Effect of Rhizobium and Bacillus strains on the growth, symbiotic properties and nitrogen and phosphorus content of lablab bean (Lablab purpureus L.).
Legumes are capable of developing root nodules through the symbiotic relationship with N-fixing bacteria. They can be used for human food and animal feed
Forage legumes have many uses; thy can be used as green manure, cover crops and as animal feed. Like other legumes, they improve soil nitrogen content through nitrogen fixation.
Lablab bean (Lablab purpureus L.) is a fest growing annual legume. In Sudan, it could be sown for grain as well as forage with maize and sorghum or alone. Generally, it is grown in River Nile, Gezira and Khartoum states . It could be sown all over the year although seed productivity is reduced in winter.
Biofertilizers are substances which contain living microorganisms which when applied to seed, plant surface or soil colonize the rhizosphere or the plant and promote growth by increasing the supply or availability of nutrients to the host plant . They include the nitrogen fixing, phosphate solubilizing and plant growth promoting microorganisms .
Biological nitrogen fixation is an important part of the microbial process. A wide range of organisms have the ability to fix nitrogen. An examination of the history of biological nitrogen fixation showed the interest on the symbiotic system of leguminous plants and rhizobia. These associations have the greatest quantitative impact on the nitrogen cycle .
The N2-fixing capability of rhizobia varies greatly up to 450kg N/ha among host plant species and bacterial strains .Selection of the best strain must take into account rhizobia-host compatibility. The strain must have high N2-fixation rate and be able to compete with the indigenous rhizobia .
Phosphorus is the second limiting plant nutrient after nitrogen . Soils usually contain a high amount of total phosphorus but its availability to plant is very low. In addition to traditional methods of mineral phosphate fertilization, microbial phosphate solubilization may increase the availability of phosphorus in arable soils .
Phosphate solubilizing microorganisms include largely bacteria and fungi. The most efficient phosphate solubilizing microorganisms belong to genera Bacillus and Pseudomonas in bacteria and Aspergillus, Penicillum and mycorrhza in fungi . Phosphate solubilizing microorganisms play a key role in the plant metabolism and crop productivity. They have been reported to increase the availability and uptake of native soil phosphorus in different crops .
Several studies have conclusively shown that the phosphate solubilizing microorganisms solubilized and fixed soil phosphorus and applied phosphate resulting in higher crop yields .
As they share common microhabitat in the root-soil surface, rhizobia and plant growth promoting rhizobacteria must interact during their process of root colonization-same plant growth promoting rhizobacteria can improve nodulation and nitrogen fixation in legumes . Co-inoculation of Rhizobium and phosphate solubilizing Bacillus increased germination, nutrient uptake, plant hight, number of branches, nodulation, yield and total biomass of chick pea .
Thy increased nodulation and nirtogenase activity of Bradyrhizobium japonicum in soybean culture system .
Materials and methodes
Two field experiments were conducted in the same season in two different locations. The first location was at the experimental farm of El Hudaiba Research Station, El Hudaiba, River Nile State. The second one was at the Demonstration Farm of the Faculty of Agriculture, University of Sudan, Shambat, Sudan. The objectives of the study are to assess the effects of biofertilizers on the symbiotic properties of lablab bean and nitrogen and phosphorus content of the plant.
Randomized complete block design was adopted in each experiment in a factorial combination of 5 Rhizobial strains x 3 BMP x 4 replications x 2 times of sampling.
In both experiments, the land was prepared by ploughing, leveling and ridging. The land was then divided into plots 4 x4 meters each. Five ridges were made per plot with 60 cm between then.
Seeds were inoculated with charcoal based inoculums of the appropriate rhizobial strain and/or BMP strain. Inoculated seeds were then left to air dry under shade.
Four Rhizobium strains were used. There were: cowpea strain, ENRRI 16A, TAL 169 and USDA 5019. Two BMP strains were used, these were: phosphobacterin and phosphorin.
