Introduction

Soybean-Rhizobium symbiotic system possesses the ability to fix N2 and make it available to plants.Some studies suggest that the regulation of N2-fixation has a direct effect on nitrogenase activity in the nodules(Magadlela et al., 2012; Quernéa et al., 2017; Rejili et al., 2012).The inoculation of Rhizobium is known to increase nodulation, growth, nitrogen uptake and yield of crop plants (Elkoca et al., 2008; Zhang et al.,2010).

Rhizobia can also solubilize organic and inorganic phosphate (Pandit et al., 2014; Bargaz et al., 2013).Availability of this phosphorus depends largely on microbial activity.A low and limiting P supply eventually reduces plant growth and thus reduces N demand and N2-fixation (Oberson et al., 2013).Soil in South China belongs to acidic and insoluble phosphorus soils, which phosphorus is fixed in soils that are hard to absorb by plants, including Al-P and Fe-P soil, which restrict plant growth by scarcity of P.The phenomena of fixation and precipitation of P in soil, which is highly dependant on pH, cause a low efficiency of soluble P fertilizers such as superphosphate (Abdelnaby et al., 2015; Miao et al., 2006).P predominantly presents in the forms of inorganic compounds, which belong to those of aluminium (Al-P)and iron (Fe-P) under acidic conditions.Insoluble P may affect the ability of soybean to obtain N that is sufficient to ensure a productive system.There are several ways to promote plant growth and nitrogen fixation under insoluble P.These include not only selection of soybean cultivars that are P efficient,but also inoculation with suitable bacteria, such as,Rhizobia isolated from wild legumes under stress conditions (Abdelnaby et al., 2015; Togay et al., 2008;Simon et al., 2014) or Rhizobia that are P efficient and phosphate-solubilizing microorganisms.The efficient Rhizobium strains under insoluble P condition have ability to store large quantities of P, utilization efficiency of internal P, and uptake efficiency at low external concentrations (Singh and Singh, 2014;Fankem et al., 2014; Bekere et al., 2013).

Several studies (Frankow-Lindberg and Dahlin,2013; Zhang et al., 2010; Rejili et al., 2012; Attar et al., 2012; Vesterager et al., 2007) have indicated that Rhizobium improve the growth of plants by nitrogen fixation or solubilizing insoluble P.However,little work had been done on the effect of interactions among insoluble P, Rhizobium and nitrogen fixation system in the insoluble P soil of South China.The aims of this study were to study the effect of interactions between insoluble P, Rhizobium and nitrogen fixation system, and to determine the effect of nitrogen fixation system on P uptake.

柔性垂直防渗技术是一种采用高密度聚乙烯（HDPE）膜作为防渗材料，基于将简易垃圾填埋场已经产生或可能产生的污染物控制在限制范围内的新型高效垂直防渗屏障系统，其最终目标是实现污染源的隔离与控制，实现生态环境的修复。

Materials and Methods

Inoculant

从生产空间和产业链网络共生的视角分析多种类型污染要素作用下的环境效应演变特征、传输路径和情景模拟；针对不同类型的产业部门评估产业集聚过程中排放的不同环境污染物的环境效应是需要关注的重要领域。区域环境变化是多种因素综合作用的结果，不同区域影响环境变化的主要环境污染因素存在差异，不同行业所排放的环境污染物类型和总量也存在差异，因此在评估产业集聚的环境效应时要考虑区域差异和产业差异而导致的环境效应差异，基于产业集聚发育程度进行环境效应估，并基于评估结果及时调整环境规制，实现科学动态管理生态环境。

通过对区域、起始结束时间选择，显示该段时间本区域机井的用水记录或指定具体机井查询该机井在这段时间的用水记录。

Phosphorus appeared essential for both nodulation and N2 fixation.Phosphorus was required by soybean for growth and promoted N uptake.Inoculation with Rhizobium strains affected higher root phosphorus content in Fe-P soil than Al-P soil, but some strains did not increase phosphorus content of root compared to other inoculants.Inoculation with C46 had the highest P content of plant in Al-P soil, increasing 31.6% when compared with CK U110 in Table 2.On the average,inoculation with Rhizobium strains increased higher phosphorus content of plant in Al-P soil than Fe-P soil in Tables 3-4.However, only inoculation with CW54 significantly enhanced phosphorus uptake of plant in Al-P and Fe-P soil as compared with other inoculants,whereas in Fe-P soil more higher than in Al-P soil,increasing 96.2% (Fe-P) and 8.2% (Al-P), when compared with CK U110 in Table 2, respectively.

