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1.
The effects of ozone (O3) and soil water stress, singly and in combination, on the growth and photosynthesis of Fagus crenata seedlings were investigated. Four-year-old seedlings were exposed to charcoal-filtered air (< 5 nmol mol?1 O3) or 60 nmol mol?1 O3, 7 hours per day (11:00–18:00), for 156 days from 10 May to 11 October 1999 in naturally-lit growth chambers at 20/15 °C (6:00–18:00/18:00–6:00). During the same period, half of the seedlings in each gas treatment received 250 mL of water at the 3-day intervals (well-watered treatment), while the rest received 175 mL of water at the 3-day intervals (water-stressed treatment). The exposure of the seedlings to O3 caused reductions in the leaf, stem, root and whole-plant dry weights. The net photosynthetic rate at 350 µmol mol?1 CO2, the maximum net photosynthetic rate at saturated CO2-concentration, carboxylation efficiency of photosynthesis and Rubisco content were significantly reduced by the exposure to O3. The soil water stress induced reductions in the stem, bud and whole-plant dry weights, transpiration rate and leaf water potential during the midday. The additive effects of O3 and soil water stress were observed on the dry matter production, leaf gas exchange rates and leaf water potential. As a result, the whole-plant dry weight of the seedlings exposed to both stresses was markedly reduced compared with that of the seedlings exposed to charcoal-filtered air and grown in the well-watered treatment.  相似文献   

2.
Dry matter production, net photosynthetic rate, leaf nutrient status and trunk anatomical characteristics of Fagus crenata seedlings grown in brown forest soil acidified by adding H2SO4 solution were investigated. The soil acidification leaded to decreased (Ca+Mg+K)/Al molar ratio in the soil solution. Dry mass per plant of the seedlings grown in the soil treated with H+ at 120 mg·L?1 was significantly reduced compared with the control value at 0 mg·L?1. When net photosynthetic rate was reduced in the seedlings grown in the soil treated with H+ at 120 mg·L?1, the carboxylation efficiency and maximum net photosynthetic rate at saturated CO2-concentration were lower than the control values. The addition of H+ to the soil at 120 mg·L?1iinduced a reduction in the concentration of Ca in the leaf. By contrast, the concentration of Al in the leaf was increased with increasing the amount of H+ added to the soil. The annual ring formed in the seedlings grown in the soil treated with H+ at 120 mg·L?1 was significantly narrower than that at 0 (control), 10, 30, 60 or 90 mg·L?1. Based on the results obtained in the present study, we conclude that Fagus crenata is relatively sensitive to a reduction in the (Ca+Mg+K)/Al molar ratio of soil solution compared with Picea abies.  相似文献   

3.
The cryptogamic soil crusts of the Great Basin Artemisia, Ceratoides, and Atriplex plant communities contain a significant heterotrophic N2-fixing microbial population in addition to the predominating filamentous cyanobacteria. The bacterial association with the cyanobacteria exhibits a phycosphere-like effect. Heterotrophically fixed N gains reached 17.5 μg N· g?1 of soil (23.1% increase above the initial soil N content) and 45.9 μg N·g?1 of soil (57.4% increase) after 3 and 5 weeks, respectively. (NH4)2SO4 and native plant material amendments to soil resulted in a 41–100% reduction in N2-fixation. The potential input of N to soil crusts may be reduced in the presence of shrub-produced allelochemic agents and by concurrent denitrification.  相似文献   

