氮素营养水平对大豆氮素积累及产量的影响

以“东农47”为试材,采用15N 标记的 (NH4)2SO4作为氮源,利用砂培方式研究了氮素营养水平对大豆氮素积累及产量的影响。结果表明,随外源氮水平增加,大豆植株氮素积累量和产量呈先增加后降低的变化趋势,当营养液氮浓度为50 mg/L时,植株氮素积累量和子粒产量最大。在 R4和 R5 期补充氮肥的供给明显增加植株对氮的积累,并能显著提高大豆产量。大豆生长需要一定量的“启动氮”,“启动氮”的作用维持到V3期对大豆氮的积累和产量形成效果最好。随外源氮水平增加,大豆吸收外源氮的比例增加,根瘤固氮所占比例降低,外源氮和根瘤固氮积累量随外源氮水平增加呈先增加后降低的变化趋势。当氮浓度为100 mg/L时,有利于植株对外源氮的吸收,当氮浓度为50 mg/L时,有利于根瘤固氮的积累,“启动氮”的作用维持到V3期根瘤固氮的积累明显增加; 在R4和R5期补充外源氮的供给可以显著增加对外源氮利用,以R5期效果最好。     

东北黑土区大豆生长、结瘤及产量对氮、磷的响应

氮肥和磷肥显著影响大豆的结瘤和产量。然而在土壤肥力较高、速效养分有效性差的东北地区,有关氮肥和磷肥施用量对大豆结瘤和产量影响的研究较少。本试验采用裂区田间试验,设置3个氮（N）水平（0、20 和 50 kg/hm2）和 3 个磷（P）水平（0、 20 和 40 kg/hm2）,研究氮、 磷及其交互作用对大豆生长发育、 结瘤特征及产量的影响。结果表明, 单施氮肥大豆生物量和产量随着施氮量的增加而增加,而根瘤数量、 干重、 大小和结瘤指数呈逐渐下降的趋势。单施磷肥促进大豆生物量、 产量、 根瘤数量、 干重、 大小和结瘤指数的增加,但其增幅低于施氮处理下的增幅。氮磷对大豆生长和产量促进作用高于单施氮和单施磷处理,但差异不显著;氮磷处理下的根瘤数量、 干重、 大小和结瘤指数低于单施磷处理;氮磷处理下N2（N 50 kg/hm2）处理下的大豆根瘤数量、 干重、 大小和结瘤指数高于N1处理（N 20 kg/hm2）下的,随着施磷量的增加大豆根瘤数量、 干重、 大小和结瘤指数增加,施磷能够抵消氮对大豆根瘤产生和形成的抑制。氮、 磷及其交互作用对大豆根瘤的影响都是直接的,并且不是通过促进大豆生长间接促进的。因此氮和磷均是限制东北地区大豆结瘤和产量的因素,但氮是主导因素。若要获得大豆高产,氮肥施用量需要控制在50 kg/hm2,磷肥在40 kg/hm2;但若想最大的发挥大豆的结瘤固氮功能,那么应该不施或者减少氮肥的施用量到20 kg/hm2,磷肥仍在40 kg/hm2。     

基因型影响磷镁互作下大豆生长及根瘤和菌根性状

  【目的】  明确施加镁肥在不同磷处理的土壤上对不同基因型大豆生长及根瘤和菌根性状的影响。  【方法】  田间试验采用三因素试验设计,设置施P₂O₅ 40 kg/hm2 (P40)和100 kg/hm2 (P100)两个水平,施MgO 0 kg/hm2 (Mg0)和75 kg/hm2 (Mg75)两个水平,磷高效基因型粤春03-3 (YC03-3)和磷低效基因型本地2号(BD2)两个大豆基因型。测定了大豆植株干重、单株结荚数、根系性状、根瘤性状、菌根侵染率以及植株氮、磷、镁含量。  【结果】  P100处理显著增加了两个大豆基因型的植株干重、单株结荚数、总根长、根表面积和体积以及植株氮、磷、镁积累量。施用镁肥,YC03-3在P40和P100处理下植株干重、单株结荚数、植株氮和镁积累量均显著增加,在P100条件下植株磷积累量以及根表面积、根体积、根平均直径显著增加;BD2在P40和P100处理下植株镁积累量显著增加,P40条件下植株氮积累量显著增加。磷和镁处理显著影响大豆与有益微生物的共生。P40条件下,两个大豆基因型的根瘤数和根瘤干重在Mg0和Mg75处理间无显著差异;P100条件下Mg75处理BD2和YC03-3的根瘤数分别较Mg0处理增加了135%和178%,根瘤干重分别增加了308%和197%。Mg0条件下P40处理YC03-3的菌根侵染率较P100增加了31.6%;Mg75条件下P40处理的BD2菌根侵染率较P100增加了15.0%。P40条件下,Mg75提高了BD2菌根侵染率16.3%;P100条件下,Mg75提高了YC03-3菌根侵染率32.1%。主成分分析发现,P100条件下,Mg0与Mg75处理之间差异显著,而P40条件下镁处理之间差异不明显。  【结论】  增施磷肥显著促进了两个大豆基因型的生长,改善了植株氮、磷、镁养分状况。增施镁肥可增加磷高效大豆基因型YC03-3的地上部和根部干重、单株结荚数、植株氮积累量,对磷低效型基因BD2没有显著作用。YC03-3的根瘤密度对施磷和施镁响应较BD2显著。BD2的菌根侵染率在低磷条件下对施镁的反应敏感,而YC03-3的菌根侵染率在P100条件下对施镁反应敏感。由此可见,磷和镁养分之间的互作效应受到大豆基因型的影响。     

