Beziehung zwischen dem Stickstoff-Entzug der Pflanzen und der Abnahme von spezifisch gebundenem NH4-N im Boden

Relationship between the N uptake of plants and the mobilization of nonexchangeable NH₄-N In a pot experiment with ryegrass (Lolium multiflorum) the relationship between the release of nonexchangeable NH₄⁺ and the N uptake of plants was studied. For this purpose the surface soil of an alluvial soil and of a grey brown podsolic soil was labelled with ¹⁵NH₄-N. The following results were obtained: After treating the soil with 15-N the alluvial soil contained 4,55 mg and the grey brown podsolic soil 1,64 mg nonexchangeable ¹⁵NH₄-N/100 g soil. In the alluvial soil 72% and in the grey brown podsolic soil 66% of the nonexchangeable ¹⁵NH₄⁺ had been released during the growing season when ryegrass was planted. However, without plants there was no change in the content of labelled nonexchangeable NH₄⁺ in the alluvial soil or only a slight decrease in the grey brown podsolic soil. A highly significant correlation was found between the ¹⁵NH₄-N released and the ¹⁵N uptake of ryegrass in the alluvial soil (r = 0,78⁺⁺⁺) as well as in the grey brown podsolic soil (r = 0,98⁺⁺⁺).     

Effect of residence time on the kinetics of nonexchangeable ammonium release from illite and vermiculite

The fraction of nonexchangeable ammonium (NH₄⁺) can play an important role in N cycling of soils as a sink (fixation) or a source (release) of NH₄⁺. Recently fixed nonexchangeable NH₄⁺ especially seems to be a significant source for N release. The aim of our study was to determine the effect of residence time on the kinetics of nonexchangeable NH₄⁺ release from illite and vermiculite. Calcium-saturated illite and vermiculite, containing NH₄⁺ that was “fixed” for one and 60 d, were extracted with a H-resin for 0.25 to 384 h. Both clay minerals “fixed” significantly more NH₄⁺ in 60 d than in 1 d, but vermiculite “fixed” more NH₄⁺ than illite. The kinetics of nonexchangeable NH₄⁺ release from illite and vermiculite were well described by the Elovich equation and by a heterogeneous diffusion model. In vermiculite the percentage of nonexchangeable NH₄⁺ release decreased from 84% to 78% when the time of fixation increased from 1 to 60 d. In illite time of residence has not influenced the complete release of newly fixed NH₄⁺.     

Dynamics of 15N-labeled ammonium sulfate in various inorganic and organic soil fractions of wetland rice soils

Summary The dynamics of basally applied ¹⁵N-labeled ammonium sulfate in inorganic and organic soil fractions of five wetland rice soils of the Philippines was studied in a greenhouse experiment. Soil and plant samples were collected and analyzed for ¹⁵N at various growth stages. Exchangeable NH₄ ⁺ depletion continued after 40 days after transplanting (DAT) and corresponded with increased nitrogen uptake by rice plants. Part of the applied fertilizer was fixed by 2:1 clay minerals, especially in Maligaya silty clay loam, which contained beidellite as the dominant clay mineral. After the initial fixation, nonexchangeable ¹⁵N was released from 20 DAT in Maligaya silty clay loam, but fixation delayed fertilizer N uptake from the soil. Part of the applied N was immobilized into the organic fraction. In Guadalupe clay and Maligaya silty clay loam, immobilization increased with time while the three other soils showed significant release of fertilizer N from the organic fraction during crop growth. Most of the immobilized fertilizer N was recovered in the nondistillable acid soluble (alpha-amino acid + hydrolyzable unknown-N) fraction at crop maturity. Between 61% and 66% of applied N was recovered from the plant in four soils while 52% of fertilizer N was recovered from the plant in Maligaya silty loam. Only 20% – 30% of the total N uptake at maturity was derived from fertilizer N. Nmin (mineral N) content of the soil before transplanting significantly correlated with N uptake. Twenty-two to 34% of applied N was unaccounted for possibly due to denitrification and ammonia volatilization.     

