氮添加对沙质草地氨挥发及硝态氮淋溶的影响

采用密闭室法和离子交换树脂袋法,研究了科尔沁沙质草地不同处理(水添加、氮添加、水氮添加)氧挥发的损失量和硝态氮的淋溶量.结果表明:氮添加处理和水氮添加处理显著促进了氨挥发(P＜0.05),最大氨挥发速率显著高于对照;氮添加处理和水氮添加处理的氨挥发累积量为111.80和148.64 mg·m-2,分别占氮添加量的1.1％和1.5％;水氮同时添加条件下,氨挥发累计量显著高于氨添加处理(P＜0.05),水添加处理和对照相比没有显著差异(P＞0.05);水氮添加处理显著增加了土壤深度20 cm处的硝态氮淋溶量(P＜0.05),氮添加处理和水氮添加处理的硝态氮淋溶量分别是对照的1.96和4.22倍,然而在土壤深度40 cm处各处理硝态氮淋溶量差异不显著(P＞0.05);可见,氮添加和水氮添加均促进了土壤的氧挥发,对硝态氮的淋溶没有显著影响.     

Model of ammonia volatilization from calcareous soils

A quantitative model of ammonia volatilization from the calcareous soil uppermost 1-cm layer was developed and tested. The model accounts for the following processes: ammonium-ammonia equilibration in the soil solution, cation exchange between calcium and ammonium which results in ammonium distribution between soil liquid and solid phases, nitrification of dissolved ammonium, distribution of ammonia between liquid and gaseous phases and diffusion of gaseous ammonia in the soil air. The combined effect of various characteristics such as soil pH, cation exchange capacity, water capacity and nitrification rate on ammonia losses from various soil types have been studied. The model was validated against experimental results of ammonia losses from different soils for its use as a predicting tool. The model shows that most of ammonia losses can be explained by the interactive effect of high soil pH and low cation exchange capacity. Computations show increased ammonia volatilization with decreasing soil water capacity. Increasing fertilizer application rate has a small effect on percentage of ammonia losses. Increased nitrification rate and shorter “lag” period of nitrification reduce ammonia losses considerably. Good agreement was obtained between model calculations and experimental results of ammonia volatilization from 13 soils.     

Ammonia volatilization during aerobic and anaerobic manure decomposition

Ammonia volatilization, nitrogen immobilization, carbon decomposition and formation of volatile fatty acids was investigated in a laboratory incubation experiment with fresh poultry manure, to which increasing amounts of straw were added. Less than 1% of the manure nitrogen was volatilized as ammonia during anaerobic decomposition due to low pH values. In aerobic manure alkaline conditions prevailed and between 9 to 44% of the nitrogen was volatilized as ammonia. The volatilization courses could be described by a parallel first-order model. Increasing straw additions reduced ammonia volatilization during aerobic decomposition. Straw caused no immobilization of nitrogen under anaerobic conditions. In aerobic manure, nitrogen was mainly bound in organic forms whereas in anaerobic manure about two-thirds of the nitrogen was in ammonium form. C/N ratios in the organic matter of anaerobic manure were higher (33.1–87.5) than in the aerobic manure (9.5–18.0).     

三江平原典型小叶章湿地土壤氨挥发特征及影响因素

采用通气法对三江平原典型草甸小叶章湿地和沼泽化草甸小叶章湿地土壤的氨挥发进行了原位测定,并对其主要影响因素进行了分析。结果表明,二者的氨挥发速率在生长季内的变化趋势基本一致,7月中旬前出现两次挥发高峰和一次低值,之后整体呈严格单调下降趋势,后者的氨挥发速率较高,平均为前者的1.35±0.53倍;二者累计氨挥发量的变化趋势也基本一致,7月中旬前增加迅速,且值比较接近;之后增加缓慢,但其值发生明显分异,表现为后者大于前者;生长季内,典型草甸小叶章湿地土壤的氨挥发总量为6.35 kg N.hm-2,而沼泽化草甸小叶章湿地则为6.87 kg N.hm-2,二者之比为1∶1.08;氮素物质基础不是影响二者氨挥发过程的重要限制因素,大气温度及其所引起的其它温度波动是影响氨挥发速率变化的重要因素;降水及土壤水分波动与散失是引起氨挥发速率局部波动的重要原因;土壤pH和质地是导致氨挥发速率普遍较低的根本原因;而各种因素综合作用的结果则是引起二者氨挥发速率和氨挥发量变化及差异的主要原因。     

