Chemical fixation of ammonia to soil organic matter after application of urea

Chemical fixation of NH₃ to soil organic matter was studied in two Swedish soils with different contents of organic matter: a clay soil with 2.3% C and an organic soil with 36.6% C. ¹⁵N‐labelled urea was applied at different rates to both sterilized and non‐sterilized soils. After 10 days, the soils were extracted and washed with K₂SO₄ and determined for total N and atom% ¹⁵N excess. Urea N was recovered as non‐extractable N in sterilized soil corresponding to 9.7% of supplied ^l5N‐labelled urea in the organic soil and 2.2% in the clay soil. Since no biological immobilization is thought to occur in the sterile soil, this non‐extractable N is suggested to be chemically fixed to soil organic matter. Owing to urea hydrolysis in the clay soil, pH increased from 6.3 to 9.3 and in the organic soil from 5.7 to 6.9 and 8.8, respectively, at the low and high urea supply.     

Carbon and nitrogen dynamics in a forest soil amended with purified tannins from different plant species

Tannins are purported to be an important factor controlling nitrogen cycling in forest ecosystems, and the ability of tannins to bind proteins in protein-tannin complexes is thought to be the primary mechanism responsible for these effects. In this study, we examined the influence of well-characterized tannins purified from five different plant species on C and N dynamics of a forest soil A horizon. Tannic acid, a commonly used and commercially available hydrolyzable tannin (HT), and cellulose were also included for comparison. With the exception of tannins from huckleberry (Vaccinium ovatum), the amendments increased respiration 1.4-4.0 fold, indicating that they were acting as a microbial C source. Tannic acid was significantly more labile than the five purified tannins examined in this study. All treatments decreased net N mineralization substantially, through greater N immobilization and decreased mineralization. The six tannins inhibited gross ammonification rates significantly more than cellulose. This suggests that added tannins had effects in addition to serving as an alternative C source. Tannins purified from Bishop pine (Pinus muricata) were the only tannins that significantly inhibited potential gross nitrification rates, however, rates were low even in the control soil making it difficult to detect any inhibition. Differences in tannin structure such as condensed versus HTs and the hydroxylation pattern of the condensed tannin B-ring likely explain differences observed among the tannin treatments. Contrary to other studies, we did not find that condensed tannins were more labile and less inhibitory than HTs, nor that shorter chained tannins were more labile than longer chained tannins. In addition to supporting the hypothesis that reduced N availability in the presence of tannins is caused by complexation reactions, our data suggests tannins act as a labile C source leading to increased N immobilization.     

灌丛化对干旱区草地土壤有机碳化学结构和热稳定性的影响

在典型的干旱区新疆,选取沿海拔分布的4类草地,使用固态¹³C核磁共振技术与热分析技术研究了灌丛化对草地土壤有机碳(SOC)化学结构和热稳定性的影响。结果表明：灌丛间的芳香碳比例沿海拔从温性荒漠到山地草甸逐渐降低。在温性荒漠、温性草原化荒漠、温性荒漠草原和山地草甸,灌丛下烷基碳/烷氧碳的比值相对于灌丛间分别增加了0.10、0.09、0.03、0.21。低海拔的温性荒漠和温性草原化荒漠的热易分解SOC质量(较低温度下分解的SOC)与SOC总质量的比值(%Exo₁)、SOC分解一半时的温度(TG-T₅₀)和SOC在能量释放一半时对应的温度(DSC-T₅₀)显著低于高海拔的温性荒漠草原和山地草甸。在草原化荒漠、荒漠草原和山地草甸中,灌丛下的%Exo₁和DSC-T₅₀均高于灌丛间,而TG-T₅₀低于灌丛间。在温性荒漠,从灌丛间到灌丛下,低温时SOC燃烧释放出的能量占总燃烧能量(Q)的比例减小,而高温时SOC燃烧释放出的能量增加。本研究结果表明灌...     

Changes in some enzyme activities and the nicotinamide nucleotide coenzymes in barley seedlings during vernalization

Respiratory metabolism was investigated by determining the following enzyme activities and nicotinamide nucleotide coenzyme contents in barley shoots (Hordeum vulgare L., var. Akashinriki) during vernalization : glucose-6-phosphate dehydrogenase, phosphoglucoisomerase, enolase, isocitrate dehydrogenase, malate dehydrogenase, and glutamic dehydrogenase. The activities of glucose-6-phosphate de hydrogenase and phosphoglucoisomerase in vernalized shoots were slightly lower than those in non-vernalized samples. Malate dehydrogenase activity increased gradually in vernalized shoots and was always higher than in non-vernalized shoots. Activation was found in enolase, isocitrate dehydrogenase and glutamic dehydrogenase after a long vernalization treatment.