Seeds were sown by hand on the eastern side of the ridge in holes 20 cm apart. Four seeds were planted per hole. Plots were irrigated immediately after sowing and then 10-15 days intervals. Weeding was carried out by hand twice in the season.
Two saplings were carried out at 6 and 8 weeks from sowing. At each sampling, three samples were taken from the middle ridges of the plot by digging around the plants to avoid pulling the plant.
The soil was carefully removed from the roots by hand and then washed gently. Samples were kept in paper-bags and then transferred to the laboratory for parameters measurements.
For each sampling, nodules numbers, nodules dry weight, shoot and root dry weights and nitrogen and phosphorus content of the plant were measured.
Multifactor analysis of variance was performed to determine the effect of each treatment, and interaction between treatments on the measured parameters. Comparisons between means of treatments for various parameters measured were made by standard error calculation . The objectives of the statistical analysis was also to separate the variations due to intrinsic factors. Data were assessed by analysis of variance (ANOVA). . Significance was accepted at P[less than or equal to]0.05.
Results and discussion
In both location at 6 and 8 day after sowing, Rhizobium inoculation with either strain significantly (P[less than or equal to]0.05) increased lablab bean shoot dry weight over the uninoculated control plants (Tables 1). No significant differences were observed between Rhizobium strains at 6 weeks at El-Hudiba where as strain TAL 169 showed a significant (P[less than or equal to]0.05) increase in the shoot dry weight over the other strains at Shambat after 6 weeks from sowing. At 8 weeks from sowing. Cowpea strain, ENRRI 16A and USDA 5019 showed a significant (P[less than or equal to]0.05) increase in this parameter over strain TAL 169 and the uninoculated control at Shambat and no significant differences between the strains at El-Hudiba.
In both sites and at each sampling, cowpea strain was recommended the best followed by strain ENRRI 16A,TAL 19 and USDA 5019 strains.
The results obtained reflect the positive effect of Rhizobium inoculation which increased the fixed nitrogen by the symbiotic relation with lablab bean and hence increased the plant growth. Several studies displayed this positive symbiosis between Rhizobium and leguminous plants, faba bean , soybean  chick pea and lablab bean .
BMP inoculation significantly (P[less than or equal to]0.05) increased shoot dry weight over the uninoculated control in the two locations and both samplings. The results showed a significant differences between phosphorin and phosphopacterin at 6 weeks after sowing at Elhudiba but no differences were observed at 8 weeks and at the two samplings at Shambat. Generally, phosphobacterin over weighed phosphorin in the two samplings in both locations.
The results obtained may ascribed to the effect of BMP on enhancing root growth  by solubilizing phosphorus and making at available in the rhizosphere which increased the root biomass and its ability to absorb nutrients and hence increased the plant growth.
The results were in accord with the observations of  and  and  in green gram.
Co-inoculation with Rhizobium strains and BMP strain significantly (P[less than or equal to]0.05) increased shoot dry weight at El-Hudiba at both samplings but not at Shambat. At both locations and the two samplings period the interaction between phosphobacterin and either cowpea strain or strain ENRRI 16A resulted in a higher shoot dry weight compared to Rhizobium alone, BMP alone or a combination between BMP and other strains.   reported the interaction between Rhizobium and BMP strains in increasing shoot dry weight of check pea and green gram.
Table (2) showed the effect of the treatments on root dry weight of lablab bean plant. Rhizobium inoculation significantly (p[less than or equal to]0.05) increased the root dry weight per plant in the two site at the two times of sampling.
Cow pea strain and ENRRI 16A strain showed no significant difference between them but they significantly (p[less than or equal to]0.05) increased the root dry weight per plant over TAL 169 and USDA 5019 stains. Cow pea strain was superior at 6 weeks where as ENRRI 16A was superior at 8 weeks after sowing.
The fact that Rhizobium inoculation increased the root dry weight of leguminous plants was observed by many research workers  in chick pea and  in green gram and  in faba bean.