Ammonia volatilization after injection of anhydrous ammonia into arable soils of different moisture levels

Laboratory experiments have shown appreciable losses of ammonia after injection of anhydrous ammonia into dry and wet soils. In this study losses of ammonia injected into a moist (tension 10 kPa), dry (tension 160 kPa) and a wet (tension 1.6 kPa) sandy loam were measured under field conditions using wind tunnels. Losses were insignificant from a moist soil. However losses from a dry and a wet soil were 20% and 50% of injected ammonia, respectively. From the dry soil, losses of gaseous ammonia took place within the first hours after injection, which indicates a rapid transport through cracks and voids. From the wet soil, 20% of the injected ammonia was lost more gradually between 6 h and 6 d. This indicates that upward movement of water due to evaporation may be the cause of these ammonia losses which proceeded for longer periods.     

Gaseous nitrogen losses and ammonia volatilization measurement following land application of cattle slurry in the mid-Atlantic region of the USA

To provide locally-determined field data for extension and environmental management purposes, gaseous N losses were measured following cattle slurry application to an arable silty-loam soil in the mid-Atlantic region of the USA. The field had been cropped to no-till maize. NH₃ volatilization was measured with the micro-meteorological, integrated horizontal flux (IHF) method, and denitrification with a core incubation method using acetylene inhibition. An early-winter surface application (5 December 1996; 88 m³ ha⁻¹ supplying 91 kg NH ₄ ⁺ -N ha⁻¹) was either unincorporated or immediately incorporated. NH₃ volatilization was measured from the unincorporated application, and denitrification from both slurry treatments and appropriate control soils. Total NH₃ loss from the unincorporated slurry application was 19% of applied NH ₄ ⁺ -N; temperatures were cool (4–6 °C), and 25 mm of rain fell within 24 h of application. For 3 months, enhanced denitrification occurred from the two slurry treatments, with generally higher rates from the incorporated slurry. Total net denitrification loss from the surface-applied and incorporated slurry treatments was, respectively, 11 and 17% of applied NH ₄ ⁺ -N. Denitrification loss over the winter/early-spring period was appreciable but not substantial, even where NH₃ volatilization was restricted by immediate incorporation. From the spring application (30 April 1997, 39 m³ ha⁻¹ supplying 51 kg NH ₄ ⁺ -N ha⁻¹), total NH₃ loss was 71% of applied NH ₄ ⁺ -N. These NH₃ volatilization loss data and the similarity of climate suggest that NH₃ loss factors from recent NW European work are likely to be generally applicable in the mid-Atlantic region. NH₃ volatilization from the spring application was also measured using the Z-instrument (Z_INST) approach, and with a system of small wind tunnels. A comparative assessment of the three methods is reported.     

Clinoptilolite zeolite and cellulose amendments to reduce ammonia volatilization in a calcareous sandy soil