氮肥对大豆结瘤固氮、籽粒产量和蛋白质含量的影响

  【目的】  合理施用氮肥不仅可提高大豆结瘤固氮能力,还可减少农业污染,实现大豆生产的高产优质高效。研究施氮时期和施氮量对大豆结瘤固氮、产量及蛋白质含量的影响,为大豆高产优质提供理论基础及科学依据。  【方法】  采用盆栽试验,供试大豆品种为‘东生35’,试验设2个氮肥施用时期(V2期和R1期)和3个氮肥施用量[N 0、5、100 mg/(kg, 土)],表示为N0、N5和N100。在大豆R2期(盛花期)和R5期(鼓粒期)取样分析了地上部干物质积累量、根瘤数量、根瘤干重和固氮酶活性。在R8期(成熟期)调查了大豆籽粒产量和蛋白质含量。  【结果】  施氮时期和施氮量对大豆地上干物质积累、结瘤和固氮能力均有显著影响。不论是V2期还是R1期施氮,大豆地上部干物质积累量均随着施氮量的增加而增加,而根瘤干重、数量则呈降低的趋势。R1期施氮条件下,N100处理的大豆盛花期根瘤数量和根瘤干重比N0分别下降了42.3%和32.8%,而固氮酶活性则均以N5处理最高;V2期施氮条件下,N5处理的大豆固氮酶活性在R2期和R5期较N0处理分别增加15.3%和27.1%。大豆籽粒产量和蛋白质含量均以N5处理最高,籽粒蛋白质含量较N0处理增加了6.3%～9.4%。结构方程结果表明,施氮量正向调控固氮酶活性,间接影响大豆产量;负向调控根瘤数量,间接影响大豆籽粒蛋白质含量。施氮时期直接负向调控大豆籽粒产量,正向调控籽粒蛋白质含量。  【结论】  合理施氮有利于大豆高产优质,早期(V2期)施用氮肥有利于大豆产量提升,而推迟到始花期(R1期)施用氮肥更有利于大豆固氮和籽粒蛋白质含量的增加。盆栽条件下,施氮量对大豆产量和蛋白质含量的影响大于施肥时期,施氮量均以控制在N 5 mg/(kg, 土)为宜。     

不同大豆品种根瘤固氮酶活性与固氮量差异研究

大豆根瘤固氮酶活性与固氮量是衡量大豆固氮能力的重要指标,也是合理施用氮肥的依据.试验采用框栽方法,应用15N示踪技术,研究了不同大豆品种根瘤固氮酶活性与固氮量差异.结果表明:4个供试大豆品种根瘤固氮酶活性、根瘤干重及根瘤固氮潜力都呈现先升后降的变化趋势,但品种间有显著差异;生育期短的大豆品种根瘤固氮酶活性高于生育期长的品种,根瘤干重则相反,生育期越长,根瘤干重越大;根瘤固氮潜力随大豆品种生育期的延长而增加.大豆植株氮素构成品种间存在明显的差异性,随着品种生育期的延长,根瘤固氮所占的比例提高;在大豆品种黑河41氮素构成中,土壤氮和根瘤固氮所占比例相同,其他品种均以根瘤固氮为主,其次是土壤氮,肥料氮所占的比例很低.     

