Forms of nitrogen in cultivated soil profiles in Tanzania

In cultivated soils, total soil N, organic C and C-to-N ratios were in the range of 0.24–0.49%, 3.1–5.8% and 10.7–15.0, respectively in the surface horizons and decreased with depth. Native fixed NH⁺₄-N accounted for 2.3–3.0% of total soil N in surface horizons but while the quantities of fixed NH⁺₄-N decreased with depth, the proportion to total soil N increased. Exchangeable NH⁺₄-N ranged from 15 to 32 and NO^?₃-N from 26 to 73 μg g^?1 soil in surface horizons, and both decreased with depth. Exchangeable-N accounted for 1.1–2.4% of total soil N. Over 97% of total soil N was organically bound.Of the total soil N in the surface horizons, 29.0–79.0% was acid hydrolysable and 21.0–71.0% was nonhydrolysable. The range of proportions of each of hydrolysable NH⁺₄-N, hexosamine-N, serine plus threonine α-amino acid-N, identified-N, and unidentified-N to total soil N in the surface horizons were 14.5–22.4, 4.8–9.2, 0.2–5.8, 4.0–16.7, 23.3–48.8, and 0.3–41.5%, respectively. Hydrolysable NH⁺₄-N constituted the largest proportion of the identified-N fraction. Distribution patterns of the organic-N fractions in the profiles varied from soil to soil. Sixteen amino acids were identified which accounted for 82–100% of the α-amino acid-N fraction in the soils; glycine and alanine alone accounted for 35–40%. All the organic-N fractions were transformed to varying degree during aerobic incubation.     

Contribution of α-amino N to extractable organic nitrogen (DON) in three soil types from the Scottish uplands

Organic nitrogen (DON) was extracted from two improved pasture soils, one of which had been re-colonized by acid heath vegetation, and a blanket peat. Although the quantities extracted in H₂O, 10 mM CaCl_2, 500 mM K₂SO₄ and 50 mM Na₂HPO₄ were not consistent, mean extractable DON as a proportion of total N was greater in the two grazed pastures (0.4%) than in the peat (0.2%). Averaged over the four extractants, free α-amino N was greater in the peat and least in the improved pasture soil and accounted for 26% of DON in the peat and less than 5% in the mineral soil. Amino N increased after 6 M HCl hydrolysis, and this combined N contributed 56% to DON in extracts of the mineral soil compared with only 36% in the peat This variation in the relative contributions of free and combined amino N to DON indicated qualitative differences in the composition of DON between the three soils.     

Free amino acid composition of quince (Cydonia oblonga Miller) fruit (pulp and peel) and jam

Twenty-one free amino acids present in several samples of quince fruit (pulp and peel) and quince jam (homemade and industrially manufactured) were analyzed by GC/FID. The analyses showed some differences between quince pulps and peels. Generally, the highest content in total free amino acids and in glycine was found in peels. As a general rule, the three major free amino acids detected in pulps were aspartic acid, asparagine, and hydroxyproline. For quince peels, usually, the three most abundant amino acids were glycine, aspartic acid, and asparagine. Similarly, for quince jams the most important free amino acids were aspartic acid, asparagine, and glycine or hydroxyproline. This study suggests that the free amino acid analysis can be useful for the evaluation of quince jam authenticity. It seems that glycine percentage can be used for the detection of quince peel addition while high alanine content can be related to pear addition.     

Peat decomposition in a transitional mire in central Poland

The goal of our work was to estimate the rate of the peat formation and mineralization at two depths: 30 cm (the aerobic zone) and 60 cm (the anaerobic zone). An experiment on peat incubation was performed for two years. In the first year, at the depth of 30 cm, the peat lost about 14% of its mass in the course of the mineralization and was replenished with plant residues, including roots of Eriophorum vaginatum. As a result, the apparent loss of peat was only about 0.8% of its initial mass. At the depth of 60 cm, the mineralization loss of peat in the first year was completely recovered due to the additional input of the root mass. In the second year, the rate of the peat mineralization increased. Over the two years of the studies, the apparent losses of the peat mass at the depths of 30 and 60 cm reached 7.5 and 2.8% of the initial peat mass, respectively.     

