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1.
Domestication of biennial Lepidium campestre L. offers possibilities for more varied crop rotations in cold regions, with increased crop cover during winter. In the first winter after sowing, L. campestre can reduce nitrogen (N) leaching before harvesting in the second year. In this system no soil tillage is needed during the first year, unlike in systems with annual crops. A three-year leaching study on loam soil in southern Sweden revealed significantly (p?<?0.05) lower flow-weighted mean total nitrogen (TN) concentration in drainage water under L. campestre (5.8 mg TN L?1) compared with a control treatment (no catch crop and autumn mouldboard ploughing) (9.6 mg TN L?1). In two years of observations, Lepidium campestre had lower flow-weighted mean TN concentration (6.2 mg L?1) than a mixed Vicia villosa L. (hairy vetch)/Secale cereale (winter rye) catch crop (10.2 mg L?1) and rather similar concentration to a Raphanus sativus (oilseed radish) catch crop (5.7 mg TN L?1), both sown after harvest of the main crop. However, L. campestre appeared to have a negative effect on total phosphorus (TP) leaching, with TP concentration in drainage of 0.05 mg L?1 compared with 0.01–0.02 mg L?1 for the other catch crops and the control.  相似文献   

2.
Nitrate leaching from short-rotation coppice   总被引：1，自引：0，他引：1  
In the UK, short‐rotation coppice (SRC) is expected to become a significant source of ‘bio‐energy’ over the next few years. Thus, it is important to establish how nitrate leaching losses compare with conventional arable cropping, especially if SRC is grown in Nitrate Vulnerable Zones. Nitrate leaching was measured using porous ceramic cups in each of the three phases in the lifespan of SRC, establishment, harvest and removal and was compared with conventional arable cropping. Nitrogen concentrations were increased in drainage water as soon as the crop cover was destroyed to plant the SRC (peak 70 mg L?1 nitrate‐N) and increased further (peak 134 mg L?1 nitrate‐N) on cultivation. Once the coppice crop was established, concentrations returned to a smaller level (average 18 mg L?1 nitrate‐N). Concentrations were not affected by the harvesting operation, and annual applications of nitrogen (40, 60 and 100 kg ha?1 N in the first, second and third years, respectively) had little effect. By contrast, concentrations in the arable rotation showed a regular pattern of increase in the autumn, and the average peak value over the 4 years was 54 mg L?1 nitrate‐N. When the SRC was ‘grubbed up’ and roots removed, the soil disturbance resulted in a flush of mineralization which, combined with a lack of crop cover, led to increased nitrate‐N in leachate (peak 67 mg L?1 nitrate‐N). In a normal life‐span of SRC (15–30 years), the relatively large nitrate losses on establishment and at final grubbing up would be offset by small losses during the productive harvest phase, especially when compared with results under the arable rotation.  相似文献   

3.
ABSTRACT

Influences of nickel (Ni) concentrations in the nutrient solution on yield, quality, and nitrogen (N) metabolism of cucumber plants (Cucumis sativus cv ‘RS189’ and ‘Vikima’) were evaluated when plants were grown either with urea or nitrate as the sole N source. The cucumber plants were treated with two N sources, urea and nitrate as sodium nitrate (NaNO3) at 200 mg L?1, and three concentrations of Ni as nickel sulfate (NiSO4·6H2O; 0, 0.5, and 1 mg L?1). Treatments were arranged in a randomized block design with six replicates. The highest concentration of Ni in the leaves (1.2 mg kg?1 Dwt) was observed in the urea-fed plants at 1 mg L?1 Ni concentration. Additions of Ni up to 0.5 mg L?1 had no effect on the fruit Ni concentration in the both urea and nitrate-fed plants. Yield significantly (p < 0.05) increased with the Ni supplements from 0 to 0.5 mg L?1 (10 and 15% in ‘RS189’ and ‘Vikima’, respectively), but decreased when 1 mg L?1 Ni applied to the solutions in urea-fed plants. Nitrate-fed plants had a higher percentage of total soluble solids compare to those urea-fed plants. Nitrate concentrations of the fruits in urea-fed plants in both cultivars were reduced by approximately 50% compared to those nitrate-fed plants. The reduction of nitrate concentration in the fruits became more pronounced as the Ni concentration increased in the solution. The rate of photosynthesis (Pn) increased with the increase of the Ni concentration in the solution with urea-fed plants. Both N concentration and nitrate reductase (NR) activity of young leaves were higher in urea-fed plants at 0.5 mg l?1 Ni concentration. Ni supplements enhanced the growth and yield of urea-fed plants by increasing Pn, N concentration and NR activity. It can be concluded that Ni supplements (0.5 mg l?1) improve yield, quality, and NR activity in urea-fed cucumber plants.  相似文献   

