29 mm with improved management practice. The average annual cumulative nitrate leaching during the vegetable‐growing period amounted to 301 kg ha–1 and 13 kg ha–1 in the traditional and improved management practices, respectively. Vegetable yields were not significantly different under the traditional and improved management practices.  相似文献   

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