4.
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   

5.
Abstract

To determine the relationships between microbial biomass nitrogen (N), nitrate–nitrogen leaching (NO3-N leaching) and N uptake by plants, a field experiment and a soil column experiment were conducted. In the field experiment, microbial biomass N, 0.5 mol L?1 K2SO4 extractable N (extractable N), NO3-N leaching and N uptake by corn were monitored in sawdust compost (SDC: 20 Mg ha?1 containing 158 kg N ha?1 of total N [approximately 50% is easily decomposable organic N]), chemical fertilizer (CF) and no fertilizer (NF) treatments from May 2000 to September 2002. In the soil column experiment, microbial biomass N, extractable N and NO3-N leaching were monitored in soil treated with SDC (20 Mg ha?1) + rice straw (RS) at five different application rates (0, 2.5, 5, 7.5 and 10 Mg ha?1 containing 0, 15, 29, 44 and 59 kg N ha?1) and in soil treated with CF in 2001. Nitrogen was applied as (NH4)2SO4 at rates of 220 kg N ha?1 for SDC and SDC + RS treatments and at a rate of 300 kg N ha?1 for the CF treatment in both experiments. In the field experiment, microbial biomass N in the SDC treatment increased to 147 kg N ha?1 at 7 days after treatment (DAT) and was maintained at 60–70 kg N ha?1 after 30 days. Conversely, microbial biomass N in the CF treatment did not increase significantly. Extractable N in the surface soil increased immediately after treatment, but was found at lower levels in the SDC treatment compared to the CF treatment until 7 DAT. A small amount of NO3-N leaching was observed until 21 DAT and increased markedly from 27 to 42 DAT in the SDC and CF treatments. Cumulative NO3-N leaching in the CF treatment was 146 kg N ha?1, which was equal to half of the applied N, but only 53 kg N ha?1 in the SDC treatment. In contrast, there was no significant difference between N uptake by corn in the SDC and CF treatments. In the soil column experiment, microbial biomass N in the SDC + RS treatment at 7 DAT increased with increased RS application. Conversely, extractable N at 7 DAT and cumulative NO3-N leaching until 42 DAT decreased with increased RS application. In both experiments, microbial biomass N was negatively correlated with extractable N at 7 DAT and cumulative NO3-N leaching until 42 DAT, and extractable N was positively correlated with cumulative NO3-N leaching. We concluded that microbial biomass N formation in the surface soil decreased extractable N and, consequently, contributed to decreasing NO3-N leaching without impacting negatively on N uptake by plants.  相似文献   

6.
Tomato (Lycopersicon esculentum Mill.) plants were grown in silica sand in controlled environments. In the first experiment Ni was added as NiSO4 · 6 H2O to the nutrient solution at 0, 1.5, 7.5, or 37.5 mg L?1 for 6 day beginning 14 day from seeding, them plants were exposed to 0, 0.15, or 0.30 μL L?1 O3, and harvested 3 day later. Visible symptoms of Ni injury developed rapidly and there was distinctive O3 injury. Growth variables were markedly reduced by Ni but O3 response depended on Ni level. In the second experiment 0, 0.3, or 1.5 mg L?1 Ni was provided from the 5th or 14th day onward. There was little effect of duration of Ni treatment on growth. Increasing Ni and increasing O3 decreased growth but there was no interaction. In the third experiment 0, 1.5, and 3.0 mg L?1 Ni treatments were combined with 0, 3.0, and 6.0 mg L?1 Cu prior to 0 or 0.25 μL L?1 O3 treatment. There were complex interactive effects of all three factors on plant growth. Soybean (Glycine max Merr.) plants exposed to Ni and O3 were only slightly affected by Ni or O3 and there was no interaction.  相似文献   

7.
The effect of organic amendments and irrigation management in the field were studied with respect to Eh, NO3?, and soluble organic C concentrations in the soil solution, and gaseous concentrations of N2O, CO2, and the ratio N2 to O2. Duplicate plots were treated with fresh bovine manure as follows: control 45t·ha?1, 180 t·ha?1 with a standard irrigation cycle (SI), and 180 t·ha?1 with a double irrigation (DI). Samples to 230cm were obtained at several depths in each profile during the 84-day study. The general order for treatment effects upon CO2 concentrations and soluble C was the same: SI > DI > 45 t·ha?1 > control. The order for N2/O2 was 180 t·ha?1 (SI and DI) > 45 t·ha?1 and control. The order for both N2O and NO?1 was the same: 45 t.ha?1 and DI > SI and control. The most important factor affecting N2O concentrations was the NO3? concentration; soil solution concentrations greater than 16 μN·ml?1 had much higher frequencies of high N2O concentrations. The sequential reduction of NO?13→ N2O → N2 was noted in all treatments by the following observations: (i) the concentrations of both NO?3 and N2O were highest at the beginning of the experiment; (ii) the concentrations of CO2 and N2/O2 were higher near the end: (iii) sub-ambient concentrations of N2O were more frequent near the end of the study. Use of N2O as an indicator of denitrification is cautioned since one of the highest manured treatments (SI) had N2O concentrations no different than the control, but had much higher CO2 and N2/O2 concentrations and more reduced (Eh) conditions. We conclude that use of a single irrigation method is far superior to the double irrigation method with respect to reducing losses of NO3? and N2O and for conserving organic N arid water.  相似文献   

