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1.
Keletso C. Mohale Alphonsus K. Belane Felix D. Dakora 《Biology and Fertility of Soils》2014,50(2):307-319
Bambara groundnut (Vigna subterranea L. Verdc) is the second most important indigenous food legume in Africa. The aim of this study was to evaluate plant growth, N2 fixation, N contribution, C accumulation, and plant water relations of Bambara groundnut grown in 26 farmers’ fields in Mpumalanga Province of South Africa. The data revealed marked (p?≤?0.05) differences in plant dry matter (DM) yield, N concentration and content, δ15N, the proportion of N derived from symbiotic fixation (%Ndfa), and actual amounts of N-fixed between and among the 26 farms surveyed. Bambara groundnut plants obtained 33–98 % (mean?=?72 %) of their N nutrition from symbiotic fixation and contributed 4–200 kg N-fixed ha?1 (mean?=?102 kg N-fixed ha?1). Plant density correlated positively with %N (r?=?0.31***), δ15N (r?=?0.126***), and amount of N-fixed (r?=?0.15*), indicating that the high %Ndfa values obtained for Bambara groundnut in this study and the low symbiotic N yield associated with some farms were due to low plant density rather than poor symbiotic functioning. Bambara groundnut obtained more N from soil (e.g., 173 kg N ha?1) than from symbiosis (e.g., 135 kg N-fixed ha?1) in some fields, implying that the N2-fixing efficacy of the microsymbionts nodulating Bambara groundnut was low at some locations in South Africa. The data from this study showed δ13C values ranging from ?28.01 to ?26.20?‰, which indicates differences in plant water use efficiency on the different fields studied. Furthermore, the positive correlations between δ13C and N-fixed (r?=?0.15*) and between δ13C and N content (r?=?0.14*) suggest a functional relationship between water use efficiency and N2 fixation, just as the positively significant correlations between δ15N and DM yield (r?=?0.24***), N-fixed and DM weight (r?=?0.76**), and N content and DM yield (r?=?0.99*), as well as N-fixed and C content (r?=?0.76**) also indicate a functional relationship between N2 fixation and photosynthesis. In the same way, the positive correlation between δ13C and DM weight (r?=?0.14*), or δ13C and C content (r?=?0.15*), also implies a functional link between water use efficiency and plant growth. Thus, an increase in water use efficiency in Bambara groundnut, whenever it occurs, seems to functionally enhance plant growth, symbiotic N2 fixation, and photosynthetic activity, just as N2 fixation in nodules also seems to stimulate leaf photosynthesis. 相似文献
2.
Effect of the herbicide glyphosate on nitrification,denitrification, and acetylene reduction in soil
The effect of glyphosate on N2 fixation, denitrification, and nitrification in an agricultural soil was investigated. Effects of the pure herbicide and commercial formulation, Roundup+ (Monsanto Company), were compared in soil under aerobic and anaerobic conditions. Anaerobic C2H2 reduction was inhibited by high herbicide levels. Denitrification in non-amended soil was either unaffected (N2O reduction) or stimulated (NO inf3 sup? reduction); in glucose-amended soil, N2O reduction was inhibited and NO3-reduction unaffected by both glyphosate and Roundup. Roundup caused greater stimulation of N2O reduction than pure glyphosate; no other significant formulation effects were observed. Nitrification was inhibited by the two formulations. Ammonium oxidation were both influenced. Pure glyphosate was more inhibitory than Roundup. No toxicity to any of these activities should be seen at recommended field application rates of the herbicide. 相似文献
3.
The C2H2 reduction (A.R.) assay was investigated for quantitative measurement of symbiotic N2 fixation in established legume-based pastures under field conditions.It was found that the rate of C2H4 production was relatively constant for approx 6 h. For an accurate estimation of the N2 fixing activity, many field samples are required to overcome the errors due to the inherent spatial distribution of white clover (Trifolium repens L.) within the pasture. Furthermore, it is necessary to physically integrate the day-to-day and diurnal variations in the N2 fixing activity of the legume to obtain a reliable estimate of the rate of C2H4 production and hence symbiotic N2 fixation.The A.R. assay and an 15N technique were compared for measuring symbiotic N2 fixation in established pastures. A 3 h incubation in the A.R. assay gave the best estimate of symbiotic N2 fixation relative to the 15N technique. The 1 h incubation over-estimated and the 6 h incubation under-estimated the rate of symbiotic N2 fixation. 相似文献
4.