春大豆生长中对不同氮源的吸收利用

利用15N示踪技术和框栽方法,对大豆不同生育期(苗期V4,初花期R1,盛花期R2,结荚初期R4,鼓粒期R5,成熟期R6,收获期R8)各部位及全株氮素来源进行系统的研究。结果表明,在大豆生育前期土壤氮和肥料氮是根、茎、叶片氮素的主要来源,在生育后期根瘤固氮开始增加;随生长大豆荚果氮素中土壤氮所占比例逐渐减小,根瘤固氮所占比例逐渐增加,并在收获期(R8)达到总量的70.6%,肥料氮所占比例一直很低。苗期至初花期(V4~R1)是无机氮营养期,大豆主要依靠土壤氮和肥料氮;初花期至鼓粒期(R1~R5)是无机氮营养与根瘤固氮并行期,既依靠土壤氮和肥料氮,又有根瘤固氮的供应;鼓粒期至收获期(R5~R8)是根瘤固氮营养期,主要依靠根瘤固氮。     

大豆鼓粒期对肥料氮的吸收与分配研究

采用15N分阶段标记的方法,研究了鼓粒期间大豆植株对氮素的同化吸收,尤其是肥料氮在各器官中的积累与分配。结果表明:1)5次标记试验期间积累的氮素总量为291.4 mg/plant,占标记试验Ⅴ结束时(鼓粒末期)大豆植株氮素积累总量的48.9%,说明鼓粒期间的氮素积累对于大豆氮素积累具有重要作用;2)从鼓粒始期到鼓粒末期,大豆植株氮素阶段积累量急剧降低,由标记试验Ⅰ的109.5 mg/plant下降到标记试验Ⅴ的19.6 mg/plant;3)鼓粒期大豆植株所吸收的氮素主要来自根瘤固氮,该部分氮占总同化量的67.4%,而肥料氮只占32.6%;4)根瘤固氮和肥料氮的同化量均随着鼓粒进程的推进而下降,分别由标记试验Ⅰ的67.5和42.0 mg/plant下降到标记试验Ⅴ的10.8和8.8 mg/plant;5)5次标记试验中,不同器官中肥料氮的积累量均表现出一致的规律性,为子粒叶片茎根系荚皮,并且分配到子粒中的肥料氮比例是逐渐增加的,由标记试验Ⅰ的27.9%增加到标记试验Ⅴ的85.0%。     

锰胁迫对大豆氮素积累的影响

采用15N示踪技术与沙培相结合的方法,以最适锰浓度为对照,设置锰缺乏(分别为对照浓度的1/25和1/5作为重度和轻度锰缺乏处理)和锰过量(分别为对照浓度的5倍和25倍作为轻度和重度锰过量处理)4个锰胁迫处理,研究了锰胁迫对大豆氮素积累的影响。结果表明:与对照相比,锰胁迫并未明显影响生育前期大豆植株氮素积累,但对中后期氮素积累起显著抑制作用(P0.01),并且抑制作用随胁迫程度的加深而加重;锰胁迫对苗期(V4)肥料氮的积累无影响,但对其他生育时期肥料氮的积累均表现出不同程度的抑制作用;在整个生育期间,锰胁迫显著抑制了根瘤固氮的积累,大幅度减少了鼓粒期间根瘤固氮的积累;锰胁迫不仅显著减少了成熟期(R8)大豆营养器官和子粒中肥料氮、根瘤固氮、总氮的积累,还在一定程度上增加了营养器官中肥料氮、根瘤固氮、总氮的积累比例,子粒则相应减小。综合分析表明,锰胁迫对大豆肥料氮、根瘤固氮、以及总氮的积累均有抑制作用,抑制效果在大豆生育中后期表现明显,并且锰胁迫改变了成熟期大豆营养器官和子粒中肥料氮、根瘤固氮和总氮的积累比例。本试验所得结果丰富了锰胁迫与大豆氮素营养的相关研究内容,并为进一步的机理研究奠定了基础。     