8.
Simultaneous determination of nitrogen transformation rates in soil columns using 15-N: N-Model of a Terra fusca-Rendzina soil Rates of ammonification, nitrification, immobilization, and denitrification were determined in undisturbed columns of a Terra fusca Rendzina soil. A steady input of 15-N labelled ammoniumsulfate with the irrigation water created a steady state of the turnover processes in the soil resulting in a constant output of 15-N-nitrate. In this state the rate constants (8°C) were K1 = 0.64 for the netto-N-nitrification, K2 = 0.11 for the netto-N-denitrification, and K3 = 0.25 for the netto-N-immobilization. 64% of the nitrate was leached, 25% immobilized in organic matter, and 11% denitrified. Relating these rate constants to the turnover of the soil nitrogen one can calculate the mean annual rates for the different processes of a forest soil, using the mean annual temperature. For the Göttinger Wald situation (T = 6.9°C) the following rates were calculated; Ammonification = 183 kg N·ha?1·a?1, immobilization = 44 kg N·ha?1·a?1, netto N-denitrification = 19 kg N·ha?1·a?1, and netto-N-mineralization = 120 kg N·ha?1·a?1.  相似文献   

9.
The effects of inoculating arbuscular mycorrhizal (AM) fungi on the growth, phosphorus (P) uptake, and yield of Welsh onion (Allium fistulosum L.) were examined under the non-sterile field condition. Welsh onion was inoculated with the AM fungus, Glomus R-10, and grown in a glasshouse for 58?days. Non-inoculated plants were grown as control. Inoculated and non-inoculated seedlings were transplanted to a field with four available soil P levels (300, 600, 1,000, and 1,500?mg P2O5?kg?1 soil) and grown for 109?days. AM fungus colonization, shoot P concentration, shoot dry weight, shoot length, and leaf sheath diameter were measured. Percentage AM fungus colonization of inoculated plants was 94% at transplant and ranged from 60% to 77% at harvest. Meanwhile, non-inoculated plants were colonized by indigenous AM fungi. Shoot length and leaf sheath diameter of inoculated plants were larger than those of non-inoculated plants grown in soil containing 300 and 600?mg P2O5?kg?1 soil. Shoot P content of inoculated plants was higher than that of non-inoculated plants grown in soil containing 300 and 600?mg P2O5?kg?1 soil. Yield (shoot dry weight) was higher for non-inoculated plants grown in soil containing 1,000 and 1,500?mg P2O5?kg?1 soil than for those grown in soil containing 300 and 600?mg?P2O5 kg?1 soil. Meanwhile, the yields of inoculated plants (200?g plant?1) grown in soils containing the four P levels were not significantly different. Yield of inoculated plants grown in soil containing 300?mg P2O5 kg?1 soil was similar to that of non-inoculated plants grown in soil containing 1,000?mg P2O5?kg?1 soil. The cost of AM fungal inoculum for inoculated plants was US$ 2,285?ha?1 and lower than the cost of superphosphate (US$ 5,659?ha?1) added to soil containing 1,000?mg P2O5 kg?1 soil for non-inoculated plants. These results indicate that the inoculation of AM fungi can achieve marketable yield of A. fistulosum under the field condition with reduced application of P fertilizer.  相似文献   

10.

Purpose

The application of roxarsone (ROX), an arsenic-containing compound, as a feed additive in the animal production industry results in elevated soil levels of ROX and its metabolites, namely, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As(V)), and arsenite (As(III)). This study was conducted to study the extraction and speciation analysis of ROX-related arsenicals in soils with different physicochemical properties and the possible effects of soil properties on the extraction of ROX and its metabolites.

Materials and methods

Analytical method based on high-performance liquid chromatography (HPLC)-inductively coupled plasma–mass spectrometry (ICP-MS) was employed to determine the concentrations of As(III), DMA, MMA, As(V), and ROX extracted by different extraction solvents from different soils spiked by arsenicals. Validity of the developed method was assessed by the recovery efficiencies of arsenic species in soil-dissolved matter solutions containing 20 μg As?·?L?1 of each arsenic species. Effects of soil properties on the extraction of ROX and its metabolites were analyzed by Pearson’s correlation.