The contents of total nicotinamide nucleotide coenzymes increased during the early germination stage in both treatments, then decreased gradually in the succeeding stage.     

Aluminum concentrations in sclerotia from a buried humic horizon of volcanic ash soils in Mt. Myoko,Central Japan

The morphology and chemical composition of fungal sclerotium-like grains collected from the buried humic horizon of volcanic ash soil in Mt. Myoko were examined using a scanning electron microscope (SEM), energy dispersion xray micro-analyzer (EDX), and electron probe micro-analyzer (EPMA). A high C content, low level of Si and high concentration of Al characterized the grains considered to correspond to the sclerotia of Cenoccocum graniforme. The ²⁷Al MAS NMR spectrum of the sclerotia showed the existence of 6- and 4-coordinated Al. X-ray diffraction analyses supported the presence of amorphous Al (ex. Al-humus complex) in the sclerotia.     

应用15N核磁共振技术对苯聚合物结合蛋白中氮形态的研究

Phenolic polymers synthesized by reactions by reactions of p-benzoquinone with 15N-labelled protein or (15NH4)2SO4 were studied by using 15N CP-MAS NMR technique in combination with chemical approaches.Results showed that more than 80% of nitrogen in quinone-protein polymers was in the form of amide with some present as aromatic and /or aliphatic amine and less than 10% of nitrogen occurred as heterocyclic N.The nitrogen distribution in the non-hydrolyzable residue of the quinone-protein polymers was basically similar to that of soil humic acid reported in literature with the exception that a higher proportion of N as heterocyclic N and aromatic amine and a lower proportion of N as amide and aliphatic amine were found in the former than in the latter,More than 70% of total nitrogen in quinone-(NH4)2OS4 polymer was acid resistant ,of which about 53% occurred as pyrrole,nitrile and imion type N.The possible roles of the reactions of phenols or quinones with proteins in the formation of humic acid.especially the non-hydrolyzable nitrogen in humicacid,are discussed.     

Nutrient Solution and Nutrient Soil Solution Parameter Evolution in Tomato with Dynamic Fertigation under Saline Conditions

This trial was carried out to study the evolution of the nutrient parameters of the nutrient solution applied to tomato plants (Lycopersicum sculentum Mill. Forteza) cultivated in Mediterranean greenhouse conditions under different fertigation management models. The dynamic model is based on soil water content, which was measured by tensiometers, and on soil solutions obtained with suction cups (porous ceramic cup water samplers). The local traditional method consists of following technical recommendations, and the classical model requires the estimation of Crop Factor (Kc) and knowing the nutrient extraction. Nutrient solution and water applied are functions of the fertigation management criteria. The water used for fertigation was classified as C₄-S₃ according to the Riverside classification system. The cultivation period lasted from 15 August to 20 April. The nutrient parameters studied in nutrient and soil solution were pH, electrical conductivity (EC), nitrate (NO₃ ^?), phosphate (H₂PO₄ ^?), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺), and chloride (Cl^?). The pH shows similar trends under the different treatments. Electrical conductivity is in the range of 2.8–4.5 dS m^?1. Chloride, sodium, magnesium, and sulfate are exclusively modified by the salt concentration in the irrigation water, so it can be assumed that the three treatments vary equally. Nitrate, potassium, phosphate, and calcium are modified depending on each fertigation management method. Soil solution is modified by the nutrient solution applied. Dynamic management allows low nutrient concentration in the nutrient solution to be maintained and keeps soil nutrient concentration low, reducing fertilizer losses and therefore aquifer contamination.     

Effects of Salinity and Nitrogen on Growth,Contents of Pigments,and Ion Accumulation of a Euhalophyte Suaeda Salsa in an Intertidal Zone and on Saline Inland

The different responses of two populations of Suaeda salsa (Linn.) Pall. (saline seepweed) from an intertidal zone and a saline inland zone to salinity [1 or 500 mM sodium chloride (NaCl)] and nitrogen [N; 0.05, 1, or 10 mM nitrate (NO₃ ^?)‐N] were investigated. Greater NO₃ ^?‐N supply (10 mM) increased shoot dry weight for the two populations of S. salsa, especially for S. salsa from the saline inland zone. Greater NO₃ ^?‐N supply (10 mM) increased the concentrations of chlorophyll and carotenoid in leaves and the NO₃ ^? and potassium (K⁺) concentrations in shoots for both populations. Greater NO₃ ^?‐N supply (10 mM) increased shoot Na⁺ in S. salsa from the intertidal zone. In conclusion, S. salsa from the saline inland zone is more responsive to NO₃ ^?‐N supply than the intertidal population. Greater NO₃ ^?‐N supply can help the species, especially the intertidal population, to grow and to mediate ion homeostasis under high salinity.     