大豆植株苗期至结荚初期对肥料氮的吸收与分配

采用砂培与15N分阶段标记的方法,研究了苗期至结荚初期大豆植株对氮素的同化吸收,尤其是肥料氮在不同器官和节中的积累与分配。结果表明:(1)苗期至结荚初期大豆植株氮素积累量逐渐增加,由标记试验Ⅰ的64.08g/plant逐渐增加到标记试验Ⅴ的307.17mg/plant;(2)不同器官中肥料氮积累存在差异,叶是苗期至结荚初期肥料氮积累的主要器官,所占比例为55.2%,根系次之为25.9%,茎最小为18.9%;(3)苗期至结荚初期肥料氮积累量和所占比例逐渐减小,而根瘤固氮则逐渐增加,其中苗期至盛花期肥料氮是大豆植株氮素主要来源,盛花期以后以根瘤固氮为主;(4)不同成长程度叶对肥料氮的积累存在差异,表现为成长中叶>新生叶>成熟叶;(5)新生茎叶氮素构成随全株氮素构成的变化而变化,苗期至初花期以肥料氮为主,初花期至结荚初期根瘤固氮逐渐转为主体。     

短期低温对大豆苗期生长和结瘤固氮的影响

采用早熟大豆品种“黑河43”、晚熟大豆品种“东农53”进行盆栽试验,出苗后进行连续7d的低温处理（LT）,昼夜温度设定为13℃/3℃,以25℃/10℃为对照,从大豆出苗28d开始,每7d进行破坏性取样共4次,测定地上部和根干物质量、根瘤生物量、全氮含量及根瘤固氮量,研究苗期短期低温对大豆生长、结瘤和固氮能力的影响。结果表明：（1）大豆出苗后7d短期低温胁迫会延缓大豆生长发育。出苗后28～42d大豆生物量显著低于CK处理,出苗后49d低温胁迫对两个大豆品种生物量均无显著影响。（2）与CK相比,低温对“东农53”和“黑河43”根瘤形成的显著抑制作用分别出现在苗后42d和35d,根瘤数量分别降低了58.8%和72.0%。出苗后49d,低温使“东农53”和“黑河43”根瘤干重分别减少48.9%和48.5%。（3）低温刺激了两个品种大豆的生物固氮能力。在出苗后49d,低温处理“东农53”和“黑河43”的生物固氮量、单位根瘤生物量的固氮量和单个根瘤的固氮量分别增加了89.9%、118.9%,249.3%、172.6%,150.6%、114.2%。生物固氮百分率分别增加了26.4个和24.5个百分点...     

Effects of hairy vetch foliage application on nodulation and nitrogen fixation in soybean cultivated in three soil types

We investigated the effects of applying hairy vetch foliage on nodulation and atmospheric nitrogen (N₂) fixation in soybean cultivated in three soil types in pot experiments. Soybean plants were grown in Gley Lowland soil (GLS), Non-allophanic Andosol (NAS), and Sand-dune Regosol (SDR) with hairy vetch foliage application in a greenhouse for 45 days. In GLS, the nodule number was not influenced by the application, however, nodule dry weight and N₂ fixation activity tended to increase. In NAS and SDR, nodule formation was depressed by foliage application. Soybean plant growth was promoted in GLS and SDR but not in NAS. These promotive effects of hairy vetch foliage application on soybean plant growth in GLS were considered to be mainly caused by the increase in N₂ fixation activity of the nodules, whereas it was considered to be mainly caused by the increase in nitrogen uptake activity of the roots in SDR. The varying effects of hairy vetch foliage application on soybean nodulation may be due to soil chemical properties such as pH and cation exchange capacity, which are related to soil texture. Therefore, we conclude that it is important to use hairy vetch for soybean cultivation based on the different effects of hairy vetch on soybean plant growth in different soil types.     

Effects of changes in applied nitrogen concentrations on nodulation,nitrogen fixation and nitrogen accumulation during the soybean growth period

ABSTRACT

The specific mechanism by which nitrogen application affects nodulation and nitrogen fixation in legume crops remains uncertain. To further study the effects of nitrogen application on soybean nodulation and nitrogen accumulation, three consecutive tests were performed during the VC-V4, V4-R1 (10 days), and R1-R2 (10 days) growth periods of soybean. In a dual-root soybean system, seedlings on one side were watered with a nutrient solution containing NH₄⁺ or NO₃^? as the N source (N+ side), and those on the other side were watered with a nitrogen-free nutrient solution (N- side). During the VC-R2 period, on the N+ side, high nitrogen treatment inhibited nodule growth and nitrogenase activity (EC 1.18.6.1), and the inhibition was significantly increased with increasing high nitrogen supply time (10 days, 20 days). When the high nitrogen treatment time reached 20 days, the specific nitrogenase activity (C₂H₄ μmol^?1 g^?1 nodule dry mass h^?1) was similar to that in the low nitrogen treatment, indicating that the nitrogen fixation capacity per gram of dry mass nodules was almost the same. Therefore, it is assumed that long-term high nitrogen treatment mainly reduces nitrogen fixation by reducing the nodule number. The effect of nitrogen concentration on the roots on the N+ side was greater than that on the N- side. Taken together, these results indicate that nitrogen application affects a contact-dependent local inhibition of root nodule growth, nitrogenase activity, and nitrogen accumulation. The whole plant systematically regulates specific nitrogenase activity, and high nitrogen inhibition is recoverable.     