Results and discussion

Arsenic species were separated using gradient elution of water and 20 mmol?·?L?1 (NH4)2HPO4 + 20 mmol?·?L?1 NH4NO3 + 5 % methanol (v/v) within 27 min. The linear ranges of all arsenicals were 0–200 μg As?·?L?1 with R 2?>?0.9996. The developed method provided lower limits of detection for As(III), DMA, MMA, As(V), and ROX (0.80, 0.58, 0.35, 0.24, and 1.52 μg As?·?L?1, respectively) and excellent recoveries (92.52–102.2 %) for all five species. Arsenic speciation was not altered by 0.1 mol?·?L?1 NaH2PO4 + 0.1 mol?·?L?1 H3PO4 (9:1, v/v), which offered better average extraction efficiencies for As(III), As(V), DMA, MMA, and ROX (32.49, 92.50, 78.24, 77.64, and 84.54 %, respectively). Extraction performance of arsenicals was influenced by soil properties, including pH, cation exchange capacity (CEC), total Fe, and amorphous Fe.

Conclusions

ROX and its metabolites from soils could be satisfactorily separated by the developed method for the studied arsenicals. To extract arsenic species from soils, 0.1 mol?·?L?1 NaH2PO4 + 0.1 mol?·?L?1 H3PO4 (9:1, v/v) was recommended. Extraction efficiencies of arsenicals were influenced more by solvent composition than soil physicochemical properties. The present study provides a valuable tool and useful information for determining the concentrations of ROX and its metabolites in contaminated soils.
  相似文献   

11.
运用~(15)N示踪及非损伤微测技术,研究了不同供磷水平(0 mmol×L~(-1)、1.0 mmol×L~(-1)、2.0 mmol×L~(-1)、3.0 mmol×L~(-1)、4.0 mmol×L~(-1)、6.0 mmol×L~(-1)、8.0 mmol×L~(-1)、12.0 mmol×L~(-1)和16.0 mmol×L~(-1) H_2PO_4~-)对平邑甜茶幼苗NO_3~--N吸收及利用特性的影响,为提高果园氮肥利用效率提供理论依据。结果表明,在低磷水平(0~1.0 mmol×L~(-1))时,平邑甜茶根系长度、根系总表面积较小,且根尖数较少。随着供磷水平的增加,在2.0~4.0 mmol×L~(-1)磷浓度处理时,平邑甜茶幼苗生物量、根系长度、根系总表面积及根尖数显著高于其他处理。而在6.0~16.0 mmol×L~(-1)时,过量供磷抑制了根系的生长,使平邑甜茶幼苗根系长度、表面积均大幅降低,根尖数量骤降。非损伤扫描离子选择电极测试表明,当生长介质磷浓度在3.0~6.0 mmol×L~(-1)时,平邑甜茶对NO_3~-有吸收作用,并在3.0 mmol×L~(-1)磷浓度时其吸收速率最高。而在0~2 mmol×L~(-1)及8.0~16.0 mmol×L~(-1)磷浓度处理下,平邑甜茶对NO_3~-有外排作用。随供磷水平的增加,各器官从肥料中吸收分配到的~(15)N量对该器官全氮量的贡献率(Ndff)及植株氮素利用率呈现先升高后降低的趋势,4.0 mmol×L~(-1)磷浓度时植株氮素利用率最大,为42.24%,超过4.0 mmol×L~(-1)植株氮素利用率显著降低。适当充足的供磷刺激了幼苗根系生长,从而促进平邑甜茶对氮素的获取,过量的NO_3~-抑制了平邑甜茶根系的生长,同时叶片硝酸还原酶的活性受到抑制,因此其氮素吸收和利用效率较低。因此,磷浓度在3.0~4.0 mmol×L~(-1)时最有利于平邑甜茶幼苗的生长及氮素的吸收利用。  相似文献   