4.
The B concentration was determined in bulk deposition and in surface freshwaters (lakes and rivers) of the river Po watershed in Northern Italy. The curcumin photometric method was used to determine B content for all analyses. The B concentrations were under detection limits (0.06 mg B L?1) in bulk deposition and below 0.09 mg B L?1 in lake waters. Approximately 65 % of river samples measured had B concentrations close to natural background levels for natural waters (0.1 mg B L?1). There was a strong correlation (r < 0.85) between B concentration and those of both total dissolved P and anionic detergents. The elevated B concentrations may be related to anthropogenic sources.  相似文献   

5.
Leaching losses of nitrogen (N), phosphorus (P) and potassium (K) from arable land can be high, with N and P contributing significantly to the eutrophication of lakes and coastal waters. This study examined whether agriculture management and drain repair changed the chemical properties of shallow groundwater and affected nutrient leaching in the field. The hydrology of a subsurface-drained agricultural observation field included in the Swedish water quality monitoring programme was simulated for the period 1976–2006 using the process-based, field-scale model DRAINMOD. On the assumption that the drainage system operated similarly before and after repair, 54% more water was assigned to low-moderate flow events. Measured concentrations of sulphate-sulphur (SO4-S), sodium (Na), chloride (Cl) and potassium (K) were significantly lower in shallow groundwater in the period before drainage system repair (1980–1998) than afterwards (1998–2010). The concentrations were also significantly correlated with the corresponding concentrations in near-simultaneously sampled drain water. A similar connection was not observed for Na and Cl in the period before drain repair. Elevated concentrations of nitrate-nitrogen (NO3-N) were recorded both in shallow groundwater and in drainage water from 1998 to 2010, especially after incorporation of chicken manure into the soil in 1998. Based on simulated discharge (assuming a functioning measuring station throughout), estimated flow-weighted mean NO3-N concentration in drainage water increased from 5.6 mg L?1 (1977–1998) to 15.7 mg L?1 in the period 1998–2000. Simultaneously, mean NO3-N concentration in shallow groundwater increased from 0.2 to 4.0 mg L?1, and then to 4.8 mg L?1 in the period 2000–2012. It was estimated that after drain repair, a greater proportion of infiltrated NO3-N entered the receiving stream directly via the outlet of the tile drainage system close to the field's monitoring station than was the case before repair.  相似文献   

6.
The quality of water from 388 wells in 6 regions in the Kingdom of Saudi Arabia has been investigated with respect to pH, total dissolved salts (TDS), nitrite, ammonium, nitrate, and faecal coliforms. Concentration of TDS varied widely, from 180 to 9350 mg L?1, with a mean of 754 mg L?1. Of the 388 wells, 72 (18.6%) were above the WHO limit of 1000 mg L?1. The levels of nitrate varied significantly, ranging from 0.0 to 95.2 mg L?1, with an average value of 20.7 mg L?1. About 7.7% of the tested wells had nitrate content above the WHO limit of 45 mg L?1, and 16% of the wells showed NH4 + levels greater than 0.05 mg L?1. Faecal coliforms were present in 21.4% of the tested well waters. The results indicated that significant nutrient and faecal coliforms contaminated of well water was occurring.  相似文献   