Release of nonexchangeable NH4-N after planting of ryegrass in relation to soil content and as affected by nitrate supply

The uptake of N by ryegrass grown in pot culture on a range of soils differing widely in content of nonexchangeable NH₄-N (topsoils: 117 to 354 mg kg^?1 soil; subsoils: 117 to 270 mg kg^?1 soil) was measured to indicate whether the amounts of NH₄-N released from clay minerals were correlated with soil NH₄-N. After two cuts soil analysis revealed that the amounts of mobilized nonexchangeable NH₄-N were between 3.5 and 25.2 mg kg^?1 from topsoils and between 0 and 8.2 mg kg^?1 from subsoils. There was no correlation between soil nonexchangeable NH₄-N content and release. The NH₄-N extracted with 1 N HCl and the actual N uptake of the plants correlated highly significant. Assuming that the whole of the NH₄-N released was taken up by ryegrass, NH₄-N accounted for 11.2 to 75.0% of total N uptake from topsoils and 0 to 37.3% from subsoils. The release of nonexchangeable NH₄-N was increased by the application of nitrate.     

Fixed ammonium in some Bangladesh soils

Nitrogen is the most deficient element and the most limiting factor for crop production in Bangladesh. The total N content in Bangladesh soils ranges between 0.02 and 0.12% (Ahsan and Karim 1988). The low N content indicates the presence of a small organic N pool and suggests that inorganic N plays an important role as a N source for crops. Contribution of “fixed” or “nonexchangeable” NH₄ ⁺ to the N economy of soil has been reported for many tropical soils (Rodrigues 1954; Moore and Ayeke 1965; Dalal 1977; Sahrawat 1995). However, there are few reports on fixed NH₄ ⁺ status in Bangladesh. In the present study, therefore, attempts were made to collect data on fixed NH₄ ⁺ of some major soil series from the important physiographic units of Bangladesh.     

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.     

Verhalten von Dünger-NH4 in Böden unterschiedlicher tonmineralischer Zusammensetzung im Inkubationsversuch

Fate of fertilizer ammonium in soils with different composition of clay minerals in an incubation experiment In an incubation experiment with three different soils (gray brown podsolic soil from loess, alluvial gley, and brown earth, derived from basalt) the specific adsorption (fixation) and release of fertilizer NH₄⁺ was investigated. In one treatment 120 mg NH₄–N/kg soil was added, while the other treatment (control) received no nitrogen. Soils samples were taken every ten days and analyzed for nonexchangeable and exchangeable NH₄⁺ and NO₃^?. The experimental results are showing that the specific adsorption of applied NH₄⁺ was related to the type of clay minerals. While the loess soil, rich in illite, and the alluvial soil, rich in expansible clay minerals, bound about 40% of the added NH₄⁺ specifically, the soil derived from basalt with mainly kaolinite bound only about 10 %. From the recently “fixed” fertilizer NH₄⁺ about a half was nitrified during the incubation period of about 9 weeks. In the control there was no significant release of specifically bound NH₄⁺. Obviously this NH₄⁺ is located more deeply in the interlayers of the clay minerals and not available to microorganisms.     

Organic nitrogen compounds extracted from arable and forest soils by electro-ultrafiltration and recovery rates of amino acids

Summary Extraction of synthetic amino acids dissolved in water by means of electro-ultrafiltration (EUF) showed average recovery rates of about 75%. Higher losses were obtained, particularly with cysteine, methionine and NH₄ ⁴; the latter, probably being deprotonated at the cathode, may be lost in form of NH₃. The EUF extracts of three arable and two forest soils were investigated for their N compounds. In the arable soils only about 3% of the total organic N extracted by EUF was free amino acids; about 23%–55% consisted of amino N (hydrolysable N) and the rest was non-hydrolysable N. The two forest soils contained higher amounts of EUF-extractable organic N compared with the arable soils. In the two forest soils the content of free amino-acid N amounted to 8% and 11% of the EUF organic N, and the proportion of hydrolysable N from total EUF-organic N was 41% and 46%. It is suggested that the amino-acid N and the hydrolysable N can be easily mineralized.     

Effect of potassium fertilizer composition on the potassium status of soddy-podzolic soils under model experimental conditions

A model experiment was conducted with samples from arable horizons of loamy sandy and loamy soddy-podzolic soils under laboratory conditions. The samples were stored with KCl, K₂SO₄, and Potassium-E was added at rates of 240 and 960 kg/ha under alternating moistening and drying for 90 days. The contents of nonexchangeable, exchangeable, and easily exchangeable potassium and the K⁺ activity in 1: 2.5 water suspensions were measured in the original samples and after the end of the experiment. The contents of nonexchangeable, exchangeable, and easily exchangeable potassium were found to not be reliably affected by the composition of potassium fertilizers; the K⁺ activity was lower when potassium was added as K₂SO₄ than in the cases of KCl and Potassium-E.     

