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.     

玉米/大豆、玉米/花生间作对作物氮素吸收及结瘤固氮的影响

禾本科与豆科作物间作具有显著的增氮作用。为探明玉米/大豆、玉米/花生间作模式的氮素吸收、氮营养竞争能力及豆科结瘤特性的变化,解释玉米与豆科间作体系的增氮效应,通过田间试验,设置玉米单作（MM）、大豆单作（SS）、玉米/大豆间作（MS）、花生单作（PP）、玉米/花生间作（MP）等5种种植模式,研究不同种植模式对作物氮素积累、氮营养竞争强弱及豆科结瘤固氮特性的调控作用。结果表明,与单作相比,间作显著降低玉米和大豆的氮素积累量,对花生的氮素积累量影响不显著。5种模式系统氮素积累总量表现为MS > SS > MP,PP和MM处理最低且差异不显著,MS处理比MP处理显著高21.8%。与MM处理相比,MS和MP处理的玉米氮素积累量分别降低20.5%和11.7%,其中MP处理籽粒、叶片和茎秆氮素积累量比MS处理高8.9%、21.2%和14.3%。与SS处理相比,MS处理的大豆氮素积累量降低28.5%,其中,中行、边行分别降低10.1%、15.4%。玉米相对大豆氮营养竞争比率表现为强（CR_ms>1）,相对花生则表现为弱（CR_mp<1）。与SS处理相比,五叶期MS处理的大豆根瘤数量显著增加,根瘤鲜重无显著差异,盛花期后根瘤数量和鲜重均显著降低;MS处理的大豆根瘤固氮酶活性均降低,且中行降低幅度更大。与PP处理相比,开花期MP处理的花生根瘤数量和鲜重均显著增加,下针期后均显著降低;MP处理的花生根瘤固氮酶活性均降低,且边行降低幅度更大。各间作模式作物的氮素积累量虽然降低,但间作模式的系统氮素积累量却显著高于各单作模式,两种间作模式中MS处理的氮素积累总量最高。     

Effects of soil fertility on growth,tuber yield,nodulation and nitrogen fixation of yam bean (Pachyrhizus erosus (L.) urban) grown on a typic eutrustox

The tuberous legume, Yam Bean, (Pachyrhizus erosus (L.) Urban, has been utilized as a food crop for many centuries. The large, starchy tubers have higher aitrogen content than potatoes, cassava and taro roots with 20% or more of the N fraction as ureidoglyco‐lates. Yam Bean (Jicama) tuber growth within the neotropical regions of the world is influenced by soil productivity. The objective of this study was to determine effects of soil fertility treatments on tuber yield, nodulation characteristics and nitrogen fixation.

Highly significant increases in growth and tuber production resulted with P additions, and to Ca and K levels when combined with P. Nodule weight and nitrogenase activity were similar in response to factorial soil treatments as were the tuber and total above ground plant growth. Total ureide content of tuber epiperi‐derm tissue increased significantly with P, Ca, and P + Ca treatments and increased quadratically with increased K additions when combined with P, Ca, and P + Ca treatments. Multiple regression for nitrogenase = 3.4 g top wt. + 3.5 g tuber wt. + 4.9 g nodule wt. + 3.7 umol ureide, R² = 0.88 and C.V. = 16.5%. The percent nonstructural tuber carbohydrates was not significantly influenced by soil treatments although total tuber N content significantly increased with the P treatments. Content of plant nutrient elements within nodule cytosol generally increased significantly with addition of the corresponding element in the soil fertility treatments. Increased K content was quadratic for increased K additions with concomitant decrease in Na content having highly significant negative correlation (r = ‐0.72). Adequate available soil P, Ca and K favorably influenced Yam Bean tuber growth and nitrogen fixation with P a first limiting factor for desirable high tuber yields.     

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.     