A wide range of bacteria capable of nitrogen fixation (free-living and associative) can be found in all agricultural soils across Australia, however measurement of their effectiveness in N2 fixation has proved to be problematic because rates are low compared to symbiotic systems and quantitative methodologies barely adequate. It is generally believed that associative N2 fixation rates may be greater than free-living N2 fixation rates in ecosystems where grasses (including cereals) dominate, although this has not been unequivocally proven. Conditions promoting asymbiotic N2 fixation are reduced availability of oxygen, high temperature and soil water, and large amounts of microbially available C in the soil. The most direct measure of N2 fixation, incorporation of 15N2, has rarely been used in undisturbed systems, and we can find no examples of its field application in Australia. Nitrogen balance calculations, based on long-term changes in total soil N of systems and crop N removal, have been used to infer asymbiotic N2 fixation, but do not measure it directly. Such N balance studies can thus only give an indication of potential asymbiotic N2 fixation over long periods of time, but cannot confirm it. There are no robust N balances published for Australian ecosystems. The acetylene reduction assay for nitrogenase activity has been used in Australia to study responses of both free-living and associative N2 fixation systems to regulating factors. These studies have highlighted the importance of C supply, high soil water content and temperature in increasing asymbiotic N2 fixation in soils. However significant methodological limitations do not allow field scale quantification using this assay. On balance we would concur with the authors of several earlier global reviews of this topic and conclude that (in Australia) contributions of nitrogen to crop growth from asymbiotic N2 fixation are likely to be <10 kg N ha?1 y?1 and generally not of agronomic significance under low rainfall conditions. In tropical environments where higher rainfall and temperatures coincide, rates are likely to be greater if soil mineral N is low and carbon substrates are available for N2 fixing microorganisms. If asymbiotic N2 fixation is to be encouraged or profitably managed, there is a need for more reliable field measurement and a combination of methodologies including 15N might provide more definitive quantitative indications. 相似文献
5.
Phosphorus (P) is a major nutrient factor influencing nitrogen (N) accumulation and partitioning of photosynthates in plants, especially the symbiotic N2‐fixation in legumes. This study was conducted to investigate how P application (0, 20, 40, and 60 kg P2O5/ha) affects symbiotic N2‐fixation of three cultivars (C 235, Pusa 408, and Pusa 417) of chickpea (Cicer arietinum L.). Application of P in general significantly increased leaf area, shoot dry weight, and the rate of acetylene (C2H2) reduction. Phosphorus concentration of shoots and roots, soluble sugar content of nodules, and shoot N accumulation were also significantly increased, especially by P at the 40 kg P2O5/ha rate. The P concentration in nodules was, however, not affected by different levels of P. The Pusa 417 cultivar responded better than the others to the P treatments. Phosphorus‐deficient plants accumulated sugar in their leaves. The interaction effect was found significant on leaf area, shoot dry weight, nodule number, and shoot N accumulation. Pusa 417 gave greatest response to 40 kg P2O5/ha but Pusa 408 and C 235 interacted best with the 20 kg P2O5/ha rate only. The increased nodulation and symbiotic N2‐fixation on P application seem to be the result of morphologically advanced shoots which are making more photosynthates for transport to nodules and not the direct effect of P on the nodules. 相似文献
6.
Abstract Combined nitrogen [nitrate (NO3‐), ammonium (NH4+), and urea] will inhibit all components of symbiotic nitrogen (N2) fixation if present in sufficient concentrations. It is generally accepted that nitrate is particularly inhibitory to nodule growth and nitrogenase activity, and somewhat less inhibitory to the infection process. This project examined whether providing low (0.1 ‐ 0.5 mM) static concentrations of NO3‐ to pea (Pisum sativum L. cv. Express), seedlings could avoid the period of N hunger experienced prior to the establishment of N2 fixation, without delaying or reducing the symbiotic N2 fixation. All concentrations of NO3 ? tested significantly inhibited all measured components of N2 fixation. The nodulation process as measured by nodule number was inhibited to a similar degree as the other parameters. A concentration dependent response was evident, with 0.1 mM NO3 ? causing less inhibition than the 0.2 or 0.5 mM concentrations. Our results indicate the within the concentrations of 0.1 mM and 0.5 mM NO3 ?, it is not possible to stimulate the growth of pea plants without inhibiting nodulation and N2 fixation. 相似文献
7.