The in vivo and in vitro effects of Ca2+ and Al3+ upon ATPases from barley roots

Experiments were performed to test the effect of Ca²⁺ and Mg²⁺ upon ATPases (E.C. 3.6.1.3) from barley roots (Hordeum distichon L. cv. MULTUM) that had or had not taken up Al³⁺. Furthermore, the effect of the uptake period was examined. With longer duration of the Al³⁺ uptake, the activity of the ATPases dropped, independently of whether they were activated by Ca²⁺ or by Mg²⁺. Mg²⁺ stimulated the activity of the ATPases if no Al³⁺ had been taken up with lacking Ca²⁺ in the assay. If Al³⁺ had been taken up no additional activation by Mg²⁺ to the Ca²⁺ stimulation could be observed, and in some cases Mg²⁺ decreased the Ca²⁺ stimulation.     

Kinetics of ammonia volatilization of anhydrous ammonia applied to a vertisol as influenced by Farm Yard manure,sorbed cations and cation exchange capacity

Abstract

In laboratory experiments, effects of added Farm Yard Manure (FYM), sorbed cations and cation exchange capacity (CEC) on NH₃ volatilization of anhydrous ammonia applied to a Vertisol were studied at 0.3 bar soil Moisture Tension and 25 ± 1°C. On addition of FYM or with increase in CEC the volatilization of retained ammonia was reduced while the effect of the sorbed cations was in the order : K‐Soil > Na‐Soil > Ca‐Soil > Mg‐Soil. The results suggest that the volatilization of retained NH₃ followed First order reaction kinetics, with a rapid rate of volatilization in the initial 8 to 10 h followed by a retarded rate up to 144 h.     

Nitrapyrin effectiveness in reducing nitrous oxide emissions decreases at low doses of urea in an Andosol

In the tropics,frequent nitrogen(N)fertilization of grazing areas can potentially increase nitrous oxide(N₂O)emissions.The application of nitrification inhibitors has been reported as an effective management practice for potentially reducing N loss from the soil-plant system and improving N use efficiency(NUE).The aim of this study was to determine the effect of the co-application of nitrapyrin(a nitrification inhibitor,NI)and urea in a tropical Andosol on the behavior of N and the emissions of N₂O from autotrophic and heterotrophic nitrification.A greenhouse experiment was performed using a soil(pH 5.9,organic matter content 78 g kg^-1,and N 5.6 g kg^-1)sown with Cynodon nlemfuensis at 60%water-filled pore space to quantify total N₂O emissions,N₂O derived from fertilizer,soil ammonium(NH₄⁺)and nitrate(NO₃^-),and NUE.The study included treatments that received deionized water only(control,NI).No significant differences were observed in soil NH₄⁺content between the UR and UR+NI treatments,probably because of soil mineralization and NO₃^-produced by heterotrophic nitrification,which is not effectively inhibited by nitrapyrin.After 56 d,N₂O emissions in UR(0.51±0.12 mg N₂O-N concluded that the soil organic N mineralization and heterotrophic nitrification are the main processes of NH₄⁺and NO₃^-production.Additionally,it was found that N₂O emissions were partially a consequence of the direct oxidation of the soil's organic N via heterotrophic nitrification coupled to denitrification.Finally,the results suggest that nitrapyrin would likely exert significant mitigation on N₂O emissions only if a substantial N surplus exists in soils with high organic matter content.     