No significant differences were observed between phosphobacterin in El-Hudaiba or Shambat. Both of them showed a significant (p[less than or equal to]0.05) increased in the root dry weigh over the control uninoculated plants at 6 or 8 weeks after sowing in the two sites. The results could be taken as an evidence for the effectiveness of the BMP strains on solubilizing phosphorus and making it available to the plant  and enhancing root growth .
Co-inoculation with Rhizobium and BMP significantly (p[less than or equal to]0.05) increased root dry weight, with the superiority of cow pea strain in combination with phosphobacterin in the two sites at both times of sampling. Similar results were obtained by  in chick pea.
Table (3) showed the effect of the treatment on lablab bean nodulation. Rhizobium inoculation significantly (P[less than or equal to]0.05) increased nodules numbers per plant at both sites at 6 and 8 weeks from sowing over the uninoculated plants. No significant differences were observed between the strains although the cowpea strain was superior at Shambat sites in both samplings and at 6 weeks after sowing in El-Hudiba followed by ENRRI 16 and USDA 5019.
The findings that Rhizobium inoculation increased nodulation in legumes were reported by many research workers,  in chickpea and  in soybean.
BMP inoculation as phosphorin or phosphobacterin significantly (P[less than or equal to]0.05) increased nodules number per lablab bean plant. No significant differences were observed between the two strains at Shambat site and at Elhudiba after 6 weeks from sowing. Phosphobacterin inoculation resulted in a higher nodule numbers.
At 8 weeks after sowing, at Elhudiba site, phosphobacterin strain showed a significant increase in nodulation over phosphorin strain. These results were in accord with many findings that showed the positive effects of BMP inoculation on nodulation of chickpea and faba bean .
In both locations, the interaction of Rhizobium and BMP inoculation showed no significant differences in nodulation at 6 weeks after sowing. At 8 weeks sampling a significant (P[less than or equal to]0.05) differences were observed. Cowpea strain and TAL 169 with phosphobacterin showed the higher nodules number per lablab bean plant in both sites.
From the results shown in Table (4), the two sites, more or less show thee same pattern in the dry weight of the nodules. Rhizobium inoculation by either strain significantly (P[less than or equal to]0.05) increased nodules dry weight per plant compared to uninoculated control plants in the two samplings. Cowpea strain and ENRRI 16A strain over weighed other strains. Previous results showed this significant increase in this parameter .
BMP inoculation alone significantly (P[less than or equal to]0.05) increased nodules dry weight per lablab plant. Phosphopacterin have the better nodules dry weight at 6 and 8 weeks after sowing.  and  observed the same results.
Co-inoculation with Rhizobium and BMP has no significant effect on nodules dry weight per plant at 6 weeks after sowing although a significant (P[less than or equal to]0.05) increase was observed at 8 weeks after sowing. Phosphobacterin with either cowpea strain or ENRRI 16A produced the higher dry weight of nodules. Other research workers observed the same results,  and .
Rhizobium inoculation by either strain significantly (p[less than or equal to]0.05) increased nitrogen content of lablab bean shoot at the two experimental site (Table 5) no significant difference in plant nitrogen content were observed between cow pea strain and ENRRI 16A strain but both of them significantly (p[less than or equal to]0.05) increased the nitrogen content over USDA 5019 and TAL 169 strains. Increasing the nitrogen content in the plant shoot by Rhizobium can be used as a direct criterion to determine the effectiveness of the Rhizobium strains on fixing nitrogen. .
BMP inoculation significantly (p[less than or equal to]0.05) increased the oa nitrogen content. At El-Hudiba, site no significant differences were observed between phosphobacterin and phosphorin, where as a significant difference between them was observed at Shambat site. In both sites phosphobacterin gave the highest amount of the nitrogen accumulated in the shoot.
At both locations, the co-inoculation with Rhizobium and BMP significantly (p[less than or equal to]0.05) increased shoot nitrogen content of the plant. The interaction between phosphobacterin and cow pea strain or ENRRI 16A showed the higher nitrogen content follow by phosphorin with cowpea strain.