不同保藏年代的大豆根瘤菌冻干菌种的生物学活性研究

对实验室保藏的4～25年的冷冻干燥管大豆根瘤菌菌种进行了生物学活性测定。结果表明,供试4种大豆根瘤菌都有结瘤能力和固氮能力,它们之间的单株结瘤数和固氮酶活没有显著差异。同时证明冷冻干燥法是保藏根瘤菌的良好方法。     

Mycorrhiza and soil fertility effects with growth,nodulation and nitrogen fixation of leucaena grown on a typic eutrustox

Abstract

The rapidly growing, woody perennial legume, Leucaena (Leucaena leucocephala (Lam.) de Wit), is adaptable to a wide range of neotropical soil conditions. Effective Rhizobium inoculation and endophyte mycorrhizal colonization are essential for high levels of production and symbiotic N₂ fixation. The objective of this study was to determine growth, nodulation, nitrogenase activity and nodule composition of inoculated Leucaena as affected by mycorrhizal colonization and factorial soil fertility treatments of a Typic Eutrustox. Highly significant increases in top growth, nodule fresh wt. and nitrogenase activity resulted with Glomus fasciculatum colonization, soil K and linear increases with low‐soluble P fertilization to 300 mg P kg^‐1 soil. Highly significant interactions for increased nodulation and nitrogenase activity resulted with K × mycorrhiza. Interactions of all three factors P, K and mycorrhiza were highly significant for nodule fresh wt. However, responses comparing inoculation with G. fasciculatum and with combined G. fasciculatum, G. microcarpus and G. clavium were not significant. Highly significant increases with applied K levels to 300 mg K kg^‐1 soil resulted with top and root growth, nodulation and nitrogenase when applied with soluble P at 100 mg kg^‐1 soil and 500 mg Ca kg^‐1 soil. Significant and highly significant interactions of P, Ca and K level resulted for all parameters. Plant nutrient element composition of nodules increased with the fertilization treatments for P, Ca and increased K levels. A highly significant inverse relation was apparent with decreased Na resulting with increased K levels. Half or more of total nodule K, P and Mg but less than 20% of Ca and Na were within the nodule cytosol. Sodium, Mg, P, and Ca decreased in the cytosol fraction with increased K content.     

钼对甘蔗体内固氮菌的固氮酶活性的影响

以巴西固氮甘蔗品种B1和B8为材料,在温室桶栽砂培条件下,对甘蔗施以含不同钼水平的营养液,以了解钼对甘蔗体内固氮菌的固氮酶活性的效应。结果表明,在含氮条件下,较低浓度的钼处理能提高甘蔗根内固氮菌的固氮酶活性,高浓度钼处理则能提高B1茎、叶片和B8茎中固氮菌的固氮酶活性;在无氮条件下,钼处理提高了B1叶片和茎中固氮菌的固氮酶活性,而B1根及B8根、茎、叶中固氮菌的固氮酶活性有所降低。此外,甘蔗根、茎、叶中固氮菌的固氮酶活性之间关系较为密切,根中固氮菌的固氮酶活性与叶片和茎中的都呈负相关。上述结果说明:巴西甘蔗在本地也具有一定的固氮能力;在不缺氮条件下,钼处理较利于调节甘蔗体内固氮菌的固氮酶活性,促进其固氮;而在缺氮条件下,钼处理不利于调节甘蔗体内固氮菌的固氮酶活性,抑制其固氮作用。     

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.     

减量施氮与间作模式对甜玉米AMF侵染和大豆结瘤及作物氮磷吸收的影响

通过4季(2014年秋季,2015年春、秋,2016年春季)大田定位试验,对比研究了两种施氮水平[300 kg·hm~(-2)(N1:减量施氮)和360 kg·hm~(-2)(N2:常规施氮)]和4种种植模式[甜玉米|菜用大豆2∶3(S2B3)、2∶4(S2B4)间作、甜玉米单作(SS)和菜用大豆单作(SB)]对华南地区甜玉米和大豆产量、甜玉米AMF侵染率、大豆根瘤菌等的影响。结果表明,减量施氮间作处理的甜玉米产量显著高于单作。2016年春季S2B3-N1处理大豆的根瘤数显著高于S2B3-N2处理;4季减量施氮和间作处理对大豆根瘤干重均没有显著影响。2015年春秋两季两种施氮水平间作处理的甜玉米生物量和氮含量均显著高于相应的单作处理;且减量施氮间作模式甜玉米AMF侵染率显著高于常规施氮处理。2015年秋季减量施氮间作模式处理甜玉米的磷含量显著高于单作处理。减量施氮与间作菜用大豆显著提高了甜玉米氮和磷含量、AMF侵染率、生物量及产量,是华南地区甜玉米资源高效利用的可持续生产模式。     