Growth,Nitrate Accumulation,and Macronutrient Concentration of Pakchoi as Affected By External Nitrate-N: Amino Acid-N Ratio

ABSTRACT

A study was carried out to determine the influence of nitrogen (N) sources on the growth, nitrate (NO₃ ^?) accumulation, and macronutrient concentrations of pakchoi (Brassica chinensis L.) in hydroponics. Plants were supplied with NO₃ ^? and two amino acids (AA), glutamic acid (Glu), and glutamine (Gln), at six NO₃ ^?-N/AA-N molar ratios: (1) 100:0, (2) 80:20, (3) 60:40, (4) 40:60, (5) 20:80, (6) 0:100. The total N concentration was 12.5 mmol/L for all treatments in nutrient solutions. Both AAs reduced plant growth with decreasing NO₃ ^?-N/AA-N ratios, but the reduction was for Gln than for Glu. At 80:20 NO₃ ^?-N: Gln-N ratio, the Gln had no significant effect on pakchoi fresh weights. Decreasing NO₃ ^?-N/AA-N ratios reduced NO₃ ^? concentrations in the plant, regardless of AA sources. Adding an appropriate portion of AA-N to nutrient solutions for hydroponic culture increased concentrations of N, phosphorus (P), and potassium (K) in pakchoi shoots. Substituting 20% or less of NO₃ ^?-N with Gln-N in hydroponic culture will increase the pakchoi quality by reducing NO₃ ^? concentration and increasing mineral nutrient concentrations in shoots without significant reduction of crop yields.     

Nitrogen turnover rates in a riparian fen determined by 15N dilution

Summary Gross rates of N mineralization, assimilation, nitrification, and NO _in3 ^sup- reduction were determined in soil from a wet riparian fen by 1-day incubations of soil cores and slurries with ¹⁵N-labelled substrates. N mineralization transformed 0.1% of the total organic N pool daily in the soil cores, of which 25% was oxidized through autotrophic nitrification and 53%–70% was incorporated into microorganisms. N mineralization and nitrification were markedly inhibited below 5 cm in soil depth. At least 80% of the NO _in3 ^sup- reduction in aerated cores occurred through dissimilatory processes. Dissimilatory reduction to NH _in4 ^sup+ (DNRA) occurred only below 5 cm in depth. The results show that NH _in4 ^sup+ oxidation was limited by available substrate and was itself a strong regulator of NO _in3 ^sup- -reducing activity. NO _in3 ^sup- reduction was significantly increased when the soil was suspended under anaerobiosis; adding glucose to the soil slurries increased NO _in3 ^sup- reduction by 2.4–3.7 times. Between 3% and 9% (net) of the added NO _in3 ^sup- was reduced through DNRA in the soil slurries. The highest percentage was observed in soil samples from deeper layers that were pre-incubated anaerobically.     

不同形态氮对掌叶半夏生长及块茎主要化学成分影响研究

【目的】本文利用盆栽试验,探讨了不同铵态氮、 硝态氮供应比例对掌叶半夏生长、 相关生理指标及块茎中主要活性成分含量的影响,以期为掌叶半夏的合理施肥、 科学种植提供技术依据。【方法】盆栽试验以蛭石为栽培基质,以掌叶半夏为试验材料,采用不同铵态氮、 硝态氮比例处理,分析不同铵硝比例处理下掌叶半夏叶片中抗氧化保护酶（SOD、 CAT）, 叶片、 块茎中氮代谢关键酶（NR）的活性及块茎中次生代谢产物（MDA、 硝酸盐及主要活性成分）的含量变化。【结果】 1）叶片鲜重、 块茎鲜重及总叶绿素含量总体均随铵态氮比例的升高而呈逐渐增加趋势,其中在全铵营养下,块茎鲜重和总叶绿素含量均达到最高值。2）随着铵态氮比例的升高,植株叶片中SOD、 CAT酶活性呈先升高后降低趋势; 当铵硝比为50∶50时,SOD、 CAT酶活性最高,此时,叶片中NO-3-N含量也达到最高。3）在全铵营养或全硝营养下,MDA含量均高于其他处理; 当铵硝比为50∶50时,MDA累积量最低。4）在全硝营养下,叶片、 块茎中的NR活性均达到最高值,同处理水平下叶片中NR活性要高于块茎; 并且随着铵态氮比例的增加叶片中NR活性呈逐渐降低的趋势,而块茎中的NR活性则呈逐渐增加的趋势。5）块茎中主要活性成分的累积更依赖于两种氮素的配施作用,在较高的铵态氮配施处理下（75∶25时）,总生物碱、 总有机酸及腺苷的积累量均取得最高值。【结论】适宜比例的铵硝配比可以促进掌叶半夏生长及产量的形成,其促进效果也显著高于全硝营养; 当铵硝比为50∶50时,其植物体内的相关酶活性也达到最高,说明适宜的铵硝配比能减轻膜质过氧化对植株细胞膜造成的损伤; 同时,较高的NH+4-N也有利于块茎中主要活性成分的积累,尤以铵硝比为75∶25时,累积效果最显著。     