The efficiency of symbiotic dinitrogen (N2) fixation in Vicia faba L. in combination with 3 different Rhizobium leguminosarum strains was studied in a pot experiment during vegetative and reproductive growth. The objective of the experiments was to assess variability among Rhizobium strains inoculated on single legume species and determine possible reasons for observed variations. Dry matter formation, N2 fixation and the carbon (C) costs of N2 fixation were determined in comparison with nodule free plants grown with urea. Nodule number and the capacity of different respiratory chains in the nodules were also measured. The plants inoculated with the Rhizobium strain A 37 formed less dry matter and fixed less N compared to the other two Rhizobium strains (Vic 1 and A 150). This coincided with a lower number of nodules and higher C costs of N2 fixation. The C costs for N2 fixation were in all cases significantly lower during reproductive growth compared to vegetative growth. Neither the latter nor the differences in C expenditure for N2 fixation between the Rhizobium strains could be explained in terms of differences or shifts in the capacity of different respiratory chains in the nodules. 相似文献
8.
Influence of inoculation with arbuscular mycorrhizal fungi on stable isotopes of nitrogen in Phaseolus vulgaris 总被引：1，自引：0，他引：1
D. Redecker P. von Berswordt-Wallrabe D. P. Beck D. Werner 《Biology and Fertility of Soils》1997,24(3):344-346
The interactions between Phaseolus vulgaris, Rhizobium spp. strains nodulating P. vulgaris, and arbuscular mycorrhizal (AM) fungi were assessed under greenhouse conditions in a nonsterilized Typic Haplustalf soil
from Cauca, Colombia. Our results indicate a specific involvement of AM fungal species in nitrogen acquisition by the legume
plants from symbiotic nitrogen fixation and from soil. A significant specific influence of inoculation with Glomus spp. on the 15N/14N ratio in plant shoots was dependent on the inoculated rhizobial strain, but AM fungal inoculation had no significant effect
on shoot dry weight or nodule occupancy in the two different rhizobial strain treatments. The results imply that in low P
soils the effects of an improved mycorrhizal symbiosis may include improved symbiotic N2 fixation efficiency and/or improved soil N uptake.
Received: 11 May 1996 相似文献
9.
10.
E.B. Roslycky 《Soil biology & biochemistry》1982,14(2):87-92
Limited information on the effect of glyphosate (N-phosphonomethylglycine) on soil microorganisms justified an inquiry into the response of soil actinomycetes, bacteria and fungi in terms of their respiration, and sensitivity of isolates. Low concentrations of glyphosate had little effect on total populations of these organisms during the 214-day experiment, while high concentrations initially increased actinomycete and bacterial numbers by 2 and 1 logs, respectively. The stimulation was followed by a decline and fluctuation showing a gradual increase in numbers. The respiration rates of the soil microbiota in soil suspensions, showed some irregular stimulation and retardation with up to 10 μg glyphosate ml?1. In contrast high doses suppressed O2 uptake by the microbiota. Fungi were the least affected. Pronounced inhibition of actinomycete and bacterial respiration was in agreement with the results from isolate replication. The results indicated both stimulation and inhibition of O2 uptake by some organisms within these groups. In contrast to some reports of limited, short-term inquiries these results showed considerable effects of glyphosate on soil microorganisms. 相似文献
11.
Hmissi Imen Bargaz Adnane Bouraoui Manel Yassine Mabrouk Mouldi Saidi 《Journal of plant nutrition》2015,38(11):1656-1671
The use of phosphate-solubilising bacteria as inoculants increases plant phosphorus (P) uptake and thus crop yield. Strains from the genus Mesorhizobium are among the most powerful phosphate solubilizing microorganisms. In order to study efficiency in P uptake and N2 fixation in chickpea (Cicer aritenium), forty-two rhizobia strains natively from Tunisian soils were studied in symbiosis with the chickpea variety “Béja1” which is frequently cultivated in Tunisia. Plants were inoculated separately with these strains under controlled conditions in perlite under two sources of P i.e. soluble (KH2PO4) and insoluble P (Ca2HPO4). At flowering stage, growth, nodulation, P uptake and N2 fixation were assessed in all symbiotic combinations. The results showed that the S27 strain efficiently mobilized P into plants, observed as a significant increase of plant P content when insoluble P (Ca2HPO4) was supplied to the soil. This was associated with a significant increase in plant biomass, nodule number and N content under insoluble P conditions. Additionally, inoculation with the Mesorhizobium strain S27 significantly increased the root acid phosphatase activity under insoluble P. This study also shows significant correlations found between plant P content and acid phosphatase activity under low P conditions which may highlight the contribution of acid phosphatases in increasing P use efficiency. A field experiment also showed that most of the chickpea analyzed parameters were improved when plants inoculated with two selected rhizobia strains (S26 and S27) and supplied with P2O5. Overall, these findings postulate that rhizobial inoculation should not only be based on the effectiveness of strains regarding N fixation, but also to other traits such as P solubilisation potential. 相似文献
12.