Variation of nitrogen accumulation and yield in response to phosphorus nutrition of soybean (Glycine max L. Merr.)

Phosphorus (P) is essential macronutrient for soybean [Glycine max (L.) Merr.] growth and function. The objective of this study was to determine effect of phosphorus nutrition (including phosphorus nutrition level and interruption of phosphorus supply) on nitrogen accumulation, nodule nitrogen fixation and yield of soybean plants by ¹⁵N labeling with sand culture. The results showed that they all presented a single peak curve with improvement of phosphorus nutrition level, when phosphorus concentration of nutrient solution was about 31 mg/L, they all reached the maximum and effect of phosphorus nutrition level on nodule nitrogen fixation was lower than that on yield formation level. Interruption of phosphorus supply during soybean growth period, nitrogen accumulation and nodule nitrogen fixation were seriously inhibited, and yield was decreased significantly when interruption of phosphorus supply during V₃-R₁ and R₁-R₅ period, while interruption of phosphorus supply during R₅-R₇ period had no significant effect on nitrogen accumulation, nodule nitrogen fixation and yield. So soybean nitrogen metabolism and yield were sensitive to phosphorus nutrition in the V₃-R₅ period, those were not sensitive to phosphorus nutrition after R₅ period.     

Adequate range of boron nutrition is more restricted for root nodule development than for plant growth in young soybean plant

A pot experiment was conducted under growth chamber conditions to determine the lower and upper critical levels of boron (B) for plant growth, nodule development, and nodule acetylene reduction activity (ARA) in young soybean plants. Plants of a soybean cultivar, Tachinagaha, were grown in pots containing river sand to which a nutrient solution with different B levels was added and were inoculated with Bradyrhizobium japonicum A1017. At 8, 12, and 16 d after sowing (DAS), among the plants supplied with the solution at 0, 1.0, and 2.0 mg B L^-1 , plants with 1.0 mg B L^-1 showed the highest values for dry shoot and fresh root weight, root length, total number of developing nodules and meristematic nodules (DMN), and ARA. At 20 DAS plants grown with 11 B levels (0-2.0 mg L^-1) were compared. The B critical deficiency levels for soybean dry shoot weight, fresh root weight, root length, DMN, number of complete nodules, and ARA were approximately 46, 35, 34, 57, 60, and 50 mg B kg^-1 dry matter, and the critical toxicity levels were approximately 114, 137, 134, 97, 104, and 89 mg B kg^-1 dry matter, respectively. The optimum B levels for the growth characters were approximately 34 to 137 mg B kg^-1 dry matter. The optimum range of B levels for nodule formation and function was more restricted than that for the growth characters. Based on the results of treatments with various B concentrations, 0.4 mg B L^-1 was found to be the concentration most beneficial for all the growth characters including nodule formation at the early stage (20 DAS) of development of soybean plants.     

Long-Term Effect of Nitrate Application from Lower Part of Roots on Nodulation and N2 Fixation in Upper Part of Roots of Soybean (Glycine max (L.) Merr.) in Two-Layered Pot Experiment