Determination of nonprotein amino acids and betaines in vegetable oils by flow injection triple-quadrupole tandem mass spectrometry: a screening method for the detection of adulterations of olive oils

A novel screening method using an automated flow injection electrospray ionization tandem mass spectrometry system is proposed for the simultaneous determination of five nonprotein amino acids (β-alanine, alloisoleucine, ornithine, citrulline, pyroglutamic acid) and three betaines (glycine betaine, trigonelline, proline betaine) after derivatization with butanolic HCl. MS/MS experiments were carried out in a triple-quadrupole instrument using multiple reaction monitoring mode in <2 min. The proposed method provided high fingerprinting power to identify the presence of five of the studied compounds in different types of vegetable oils (soybean, sunflower, corn, olive) with LODs at parts per billion levels. The method was validated, and different mixtures of extra virgin olive oil with seed oils were analyzed, achieving the typification for the detection of adulterations in extra virgin olive oils up to 2% w/w. The nonprotein amino acid ornithine was confirmed as a marker for adulteration in the olive oils analyzed.     

Yield and protein quality of five soft red winter wheat cultivars as affected by nitrogen fertilization rate

Abstract

This study reports the relationship between N levels (22, 56 and 112 kg/ha) and its effect on yield and protein quality for five cultivars of soft winter wheat (Triticum aestivum L. em. Thell). The objective was to determine the relationship of amino acid content and total protein at various levels of N. The 56 and 112 kg N/ha rates resulted in higher wheat yields than the 22 kg N rate over the 3 yr. mean. A cultivar x N level interaction for yield occurred when certain cultivars did not respond to higher N rates in 1972. Total seed protein increased with each increase in If. Increasing N levels generally resulted in a higher amlno acid content of the seed. Cultivar effects were found for 6 of the 17 amino acids (threonine, serine, glutamic acid, proline, glycine and lysine) indicating that cultivars differed in total amino acid content. Cultivars Arthur and Holley gave the greatest response (percentage amino acid) to N application. Coker 68–8 was intermediate in response while Coker 68–15 and Blueboy showed small inconsistent responses to H application.     

A method for modelling peat depth in blanket peatlands

Inventories of peat volume and carbon storage often include general values for peat depth, but more spatially explicit and accurate estimates are required if carbon management strategies are to be developed at scales appropriate for the management. This article presents a methodology for estimating peat depth for large blanket peat areas using field sampling and GIS modelling to map peat depth on Dartmoor in south‐west England. The study area was divided into carbon unit areas (CUAs) based on soil and vegetation. Approximately 1000 peat depth measurements were taken, each consisting of a mean (n = 5) from depths within a 32 m² area. Sampling points were stratified according to CUA area and proportional extent of slope and elevation classes. Regression analyses were used to determine the relationships between slope, elevation and peat depth within each CUA. The strongest relationship was for blanket peat (r² = 0.53), with weaker ones for areas where peat was shallow and depth was less variable. A digital elevation model was used in a GIS to model peat depths for the whole of Dartmoor. Results were tested against a data set of 200 peat depths on a 250 m grid covering 1325 ha. We conclude that peat depth can be modelled using easily available topographic data combined with well‐designed field sampling over larger spatial scales. The approach can result in accurate mapping of peat depth and carbon storage for blanket peatlands in the United Kingdom and perhaps also elsewhere.     

Amino acid pool of a typical chernozem of Moldova

New data on the content and composition of the amino acids in a typical chernozem of Moldova were obtained. Eighteen amino acids were identified. Among the usually found amino acids, tryptophan was not identified. It was found that the total content of free and bonded amino acids in the studied chernozem varies from 197 to 317 mg of N/kg of soil, which constitutes 8–11% of the total pool of nitrogen. The predomination of alanine (13.88–17.26%), glycine (10.66–14.51%), aspartic (9.15–13.29%), glutamine (7.26–11.30%), and arginine (8.12–11.99%) is typical of the chernozem. The size and composition of the amino acid pool in this chernozem correlated well with the soil’s organic matter content.     

Compositional characteristics and antioxidant properties of fresh and processed sea cucumber (Cucumaria frondosa)

The antioxidant activity of fresh and rehydrated sea cucumber (Cucumaria frondosa) samples with/without internal organs was evaluated for the first time. In addition, their proximate, amino acid, and fatty acid compositions were examined. Rehydrated sea cucumber samples in distilled water were prepared from oven-dried products. All samples contained 83-90% moisture, but showed a significant difference among groups in their protein and lipid contents. Glutamic acid was the predominant amino acid in sea cucumber, followed by glycine and aspartic acid. Essential amino acids such as leucine and lysine were also present at high levels. The trend for free amino acid was different from that of total amino acids and varied among groups. Lipids in sea cucumber were dominated by eicosapentaenoic acid (EPA, C20:5n-3), ranging from 43.2 to 56.7% of the total fatty acids. Docosahexaenoic acid (DHA, C22:6n-3) was present at a much lower concentration of 2.0-5.8%. All sea cucumber samples exhibited radical scavenging property against 2,2'-azobis(2-aminopropane) dihydrochloride (AAPH) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, with rehydrated samples, especially those with internal organs, possessing higher antioxidant activity than their fresh counterparts. No correlation existed between radical scavenging capacity and total phenolics content, suggesting that other components, in addition to phenolic compounds, contribute to the antioxidant activity of sea cucumber.     