The results are in accord with the findings of  who reported that the combined inoculation of Rhizobium and BMP gave a higher nutrient uptake compared to individual inoculation or uninoculated control.
Although  showed that the phosphorus that has been available by the treatments utilized by the plant, lablab bean inoculation with Rhizobium or BMP alone or together significantly (p[less than or equal to]0.05) increased shoot phosphorus content in the two experimental sites. Cowpea strain followed by ENRRI 16A gave the highest results compared to USDA 5019 or TAL 169 strains. Likewise, phosphopacterin gave the best values.
Phosphobacterin and cowpea strain co-inoculation resulted in higher amount of phosphorus shoot content in both sites. While phosphorin and cowpea strain be the second at Shambat site, phosphobacterin with ENRRI 16A was the second at El-Hudiba (Table 5).
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Tagelsir Hassan Mohamed Ahmed, Faculty of science and Technology, Shendi Universiy, Shendi, Sudan. E-mail: firstname.lastname@example.org Tel. 00249901236920 Fax 00249157793418
(1) Tag elsir Hassan Mohamed Ahmed, (2) Gadalla Abdalla Elhassan, (3) Migdam Elsheikh Abdelgani and (3) Ammar salama Abdalla
(1) Faculty of science and Technology, Shendi Universiy, Shendi, Sudan.
(2) Faculty of Agriculture, Sudan University for Science and Technology, Khartoum, Sudan.
(3) Environment and National Research Institute, the National Centre for Research, Khartoum, Sudan.
Tag elsir Hassan Mohamed Ahmed; Gadalla Abdalla Elhassan; Migdam Elsheikh Abdelgani and Ammar salama Abdalla; Effect of Rhizobium and Bacillus strains on the growth, symbiotic properties and nitrogen and phosphorus content of lablab bean (Lablab purpureus L.)
Table 1: Effect of Rhizobium and BMP inoculation on shoot dry weight (gm/plant) BMP strain Rhizobium strain El-Hudaiba Site 6 weeks Uninoculated uninoculated 1.975 Cowpea strain 4.175 ENRRI 16A 4.025 TAL 169 4.975 USDA 5019 4.050 3.840 Phosphorin uninoculated 4.350 Cowpea strain 4.725 ENRRI 16A 4.475 TAL 169 5.000 USDA 5019 4.275 4.565 Phosphobacterin uninoculated 4.200 Cowpea strain 4.350 ENRRI 16A 3.575 TAL 169 4.900 USDA 5019 5.250 4.655 LSD for BMP (P) [+ or -] 0.417 LSD for Rhizobium (R) [+ or -] 0.539 LSD for P * R [+ or -] 0.933 BMP strain Rhizobium strain 8 weeks Uninoculated uninoculated 17.125 Cowpea strain 17.975 ENRRI 16A 17.750 TAL 169 22.075 USDA 5019 22.250 19.435 Phosphorin uninoculated 22.000 Cowpea strain 32.725 ENRRI 16A 33.650 TAL 169 28.250 USDA 5019 24.200 28.165 Phosphobacterin uninoculated 23.075 Cowpea strain 32.725 ENRRI 16A 32.025 TAL 169 36.950 USDA 