12.
Wildfires often modify soil properties, including the N status and net N mineralization rates, but their impacts on gross N fluxes have been scarcely evaluated. We aimed to ascertain the immediate effects of a medium–high severity wildfire on soil N transformations. Net and gross N rates were analytically and numerically (FLUAZ) quantified in burned (BS) and unburned (US) topsoils from the temperate–humid region (NW Spain). Analytical and numerical solutions were significantly correlated for both gross N mineralization (m) (r 2?=?0.815; p?<?0.001) and gross nitrification (n) (r 2?=?0.950; p?<?0.001). In BS, all NH4 +-N fluxes (net m, gross m and gross NH4 +-N immobilization, ‘ia’) increased, while those of NO3 ?-N decreased (gross n and gross NO3 ?-N immobilization, ‘in’) or did not vary (net n). In US and BS, gross m (0.26–3.60 and 4.70–15.42 mg N kg?1 day?1, respectively) predominated over gross n (0.026–2.45 and 0.001–0.002 mg N kg?1 day?1, respectively), and the same was true for the net fluxes. Compared with the few available data on recently burned soils (m?=?8–55 mg N kg?1 day?1; n?=?0.50–1.83 mg N kg?1 day?1), our gross m and n rates were similar and very low, respectively; gross n showed that nitrifiers were active in US and also in BS, despite the 98 % reduction observed immediately after the fire. For gross fluxes, m increased more than ia suggesting an NH4 +-N accumulation, but there is no risk of NO3 ?-N leaching because n decreased more than in.  相似文献   

13.
Abstract

A soil test for mineralizable soil N had been calibrated for winter wheat in the Willamette Valley of western Oregon. Seventy‐eight percent of the variation in spring N uptake by unfertilized wheat was explained by N mineralized from mid‐winter soil samples incubated anaerobically for 7 days at 40°C. Mineralizable N (Nmin) ranged from 10 to 30 mg N kg?1 and was used to predict N fertilizer needs. Recommended rates of N were correlated (R2=0.87) with maximum economic rates of N fertilizer. Subsequent farmer adoption of no‐till sowing and a high frequency of soil tests>30 mg N kg?1 prompted reevaluation of the soil test. Four N fertilizer rates [0, 56, G, and G+56 kg N ha?1] were compared in 12 m×150 m farmer‐managed plots. Grower's N rates (G) ranged from 90 to 180 kg N ha?1 and were based on Nmin and NH4‐N plus NO3‐N soil tests. Averaged across ten no‐till and five conventionally tilled sites, grain yield and crop N uptake were maximized at the recommended rate of N. Results demonstrate that N fertilizer needs for winter wheat can be predicted over a wide range of mineralizable soil N (10 to 75 mg N kg?1) and that the same soil test calibration can be used for conventionally sown and direct‐seeded winter wheat.  相似文献   

14.
Abstract

The experiment was conducted at Kulumsa, South East Ethiopia, using four levels of nitrogen (N) (0, 50,100 and 150?kg N ha?1) and four levels of phosphorus (P) (0, 35, 70 and 105?kg P2O5 ha?1) fertilizers arranged in 4?×?4 factorial arrangements in randomized complete block design with three replications. The available P was increased after harvest due to the application of N and P fertilizer at the rates of 100 or 150?kg N ha?1 and 70 or 105?kg P2O5 ha?1. More specifically, nutrients concentration and nutrient uptake were significantly (p?<?.01) varied among treatment combinations and nutrient use efficiency was declined by increasing N and P after optimum rates. The higher physiological efficiency of N (53.47?kg kg?1) and P (580.41?kg kg?1) and the highest apparent recovery of N (19.62%) and P (2.47%) was recorded from application of 50?kg N ha?1 and P at 70?kg P2O5 ha?1 and the highest agronomic efficiency of N (10.78?kg kg?1) and P (15.25?kg kg?1) was recorded from N at the rate of 50?kg N ha?1 and P at 35?kg P2O5 ha?1, respectively. The combination of N at 100?kg N ha?1 and P at 70?kg P2O5 ha?1 was promising combination that generated highest net benefit 488,878.5 ETB (Ethiopian birr) ha?1 with the highest marginal rate of return (36638%) and gave the highest seed yield (1858.82?kg ha?1) with yield increment of about 57.72% over the control.  相似文献   