Effective Rhizobium strains were isolated from the nodules of wild or cultivated soybeans, wild strains were designated as W (W5), cultivated strains were designated as C (C46), as well as combined strains of cultivated and wild were designated as CW (CW53,CW54).USDA110 (U110) was used as a control strain(Taylor et al., 1991).The inocula for strains were prepared by resuspending the cells from 2-3 days old yeast extract mannitol agar cultures, in sterile saline(0.85% NaCl) solution containing 1% methyl cellulose(Van et al., 2014) at 28℃ for 1 week and collected by centrifugation at 3 000 r · min-1 for 10 min.Rhizobium pellets were suspended in N-free Arnon-Hoagland solution containing (mmol · mL-3): 400 CaCl2; 200 MgSO4; 400 K2SO4; 100 NaH2PO4; 50 H3BO4; 50 FeC6H5O7; 20 MnSO4; 2 ZnSO4; 1 Na2MoO4; 0.5 CuSO4; 0.5 NiSO4; and 0.5 CoCl3 (Adrian et al., 2012)diluted to 500-fold of packed cell volume.The diluted suspension was used inoculant.

Cultivation of plants

Low-P soil was used with pH 5.5, 65.60 mg · kg-1 N, 10.06 mg · kg-1 P and 75.20 mg · kg-1 K.Plastic pots were filled with 2.5 kg of the soil.Insoluble phosphorus, Al-P (AlPO4) and Fe-P (FePO4 · 4H2O),was mixed into pots at 196.7 mg Al-P per pot and 359.5 mg Fe-P per pot (equivalent to 20 mg P per pot),respectively.

The soybean seeds of 'HUAXIA 3' (Glycine max L.)were sown directly in pots at a depth of 2 cm.Pots were watered to field capacity every other day and maintained free of weeds throughout the experiment.One milliliters of the diluted Rhizobium inoculant was supplied for each pot at the time of seedlings developed cotyledon, after a week, three milliliters of the diluted Rhizobium was inoculated again.Plants were harvested on the 30th day after sowing and separated into root and aerial portions at the soil level.Then the growth parameters of dry weight, P and N contents of plant were determined.Dry weights of plant samples of shoot and root were recorded after drying in an oven at 75℃.P was determined after digestion of 0.1 g dry weight in pure sulfuric acid,following the molybdenum-blue method (Murphy and Riley, 1962).N content was also determined on 0.1 g dry weight digested in pure sulfuric acid, thereafter distilled and titrated according to Kjeldahl analysis method (Bremner and Mulvaney, 1982).

Measurement of nitrogen- fixing activity

比较各类院校的文化课程情况，差别是客观存在，但差别的产生往往取决于不同的教学环境。院校类别不同，专业位置也不同。外语类院校的英语专业往往是骨干专业，历史积淀丰厚，建设力度大，投入多，文化课程建设形成了完善的体制。而英语专业在其他院校办学历史较短，往往难以跻身主流专业，在理工类或其他类院校尤其如此，常常旁落为弱势学科。倘若投入不足，师资不足，会形成恶性循环，难以有长足发展。无论在哪一类院校，外语专业都要积极争取自己的生存和发展空间。既要靠自身的努力，在教学和科研上出成果，也要不断向校方和其他专业推介自己，引起足够的重视。这一点在以理科为主的院校尤其如此。

综上所述，缬沙坦、氨氯地平联合治疗社区老年原发高血压合并糖尿病的效果较好，对患者舒张压、收缩压及血糖水平的降低效果明显，因此，值得推广。

Nitrogen-fixing activity of nodulated roots was measured by the acetylene reduction method of Sasakawa et al (1986).