5019 39.725 32.900 LSD for BMP (P) [+ or -] 2.213 LSD for Rhizobium (R) [+ or -] 2.856 LSD for P * R [+ or -] 4.948 BMP strain Rhizobium strain Shambat Site 6 weeks Uninoculated uninoculated 1.767 Cowpea strain 5.970 ENRRI 16A 3.283 TAL 169 5.500 USDA 5019 5.560 4.416 Phosphorin uninoculated 1.743 Cowpea strain 5.603 ENRRI 16A 4.400 TAL 169 4.980 USDA 5019 6.13 4.572 Phosphobacterin uninoculated 3.953 Cowpea strain 5.787 ENRRI 16A 5.400 TAL 169 8.190 USDA 5019 6.377 5.941 LSD for BMP (P) [+ or -] 0.916 LSD for Rhizobium (R) [+ or -] 1.182 LSD for P * R [+ or -] 2.048 BMP strain Rhizobium strain 8 weeks Uninoculated uninoculated 8.583 Cowpea strain 16.167 ENRRI 16A 16.033 TAL 169 14.450 USDA 5019 14.763 14.399 Phosphorin uninoculated 10.350 Cowpea strain 25.387 ENRRI 16A 24.720 TAL 169 18.550 USDA 5019 21.323 20.066 Phosphobacterin uninoculated 10.667 Cowpea strain 28.857 ENRRI 16A 27.993 TAL 169 23.523 USDA 5019 23.553 22.919 LSD for BMP (P) [+ or -] 1.461 LSD for Rhizobium (R) [+ or -] 1.886 LSD for P * R [+ or -] 3.266 Table 2: Effect of Rhizobium and BMP inoculation on root dry weight (gm/plant) MP strain Rhizobium strain El-Hudaiba Site 6 weeks Uninoculated uninoculated 0.196 Cowpea strain 0.387 ENRRI 16A 0.357 TAL 169 0.341 USDA 5019 0.337 0.324 Phosphorin uninoculated 0.261 Cowpea strain 0.684 ENRRI 16A 0.568 TAL 169 0.459 USDA 5019 0.466 0.488 Phosphobacetrin uninoculated 0.299 Cowpea strain 0.753 ENRRI 16A 0.711 TAL 169 0.488 USDA 5019 0.472 0.545 LSD for BMP (P) [+ or -] 0.037 LSD for Rhizobium (R) [+ or -] 0.048 LSD for P * R [+ or -] 0.083 MP strain Rhizobium strain 8 weeks Uninoculated uninoculated 0.875 Cowpea strain 2.500 ENRRI 16A 2.25 TAL 169 2.465 USDA 5019 2.625 2.143 Phosphorin uninoculated 2.638 Cowpea strain 2.550 ENRRI 16A 3.700 TAL 169 2.900 USDA 5019 3.650 3.088 Phosphobacetrin uninoculated 1.725 Cowpea strain 3.663 ENRRI 16A 3.750 TAL 169 2.900 USDA 5019 2.475 2.903 LSD for BMP (P) [+ or -] 0.245 LSD for Rhizobium (R) [+ or -] 0.355 LSD for P * R [+ or -] 0.378 MP strain Rhizobium strain Shambat Site 6 weeks Uninoculated uninoculated 0.190 Cowpea strain 0.426 ENRRI 16A 0.389 TAL 169 0.477 USDA 5019 0.366 0.362 Phosphorin uninoculated 0.297 Cowpea strain 0.507 ENRRI 16A 0.483 TAL 169 0.406 USDA 5019 0.441 0.427 Phosphobacetrin uninoculated 0.268 Cowpea strain 0.650 ENRRI 16A 0.577 TAL 169 0.429 USDA 5019 0.25 0470 LSD for BMP (P) [+ or -] 0.031 LSD for Rhizobium (R) [+ or -] 0.04 LSD for P * R [+ or -] 0.069 MP strain Rhizobium strain 8 weeks Uninoculated uninoculated 1.020 Cowpea strain 2.813 ENRRI 16A 2.700 TAL 169 2.233 USDA 5019 2.300 2.213 Phosphorin uninoculated 2.080 Cowpea