Changes in 15N abundance and amounts of biologically active soil nitrogen

 Estimation of the capacity of soils to supply N for crop growth requires estimates of the complex interactions among organic and inorganic N components as a function of soil properties. Identification and measurement of active soil N forms could help to quantify estimates of N supply to crops. Isotopic dilution during incubation of soils with added ¹⁵NH₄ ⁺ compounds could identify active N components. Dilution of ¹⁵N in KCl extracts of mineral and total N, non-exchangeable NH4₄ ⁺, and N in K₂SO₄ extracts of fumigated and non-fumigated soil was measured during 7-week incubation. Samples from four soils varying in clay content from 60 to 710 g kg^–1 were used. A constant level of ¹⁵N enrichment within KCl and K₂SO₄ extracted components was found at the end of the incubation period. Total N, microbial biomass C and non-exchangeable NH₄ ⁺ contents of the soils were positively related to the clay contents. The mineralized N was positively related to the silt plus clay contents. The active soil N (ASN) contained 28–36% mineral N, 29–44% microbial biomass N, 0.3–5% non-exchangeable NH₄ ⁺ with approximately one third of the ASN unidentified. Assuming that absolute amounts of active N are related to N availability, increasing clay content was related to increased N reserve for crop production but a slower turnover. Received: 7 July 1998     

Etude de la nutrition potassique du sorgho II‐ incidence du remplacement du potassium par le sodium sur la teneur en acides organiques des feuilles

Abstract

An Investigation was conducted to determine the content and distribution of total and DTPA‐extractable Zn in the genetic horizons of 72 agriculturally important soils from the six major mineral soil areas in Louisiana.

The concentration of total Zn appeared to vary more with the clay constituents of the soils and the amount of the element in the parent materials than with soil depth. The majority of the soils had the largest amounts of total Zn in the subsurface horizons. The range in total Zn for all soils and horizons was from 7.0 to 150.0 ppm.

The DTPA‐extractable Zn in all of the soils and horizons ranged from 0.08 to 4.22 ppm. In the majority of the soil profiles the highest concentration of extractable Zn was in the surface horizons. There was a decrease in the extractable Zn with increasing soil depth. The alluvial soils along the Ouachita and Mississippi Rivers, and the Mississippi Terrace soil areas contained relatively large amounts of DTPA‐extractable Zn.

In some soils the extractable Zn significantly correlated with total Zn. There was also a close relationship between extractable Zn and organic matter content, especially in the Ap horizons.     

Errata

The content of fixed ammonium was analyzed for 12 samples of upland soils, including Saline soils, Sols lessives, Meadow soils, Black-colored soils, and Dark-brown forest soils, collected from Jilin and Liaoning provinces, Northeast China. The content of fixed NH₄ ⁺ -N ranged from 0.11 to 0.27 g kg^-1 and no appreciable differences among the soil types were observed. Fixed NH₄ ⁺-N accounted for 9 to 23% of total N in the Ap horizons.     

Die Bedeutung von hohen Aluminiumgehalten für die Humusanreicherung in sauren Waldböden

The role of aluminium on humus accumulation in acid forest soils The impact of soil-borne aluminum on humus accumulation was investigated in a forest soil of the chestnut zone (Castanea sativa) in southern Switzerland (Ticino). Soil samples of two soils formed on bedrocks which differ mainly in their aluminum content were extracted with HNO₃, NH₄Ac.-EDTA, NH₄Cl, KCl, and NH₄F-HCl and analyzed for the most abundant elements. On gneiss which contains up to about 10% of total aluminum the common soil type in this area is a Cryptopodzol. This soil is similar to the nonallophanic Udands. It is rich in wellhumified organic matter and shows dark-colored A_h-, A(E)- and B_h-horizons. The soil samples of these horizons are extremely rich in nonexchangeable aluminum which is, however, extractable with NH₄Ac.-EDTA. It is assumed that this Al is intimately bound to the organic matter. The soil samples of these horizons contain large amounts of HNO₃-extractable phosphorus. Up to 90% of this P appears in the organic fraction. The content of NH₄F-HCl-extractable P is only 0.7 to 3.4 mg/kg. It is concluded that due to excessive Al in the organic matter the humus mineralization is inhibited compared to the Haplumbrepts of the region.     