Fifteen strains were researched by nodulation checking, and it was found that all the strains were all Rhizobia (data not shown).The results indicated that Rhizobia of W5 and C46 were more effective in their symbiosis with soybean than others.Plant nodule number, nodule weight, and nodule nitrogenase activity per plant were found to be enhanced by the combined inoculation compared to individual inoculation.The combined strains of inoculation with CW54 had the highest effects, nodule number,nodule weight and nodule nitrogenase activity were markedly stimulated, increasing 89.2%, 57.1% and 81.1%, when compared with CK U110, followed with CW53 in Figs.1, 2 and 3.

The experimental design was a completely randomized blocks design with three replications.The treatments included CK (without inoculation) and inoculation (106 strains of Rhizobium on the surface of each seed during inoculation).Each plot was 15 m2 with row width of 50 cm and plant space of 15 cm.

The filed trial was conducted in Zhanjiang City of Guangdong Province, where the soil belongs to red soil type with pH 5.0, 65.60 mg · kg-1 N and 10.06 mg · kg-1 P.Inoculants C46 and CW54 were used to inoculate soybean cultivar "Huaxia 3".The inoculants were prepared as mentioned above.

Pot experiment

Results

Five plants were randomly sampled at pod filling stage and maturity, respectively.The biomass of shoot,plant height, the number of nodule, weight of nodule,N and P contents were determined at the first harvest.The yield was measured after harvesting mature plants.The data obtained were statistically analyzed by students' F-test (Stat View 5.0, SAS Institute Inc.).

Effects of inoculation Rhizobium on soybean root nodule growth

Field evaluation

Fig.1　Effect of inoculation Rhizobium on root nodule number of soybean

Fig.2　Effect of inoculation Rhizobium on root nodule weight of soybean

Fig.3　Effect of inoculation Rhizobium on acetylene reducing activity of soybean root nodule

Effects of inoculation Rhizobium on soybean growth

从以上我们不难发现，如果译者根据字面意义采取字对字的直译方法，那么蕴气式可以表达为“qunqi shi”，那么读者就会感到茫然，尤其是对第一次接触中国传统文化——气功的人来说，他们会感到很奇怪。“蕴气”“凝神静气、呼吸自然”和“深、平、稳”的方式为中国气功的运气方式。运气，对调动人体的精、气、神，都有很好的效果。译者此处采取了归化的翻译策略，可以说恰当地传达出意义，使读者一目了然。“盘龙”翻译为“coiling dragon”也不失为上策，相信译语读者获取的意义与源语读者阅读“盘龙”二字所获取的信息是相同的，效果应该是一致的。

In insoluble P soil, inoculation with CW54, CW53 and C46 strains significantly increased plant dry weight as compared to CK U110.Inoculation in Al-P soil had higher dry weight of shoot or the whole plant than Fe-P.The strains CW54 and CW53 showed the same response to both Al-P and Fe-P.CW54 strain was the most effective on shoot dry weight with an increase of 33.9% in Al-P and 16.2% in Fe-P as compared with CK U110 shown in Figs.4 and 5, respectively.In addition, CW 53 and C46 also significantly enhanced shoot dry weight in Al-P soil, 23.2% and 17.9% as compared with CK U110, but no difference in root dry weight was observed, while in Fe-P conditions, it was significantly promoted only by inoculation W5 strains, increasing approximately 21% as compared with CK U110 shown in Figs.4 and 5.U110 performed well in Fe-P than in Al-P.The results indicated that effects of inoculation were obvious in terms of plant growth.

Fig.4　Effect of inoculation Rhizobium on shoot dry weight of soybean

Al-P, Fe-P replace of aluminum phosphate, iron phosphate respectively.