Distribution and partial characterisation of acid hydrolysable organic nitrogen in six New Zealand soils

Six New Zealand topsoils of widely different origins and properties were subjected to 6m HC1 hydrolysis and the distribution of N fractions and amino acids were determined qualitatively and quantitatively.Of the total-N in the soils studied 83–91%, was hydrolysable with 6m HCl. The largest proportion of the hydrolysable N was α-amino acid N (38– 42%). followed by hydrolysable-unknown N (HUN) (14–24%), and NH₄⁺-N (14–22%). A significant proportion (25–50%) of the HUN fraction was accounted for by the non α-amino acid-N. Oxidative (3% H₂O₂) hydrolysis released N-phenoxy amino acid-N and possibly N-compounds which were complexed with phenols and sugars. All soils had a similar amino-acid composition with a predominance of acidic amino-acids.     

Effects of nitrogen rate and nitrogen form on glycine uptake by pakchoi (Brassica chinensis L.) under sterile culture

It is well known that plants are capable of taking up intact amino acids. However, how the nitrogen (N) rates and N forms affect amino acid uptake and amino acid nutritional contribution for plant are still uncertain. Effects of the different proportions of nitrate (NO₃^?), ammonium (NH₄⁺) and ¹⁵N-labeled glycine on pakchoi seedlings glycine uptake were investigated for 21 days hydroponics under the aseptic media. Our results showed that plant biomass and glycine uptake was positively related to glycine rate. NO₃^? and NH₄⁺, the two antagonistic N forms, both significantly inhibited plant glycine uptake. Their interactions with glycine were also negatively related to glycine uptake and glycine nutritional contribution. Glycine nutritional contribution in the treatments with high glycine rate (13.4%–35.8%) was significantly higher than that with low glycine rate (2.2%–13.2%). The high nutritional contribution indicated amino acids can serve as an important N source for plant growth under the high organic and low inorganic N input ecosystem.     

尕海湿地泥炭土土壤理化性质

泥炭是一种宝贵的自然资源,同时也是重要的生态资源,尕海湿地的泥炭土在涵养水源、储存碳汇方面有着举足轻重的作用。研究采用野外调查与室内分析相结合的方法,对尕海湿地泥炭土土壤的理化性质进行测定。结果表明:尕海湿地泥炭土的平均含水量为122.29%,说明尕海湿地具有较强的蓄水功能;土壤容重平均值为0.478 6g/kg,土壤总孔隙度平均值为78.186%。随着土层加深,土壤容重呈现出增大趋势,而总孔隙度呈现出降低趋势。(2)尕海湿地泥炭土的有机质、全氮、全磷、全钾平均含量依次为302.04,10.37,0.81,13.93g/kg,空间变异程度均属中等水平。随着土层加深,土壤有机质、全氮、全磷平均含量均呈现出下降的趋势,而土壤全钾平均含量呈现出先降低后升高的趋势,说明不同深度土壤中生物量的积累对土壤养分含量有重要影响。     

Regulation of amino acid biodegradation in soil as affected by depth

Dissolved organic nitrogen (DON) and in particular free amino acids represent a key pool in the terrestrial soil C and N cycle. The factors controlling the rate of turnover of this pool in soil, however, remain poorly understood. We investigated the factors regulating the rate of amino acid turnover at different depths (up to 1.2 m) in five low-input, acid soil profiles. Within the root zone (0–60 cm), amino acids constituted 8% of the DON and represented only a small fraction of plant available N. In all the soil profiles, the rate of amino acid mineralisation decreased progressively with depth. The average half-life of the exogenously added amino acids in the soil was 5.8 h in topsoils (0–10 cm), falling to 20 h at a depth of 50 cm and to 33 h at 100 cm. Generally, the rate of amino acid mineralisation correlated positively with total soil C and N, soil microbial activity (basal soil respiration rate) and soil content. The relatively rapid rates of microbial amino acid assimilation in subsoils below the root zone (>60 cm) indicate that long-term transport of amino acids (e.g. from soil to freshwaters) will be low. Based upon the C-to-N ratio of the amino acid substrate and the microbial C assimilation efficiency, we estimate that approximately 40–60% of the amino acid-N will be excreted as . In conclusion, the rapid rate of free amino acid turnover and their low concentration in soil solution indicate that the formation of inorganic N ( and ) in soil is limited primarily by the rate of free amino acid appearance in soil and not by the rate of amino acid mineralisation.     