15.
Height, diameter, and biomass were measured for loblolly pine (Pinus taeda L) seedlings grown in soil containing 15 or 35 Μg Mg g?1 and exposed from May to October in 1987, 1988, and 1989 to three O3 concentrations (sub-ambient, ambient, or twice-ambient) and to rain pH levels of 3.8 or 5.2. Reduction in biomass accumulation in seedlings exposed to twice-ambient O3 vs sub-ambient O3 was 14% (P = 0.03) in 1987, 11.4% (P = 0.002) by 1988, and 8% (P = 0.15) by 1989. The greatest height growth occurred in seedlings exposed to twice-ambient O3, and the greatest stem diameter growth occurred in seedlings exposed to sub-ambient O3. A comparison of stem volume (d2h) with stem biomass suggested that tissue density was reduced by elevated O3. Biomass accumulation response to rainfall chemistry was small (5.5% reduction in the low pH treatment in 1989) and not statistically significant for most plant tissues. Growth response to soil Mg status was not significant. Hoewever, in 1989 treatment interactions between rainfall chemistry and soil Mg status were observed. Height was 5% greater (P = 0.02) and biomass was 6% greater (P = 0.10) in seedlings grown in higher-Mg soil and receiving higher-pH rainfall than seedlings grown in any of the other pH-Mg treatment combinations. The data suggest direct adverse effects of near ambient O3 and indirect, slower acting and interacting adverse effects of rainfall chemistry and soil nutrient status on growth of loblolly pine.  相似文献   

16.
Abstract

The rate and timing of manure application when used as nitrogen (N) fertilizer depend on N‐releasing capacity (mineralization) of manures. A soil incubation study was undertaken to establish relative potential rates of mineralization of three organic manures to estimate the value of manure as N fertilizer. Surface soil samples of 0–15 cm were collected and amended with cattle manure (CM), sheep manure (SM), and poultry manure (PM) at a rate equivalent to 200 mg N kg?1 soil. Soil without any amendment was used as a check (control). Nitrogen‐release potential of organic manures was determined by measuring changes in total mineral N [ammonium‐N+nitrate‐N (NH4 +–N+NO3 ?–N)], NH4 +–N, and accumulation of NO3 ?–N periodically over 120 days. Results indicated that the control soil (without any amendment) released a maximum of 33 mg N kg?1soil at day 90, a fourfold increase (significant) over initial concentration, indicating that soil had substantial potential for mineralization. Soil with CM, SM, and PM released a maximum of 50, 40, and 52 mg N kg?1 soil, respectively. Addition of organic manures (i.e., CM, SM, and PM) increased net N released by 42, 25, and 43% over the control (average). No significant differences were observed among manures. Net mineralization of organic N was observed for all manures, and the net rates varied between 0.01 and 0.74 mg N kg?1 soil day?1. Net N released, as percent of organic N added, was 9, 10, and 8% for CM, SM, and PM. Four phases of mineralization were observed; initial rapid release phase in 10–20 days followed by slow phase in 30–40 days, a maximum mineralization in 55–90 days, and finally a declined phase in 120 days. Accumulation of NO3 ?–N was 13.2, 10.6, and 14.6 mg kg?1 soil relative to 7.4 mg NO3 ?–N kg?1 in the control soil, indicating that manures accumulated NO3 ?–N almost double than the control. The proportion of total mineral N to NO3 ?–N revealed that a total of 44–61% of mineral N is converted into NO3 ?–N, indicating that nitrifiers were unable to completely oxidize the available NH4 +. The net rates of mineralization were highest during the initial 10–20 days, showing that application of manures 1–2 months before sowing generally practiced in the field may cause a substantial loss of mineralized N. The rates of mineralization and nitrification in the present study indicated that release of inorganic N from the organic pool of manures was very low; therefore, manures have a low N fertilizer effect in our conditions.  相似文献   