Leaching of nitrate (NO₃^–) below the root zone and gaseous losses of nitrogen (N) such as ammonia (NH₃) volatilization, are major mechanisms of N loss from agricultural soils. New techniques to minimize such losses are needed to maximize N uptake efficiency and minimize production costs and the risk of potential N contamination of ground and surface waters. The effects of cellulose (C), clinoptilolite zeolite (CZ), or a combination of both (C+CZ) on NH₃ volatilization and N transformation in a calcareous Riviera fine sand (loamy, siliceous, hyperthermic, Arenic Glossaqualf) from a citrus grove were investigated in a laboratory incubation study. Ammonia volatilization from NH₄NO₃ (AN), (NH₄)₂SO₄(AS), and urea (U) applied at 200 mg N kg^–1 soil decreased by 2.5-, 2.1- and 0.9-fold, respectively, with cellulose application at 15 g kg^–1 and by 4.4-, 2.9- and 3.0-fold, respectively, with CZ application at 15 g kg^–1 as compared with that from the respective sources without the amendments. Application of cellulose plus CZ (each at 15 g kg^–1) was the most effective in decreasing NH₃ volatilization. Application of cellulose increased the microbial biomass, which was responsible for immobilization of N, and thus decreased volatilization loss of NH₃–N. The effect of CZ, on the other hand, may be due to increased retention of NH₄ in the ion-exchange sites. The positive effect of interaction between cellulose and CZ amendment on microbial biomass was probably due to improved nutrient retention and availability to microorganisms in the soil. Thus, the amendments provide favorable conditions for microbial growth. These results indicate that soil amendment of CZ or CZ plus organic materials such as cellulose has great potential in reducing fertilizer N loss in sandy soils.     

Effects of iron,copper, zinc,calcium, and magnesium on human lymphocytes in culture

The effects of simultaneous changes of calcium, magnesium, iron, copper, and zinc concentrations were evaluated in normal human T and B lymphocytes, cultured in cation-depleted media. Optimal concentrations for thymidine incorporation (TI) in both cell populations were Fe and Zn 15 μM and Cu 5 μM; for t cells Ca 2 mM and Mg 4 mM; for B cells Ca 4 mM and Mg 6 mM. TI decreased with increasing molarity of cations and the decrease was particularly apparent with Cu. Minimal amounts of Ca and Mg (0.5 mM) were necessary for growth, even in presence of optimal concentrations of Fe, Cu, and Zn. Fe and Cu showed synergistic stimulatory effects at low concentrations and synergistic inhibitory effects at high concentrations. Antagonism between Fe and Zn, Cu and Zn, and Ca and Zn was also demonstrated. CD4/CD8 increased with PHA stimulation in presence of Zn, and decreased with ConA stimulation in presence of Zn or Fe. The results demonstrate: (1) the relationship and interdependence of Fe, Cu, and Zn concentrations in modulating the growth of normal lymphocytes; (2) the stimulatory effects of Fe on B cells and Zn on CD8 positive cells; (3) the inhibitory effect of Cu at concentrations lower than those of Fe and Zn; (4) the requirement of Ca and Mg in certain concentration and ratio for the action of the other cations; and (5) the Ca and Mg requirement for the growth of B cells higher than T cells.     

Maltobionic acid enhances intestinal absorption of calcium and magnesium in rats

ABSTRACT

In Experiment 1, the effects of calcium maltobionate (MBCa) on calcium and magnesium absorption were examined using male rats. Four diets were designed in which 25%, 50%, and 100% of calcium carbonate (CaCO₃, Control) were substituted with MBCa and were designated as MBCa-25, MBCa-50, and MBCa-100, respectively. The cecal concentration of short-chain fatty acids was significantly higher in groups MBCa-50 and MBCa-100; however, pH of cecal contents did not significantly differ among the groups. Retention rates of calcium and magnesium were significantly higher in all MBCa groups as compared to the Control. In Experiment 2, the efficiency of calcium absorption was compared using everted sacs of jejunum and ileum with CaCO₃ and MBCa as calcium sources. More calcium from MBCa was absorbed as the concentration of calcium increased in comparison to CaCO₃. It was concluded that MBCa is a better calcium source than CaCO₃ in terms of both calcium retention and absorption.

Abbreviations: ANOVA: analysis of variance; Ca: Calcium; CaCO_3: calcium carbonate; ICP-OES: Inductivity coupled plasma optical emission spectrometer; Mg: magnesium; MBCa: calcium maltobionate; OCPC: o-cresolphthalein complexone; SCFAs: short-chain fatty acids; SE: standard error; TRPM6: transient receptor potential melastatin 6.     