Jeff R. Powell Rachel G. Campbell Kari E. Dunfield Robert H. Gulden Miranda M. Hart David J. Levy-Booth John N. Klironomos K. Peter Pauls Clarence J. Swanton Jack T. Trevors Pedro M. Antunes 《Applied soil ecology》2009,41(1):128-136
Most soybeans grown in North America are genetically modified (GM) to tolerate applications of the broad-spectrum herbicide glyphosate; as a result, glyphosate is now extensively used in soybean cropping systems. Soybean roots form both arbuscular mycorrhizal (AM) and rhizobial symbioses. In addition to individually improving host plant fitness, these symbioses also interact to influence the functioning of each symbiosis, thereby establishing a tripartite symbiosis. The objectives of this study were to (1) estimate the effects of glyphosate on the establishment and functioning of AM and rhizobial symbioses with GM soybean, and (2) to estimate the interdependence of the symbioses in determining the response of each symbiosis to glyphosate. These objectives were addressed in two experiments; the first investigated the importance of the timing of glyphosate application in determining the responses of the symbionts and the second varied the rate of glyphosate application. Glyphosate applied at recommended field rates had no effect on Glomus intraradices or Bradyrhizobium japonicum colonization of soybean roots, or on soybean foliar tissue [P]. N2-fixation was greater for glyphosate-treated soybean plants than for untreated-plants in both experiments, but only when glyphosate was applied at the first trifoliate soybean growth stage. These data deviate from previous studies estimating the effect of glyphosate on the rhizobial symbiosis, some of which observed negative effects on rhizobial colonization and/or N2-fixation. We did observe evidence of the response of one symbiont (stimulation of N2-fixation following glyphosate) being dependent on co-inoculation with the other; however, this interactive response appeared to be contextually dependent as it was not consistent between experiments. Future research needs to consider the role of environmental factors and other biota when evaluating rhizobial responses to herbicide applications. 相似文献
13.
《Soil Science and Plant Nutrition》2013,59(5):760-772
Abstract The annual nitrogen (N) budget was measured in a soybean-cultivated upland field during the first year after conversion from a paddy field on gray lowland soil, which is typically found on the Sea of Japan side of northern Japan. Forage rice was cultivated on lysimeter fields for 4 consecutive years with applications of chemical fertilizer, immature compost, or mature compost (the control, immature compost, and mature compost plots, respectively), and then the fields were converted to upland fields for soybean (Glycine max [L.] Merrill cultivar Ryuho) cultivation. Input (seed, bulk N deposition, and symbiotic dinitrogen [N2] fixation) and output (harvested grain, leached N via drainage water, and nitrous oxide emission) N flows were measured, and the field N budget was estimated from the difference between the input and output. The soybean plants in the immature and mature compost plots grew well and had higher yields (498–511 g m)?2) compared to the control plot (410 g m)?2). Total N accumulation in the soybean plants derived from N2 fixation (g N m)?2) in the mature compost plot (27.7) was higher than those in the control (18.1) and immature compost plots (19.9). Percentages of soybean N accumulation derived from N2 fixation ranged from 53% to 74%. N derived from symbiotic N2 fixation accounted for more than 90% of the total N input, whereas harvested grain accounted for approximately 85% of the total N output. N leaching mainly occurred during the fallow period, accounting for 13–15% of the total N output. The annual N budgets were negative (?10.0,?14.2, and ?6.4 g N m)?2 year)?1 for the control, immature compost, andmature compost plots, respectively). The Nloss from the immature compost plot was higher than that of the control plot, because the N output in harvested grain was higher, and the N input by N2 fixation was similar between plots. While the N loss from the mature compost plot was lower than that of the control plot because the N output in harvested grain was higher, as was the case in the immature compost plot, the N input by N2 fixation was also higher. Preceding compost application—whether immature or mature compost—to paddy fields increased the subsequent soybean yield during the first year after conversion. This result suggests that N loss and the following decrease in soil N availability in the field could be mitigated by increased N2 fixation resulting from mature compost application with an appropriate application practice. 相似文献
14.