17.
Swine lagoon sludge is commonly applied to soil as a source of nitrogen (N) for crop production but the fate of applied N not recovered from the soil by the receiver crop has received little attention. The objectives of this study were to (1) assess the yield and N accumulation responses of corn (Zea mays L.) and wheat (Triticum aestivum) to different levels of N applied as swine lagoon sludge, (2) quantify recovery of residual N accumulation by the second and third crops after sludge application, and (3) evaluate the effect of different sludge N rates on nitrate (NO3-N) concentrations in the soil. Sludge N trials were conducted with wheat on two swine farms and with corn on one swine farm in the coastal plain of North Carolina. Agronomic optimum N rates for wheat grown at two locations was 360 kg total sludge N ha?1 and the optimum N rate for corn at one location was 327 kg total sludge N ha?1. Residual N recovered by subsequent wheat and corn crops following the corn crop that received lagoon sludge was 3 and 12 kg N ha?1, respectively, on a whole-plant basis and 2 and 10 kg N ha?1, respectively, on a grain basis at the agronomic optimum N rate for corn (327 kg sludge N ha?1). From the 327 kg ha?1 of sludge N applied to corn, 249 kg N ha?1 were not recovered after harvest of three crops for grain. Accumulation in recalcitrant soil organic N pools, ammonia (NH3) volatilization during sludge application, return of N in stover/straw to the soil, and leaching of NO3 from the root zone probably account for much of the nonutilized N. At the agronomic sludge N rate for corn (327 kg N ha?1), downward movement of NO3-N through the soil was similar to that for the 168 kg N ha?1 urea ammonium nitrate (UAN) treatment. Thus, potential N pollution of groundwater by land application of lagoon sludge would not exceed that caused by UAN application.  相似文献   

18.
To test the possible use of tree ring chemical properties as proxies for precipitation acidity ([H+]), we investigated the relationships between tree ring chemistry (δ13C, δ15N, Ca-to-Al ratio, and N concentration) of Pinus densiflora and precipitation [H+] between 1992 and 2005 in an industrial area in the southwest region of South Korea. Statistical analyses showed that all tree ring chemistry parameters were significantly correlated with precipitation [H+]. Tree ring δ13C was negatively correlated with precipitation acidity (r?=??0.67, P?<?0.01), reflecting the photosynthetic fixation of 13C-depleted CO2 from fossil fuel combustion that would be the primary source of precipitation acidity. A positive correlation of N concentration (r?=?0.89, P?<?0.001) and a negative correlation of δ15N (r?=??0.63, P?<?0.05) in tree rings with precipitation acidity most likely reflected the influence of 15N-depleted N compounds deposited via precipitation. The Ca-to-Al ratio was negatively (r?=??0.58, P?<?0.05) correlated with precipitation acidity, indicating that soil acidification caused the loss of Ca from the soil and solubilization of Al resulting from acid precipitation. Such relationships suggest that δ13C, δ15N, N concentration, and Ca-to-Al ratio in tree rings can be reliably used to evaluate the impact of acid precipitation on the studied P. densiflora stands.  相似文献   

19.
Abstract

The single‐year response of soil inorganic nitrogen (N) content and indices of red raspberry (Rubus ideaus L.) yield, vigor, and N status to rate and source of fertilizer N were determined. Twenty‐nine trials were conducted in commercial plantings from 1994 to 1996. Treatments were 0, 55, or 110 kg N ha?1 as ammonium nitrate or 55 kg N ha?1 as a slow‐release fertilizer product containing 60% polycoated sulfur‐coated urea and 40% urea. Soil nitrate (NO3) content frequently increased during the growing season, indicating that soil N supply was nonlimiting. The plant indices were generally insensitive to fertilizer‐N rate under these high‐N fertility conditions. Soil nitrate content measured after berry harvest was frequently excessive even at the recommended N rate and can be used to identify fields with excess N fertility. The slow‐release N fertilizer provided limited benefits compared with use of ammonium nitrate.  相似文献   

20.
Denitrification losses from a horticultural soil as affected by mineral N-fertilization To investigate denitrification in the Ap-horizon from a horticultural cambisol as affected by mineral N-fertilization, measurements of N2O-release from the soil surface and N2O-production in the upper 10 cm soil layer were carried out. The acetylene inhibition technique was used. The loamy sand was amended with 86 and 186 kg N·ha?1 (ammonium nitratecalcium carbonate mixture). The field was cropped with celeriac (Apium graveolens L. var. rapaceum). Denitrification rates as well as soil temperature, moisture, nitrate and watersoluble carbon were measured from mid July until the end of October. In both N treatments denitrification rates were low, but higher rates could be measured in the higher N-treatment. They reached amounts of 0.6 to 134.3 g N2O-N·ha?1day?1. Estimated N-loss by denitrification totalled about 3.5 in the low and 4.9 kg N·ha?1 in the high N-treatment for the whole sampling period (107 days). Spatial variability of denitrification rates was high (39–283%). The relationship between soil temperature, moisture, nitrate content as well as watersoluble carbon and denitrification rate was shown by regression analysis.  相似文献   

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