The long-term effect of the concentration and duration of application of nitrate from the lower part of soybean roots on the nodulation and nitrogen fixation in the upper part of roots was investigated using a two-layered pot system separating the upper roots growing in a vermiculite medium and the lower roots growing in a nutrient solution. Continuous absence of nitrate (hereafter referred to as “0–0 treatment”), and continuous 1 mM (1–1 treatment) and 5 mM (5–5 treatment) nitrate treatments were imposed in the lower pot from transplanting to the beginning of the maturity stage. In addition, 5 mM nitrate was supplied partially from the beginning of the pod stage till the beginning of the maturity stage (0–5 treatment) or from transplanting till the beginning of the pod stage (5–0 treatment). The values of the total plant dry weight and seed dry weight were highest in the 5–5 treatment, intermediate in the 1–1, 5–0, 0–5 treatments, and lowest in the 0–0 treatment. The values of the nodule dry weight and nitrogen fixation activity (acetylene reduction activity) were lowest in the 5–5 treatment. The value of the nodule dry weight in the upper roots was highest in the plants subjected to the 1–1 treatment and exceeded that in the 0–0 treatment. Total nitrogen fixation activity of the upper nodules per plant at the beginning of the pod stage was also highest in the 1–1 treatment. These results indicated that long-term supply of a low level of nitrate from the lower roots could promote nodulation and nitrogen fixation in the upper part of roots. Withdrawal of 5 mM nitrate after the beginning of the pod stage (5–0 treatment) markedly enhanced nodule growth and ARA per plant in the upper roots at the beginning of the maturity stage when the values of both parameters decreased in the other treatments. The nitrate concentration in the nodules attached to the upper roots was low, including the 5–5 treatment regardless of the stages of growth. This indicated that the inhibitory effect of 5 mM nitrate or promotive effect of 1 mM nitrate supplied from the lower roots was not directly controlled by nitrate itself, but was mediated by some systemic regulation, possibly by the C or/and N requirement of the whole plant.     

Nitrogen fixation of Sesbania rostrata: Contribution of stem nodules to nitrogen acquisition

Abstract

Nitrogen contents, nodule numbers, and nodule dry weights of 6-week-oId Sesbania rostrata plants grown in sand culture with only root nodules, only stem nodules or with both were compared and the root nodules were found to contribute to nitrogen acquisition more significantly than the stem nodules. Similar findings were obtained in ¹⁵N₂-fixing experiments. An 8-week-old plant with both stem and root nodules fixed 1.50 mg nitrogen in a 12 h light period, while the fixation decreased to 1.15 mg nitrogen after the removal of the stem nodules, suggesting that root nodules played major role in nitrogen fixation. However, acetylene-reducing activities per nodule dry weight were higher in the stem nodules. Under flooding conditions, the aerenchyma tissues contributed to about 40% of N₂ transport to root nodules, and 60% was supplied through stem.     

Soil fertility effects on growth,yield, nodulation and nitrogenase activity of Austrian winter pea

Austrian winter pea (Pisum sativum subspecies arvense (L.) Poir) is grown as a cool season annual to produce high protein seed and forage as well as for soil fertility improvement. This legume is grown on a wide range of soil types with many different cropping systems. The objective of these studies was to determine the influence of K levels, with and without P and Ca fertilization, for increased growth, yield, nodulation and nitrogenase activity. Results were from 3 years’ field and greenhouse experiments with a Psammentic Paleustalf (Eufaula series) utilizing Rhizobium leguminosarum (Frank), ATCC 10314 as inoculum. Soil fertility effects on composition and histology of field‐grown nodules are presented.

Available soil P was a limiting plant nutrient in field studies with significant response to K resulting with PK combinations for top growth, tillers, pods, seed yield, nodule mass, and nitrogenase activity levels (C₂H₂, red.). Multiple regression for nitrogenase (umol C₂H₄ h^‐1) = 1.09 tiller number + 3.37 nodule weight + 2.29 pod number, R² = 0.837, C.V. = 29.9%. Results from the greenhouse experiments indicated significant responses with increased K application levels when combined with P and Ca fertilization for top growth, nodule weight, number of nodules and nitro‐genase activity. Highly significant correlations resulted with nitrogenase x nodule weight (r=0.538) and nitrogenase x top growth (r=0.359) with multiple regression of treatment effects for nitrogenase (μmol C₂H₄ h^‐1) = 2.73 P + 1.04 K + 4.92 Ca, R² = 0.797 and C.V. = 48.8%. Soil addition of plant nutrients resulted in significantly increased concentrations of those elements within nodules. Magnesium content was not consistently influenced by P, Ca, and K amendments. Sodium decreased with increased K fertilization. Multiple regression of elemental composition (mg g^‐1 nodule) for nitrogenase (pmol C₂H₄ h^‐1) = 0.21 P + 0.86 K + 2.35 Ca ‐ 2.01 Na, R² = 0.772, C.V. = 55.6%. The proportion of plant nutrients in nodules contained within the nodule cytosol was highest for K (56.2%) and lowest for Ca (21.4%) with intermediate levels of Mg (50.2%), P (45.4%), and Na (37.2%).

Practical application from these data include the requirement of adequate available soil K for increased yield and nitrogen fixation with favorable P and Ca soil levels in Austrian winter pea production.