7.
The water chemistry of 21 outlet brooks in undisturbed, forested catchments (0.074–38 km2) in Finland was monitored during three years (1997–1999) in order to estimate the background levels and leaching of total organic carbon (TOC), iron, nitrogen and phosphorus, and examine the relationships between catchment characteristics and brook water quality in pristine forested areas. The studied catchments are located throughout Finland except the northernmost parts of the country. The concentrations of TOC were relatively high, on average 20 mg L-1. Annual leaching of TOC ranged from 3000 to 10 000 kg km-2. The average total nitrogen concentration and annual leaching were 430 μg L-1 and 140 kg km-2, respectively. The average total phosphorus concentration and annual leaching were 15 μg L-1 and 5.4 kg km-2, respectively. On a national level temperature and discharge conditions were the most important variables for predicting total phosphorus, total nitrogen and TOC concentrations. Both total nitrogen and total phosphorus concentrationsdisplayed positive correlation with temperature, and thus the concentrations were higher in the south than in the north. Nitrogen was mainly organic and showed strong correlation with TOC. On the catchment level, both TOC and total nitrogen concentrations and export had a strongpositive correlation with the abundance of Norway spruce (Piceaabies Karsten) and a strong negative correlation with the abundance of Scots pine (Pinus sylvestris L.). Nitrate concentrations and leaching were related to average site type. The more fertile the average site type was in the catchment, the higher the nitrate concentrations and export were.  相似文献   

8.
Subsurface drainage systems have been installed in about 10000 ha of agricultural land in the flat part of the Emilia-Romagna Region in northern Italy. Nitrate loss in drainage water from a representative farm in this area was measured for three consecutive years (1986, 1987, 1988). During this period a total of 369 water samples were collected, filtered at 0.45 µm and analyzed. The nitrate concentration exceeded the limits for surface water set by Italian law regarding water pollution (90 mg NO3 ?L?1 = 20 mg N L?1) in 84% of the samples. The greatest nitrate loss was recorded during the winter and early spring when drainage was high. After this period loss of nitrate, via drainage water, progressively decreased. This was attributed to a decrease in the amount of drainage water and increase in crop uptake of N. The average annual nitrate loss via drainage water was around 200 kg of NO inf3 sup? ha?1. Annual nitrate losses of this order of magnitude (? 50 kg N ha?1) indicate an urgent need for implementation of management practices directed towards achieving considerable reductions in these losses.  相似文献   

9.
Agricultural, urban, forest and groundwater protection areas as well as nitrate and chloride concentrations are documented in maps. Areal distribution shows regionally elevated nitrate and chloride concentrations in connection with urban areas and agricultural use. Transport of nitrate and chloride tends to be conservative in the groundwater of the investigated area. Therefore, the elevated concentrations of these anions are suitable as indicators of anthropogenic impact on the groundwater. The average concentration of nitrate and chloride from all surveyed wells amounts to 26 and 17 mg L?1, respectively. It is shown that wells recharged through forests have lower nitrate and chloride concentrations (average: 21 and 13 mg L?1, respectively). Wells affected by waste deposits have an average nitrate concentration of 35 mg L?1 and chloride concentration of 24 mg L?1. Urban use results in an average value of 28 mg L?1 nitrate and 24 mg L?1 chloride. As nitrate and chloride concentrations are stable with respect to the depth of the groundwater table, degradation processes or other protective effects of the unsaturated zone can be omitted.  相似文献   

10.
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   

11.
Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 – 23.5 kg ha?1 yr?1 (annual inorganic total N deposition: 9.6 – 10.7 kgN ha?1 yr?1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 µg g?1 (the range: 21.1 – 429 µg g?1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L?1 (the range: 2.38 – 20.6 mg L?1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.  相似文献   

12.
ABSTRACT

Impatiens (Impatiens wallerana Hook. f.) is the most important annual bedding plant in the United States, based on wholesale dollar volume. Production of high-quality plants requires optimization of the nutrition regimen during growth, especially the total nitrogen (N) concentration and the ratio of N sources. The objective was to determine the N concentration and the nitrate (NO3 ??N):ammonium (NH4 +?N) ratio of N source that optimized bedding-plant impatiens growth and flower development. Four N concentrations (3.5, 7, 10.5, and 14 mmol N · L?1) were used in factorial combination with four ratios of NO3 ??N:NH4 +?N (4:0, 3:1, 1:1, and 1:3). Application of treatments was made for 30 d. Then for 10 d only deionized water was applied to reduce salt buildup. Substrate pH was lowest (4.9) with the NH4 +?N source and electrical conductivity (EC) highest, but never > 2.4 dS m?1. Nitrogen concentration and N source displayed an interaction for most growth parameters. Shoot fresh and dry weights and flower bud number were maximized at the 1:3 NO3 ??N:NH4 +?N ratio with a N concentration of 10.5 mmol L?1. However, plant diameter, leaf number, and leaf chlorophyll content responded quadratically to N form ratio, with the 1:1 ratio optimum at a concentration of 10.5 mmol N· L?1.  相似文献   