Potential importance of bacteria and fungi in nitrate assimilation in soil

Soil microorganisms can use a wide range of N compounds but are thought to prefer NH₄⁺. Nevertheless, ¹⁵N isotope dilution studies have shown that microbial immobilization of NO₃⁻ can be an important process in many soils, particularly relatively undisturbed soils. Our objective was to develop a method for measuring NO₃⁻ immobilization potential so that the relative contributions of bacteria and fungi could be determined. We modified and optimized a soil slurry method that included amendments of KNO₃, glucose, and methionine sulfoximine (an inhibitor of N assimilation) in the presence of two protein synthesis inhibitors: chloramphenicol, which inhibits bacteria, or cycloheximide, which inhibits fungi. By adding ¹⁵N-labeled KNO₃, we were able to measure gross rates of NO₃⁻ production (i.e., gross nitrification) and consumption (i.e., gross NO₃⁻ immobilization). We found that bacteria, not fungi, had the greatest potential for assimilating, or immobilizing, NO₃⁻ in these soils. This is consistent with their growth habit and distribution in the heterogeneous soil matrix.     

The Leaching Behaviour and Balances of Nitrogen and Other Elements under Spring Wheat in Lysimeter Experiment 1985–92

Abstract

In a lysimeter study it was found that moderate rates of ammonium nitrate increased utilization percentages in spring wheat, and the leaching was 10% or less of added N. Over-optimal rates reduced utilization percentages and increased leaching to almost 50% of the highest doses. Late split application of calcium nitrate increased the percentage of N in grain. Furthermore, leaching of N was not reduced, but occurred somewhat later in the fall and winter seasons. Leaching of Cl^? was more rapid and that of SO₄ ^2- was delayed relative to the leaching of NO₃ ^?. Rather large negative N balances were obtained, also after over-optimal application rates, and total N content of the soil was reduced. Compared with the N₀ treatment, differences in soil N residues amounted to 15–25% of added N in seven years. Gaseous losses had apparently taken place both from the added N and from soil N according to the total-N analysis.     

祁连山东段青海云杉林土壤有效氮研究

通过野外取样和实验室分析,对祁连山东段青海云杉林的土壤有效氮状况进行了研究。结果表明:(1)青海云杉林0—40 cm土层土壤总有效氮(铵态氮+硝态氮)的变化范围为17.26~20.76 mg/kg,铵态氮是土壤有效氮的主要存在形态,其含量占到总有效氮的66.72%以上;(2)土壤铵态氮含量随土层深度的增加而较少,硝态氮则无明显的变化规律,而且土壤硝态氮较土壤铵态氮对土壤微环境敏感;(3)土壤铵态氮与有机质相关关系显著(p<0.05),土壤硝态氮与有机质无显著相关性。研究区铵态氮为土壤有效氮的主要赋存形式,它在很大程度上取决于该区土壤pH中性值,较低温度和较高的水分含量。     

Investigations on the radioactive contamination of crop plants as a result of H-bomb detonation (Part 2) Root and foliage uptake of “Bikini ash”

The Foliar Uptake by Squash Plant

The radioactive ash for experimental use, hereafter referred to as “Bikini ash”, was prepared by igniting the heavily contaminated substances on board No. 5 Fukuryu Maru at about 650°C, followed by sifting through a 100 mesh sieve. On ignition some parts of the fission products, particularly iodine, ruthenium and tellurium would have possibly been lost to the air.     

Development of a Soil N Test for Fertilizer Requirements for Corn Production in Quebec

Corn requires high nitrogen (N) fertilizer use, but no soil N test for fertilizer N requirement is yet available in Quebec. Objectives of this research were (1) to determine the effects of soil nitrate (NO₃ ^?)-N, soil ammonium (NH₄ ⁺)-N, and N fertilizer rates on corn yields and (2) to determine soil sampling times and depths most highly correlated with yields and fertilizer N response under Quebec conditions. Soil samples were taken from 0- to 30-cm and 30- to 60-cm depths at seeding and postseeding (when corn height reached 20 cm) to determine soil NH₄ ⁺ and NO₃ ^? in 44 continuous corn sites fertilized with four rates of N in two replications using a quick test (N-Trak) and a laboratory method. The N-Trak method overestimated soil NO₃ ^?-N in comparison with the laboratory method. Greater coefficients of determination were observed for soil NO₃ ^?-N analyses at postseeding compared with seeding.