土壤微生物体氮测定方法的研究

用熏蒸-0.5mol/LK2SO4 直接浸取NH4+-N法 (简称薰蒸 铵态氮法 ) ,熏蒸 淹水培养法和熏蒸 通气培养法测定了有机质、全氮和C/N比差异较大的 15种土壤的铵态氮增量 (FN)。结果表明 ,它们之间有极显著的正相关 ,在反映土壤微生物体氮上有相同趋势。两种培养方法测定的FN 近乎一致 ,由此而计算的微生物体氮也几乎相同。对红油土铵态氮法测定值仅为两种培养法的 1/ 10。把铵态氮法中的FN 校正后 ,其结果与 2种培养法测定的微生物体氮同样近乎一致。用 3种方法测定的微生物体氮均与土壤有机碳存在显著正相关性。淹水培养和铵态氮法水分条件易控制 ,又无NH3的挥发损失 ,比通气培养法更加优越。对培养试验和长期肥料定位试验的土样测定结果表明 ,土壤中易矿化新鲜有机物料也会使熏蒸 淹水培养法测定的FN 显著下降 ,由此而计算的微生物体氮也显著减少 ,但熏蒸 铵态氮法测定的FN 不受新鲜有机物质的影响。与土壤微生物数目进行比较后发现 ,土壤中含易分解有机物质少或微生物体氮含量低时 ,选用熏蒸 淹水培养法测定误差小 ;当土壤中富含新鲜有机物质时 ,熏蒸 铵态氮法测定的结果更加可靠。用这两种方法在同类土壤上测定的FN 的比值相对稳定 ,微生物体氮 (BN)的平均比值为 0.98～1.01,不受施肥的影响     

Microbial biomass and mineralization-immobilization of nitrogen in some agricultural soils

Summary The chloroform fumigation-incubation method (CFIM) was used to measure the microbial biomass of 17 agricultural soils from Punjab Pakistan which represented different agricultural soil series. The biomass C was used to calculate biomass N and the changes occurring in NH₄ ⁺-N and NO₃ ^–-N content of soils were studied during the turnover of microbial biomass or added C source. Mineral N released in fumigated-incubated soils and biomass N calculated from biomass C was correlated with some N availability indexes.The soils contained 427–1240 kg C as biomass which represented 1.2%–6.9% of the total organic C in the soils studied. Calculations based on biomass C showed that the soils contained 64–186 kg N ha^–1 as microbial biomass. Immobilization of NCO₃ ^–-N was observed in different soils during the turnover of microbial biomass and any net increase in mineral N content of fumigated incubated soils was attributed entirely to NH₄ ⁺-N.Biomass N calculated from biomass C showed non-significant correlation with different N availability indexes whereas mineral N accumulated in fumigated-incubated soils showed highly significant correlations with other indexes including N uptake by plants.     

太湖地区主要土壤中的固定态铵及其有效性

测定了太湖地区主要土壤中固定态铵的储量和表土的固铵能力,并通过盆栽试验研究了它们的有效性。土壤的固定态铵含量和表土的固铵能力因母质而异,长江冲积物发育的土壤最高,次为黄土状物质的,第四纪红色粘土的最低。各土壤0—20厘米土层中的固定态铵总量平均占全氮总量的18.5%,0—100厘米土体中占34%。各土壤“固有的”固定态铵的有效性差异较大,视土层等的不同,在0—13%间。“新固定”的来自肥料或土壤有机质矿化释出的铵则很高,一般均能被当季作物完全吸收利用。渍水条件并不能提高固定态铵的有效性。讨论了铵的固定作用在土壤氮素肥力中的意义;指出,由于铵的固定作用和不同土壤的固铵能力各异,常用的淹水培育法所得到的土壤氮素矿化量值不但一般偏低,而且难于进行相互比较。     

Fixation and defixation of ammonium in soils: a review

Fixed NH₄⁺ (NH₄⁺ _f) and fixation and defixation of NH₄⁺ in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH₄⁺ _f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH₄⁺ _f does not necessarily reflect the fraction that is truly available to plants. The content of native NH₄⁺ _f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows that the NH₄⁺ _f-N content amounts to 10–90 mg kg⁻¹ in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg⁻¹ in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg⁻¹ in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH₄⁺ _f are mainly due to the fact that some investigators distinguished between native and recently fixed NH₄⁺ while others did not. Recently fixed NH₄⁺ is available to plants to a greater degree than the native NH₄⁺ _f, and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed NH₄⁺ suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH₄⁺ defixed during a growing season varied greatly within the groups of silty (20–200 kg NH₄⁺-N ha⁻¹ 30 cm⁻¹) as well as clayey (40–188 kg NH₄⁺-N ha⁻¹ 30 cm⁻¹) soils. The pool of recently fixed NH₄⁺ may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from soils.     