The volatilization of ammonia from cattle urine applied to soils as influenced by soil properties

The amounts of ammonia volatilized, following the application of cattle urine to 22 soils, were measured in the laboratory during an incubation period of 10 days. The urine contained 12.0 g N dm^-3 and was applied to small columns of soil at a rate equivalent to 26.5 g N m^-2. The soils were from fields of both grassland and arable cultivation and varied widely in properties. Ammonia volatilization ranged from 6.8 to 41.3% of the total urinary N, with a mean value of 26.4%. The soil property most closely related to the extent of volatilization was cation exchange capacity (CEC), and this was so whether all 22 soils were considered together or whether the 14 grassland and 8 arable soils were considered separately. In general, the higher the CEC the less the amount of ammonia volatilized. However, for a given value of CEC, volatilization tended to be greater from a grassland than from an arable soil. The pH of a soil/urine mixture measured after 24 hours was also quite closely correlated with the amount of ammonia volatilized, but the initial pH and titratable acidity of the soil were poorly correlated with ammonia volatilization. ei]H Marschner ei]H Lambers     

Ammonia volatilization from tropical legume mulches and green manures on unlimed and limed soils

In the humid tropics, legumes are harvested and surface applied as mulch or incorporated as green manure. Studies on N dynamics and budgets from these systems report unaccounted losses of N. Ammonia volatilization may account for a significant percentage of these unexplained N deficits. The main objectives of this study were to: 1) determine the rate and amount of ammonia volatilization from organic amendments, both incorporated (green manure) and unincorporated (mulch), 2) compare ammonia volatilization of organic amendments on both acid (unlimed) and limed soils, and 3) correlate quality, i.e. polyphenolic and lignin concentration and carbon-to-nitrogen ratio, of the organic amendments with ammonia volatilization and net N mineralization. In an incubation experiment, ammonia volatilization losses and net N mineralization were measured from fresh leaflets of 10 legumes over a three-week period. Ammonia volatilization losses for the 10 species ranged from 3.4 to 11.8% of the total N applied in the organic amendment. Lignin content was negatively correlated to ammonia volatilization. Ammonia volatilized from mulches but not green manures, on both unlimed and limed soils, suggesting that ammonia volatilization is a surface phenomenon and not affected by soil pH. Net N mineralization was affected by species and soil pH, but was unaffected by placement (green manure or mulch). For the farmer in low-input agriculture where N tends to be limiting, volatilization losses of N from legume mulch systems could be on the same order of magnitude as crop removal.     

Simultaneous accumulation of calcium, phosphorus, and magnesium in various human arteries

To elucidate compositional changes of the arteries with aging, the authors investigated the relationships among average contents of calcium, phosphorus, sulfur, and magnesium in the arteries by inductively coupled plasma-atomic emission spectrometry. The arteries used were the thoracic and abdominal aortas, coronary, common carotid, anterior, middle and posterior cerebral, vertebral, basilar, internal thoracic, axillary, radial, truncus celiacus, common, internal and external iliac, femoral, popliteal, and umbilical arteries. It was found that high correlations were found between the average contents of calcium and phosphorus, between the average contents of calcium and magnesium, and between the average contents of phosphorus and magnesium in the arteries, but not between the average contents of sulfur and the other elements. These correlations revealed that as the content of calcium and phosphorus increased in the arteries, the magnesium content increased simultaneously in the arteries, but the sulfur content did not. It is likely that magnesium forms compounds with phosphorus in the arteries.     

Interactive effects of synthetic nitrogen fertilizer and composted manure on ammonia volatilization from soils

The mutualism between legumes and nitrogen-fixing soil bacteria (rhizobia) is a key feature of many ecological and agricultural systems, yet little is known about how this relationship affects aboveground interactions between plants and herbivores. We investigated the effects of the rhizobia mutualism on the abundance of a specialized legume herbivore on soybean plants. In a field experiment, soybean aphid (Aphis glycines) abundances were measured on plants (Glycine max) that were either (1) treated with a commercial rhizobial inoculant, (2) associating solely with naturally occurring rhizobia, or (3) given nitrogen fertilizer. Plants associating with naturally occurring rhizobia strains exhibited lower aphid population densities compared to those inoculated with a commercial rhizobial preparation or given nitrogen fertilizer. Genetic analyses of rhizobia isolates cultured from field plants revealed that the commercial rhizobia strains were phylogenetically distinct from naturally occurring strains. Plant size, leaf nitrogen concentration, and nodulation density were similar among rhizobia-associated treatments and did not explain the observed differences in aphid abundance. Our results demonstrate that plant–rhizobia interactions influence plant resistance to insect herbivores and that some rhizobia strains confer greater resistance to their mutualist partners than do others.     