strain 4.760 ENRRI 16A 3.933 TAL 169 3.093 USDA 5019 3.467 3.467 Phosphobacetrin uninoculated 2.083 Cowpea strain 5.067 ENRRI 16A 4.967 TAL 169 .053 USDA 5019 4.033 4.041 LSD for BMP (P) [+ or -] 0.178 LSD for Rhizobium (R) [+ or -] 0.229 LSD for P * R [+ or -] 0.397 Table 3: Effect of Rhizobium and BMP inoculation on nodules number/plant BMP strain Rhizobium strain El-Hudaiba Site 6 weeks Uninoculated uninoculated 0.460 Cowpea strain 1.850 ENRRI 16A 1.075 TAL 169 1.775 USDA 5019 1.025 1.237 Phosphorin uninoculated 0.980 Cowpea strain 6.000 ENRRI 16A 5.800 TAL 169 3.813 USDA 5019 4.500 4.219 Phosphobacetrin uninoculated 1.500 Cowpea strain 6.625 ENRRI 16A 6.750 TAL 169 6.553 USDA 5019 5.583 5.402 LSD for BMP (P) [+ or -] 1.699 LSD for Rhizobium (R) [+ or -] 1.682 LSD for P * R [+ or -] 2.914 BMP strain Rhizobium strain 8 weeks Uninoculated uninoculated 1.225 Cowpea strain 4.975 ENRRI 16A 4.075 TAL 169 4.250 USDA 5019 3.500 3.605 Phosphorin uninoculated 1.775 Cowpea strain 15.375 ENRRI 16A 13.325 TAL 169 11.000 USDA 5019 9.250 10.145 Phosphobacetrin uninoculated 2.625 Cowpea strain 17.825 ENRRI 16A 16.100 TAL 169 12.250 USDA 5019 12.750 12.310 LSD for BMP (P) [+ or -] 1.379 LSD for Rhizobium (R) [+ or -] 1.78 LSD for P * R [+ or -] 3.084 BMP strain Rhizobium strain Shambat Site 6 weeks Uninoculated uninoculated 0.777 Cowpea strain 3.517 ENRRI 16A 3.577 TAL 169 2.000 USDA 5019 2.293 2.433 Phosphorin uninoculated 2.377 Cowpea strain 4.917 ENRRI 16A 4.600 TAL 169 3.600 USDA 5019 2.777 3.654 Phosphobacetrin uninoculated 2.570 Cowpea strain 5.135 ENRRI 16A 4.817 TAL 169 4.083 USDA 5019 3.533 4.035 LSD for BMP (P) [+ or -] 0.628 LSD for Rhizobium (R) [+ or -] 0.811 LSD for P * R [+ or -] 1.405 BMP strain Rhizobium strain 8 weeks Uninoculated uninoculated 0.757 Cowpea strain 5.183 ENRRI 16A 4.600 TAL 169 5.890 USDA 5019 3.890 4.064 Phosphorin uninoculated 4.443 Cowpea strain 14.890 ENRRI 16A 12.667 TAL 169 9.333 USDA 5019 8.167 9.900 Phosphobacetrin uninoculated 3.553 Cowpea strain 16.033 ENRRI 16A 14.667 TAL 169 12.000 USDA 5019 11.367 11.524 LSD for BMP (P) [+ or -] 1.124 LSD for Rhizobium (R) [+ or -] 1.452 LSD for P * R [+ or -] 2.514 Table 4: Effect of Rhizobium and BMP inoculation on nodules dry weight (mg/plant) BMP strain Rhizobium strain El-Hudaiba Site 6 weeks 8 weeks Uninoculated uninoculated 0.003 0.003 Cowpea strain 0.028 0.045 ENRRI 16A 0.034 0.038 TAL 169 0.016 0.048 USDA 5019 0.018 0.036 0.018 0.034 Phosphorin uninoculated 0.005 0.006 Cowpea strain 0.082 0.227 ENRRI 16A 0.071 0.219 TAL 169 0.057 0.127 USDA 5019 0.067 0.121 0.056 0.140 Phosphobacterin uninoculated 0.005 0.072 Cowpea strain 0.085 