Effects of inoculation Rhizobium on nitrogen content

There was a significant interaction between insoluble P and Rhizobium strains for N content of plant.Besides,inoculation with Rhizobium strains and application of insoluble P soil, respectively, had significant difference.However, N content of root was not significant different.Only inoculation with CW54 increased N content of plant in Al-P and Fe-P soil as compared with other inoculants.In Al-P soil, inoculation with CW54 resulted in the highest N content of shoot with 13.325 mg · plant-1 or plant with 15.666 mg · plant-1 in Table 1.On the average, inoculation with Rhizobium strains increased higher N content in Al-P soil than Fe-P soil.In Al-P conditions, inoculation with CW54 and C46 strains significantly stimulated N uptake of plant as compared with other strains, increasing 43.2%and 26.9% as compared with CK U110, respectively,while in Fe-P conditions, it was slightly promoted only by inoculation CW54 strains in Table 1.These results suggested that symbiotic nitrogen fixation utilized insoluble P, especially Al-P, in acidic soil.

Fig.5　Effect of inoculation Rhizobium on root dry weight of soybean

Al-P, Fe-P replace of aluminum phosphate, iron phosphate respectively.

Effects of inoculation Rhizobium on phosphorus content

影视动画作品的后期再创造作用，主要体现在四个方面：鲜明的人物特质、极具吸引力的故事结构、良好的情绪刻画、更高的可看性。所谓情绪体现就是渲染相应的气氛，从而体现出作品的整体情感。情绪体现的完整性能够增加画面的生动性与观赏性，使影视动画作品的内涵更加丰富，从而体现出后期制作的意义。

Table 1　Effect of inoculation on N content of plant in insoluble P soil

Al-P, Fe-P replace of aluminium phosphate and iron phosphate, respectively.* indicates significant difference against CK at 5% level students' F-test.No significant difference against CK at 1% level students' F-test.The same as below.

Strain N content under insoluble P (mg · plant-1)Al-P Fe-P Shoot　Root　Shoot　Root U110　8.963　1.978　8.673　2.431 C 8.727　1.994　9.072　2.315 W5　9.046　1.780　7.768　2.237 C46　11.716*　2.179　9.183　1.835 CW53　9.329　2.386　8.988　1.961 CW54　13.325*　2.341　9.696　2.309

Table 2　Effect of inoculation Rhizobium on P content of plant in insoluble P soil

Strain N content under insoluble P (mg · plant-1)Al-P Fe-P Shoot　Root　Shoot　Root U110　0.950　0.315　0.518　0.188 C 0.905　0.352　0.979*　0.408*W5　0.952　0.363　0.794*　0.330*C46　1.361*　0.305　0.806*　0.318*CW53　0.923　0.327　0.887*　0.391*CW54　1.123　0.246　0.877*　0.508*

Field experiment

Evaluation of inoculation Rhizobium under field conditions

Cultivation experiments of soybean treated with Rhizobium were achieved several times in a field from November, 2012 to April, 2016.In this paper, the most recent results were shown.Two well-inoculated strains of C46 and CW54 were selected from seven strains.The nodule numbers in the plants treated with C46 and CW54 strains were significantly increased by 150.3%and 157.9% as compared to those of the control at 21-day after inoculating, respectively.Such trend was also clearly observed at the time of soybean podding.Although statistical significance was not observed on the nodule weight, plant dry weight and phosphorus content treated with C46 and CW54 strains at 21-day after inoculating, it was significantly observed in the plants treated with C46 and CW54 strains at the period of soybean podding.The nodule weight, plant dry weight, phosphorus content of pod and the whole plants in the plants treated with CW54 strains inceased 221.1%, 86.4%, 100.3% and 92.4% significantly compared to those of the control, such trend was also clearly observed in the plants treated with C46 strains in Table 3.

Table 3　Effect of inoculation Rhizobium at 21-day after inoculating

* indicates significant difference against CK at 5% level of single-factor variance analysis by students' F-test. ** indicates significant difference against CK at 1% level of single-factor variance analysis by students' F-test.The same as below.