13.
The objective of this study was to determine the effect of nitrogen fertilization rate on growth and quality of leafy lettuce grown during the winter season in non-circulating hydroponic system. Plants were subjected to seven nitrogen (N) concentrations, i.e. 0, 30, 60, 90, 120, 150 and 180 mg L?1 N using ammonium nitrate. Nitrogen treatments did not have a significant effect on leaf fresh and dry mass, root fresh and dry mass, number leaves and leaf area. Leaf ascorbic acid and total phenolic content, and antioxidant capacity peaked at 100 and 120 mg L?1 N, whereas leaf chlorophyll concentration linearly increased with increasing N application. The results indicate that a solution N concentration of 100 and 120 mg L?1 may be sufficient to improve growth, yield and quality parameters of leafy lettuce grown in non-circulating hydroponic system.  相似文献   

14.
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   

15.
In this study, the concentrations and loads of different forms of nitrogen [nitrate nitrogen (NO3-N), total Kjeldahl nitrogen (TKN), and total nitrogen (TN)] in the headwater catchment of the Mero River (NW Spain) were analyzed. The TN concentrations were relatively low (mean: 2.57 mg L?1). Nitrate was the predominant form of N in the Mero catchment, accounting for 76.65 percent of the TN concentration. Measured NO3-N concentrations were always lower than the maximum allowed drinking water concentration. An annual TN load of 61.2 Mg was computed, representing an export of 0.94 Mg km?2 y?1, whereas annual exports NO3-N and TKN were of 0.79 and 0.15 Mg km?2 y?1, respectively.  相似文献   

16.
Engineered plant growth media must support plant growth while minimizing environmental impact. The objective of this research was to determine how different growth media influence nutrient leaching. Plant growth media contained varied amounts of soil, sand, compost that did or did not contain manure, and possible sorbents for phosphorus. If the plant growth media included compost derived partly from manure, leaching losses of nutrients were excessive due to the high nutrient load in the compost. Layering compost over the plant media mix resulted in lower nitrate concentrations in effluent (87 mg L?1) compared with mixing compost into the media (343 mg L?1); however, growth of prairie grasses was reduced because of dense media below the compost blanket (0.09 versus 0.31 g). Using lower amounts of compost that did not contain manure resulted in lower mean nitrate concentrations in effluent (101 versus 468 mg L?1). Media that had no soil (13.3 mg L?1) had greater loss of phosphorus after harvest for unsaturated drainage than media with soil (1.8 mg L?1). To reduce nitrate leaching, only small amounts of low-nutrient compost (higher C:N ratio) should be incorporated into the media. If compost is applied as a surface blanket without incorporation, then soil should be added to the sand to reduce density of the media and increase plant growth.  相似文献   

17.
Nitrogen (N) and potassium (K) fertilization play a key role in forage crops and can significantly increase yields of ‘Marandu’ palisadegrass [Brachiaria brizantha (Hochst. exA. Rich.) Stapf.], one of the most important forage crops in Brazil. This study aimed to identify the concentrations of total N and K, nitrate (NO3?), and ammonium (NH4+), chlorophyll meter readings (SPAD), and nitrate reductase activity (At-RNA) required to maximize yield. Plants were grown in quartz substrate and treated with nutrient solutions that ranged from 2 to 33 mmol L?1 for N and 0.5 to 11 mmol L?1 for K. Dry matter production and At-RNA increased with increasing N and K supplies. SPAD readings correlated strongly with N leaf concentration and dry matter production and can be used to assess the N status of this species. The supply of N and K in the fertilization promoted high yield and adequate N and K concentration for plant metabolism.  相似文献   