The redox characteristics of four peat profiles

In several previous observations on peat soils, redox potentials appeared to vary with season and depth. To clarify this variation, a systematic study was made over 1 yr at four peat sites, including wet and dry areas at high and low altitude in northern England.The coefficients of linear regressions of redox potential on seasonal temperatures became progressively more negative with increasing depth at all four sites. These observations support an hypothesis that increased aeration accompanying increased temperature played a role at the surface, but was of less importance in the deeper layers, where the reducing conditions that result from microbial activity were dominant.By using orthogonal polynomials, it was possible to demonstrate the existence of redox minima in the profiles at all sites. There were rather more minima present using this method at the lowland sites that at the upland ones where trends of redox with depth were otherwise linear or non-significant. Although the mean redox potentials over whole profiles were lower in the wetter sites than the drier, the mean depths of the redox minima were similar. These mean depths were poorly defined however having standard deviations of 30–50 per cent of the means calculated from the year's observations.Finally, it was shown that although the potentials were measured 60 s after closing the circuit, very similar conclusions would have been reached if the readings had been taken after 10 s.     

Comparative study on free amino acid composition of wild edible mushroom species

A comparative study on the amino acid composition of 11 wild edible mushroom species (Suillus bellini, Suillus luteus, Suillus granulatus, Tricholomopsis rutilans, Hygrophorus agathosmus, Amanita rubescens, Russula cyanoxantha, Boletus edulis, Tricholoma equestre, Fistulina hepatica, and Cantharellus cibarius) was developed. To define the qualitative and quantitative profiles, a derivatization procedure with dabsyl chloride was performed, followed by HPLC-UV-vis analysis. Twenty free amino acids (aspartic acid, glutamic acid, asparagine, glutamine, serine, threonine, glycine, alanine, valine, proline, arginine, isoleucine, leucine, tryptophan, phenylalanine, cysteine, ornithine, lysine, histidine, and tyrosine) were determined. B. edulis and T. equestre were revealed to be the most nutritional species, whereas F. hepatica was the poorest. The different species exhibited distinct free amino acid profiles. The quantification of the identified compounds indicated that, in a general way, alanine was the major amino acid. The results show that the analyzed mushroom species possess moderate amino acid contents, which may be relevant from a nutritional point of view because these compounds are indispensable for human health. A combination of different mushroom species in the diet would offer good amounts of amino acids and a great diversity of palatable sensations.     

Changes in the free amino acid composition with maturity of the noble cultivar of Vitis rotundifolia Michx. grape

The changes in amino acid composition that occur with maturity of the Noble cultivar of the Vitis rotundifolia Michx. (muscadine) grape were determined by HPLC. Eighteen amino acids were identified. Histidine was the most prominent amino acid followed by alanine. The concentrations of most of the major amino acids (alanine, glycine, histidine, valine, isoleucine, aspartic acid, and serine) were highest at verasion. Glutamine and threonine contents dropped sharply after fruit set, while those of arginine and proline increased gradually with maturity and ripening. Tyrosine content increased gradually with maturity and ripening following a slight drop after fruit set. In ripe grapes, seeds contained most of the amino acids in mature grapes (50%) followed by the pulp (23%), the juice (15%), and the skin (11%). Alanine, histidine, and arginine were the principal amino acids identified in the juice. Alanine, histidine, arginine, valine, glutamine, aspartic acid, proline, serine, and threonine accounted for about 90% of the amino acids in the pulp. In seeds, alanine, proline, asparagine, and histidine accounted for over 55% of the amino acids, while alanine and histidine were found to be the predominant free amino acids in the skin. The profile indicates some differences in the changes in amino acid composition with berry maturity and relative amounts of amino acids present in muscadine compared to those in nonmuscadine grape species.     