Gustavo Valverde Erasmus Otabbong 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(2):71-80
Pot and field experiments were performed to assess N2 fixation in Nicaraguan (R79 and R84) and Ecuadorian (Imba) common bean (Phaseolus vulgaris L.) cultivars, with the aim of improving their productivity by inoculating them with commercially produced Rhizobium phaseoli. With maize (Zea mays L.) as the non‐N2‐fixing control, the percentage of N2 fixed predicted by the 15N‐dilution method was significantly (P ≤ 0.05) higher than that predicted by the N‐difference method. However, the N2 amounts predicted by the two methods were not significantly different. The correlation between the two methods was significant and positive (P ≤ 0.0001, n = 36). Compared with the native rhizobial strain, symbiotic associations of the bean cultivars with UMR1073, UMR1077 and UMR1899 rhizobial inoculants did not significantly (P ≤ 0.05) influence plant dry matter (DM) and N yields, the extent of N2 fixation and uptake of soil and fertilizer N. Nevertheless, the UMR1077 and UMR1899 strains markedly increased the uptake of soil N by R84 plants, while decreasing N2 fixation. In contrast, the Imba‐UMR1899 association enhanced positive effects on all variables. About 60–70% of the total N taken up by the Imba plants was fixed N2. The R79 and R84 plants fixed about 50% of their total N uptake. N2 fixation rates were positively correlated with DM and total N yields, while being negatively correlated with soil N uptake (P ≤ 0.001, n = 36). Future research in Nicaragua should focus on selecting rhizobial strains suitable for indigenous common bean cultivars. 相似文献
15.
Giani M.B. Bohm Segundo Urquiaga Gustavo R. Xavier Cesar V. Rombaldi 《Soil biology & biochemistry》2009,41(2):420-422
Over half of the 21 Mha of soybean planted in Brazil is now transgenic glyphosate-resistant (GMRR). A field experiment was carried out to investigate whether the application of glyphosate or imazethapyr to the GMRR variety reduced the input of N2 fixation (BNF). No effects on yield, total N accumulation, nodulation and BNF (δ15N) could be assigned to the genetic modification of the plant. Imazethapyr reduced soybean yield but had no significant effect on BNF. Even though yields were not affected by glyphosate, the significant reduction of nodule mass and BNF to the GMRR suggests that the use of this herbicide could lead to an increased dependence on soil N and consequently an eventual decrease of SOM reserves. 相似文献
16.
氧化亚氮(N_2O)是主要的温室气体之一,对大气环境质量与全球气候变化具有重要的影响。N_2O排放不仅增加温室效应,同时也会导致陆地生态系统氮损失与平流层臭氧消耗。长期以来土壤被认为是陆地生态系统N_2O的主要排放源,但近年来越来越多的证据表明,植物可能是陆地生态系统N_2O排放的另一重要来源。近年来有关植物排放N_2O的报道逐年增多,但对植物排放N_2O的途径及其调控机制方面还缺乏文献综述。本文首先在总结长期以来人们普遍认为的N_2O源与汇的基础上,提出陆地植物可能是另一个尚未被广泛认可的重要的N_2O的排放源。植物排放N_2O可能有两种潜在途径:1)植物作为土壤中通过微生物产生的N_2O的运输通道,2)植物通过自身代谢或内生菌的作用产生N_2O并排放到大气中。然后分析了关键因素(养分、光照、温度和植物器官及生长阶段)对植物排放N_2O的影响机制。最后指出未来需进一步探明植物体内产生N_2O的具体途径及其对全球N_2O排放的贡献,重点是探明植物自身的生理生化过程以及与其伴生、共生的微生物在N_2O产生中的作用。 相似文献
17.