0.322 ENRRI 16A 0.077 0.307 TAL 169 0.051 0.253 USDA 5019 0.052 0.250 0.054 0.250 LSD for BMP (P) 0.016 0.026 LSD for Rhizobium (R) 0.021 0.034 LSD for P * R 0.036 0.058 BMP strain Rhizobium strain Shambat Site 6 weeks 8 weeks Uninoculated uninoculated 0.004 0.070 Cowpea strain 0.023 0.190 ENRRI 16A 0.021 0.182 TAL 169 0.024 0.173 USDA 5019 0.019 0.160 0.018 0.156 Phosphorin uninoculated 0.012 0.090 Cowpea strain 0.041 0.420 ENRRI 16A 0.037 0.400 TAL 169 0.034 0.337 USDA 5019 0.037 0.265 0.032 0.302 Phosphobacterin uninoculated 0.097 0.083 Cowpea strain 0.050 0.460 ENRRI 16A 0.047 0.450 TAL 169 0.040 0.315 USDA 5019 0.035 0.293 0.036 0.320 LSD for BMP (P) 0.073 0.03 LSD for Rhizobium (R) 0.095 0.038 LSD for P * R 0.164 0.067 Table 5: Effect of Rhizobium and BMP inoculation on shoot nitrogen and phosphorus content BMP strain Rhizobium strain nitrogen content El-Hudaiba Uninoculated uninoculated 2.083 Cowpea strain 3.950 ENRRI 16A 3.840 TAL 169 3.170 USDA 5019 3.320 3.273 Phosphorin uninoculated 2.470 Cowpea strain 5.850 ENRRI 16A 5.233 TAL 169 4.177 USDA 5019 3.850 4.316 Phosphobacetrin uninoculated 2.267 Cowpea strain 6.283 ENRRI 16A 5.750 TAL 169 4.550 USDA 5019 3.967 4.563 LSD for BMP (P) [+ or -] 0.274 LSD for Rhizobium (R) [+ or -] 0.354 LSD for P * R [+ or -] 0.613 BMP strain Rhizobium strain Shambat Uninoculated uninoculated 2.563 Cowpea strain 3.800 ENRRI 16A 3.800 TAL 169 3.297 USDA 5019 3.553 3.403 Phosphorin uninoculated 2.707 Cowpea strain 5.933 ENRRI 16A 5.793 TAL 169 4.227 USDA 5019 3.993 4.531 Phosphobacetrin uninoculated 3.033 Cowpea strain 6.100 ENRRI 16A 5.913 TAL 169 5.767 USDA 5019 5.220 5.207 LSD for BMP (P) [+ or -] 0.111 LSD for Rhizobium (R) [+ or -] 0.333 LSD for P * R [+ or -] 0.744 BMP strain Rhizobium strain Phosphorus content El-Hudaiba Uninoculated uninoculated 2.967 Cowpea strain 4.967 ENRRI 16A 4.283 TAL 169 4.733 USDA 5019 3.917 4.173 Phosphorin uninoculated 3.547 Cowpea strain 5.933 ENRRI 16A 5.650 TAL 169 4.433 USDA 5019 4.733 4.859 Phosphobacetrin uninoculated 3.883 Cowpea strain 6.400 ENRRI 16A 5.933 TAL 169 4.667 USDA 5019 4.100 4.997 LSD for BMP (P) [+ or -] 0.348 LSD for Rhizobium (R) [+ or -] 0.449 LSD for P * R [+ or -] 0.779 BMP strain Rhizobium strain Shambat Uninoculated uninoculated 3.467 Cowpea strain 4.553 ENRRI 16A 4.017 TAL 169 3.950 USDA 5019 3.667 3.931 Phosphorin uninoculated 3.467 Cowpea strain 6.467 ENRRI 16A 6.333 TAL 169 5.600 USDA 5019 5.567 5.487 Phosphobacetrin uninoculated 3.633 Cowpea strain 6.667 ENRRI 16A 6.333 TAL 169 5.933 USDA 5019 5.367 5.587 LSD for BMP (P) [+ or -] 0.305 LSD for Rhizobium (R) [+ or -] 0.394 LSD for P * R [+ or -] 0.682