Dietary zinc effects on zinc, calcium, and magnesium content in bones of growing rats

The aim of the present study was to assess dietary zinc effects on femur weight and mineral content in growing rats. For this purpose, 70 weanling Sprague-Dawley rats were divided into four groups. Each group was subject to a diet containing 2 (BZ), 5 (DZ), 10 (MZ), and 30 (CZ) ppm zinc. The calcium and magnesium content in all diets was 5 g/kg and 507 mg/kg, respectively. The animals were kept on this regime for 28 d and then sacrificed and their femurs were removed for analysis using atomic absorption spectrophotometry. The weights of the BZ and DZ groups were significantly different from the MZ and CZ groups (38.5±10.5, 89.9±13.7, 118.6±13.6 and 134±19.9 g, p<0.01) respectively. There were no differences between the MZ and CZ groups. Femur weight also varied with dietary zinc, as it was significantly different among all groups (BZ, 265±49 mg; DZ, 380±40 mg; MZ, 452±54 mg; CZ, 735±66 mg; p<0.01). The femur zinc content varied with diets, following a different pattern than the above parameters. Femur zinc from the BZ group (51.5±5.4 ppm) was significantly different from the MZ and CZ groups (115.9±14.2 and 175.0±13.5 ppm, respectively), whereas the DZ group (62.5±11.3 ppm) did not differ from the other three groups. The femur content of calcium (BZ, 83.2±9.8 mg/g; DZ, 88.0±9.2 mg/g; MZ, 90.2±13.6 mg/g; CZ, 83.1±14.7 mg/g) and magnesium (BZ, 1.82±0.13 mg/g; DZ, 1.98±0.09 mg/g; MZ, 1.93±14 mg/g; CZ, 1.83±0.19 mg/g) were not significantly different among the groups, nor was the calcium-magnesium ratio. These results suggest that although dietary zinc deficiency retards growth and causes bone fragility, bone deposition of calcium and magnesium and its ratio are not affected.     

Simultaneous accumulation of magnesium with calcium and phosphorus in aorta and iliac arteries of thai

To elucidate compositional changes of arteries with aging, the authors previously investigated age-related changes of mineral contents in the various arteries of Japanese and Japanese monkey. To examine whether there were differences between races in regard to age-related changes of mineral contents and the relationships among element contents in the arteries, the authors investigated the arteries of Thai. The subjects consisted of 13 men and 3 women, ranging in age from 39 to 84 yr. After the ordinary dissection at Chiang Mai University was finished, abdominal aortas, common iliac, internal iliac, and external iliac arteries were resected and the element contents were determined by inductively coupled plasma-atomic emission spectrometry. The contents of calcium, phosphorus, and magnesium became the highest in the fifties in the abdominal aorta, common iliac, and external iliac arteries, whereas the contents of calcium and magnesium became the highest in the sixties in the internal iliac artery, and decreased thereafter. In regard to relationships among element contents, it was found that there were high correlations between calcium and phosphorus contents, between calcium and magnesium contents, and between phosphorus and magnesium in all of the abdominal aortas and three iliac arteries. The mass ratios of magnesium to calcium and phosphorus were each similar in the abdominal aorta, common iliac, and internal iliac arteries, except for the external iliac artery, in which it was slightly high. These revealed that as calcium and phosphorus increased in the arteries with aging, magnesium increased in the arteries as well. The differences between the arteries of Thai and Japanese were discussed in the present article.     

Characterization of magnesium and calcium tenuazonate from Phoma sorghina

Phoma sorghina Sacc., the fungus implicated in the aetiology of onyalai, a haematologic disorder, produces magnesium and calcium tenuazonate as toxic constituents.     