氮肥施用量对高产甜菜纤维根系分布及活力的影响

为了解施N肥对甜菜生长的影响规律。在田间条件下,研究了不同施N量（0、90、180、270、360 kg/hm2）对甜菜（KWS2409）纤维根系生长、分布和活力变化的影响。结果表明,施N比对照增加浅层侧根数、外层和深层纤维根干重及100 cm土层纤维根总干重,并提高各生育期侧根和主根活力。其中,100 cm土层最大纤维根干重施N 比对照增加了60.4%～168.4%,最大侧根数增加了22.7%～75.1%,且以0—20 cm和40—60 cm深的外土层及80—100 cm深的内土层纤维根系增加较大,分别比对照增加了129.6%～266.8%、71.0%～234.0%和101.5%～202.8%。主根伤流液量和侧根的活力分别比对照增加了56.2%～89.9%、23.7%～63.4%。N 180 kg/hm2处理0—100 cm土层中纤维根总量、各土层中根量最大,各生育时期主根和侧根活力最强,块根产量（82609.63 kg/hm2）和产糖量（13892.64 kg/hm2）均最高,而含糖率（16.83%）较N0处理（18.34%）略降。说明合理施N量有利于甜菜纤维根系生长和提高产糖量。     

缺素培养对大豆营养生长和根系形态的影响

通过营养液栽培试验,探讨了巴西10号和本地2号两个大豆基因型在氮、磷、钾、钙、镁、硫、铁缺乏条件下的缺素症状和植株生物量变化,以及根系形态指标的改变。结果表明,缺素处理对大豆植株生长影响显著,在各种缺素条件下大豆植株生物量均明显降低,地上部与根部均表现出各种营养元素缺乏时的特有症状;缺氮、缺钾、缺钙、缺镁和缺铁处理时大豆总根长和根表面积也均显著降低。大豆对不同缺素处理的反应存在基因型差异。     

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。     

壳聚糖对NaCl胁迫下菜用大豆结瘤固氮的影响

【目的】研究壳聚糖对盐胁迫抑制菜用大豆结瘤固氮的缓解效应,为进一步探讨壳聚糖抗逆机理提供新的线索。【方法】以蛭石为基质,以菜用大豆‘特早王’–根瘤菌共生体系为研究对象,采用人工气候箱培养,研究NaCl胁迫下壳聚糖对菜用大豆根瘤形成、生物固氮的影响。菌种为与‘特早王’共生匹配性较好的快生根瘤菌N18。接种后的植株进行如下4个处理:1)叶面喷施清水,根部浇灌无氮营养液(CK);2)叶面喷施壳聚糖水溶液,根部浇灌无氮营养液(CTS);3)叶面喷施清水,根部浇灌溶有NaCl的无氮营养液(Cl);4)叶面喷施壳聚糖水溶液,根部浇灌溶有NaCl的无氮营养液(CTS+Cl)。上述各处理施用的水或水溶液均为无菌水配制,NaCl处理的浓度为50 mol/L,CTS处理的适宜浓度为200 mg/L。接种30天后,将大豆植株取出,用清水将根部蛭石冲洗干净后,立即测定根瘤固氮酶活性、根瘤数及根瘤鲜重,然后测定根瘤豆血红蛋白含量和根系活力,最后测植株干重和全氮量。【结果】氯化钠胁迫下,植株干重显著下降,与CK相比降幅达49%,喷施壳聚糖后(CTS+Cl),降低幅度显著减小,但依然显著低于CK (P <0.05)。无盐条件下,与CK相比,壳聚糖处理(CTS)增加植株干重的效果不明显。喷施壳聚糖显著增加了菜用大豆的根瘤数、根瘤鲜重、植株含氮量、根系活力、豆血红蛋白含量及固氮酶活性(P <0.05)。NaCl胁迫显著抑制了菜用大豆的结瘤固氮作用,其中根瘤数、根瘤鲜重分别较CK下降了79%、90%,而壳聚糖处理(CTS+Cl)使菜用大豆在盐逆境下的结瘤数、根瘤鲜重、植株全氮含量、根系活力、豆血红蛋白含量及固氮酶活性等均显著回升,增幅分别达对照的29%、20%、17%、48%、19%、21%,但均显著低于CK。【结论】非NaCl胁迫下,喷施壳聚糖可以显著促进菜用大豆结瘤,提高豆血红蛋白含量及固氮酶活性,最终增加植株含氮量。在NaCl胁迫下,外源壳聚糖可以显著缓解氯化钠胁迫导致的对根系活力和结瘤固氮的影响。因此,叶面喷施壳聚糖是促进菜用大豆结瘤固氮和生长的有效措施。     