Strain　Nodule number(per plant)Nodule weight(g · plant-1)Phosphorus content(mg · plant-1)CK (Untreated)　13.3　0.20　5.20　112.40　15.03 C46　33.3**　0.29　6.71　164.79*　16.19 CW54　34.3**　0.34　5.83　134.21*　14.61 Plant dry weight(g · plant-1)Nitrogen content(mg · plant-1)

The nitrogen contents of the whole plant in the plants treated with C46 and CW54 strains increased 46.6%and 19.4% at 21-day after inoculating, and 105.4%and 125.1% for the time of soybean podding compared to that of the control, respectively.The nitrogen contents of pod in the plants treated with C46 and CW54 strains were also significantly increased in Table 4.The total biomass in the plants treated with C46 and CW54 strains were significantly increased by 81.6%and 86.4%, as compared to those of the control at the time of soybean podding, and the yield were increased by 48.5% and 51.4% in Table 5, respectively.

显然,损失函数的值越小,表明模型的预测结果越准确。我们利用梯度下降法迭代地寻找损失函数的最小值,每一步迭代后通过反向传播更新网络中的权值ω,使得模型不断优化。损失函数的梯度L可以表示为:

Table 4　Effect of inoculation Rhizobium at period of soybean podding

Strain　Nodule umber(per plant)Nitrogen content　Phosphorus content mg · pod-1　mg · plant-1　mg · pod-1　mg · plant-1 CK (Untreated)　19.7　0.38　17.32　145.41　358.76　26.53　86.64 C46　 82.3**　1.40**　31.46**　267.64**　737.07**　49.24**　155.82*CW54　 63.6**　1.22**　32.29**　288.63**　807.55**　53.15**　166.70*Nodule weight(g · plant-1)Plant dry weight(g · plant-1)

Table 5　Effect of inoculation Rhizobium on yield at period of soybean podding

Different letters indicate a significant difference at 5% level of single-factor variance analysis by students' F-test.

Strain　Shoot length(cm)　Pod number　Dry weight (g)　Yield(kg · hm-2)Shoot weight　Root weight　Pod weight　Total weight CK　45.15b　39.2b　10.67b　1.68b　4.60b　17.32b　875b C46　58.69a　74.7a　19.67a　2.40a　8.00a　31.46a　1 300a CW54　55.75a　77.0a　19.90a　2.31a　8.86a　32.29a　1 325a

Discussion

Inoculation with Rhizobium not only enhanced nitrogen fixation activity, plant biomass, N content in soybean and other legumes (Oberson et al., 2013; Li et al., 2011), but also improved soil fertility and quality.Accordingly, we attempted to analyze the symbiotic nitrogen fixation effectiveness of both W-strains and C-strains.This result showed that most of W-strains were more efficient in terms of nitrogen fixation compared to C-strains.A significant increase of nodule formation and ARA in Rhizobium inoculation was shown in Figs.1, 2 and 3.Among these Rhizobium,CW54 strain gave the highest ARA of 14.21 μmol C2H4 h · plant-1 in the seedlings shown in Fig.3.A low and limiting P supply eventually reduced plant growth,besides reduced P content and N2-fixation (Oberson et al., 2013).In this study, inoculation with CW54 and W5 strains significantly increased shoot dry weight as compared with CK U110 in insoluble P soil shown in Figs.4 and 5; CW54 strains had a significant effect in Al-P soil and the shoot dry weight was at a maximum 0.75 g · plant-1, increased by 33.9% as compared to that of CK U110 in Figs.4 and 5.These results implied that inoculation Rhizobium was beneficial for nitrogen fixation and growth of soybean.Nitrogen content could be added to the cropping system by the use of N2-fixing legumes (James and Baldani, 2012;Frankow-Lindberg and Dahlin, 2013; Vesterager et al., 2007).Miao et al.(2006) reported that Al-P played an important role for nitrogen fixation system of soybean in acidic soil.It could be verified that inoculation with CW54 resulted in the highest N uptake of plant (3.006 mg · plant-1) in Al-P soil, which suggested that the suitable Rhizobium inoculation increased nitrogen fixation, and then improved nitrogen content in the insoluble P soil shown in Table 1.The phosphorus content of the whole plant was followed a similar trend to N uptake.Interestingly, the phosphorus content of root was higher in Fe-P soil, but the phosphorus content of shoot was not significantly different in Table 2.These results suggested it was not easy to utilize Fe-P for increasing phosphorus content of plant compared with Al-P in acidic soil, and also suggested that root was more sensitive than shoot in the insoluble phosphorus soil.