Influence of yeast strain and aging time on free amino acid changes in sparkling ciders

An analytical method for the determination of free amino acids in ciders is reported. It is based on high-performance liquid chromatography with an automatic precolumn derivatization with o-phthaldehyde and 3-mercaptopropionic acid and diode array detection. The method was applied to monitor the amino acids during second fermentation of sparkling ciders. This paper reports the influence of yeast strains and aging time on the amino acid composition of sparkling ciders. The application of principal component analysis enables the ciders to be differentiated on the basis of the two factors considered (yeast strain and aging time). The first principal component, which accounts for 58% of the total variance, achieved the separation according to aging time with serine, glycine, alanine, valine, ornithine, leucine, and lysine as the most important variables. The second principal component, accounting for 28% of the explained variance, is closely related to aspartic acid and asparagine and separates the samples according to the yeast strain.     

Changes in the free amino acid contents of honeys during storage at ambient temperature

This study was carried out to establish the changes in the free amino acid contents of floral honeys, honeydew honeys, and blend honeys during storage at room temperature and to test the capacity of the amino acids to distinguish the origin of the honeys after storage. For this purpose, 54 artisanal honeys (39 floral, 5 honeydew, and 10 blend) were studied. Samples were taken from recently collected honeys and at 3, 6, 9, 12, 16, 20, and 24 months after harvesting. The contents of most of the free amino acids were found to decrease with storage time, with the greatest reduction observed in the first 9 months. The contents of the amino acids aspartic acid, beta-alanine, and proline increased in the first few months after storage, reaching maximum values at 6 months, suggesting the possible existence of enzymatic activities. The application of stepwise discriminant analysis to the free amino acid content data demonstrated that the contents of the amino acids valine, beta-alanine, gamma-aminobutyric acid, serine, isoleucine, alpha-alanine, ornithine, and glutamine correctly assigned 87% of honeys to their group of origin: floral, honeydew, or blend.     

Effects of season and processing on oil content and fatty acids of baltic herring (Clupea harengus membras)

Fatty acid composition, oil content, free fatty acid content, and peroxide value of Baltic herring (Clupea harengus membras) and two processed products (fried fillets and fish burgers) were investigated. The highest oil content of the fillets was found in autumn (10%), at the time when the free fatty acids had their minimum (1.4%). The main fatty acids were oleic (18-23%), palmitic (17%), palmitoleic (8-12%), and docosahexaeneoic (8-10%) acids. The proportion of saturated fatty acids was a constant 23% all year around, whereas mono- and polyunsaturated acids varied from 34 to 39% and 33 to 37%, respectively. During processing the oil content doubled and the fatty acid composition changed to the pattern of the rapeseed oil used for frying. Oleic acid was a major fatty acid in the products comprising over 40% of the total fatty acids. The proportion of n-3 acids decreased during processing but the total amount of polyunsaturated acids remained fairly constant.     

Changes in amount of organic and inorganic fractions of nitrogen in an Eutrochrept soil after long‐term cropping with different fertilizer and organic manure inputs

The influence of 30 years of cropping with different fertilizer and farmyard manure (FYM) inputs on the contents and depth distribution of organic C, total N (N_t), soil mineralizable N, and organic and inorganic N fractions was investigated in an Eutrochrept. Continuous application of 100 %NPK(+S), 150 %NPK(+S), and 100 %NPK(+S)+FYM led to a marked increase in organic C, total N, hydrolyzable N (viz., amino acid N, hydrolyzable NH₄‐N, hexose amine N, and unidentified hydrolyzable N), and nonhydrolyzable N as compared to an adjacent fallow. The contents of the various organic N fractions were largest in surface soil and thereafter decreased with the depth. However, at 30 – 45 cm depth the content of organic C was not affected by the different treatments except 100 %NPK(+S)+FYM. On the other hand, continuous cropping without fertilization resulted in a depletion of total hydrolyzable N in control over fallow by 27.2 % (0–15 cm), 19.6 % (15–30 cm), and 4.7 % (30–45 cm). The incorporation of FYM with 100 %NPK(+S) resulted in greater contents of soil mineralizable N as compared to 100 %NPK(+S) (0–15, 15–30 cm). The proportion of hydrolyzable N (57–76 % of N_t) decreased and that of nonhydrolyzable N (22–40 % of N_t) increased with depth. The proportion of amino acid N (19–26 % of N_t), hexose amine N (2.1–3.5 % of N_t) and unidentified hydrolyzable N (17–27 % of N_t) decreased with depth. All organic soil N fractions including even nonhydrolyzable N in surface and subsurface soils were highly significantly correlated with soil mineralizable N derived from incubations under waterlogged and aerobic conditions. The best correlation to mineralizable N was found for amino acid N and the least significant correlation for nonhydrolyzable N.