The influence of four pruning frequencies on biomass, nodulation and N2 fixation was investigated on Albizia lebbeck, Gliricidia sepium and Leucaena leucocephala grown in the screenhouse for 16 months, using acetylene reduction and 15N dilution methods. Frequent prunings at 4-month intervals had no deleterious effect on symbiotic N2 fixation, which increased in Gliricidia and Leucaena in particular. Nodulation and nitrogenase activity varied inconsistently within species, and were not influenced by pruning
frequency. Cumulative assessment of pruning effect showed higher biomass, N yield and N2-fixing capacity of the woody species than at last harvest, and appeared to have more practical relevance. Across species,
cumulative total dry matter, N yields, and both percentage and absolute amount of N2 derived from atmosphere increased with pruning frequency, except when trees were pruned 3 times. Of the three species, G. sepium had the lowest biomass production, N2 fixation and N accumulation.
Received: 25 October 1995 相似文献
18.
缺磷胁迫下草甘膦对抗草甘膦大豆幼苗光合作用和叶绿素荧光参数的影响1 总被引：4，自引：0，他引：4
为探明缺磷胁迫下草甘膦对抗草甘膦大豆（RR1）幼苗叶片光合作用和叶绿素荧光参数的影响,采用溶液培养方法,在大豆长出真叶时进行缺磷胁迫,第二复叶完全展开时进行草甘膦处理,5d后测定各生理指标。结果表明, 相对于正常供磷条件的清水处理,缺磷胁迫下4.98 mL/L草甘膦处理的大豆叶片净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）、最大荧光（Fm）、PSⅡ最大光化学效率（Fv/Fm）、PSⅡ的有效量子产量［Y(Ⅱ)］、PSⅡ非调节性能量耗散的量子产量［Y(NO)］、最大电子传递速率（ETRmax）和半饱和光强（Ik）均呈下降趋势。而气孔限制值（Ls）、叶绿素a（Chl a）、叶绿素b（Chl b）、叶绿素a/b（Chl a/b）、类胡萝卜素（Car）、总叶绿素（Chl）含量和PSⅡ调节性能量耗散的量子产量［Y(NPQ)］均呈升高趋势。说明缺磷胁迫条件下喷施草甘膦显著降低了抗草甘膦大豆的光合速率。缺磷引起的气孔因素可能是导致RR大豆光合速率下降的主要原因,而光合速率的下降导致其PSⅡ反应中心的开放程度降低,活性减弱,参与CO2固定的电子较少,光化学效率较低。 相似文献
19.
《Archives of Agronomy and Soil Science》2012,58(1):110-125
ABSTRACTThis study aimed to understand the effects of Medicago spp proportion on symbiotic and non-symbiotic nitrogen (N) utilization of plants, and subsequent forage production and soil N status in an artificial Leymus chinensis grassland. By a two-year field experiment conducted in semi-arid northern China, it was found that the corresponding biomass proportions of legume in swards were 0, 39, 63, 83 and 98% when legume seedling proportions at sowing were 0, 25, 50, 75 and 100%, respectively. Increased Medicago seedling proportion (from 25 to 100%) decreased legume N2 fixation capacity from 53 to 21%, as a consequence, this reduced total symbiotic N2 fixation and its contribution to forage production with Medicago seedling proportion increasing from 50 to 75% or more. However, as increased Medicago seedling proportion enhanced legume biomass and sward uptake to soil mineral N, higher legume stands still led to the greater biomass and N yield. The cultures with 50% seedling of legume had 4–13% greater soil N concentration than the cultures with 0, 25, 75 and 100% seedling of legume. We concluded that pure Medicago stands led to the greatest forage yield, while medium Medicago stands could lead to the greater symbiotic N fixation and soil N concentration. 相似文献
20.
In the legume‐(Brady)Rhizobium symbiosis, signal exchange between the host‐plant and the symbiotic bacterium is an essential step in nodule formation. Genistein is the most effective plant‐to‐bacterium signal in the soybean [Glycine max (L.) Merr.] N2‐fixing symbiosis. Its concentration in soybean root system increases with seedling development, and decreases immediately after the onset of N2 fixation. This study was conducted to determine whether addition of genistein to the rooting medium at the onset of N2 fixation would increase nodulation thereafter. The results indicated that watering soybean plants with a solution containing genistein beginning at the onset of N2‐fixation increased nodule size, nodule number and nodule weight per plant. Shoot nitrogen (N) concentration was also increased. Soybean cultivar AC Bravor was more sensitive to genistein addition than Maple Glen. 相似文献