The ratio symbiotic N2 fixation (SNF)/phosphorus content was computed to estimate the efficiency of plant to use P for N2 fixation (Attar et al., 2012).The results showed that inoculated with CW54 (2.183 mg SNF/mg phosphorus) resulted in higher mean value of SNF/P content compared to CK U110 (0.196 mg SNF/mg P) in Fig.3 and Table 2.This was in agreement with a previous report that the phosphorus content might be involved in regulation of nodule initiation (Magadlela et al., 2012) and affected N content, SNF of plant (Oberson et al., 2013).The effects of inoculated Rhizobium in a field were similar to that in a pot.Therefore, inoculation Rhizobium was beneficial for soybean nutrient uptake, growth and yield in Tables 3, 4 and 5.These results suggested that screening Rhizobium strains, especially strains for tolerance to the insoluble P, and later testing soybean cultivars inoculated with these strains might be very helpful in identifying superior symbiotic relationships under insoluble P conditions in acid soil.However,these results needed to be further tested and verified in the field.

Conclusions

The combined Rhizobium inoculation was more effective than individual Rhizobium inoculation; the biomass in the soybean treated with CW54 strains were significantly increased as compared to those of the control in a field condition; the inodule nitrogenase activity treated with CW54 was markedly stimulated as compared to that of the control U110; the inoculation with CW54 significantly enhanced phosphorus uptake of plant in Fe-P soil higher than that in Al-P soil.Therefore, inoculation Rhizobium was beneficial for soybean nutrient uptake, growth and yield under insoluble phosphate soil conditions.

The first and second authors contributed equally to this work.

References

Abdelnaby M, Nasreldeen N, Elnesairy B, et al. 2015.Symbiotic and phenotypic characteristics of Rhizobia nodulaing cowpea (Vigna unguiculata L.Walp) grown in arid region of libya (Fezzan).Journal of Environmental Science and Engineering B, 4: 227-239.

Adrian U, Goss M J, Simon C, et al.2012.Analysis of matrix effects critical to microbial transport in organic waste-affected soils across laboratory and field scales.Water Resources Research, 48: 154-167.

Attar H A, Blavet D, Selim E M, et al.2012.Relationship between phosphorus status and nitrogen fixation by common beans (Phaseolus vulgaris L.) under drip irrigation.International Journal of Environ-mental Science and Technology, 9(1): 1-13.

Bargaz A, Lazali M, Amenc L, et al.2013.Differential expression of trehalose 6-P phosphatase and ascorbate peroxidase transcripts in nodule cortex of Phaseolus vulgaris and regulation of nodule O2 permeability.Planta, 238(1): 107-119.

Bekere W, Kebede T, Dawud J.2013.Growth and nodulation response of soybean (Glycine max L.) to lime, Bradyrhizobium japonicum and nitrogen fertilizer in acid soil at melko, South Western Ethiopia.International Journal of Soil Science, 8(1): 25-31.

Bremner J M, Mulvaney C S.1982.Nitrogen-total.In: Page A L,Miller R H, Keeney D R.Methods of soil analysis.II.Chemical and microbiological properties.2nd ed.Am Soc Agron, Madison, Wis.pp.595-624.

Elkoca E, Kantar F, Sahin F.2008.Influence of nitrogen fixing and phosphorus solubilizing bacteria on the nodulation, plant growth, and yield of chickpea. Journal of Plant Nutrition, 31(1): 157-171.

Fankem H, Ngo N L, Nguesseu N G, et al.2014.Maize (Zea mays)growth promotion by rock-phosphate solubilising bacteria isolated from nutrient deficient soils of Cameroon.African Journal of Microbiology Research, 8(40): 3570-3579.