施氮量对玉米/大豆套作系统土壤微生物数量及土壤酶活性的影响

为揭示玉米/大豆套作体系下土壤氮素转换的调控机理和根际微生态效应,以种植模式为主因素[设玉米单作(MM)、大豆单作(SS)和玉米/大豆套作(IMS)3种处理],以玉米、大豆施氮总量(玉米、大豆施氮比例为3∶1)为副因素[设不施氮(NN,0 kg?hm~(-2))、减量施氮(RN,180 kg?hm~(-2))和常量施氮(CN,240 kg?hm~(-2))3个处理],研究了玉米/大豆套作系统下不同施氮量对作物根际土壤微生物数量及土壤酶活性的影响。结果表明:与相应单作相比,套作下玉米根际土壤真菌、放线菌数量分别提高25.37%和8.79%;套作大豆根际土壤真菌、放线菌、固氮菌数量高于单作大豆;套作玉米根际土壤蛋白酶、脲酶活性和套作大豆根际土壤蛋白酶活性均显著升高。各施氮水平间,减量施氮下玉米、大豆根际土壤真菌数量较常量施氮和不施氮均有所提高;施氮提高了玉米、大豆根际土壤放线菌数量;大豆根际土壤固氮菌数量以减量施氮最高,比不施氮和常量施氮高17.78%和5.67%;玉米根际土壤蛋白酶活性、脲酶活性和大豆根际土壤脲酶活性均以减量施氮为最高。适宜的施氮量不仅能增加玉米/大豆套作土壤中真菌、放线菌、固氮菌的数量,还能提高土壤蛋白酶、脲酶活性,调节土壤氮素的转化,促进玉米/大豆对土壤中氮素的吸收,实现节能增效。     

氮素对不同大豆品种根系分泌物中有机酸的影响

采用室内溶液培养方法,分别研究了接种根瘤菌处理下,两种氮源和两种氮浓度对两个大豆品种根系分泌物中有机酸的影响。结果表明,合丰25号根系分泌的有机酸种类和数量无论苗期或花期,接种或不接种根瘤菌,均表现为硝态氮处理高于酰胺态氮处理,表明合丰25号大豆更喜硝态氮,硝态氮促进了有机酸的分泌。绥农10号在酰胺态氮下的有机酸种类和数量均高于硝态氮处理,表明其更喜酰胺态氮,酰胺态氮下根瘤菌的存在增加其根系分泌物中有机酸种类和数量。可见,大豆根系分泌物中有机酸的种类和数量因品种而异,因品种对氮源的喜好而变化;根瘤菌在不同程度上增强或减弱根系有机酸的分泌作用。柠檬酸受氮素供应浓度影响很大,当氮素供应浓度较低时,大豆根系分泌物中可检测到柠檬酸,供氮浓度升高则检测不到。     

丛枝菌根真菌与根瘤菌接种对大豆根瘤分布及磷素吸收的影响

在温室条件下,采用石英砂盆栽试验研究了大豆(冀豆6号)接种丛枝菌根真菌（Glomous mosseae）与根瘤菌 （Bradyrhizobium japonicum）对根瘤的形成、分布以及磷素吸收效率的影响。结果表明,大豆生长至开花期（接种后56 d）,与单接种根瘤菌处理相比,双接种AM真菌和根瘤菌显著增加大豆生物量、氮、磷含量、根系上的总根瘤数。单接种根瘤菌条件下,总根瘤数的48.4%分布在主根上,51.6%分布在侧根上;根瘤菌与AM真菌双接种时,总根瘤数的32.5%分布在主根上,67.5%分布在侧根上。双接种处理的侧根根瘤的固氮酶活性显著高于单接种处理的。双接种条件下大豆侧根中AMF侵染增强,尤其是结根瘤侧根上的AM真菌的侵染率高于未结瘤的侧根的菌根侵染率。接种后28 d单接种菌根真菌处理显著高于双接种处理的植株磷的吸收效率;而56 d 时趋势相反。以上结果表明,AM真菌侵染改变根瘤在大豆根系上的分布,根瘤数量、分布与结根瘤侧根上AM真菌的侵染强度存在正相关关系。     