Interaction of methyl nitrite with the inorganic and organic fractions of soils

The reactions of methyl nitrite (CH₃ONO), a gaseous product of NO^?₂ decomposition in soils, were studied by exposure of soils in closed vessels to the gas. The N transformations occurring in soils at different soil-water states were assessed by measuring CH₃ONO and other gaseous forms of N in the gas space, soil inorganic N (NH₄⁺, NO^?₂, NO₃^?) and incorporation of CH₃O¹⁵NO into the soil organic N fraction. The initial rate of uptake of CH₃ONO increased with decreasing soil-water content, but the rate of hydrolysis decreased as soil-water content decreased below – 33kPa matric potential. Uptake was not affected by y-irradiation of soils. Adsorption isotherms conformed to the Langmuir equation in each of 22 oven-dry soils studied. Langmuir adsorption maxima were positively correlated with the clay contents of the soils, and adsorption was reversible to some extent at all soil-water states. Small amounts of added CH₃ONO were recovered as N₂ and N₂O and as ¹⁵NH₄⁺ in γ-irradiated soils. From 60 to 72% of added CH₃O¹⁵NO was recovered by Kjeldahl digestion; this was indicative of a chemical reaction with soil organic matter. The results suggest that the physical process of adsorption of CH₃ONO by clay minerals and the chemical fixation of CH₃ONO by soil organic matter are key factors controlling the atmospheric concentration of CH₃ONO, and that the combined effect of these processes, together with hydrolysis in the soil solution, will inhibit the emission of CH₃ONO formed in N-fertilized soils.     

Arylamidase Activity as an Index of Nitrogen Mineralization in Soils

Abstract

The enzyme arylamidase [EC 3.4.11.2] catalyzes the hydrolysis of N‐terminal amino acids from arylamides. Because it has been proposed that this enzyme may play a major role in nitrogen (N) mineralization in soils, studies were carried out using short‐term laboratory incubations under aerobic and anaerobic conditions and chemical hydrolysis of soil organic N to assess the N mineralization in a range of 51 soils from six agroecological zones of the North Central region of the United States. The enzyme activity was assayed at its optimal pH value. With the exception of the values obtained for field‐moist soils incubated under anaerobic conditions, the amounts of N mineralized by all the biological and chemical methods studied were significantly correlated with arylamidase activity, with r values of 0.54*** for the amounts of inorganic N produced under aerobic incubation, of 0.44** for anaerobic incubation of air‐dried soils, of 0.53*** and 0.55*** for the amounts of ammonium (NH₄ ⁺)‐N released by steam distillation with PO₄‐B₄O₇ for 4 and 8 min, respectively; and of 0.49*** and 0.53*** for the amounts of NH₄ ⁺‐N released by steam distillation with disodium tetraborate (Na₂B₄O₇) for 4 min or 8 min, respectively. The amounts of N extractable with hot potassium chloride (KCl) were most significantly correlated with arylamidase activity (r=0.56***). Arylamidase activity was significantly correlated with organic carbon (C) (r=0.49***), organic N (r=0.55***), and fixed ammonium (NH₄ ⁺)‐N (r =0.42**).     

农田土壤中氮同位素分级与硝化能力的关系研究

A laboratory-based aerobic incubation was conducted to investigate nitrogen(N) isotopic fractionation related to nitrification in five agricultural soils after application of ammonium sulfate((NH4)2SO4). The soil samples were collected from a subtropical barren land soil derived from granite(RGB),three subtropical upland soils derived from granite(RQU),Quaternary red earth(RGU),Quaternary Xiashu loess(YQU) and a temperate upland soil generated from alluvial deposit(FAU). The five soils varied in nitrification potential,being in the order of FAU YQU RGU RQU RGB. Significant N isotopic fractionation accompanied nitrification of NH+4. δ15N values of NH+4 increased with enhanced nitrification over time in the four upland soils with NH+4 addition,while those of NO-3 decreased consistently to the minimum and thereafter increased. δ15N values of NH+4 showed a significantly negative linear relationship with NH+4-N concentration,but a positive linear relationship with NO-3-N concentration. The apparent isotopic fractionation factor calculated based on the loss of NH+4 was 1.036 for RQU,1.022 for RGU,1.016 for YQU,and 1.020 for FAU,respectively. Zero- and first-order reaction kinetics seemed to have their limitations in describing the nitrification process affected by NH+4 input in the studied soils. In contrast,N kinetic isotope fractionation was closely related to the nitrifying activity,and might serve as an alternative tool for estimating the nitrification capacity of agricultural soils.