18.
We analyzed surface waters from 30 Wisconsin lakes and rivers for total mercury ([Hg]T) and total suspended particulates (TSP) on a state-wide basis with trace-metal ‘ultraclean’ techniques. Mercury concentrations ranged from 0.3 to 2.9 ng L?1 in lakes and from 0.7 to 8.9 ng L?1 in rivers. TSP concentrations ranged from 0.9 to 6.6 mg L?1 in lakes and from 3.1 to 31.4 mg L?1 in rivers. Spatial trends were weak; however, [Hg] T was generally higher in the spring than in the autumn of 1991. Total mercury concentration was weakly dependent on TSP with the coefficient of determination (r 2) ranging 0.06 to 0.49 across seasonal and geophysical differences.  相似文献   

19.
Abstract

Nitrite (NO2 ?‐N) toxicity symptoms have been observed on lettuce (Lactuca sativa) at various locations in California. The objective was to evaluate the symptoms of ammonium (NH4 +‐N) and nitrite (NO2 ?‐N) toxicity on Sundevil iceberg lettuce and Paragon romaine lettuce and to determine lettuce growth and biomass production under different levels of NO2 ?‐N. Hydroponic studies under greenhouse conditions were conducted using nutrient solutions containing nitrate (NO3 ?‐N) and two other forms of nitrogen (NO2 ?‐N and NH4 +‐N) applied at a constant concentration (50 mg NL?1) or using different NO2 ?‐N levels (0, 5, 10, 20, 30, and 40 mg N L?1) and a constant NO3 ?‐N level (30 mg N L?1). Crown discoloration (brownish color) was observed for lettuce grown in both NO2 ?‐N and NH4 +‐N solutions approximately 3 weeks after transplanting into the hydroponic systems. Lettuce grown in NO3 ?‐N solution produced larger biomass and greater number of leaves per plant than lettuce grown in NO2 ?‐N or NH4 +‐N solutions. Increasing the concentration of NO2 ?‐N suppressed plant height, fresh and dry biomass yield, and number of leaves and increased the root vascular discoloration. Lettuce growth was reduced more than 50% at NO2 ?‐N concentrations greater than 30 mg N L?1. Even at 5 mg NO2 ?‐N L?1, growth was reduced 14 and 24% for romaine and iceberg lettuce, respectively, relative to that obtained in nitrate solution. Although concentrations between 5 and 40 mg NO2 ?‐N L ?1 reduced dry biomass similarly for both lettuce types, toxicity symptoms were more severe in iceberg lettuce than in romaine.  相似文献   

20.
A nutrient solution experiment was done to evaluate effects of different concentrations of nitrogen (N), phosphorus (P) and potassium (K) on leaf mineral concentrations and some enzymes activity of melon seedlings (Cucumismelo var. inodorus subvar. Khatouni). Different levels of these nutrients including 0, 53, 105, 158 and 210?mg L?1 N; 0, 8, 16, 23 and 31?mg L?1 P; 0, 59, 118, 176 and 235?mg L?1 K, all corresponding to 0, 25, 50, 75 and 100% of their concentrations in Hoagland nutrient solution, were applied to plants. The results showed that the highest leaf nitrate reductase (NR) activity was observed at highest N and P levels, whereas the three highest K levels showed the highest NR activity. The highest leaf peroxidase activity was observed at 8?mg L?1 P, 59?mg L?1 K and 158?mg L?1 N. The leaf catalase activity was highest at zero concentration of P, 158?mg L?1 N and 176?mg L?1 K; however, catalase activity was decreased by increasing P levels. Leaf protein content showed an increasing trend with increasing N, P and K levels of nutrient solution, while there was no significant difference between 158 and 210?mg L?1 N. The highest leaf concentrations of N, P, K and Mg were observed at highest nitrogen, potassium and phosphorus levels of nutrient solution, whereas the highest leaf concentration of Ca were obtained at 53 or 105?mg L?1 N, 176?mg L?1 K and 23–31?mg L?1 P. The highest iron concentration of leaves was obtained from 23 to 31?mg L?1 P, 176?mg L?1 K and 210?mg L?1 N.  相似文献   

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