Soil fertility effects on growth,nitrogen fixation,nodule enzyme activity and xylem exudates of lablab purpureus (L.) sweet,grown on a typic eutrustox

Abstract

The Lablab or Hyacinth bean, Lablab purpureus (L.) Sweet, is a drought tolerant grain‐forage legume widely grown within a wide range of neotropical regions of the world. It has been an important cultivated food grain crop for many centuries within extensive warm humid‐subhumid climatic areas and grown on widely different Ultisol and Oxisol soil types. The objective of these studies was to determine soil fertility effects of Ca, P, and K factorial combinations applied to a Typic Eutrustox on growth, nodulation, and nitrogen fixation of Lablab bean. Stem and nodule xylem components were determined along with soil pH and nitrification within the nodule rhizosphere. Highly significant increases resulted with P fertilization for stem, leaf, seed, nodulation, and nitrogenase activity. With the exception of nitrogenase, all were also increased with K additions. Both stem and seed were significantly increased with Ca treatments. Highly significant increases for total plant N content resulted with P, K, Ca, and P x K interaction. Allantoinates were initially dominant components of stem xylem exudate following decapitation but were not detected after 5 days. Amino‐amide composition remained relatively constant. Nitrates increased from 1.6 to 81.8 ug N ml^‐1 exudate during the 8 day collection period. Soil nitrate levels adjunct to decomposing nodules increased from 4.2 to 1661.1 ug g^‐1 soil. Initial high levels of ureide transforming enzymes ALTN, ALTC, and URC were not detected after 4 days. Amine‐amide enzymes AST, GS, GOGAT, and GDH were relatively constant with nitrate reductase increasing from 0.12 to 9.35 IU ml^‐1 xylem exudate during the 8 d period. Nodule xylem export components were dominated by ureides, 429.8 umol, and amines 30.3 umol ml^‐1. Enzyme activity levels were highest for AST 22.17 and GS 13.25 IU ml^‐1 with the ureide enzymes URC 2.24, ALTN 0.26, and ALTC 0.15 IU ml^‐1 . Nodule exudate composition was K 422.0, P 63.4, Ca 53.8, Mg 42.8, and Na 25.6 ug ml^‐1.     

利用15N标记研究氮素水平对大豆根瘤生长的影响

为了明确氮肥对大豆根瘤生长的影响,以东农47为试验材料,采用15N 标记和砂培的方法,进行了氮素营养水平对大豆根瘤生长及与根瘤固氮相关性的研究。结果表明,随外源氮水平增加,根瘤干重呈先增加后降低的变化趋势,当营养液氮浓度为50 mg/L时,有利于根瘤的生长;根瘤生长需要一定量启动氮,启动氮的作用维持到第3片复叶完全展开时（V3）对大豆根瘤的生长最有利;在盛荚期 （R4）和鼓粒始期 （R5）补充外源氮的供给抑制根瘤的生长。根瘤干重与植株中根瘤氮积累量、根瘤氮比例呈极显著正相关,根瘤干重与植株中氮积累量呈显著正相关。     

Effect of thiram (tetramethyl-thiuram-disulphide) application on nodulation in soybean and kidney bean plants: Observation using the root-box-culture technique

Abstract

In agricultural practice, legume seeds are often treated with fungicides to protect them from harmful soil microorganisms. Most fungicides also are toxic to rhizobial growth. Among the synthetic fungicides, thiram (TMTD: tetramethyl-thiuram-disulphide) appeared to be most suitable for leguminous seed protection, because of its low toxicity to some species of rhizobium (NifTAL Project and FAO 1984).     

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.