Accumulation of calcium and phosphorus accompanied by inevitable accumulation of magnesium in human arteries

To examine whether there were differences between races in regard to the relationships among element contents in the arteries, the authors investigated the relationships among the average contents of calcium, phosphorus, sulfur, and magnesium in the 18 kinds of the Thai artery. After ordinary dissection by medical students at Chiang Mai University was finished, the thoracic and abdominal aortas, ramifying site of the abdominal aorta into the common iliac arteries, coronary, common carotid, internal thoracic, subclavian, axillary, brachial, radial, superior and inferior mesenteric, renal, common iliac, internal iliac, and external iliac arteries were resected from the subjects who consisted of 12 men and 3 women, ranging in age from 39 to 84 yr. The femoral and posterior tibial arteries were resected from the subjects, consisting of 15 men and 5 women, ranging in age from 25 to 88 yr. The element content of the arteries was analyzed by inductively coupled plasma-atomic emission spectrometry. It was found that there were extremely significant direct correlations among the average contents of calcium, phosphorus, and magnesium in the 18 kinds of the Thai artery, but no significant correlations were found between the average contents of sulfur and elements, such as calcium, phosphorus, and magnesium. These results were in agreement with those of the Japanese arteries. Therefore, it was suggested that there was no significant difference between the arteries of the Thai and the Japanese in the relationships among calcium, phosphorus, sulfur, and magnesium.     

Regulation of calcium currents and secretion by magnesium in crustacean peptidergic neurons

The effect of varying the external Mg²⁺ concentration on Ca²⁺ currents through voltage-operated Ca²⁺ channels has been examined with the patch-clamp technique in acutely isolated neuronal somata from the X-organ-sinus gland (XOSG) of the crab,Cardisoma carnifex. Neurons from this neurosecretory system were selected for morphology associated with crustacean hyperglycemic hormone (CHH) content. In parallel, the effects of Mg²⁺ concentration on K⁺-evoked secretion of CHH from isolated, intact XOSGs have been assayed by ELISA. At physiological Ca²⁺ levels the high-voltage-activated Ca²⁺ currents were attenuated with increasing Mg²⁺ concentration, with 50% inhibition at 75 mM. Mg²⁺ block was voltage-dependent, relief from block occurring with increasing depolarization. Thus, in 24 mM Mg²⁺ inhibition of the Ca²⁺ current was 55% at –10 mV and 30% at +20 mV. Secretion of CHH varied almost linearly with the log of Mg²⁺ concentration; in 2.4 mM Mg²⁺ it was double that in 24 mM Mg²⁺ and almost completely inhibited in 100 mM. Thus, Mg²⁺ produces a parallel inhibition of Ca²⁺ currents and CHH secretion and may play a role as a physiological modulator of neuronal activity and secretion in the XOSG of these crabs.     

Ammonia volatilization from a seasonally and spatially variable grazed grassland: Yellowstone National Park

We measured ammonia volatilization at three topographic positions(hilltop, mid-slope, slope-bottom) on three grassland landscapes at threetimes during 1995 (April, May, July) on the northern winter range ofYellowstone National Park that supports large herds of native ungulates.Percent ammonia-N lost from all sites during the study ranged 1–24%of urea-N applied. Volatilization among sites was negatively related tosoil cation-exchange capacity (r = –0.85) and rates were highest inJuly. We used the relationship between soil CEC and percent Nvolatilized from urea-amended plots to estimate annual ammonia-Nvolatilization from 5 sites for which annual ungulate urine inputs werepreviously determined (Frank et al. 1994). Estimated mean annualammonia-N volatilized from those sites was 1.4 kg/ha/yr, which wasless than a previously reported regional atmospheric deposition rate (2kg/ha/yr; Swank 1984). Results indicate the need to understand theinteraction between (1) spatially heterogeneous patterns of soilprocesses, and 2) nonuniform patterns of ungulate use of landscapes todetermine rates of ecosystem-level N-gaseous loss. Findings alsosuggest that ammonia-N volatilized from urine patches should not leadto a decline in soil N in this ecosystem.