Frankow-Lindberg B E, Dahlin A S.2013.N2 fixation, N transfer, and yield in grassland communities including a deep-rooted legume or non-legume species. Plant and Soil, 370(1/2): 567-581.

James E K, Baldani J I.2012.The role of biological nitrogen fixation by non-legumes in the sustainable production of food and biofuels.Plant & Soil, 356: 1-3.

Li Q Q, Wang E T, Zhang Y Z, et al.2011.Diversity and biogeography of rhizobia isolated from root nodules of glycine max grown in Hebei Province China.Microbial Ecology, 61(4): 917-31.

Magadlela A, Kleinert A, Dreyer L L, et al.2012.Low-phosphorus conditions affect the nitrogen nutrition and associated carbon costs of two legume tree species from a mediterranean-type ecosystem.Australian Journal of Botany, 62(1): 1-9.

Miao S J, Qiao Y F, Han X Z.2006.Requirement of phosphorous for soybean cultivars nodulation and nitrogen fixation.System Sciences and Comprehensive Studies in Agriculture, 22(4): 276-278.

Murphy J, Riley J P.1962.A modified single solution method for the determination of phosphate in natural waters.Anal Chem Acta, 27:31-36.

Oberson A, Frossard E, Bühlmann C, et al. 2013.Nitrogen fixation and transfer in grass-clover leys under organic and conventional cropping systems.Plant and Soil, 371(1-2): 237-255.

Pandit R, Kunjadia P, Mukhopadhyaya P, et al. 2014.Inorganic phosphate solubilizing potential of arthrobotrys conoides and duddingtonia flagrans, a nematode trapping fungi a potential biocontrol agent.International Journal of Agricultural Technology, 10(3): 559-570.

Quernéa A, Battie-laclaua P, Dufoura L, et al.2017.Effects of walnut trees on biological nitrogen fixation and yield of intercropped alfalfa in a mediterranean agroforestry system.European Journal of Agronomy, 84: 35-46.

Rejili M, Mahdhi M, Fterich A, et al. 2012.Symbiotic nitrogen fixation of wild legumes in Tunisia: soil fertility dynamics, field nodulation and nodules effectiveness.Agriculture Ecosystems & Environment,157(157): 60-69.

Sasakawa H, Trung B C, Yoshida S.1986.Stem nodulation on Aeschynomene indica plants by isolated Rhizobia.Soil Sci Plant Nutr, 32: 145-149.

Simon Z, Mtei K, Gessesse A, et al. 2014.Isolation and characterization of nitrogen fixing rhizobia from cultivated and uncultivated soils of Northern Tanzania.American Journal of Plant Sciences,5(26): 4050-4067.

Singh A P, Singh J B.2014.Differential synthesis of alkaline phosphatase in Rhizobium species isolated from the tropics.Zeitschrift Für Naturforschung C, 39(11/12): 1038-1041.

Taylor R W, Williams M L, Sistani K R.1991.Nitrogen fixation by soybean-bradyrhizobium combinations under acidity, low P and high Al stresses.Plant and Soil, 131(2): 293-300.

Togay N, Togay Y, Cimrin K M, et al.2008.Effects of rhizobium inoculation, sulfur and phosphorus applications on yield, yield components and nutrient uptakes in chickpea (Cicer arietinum L.).African Journal of Biotechnology, 7: 776-782.

Van G J, Weissing F J, Kuipers O P, et al.2014.Density of founder cells affects spatial pattern formation and cooperation in Bacillus subtilis bio films.The ISME Journal, 8(10): 2069-2079.

Vesterager M, Nielsen N E, Høgh-Jensen H.2007.Nitrogen budgets in crop sequences with or without phosphorus fertilised cowpea in the maize-based cropping systems of semi-arid Eastern Africa.Afr J Agri Res, 2(6): 261-268.

Zhang H T, Guo L Z, Chai Q, et al.2010.Effects of nodule bacteria inoculation on growth of pea/maize system.Agricultural Research in the Arid Areas, 28(5): 92-93.