Fields showing nitrogen deficiency symptoms light green and stunted plants due to low nodule numbers or inactive nodules may respond to supplemental nitrogen. Applying 60 pounds of actual nitrogen per acre prior to full bloom should provide an economic return.
Liquid fertilizers applied at this rate will damage the foliage, so dry materials are recommended. Because soybeans require large amounts of nitrogen and biological fixation is the major source of nitrogen, producers need to learn how to maximize the amount of biological fixation occurring in their fields to achieve higher yields and be more profitable. The SMaRT project was developed to help Michigan producers increase soybean yields and farm profitability.
This article was published by Michigan State University Extension. Evaluating soybean nodulation. New soybean fields, due to low bacteria populations in the soil.
Fields containing high levels of residual soil nitrogen from a previous forage legume or manure application. Coarse-textured soils due to inadequate moisture levels to sustain bacteria. Flooded or saturated soil conditions lasting seven days or more due to oxygen deprivation. Soil pH below 5. Compacted soils due to reduced oxygen availability. Did you find this article useful? Please tell us why Submit. We postulate that this counterintuitive situation might be related to the nodulation and BNF activities of the cultivars.
Previously, it has been reported that the colonization and BNF of the endophytic bacteria could decrease the biomass accumulation of poplar and cedar plants, especially in the early growth stage Anand and Chanway, ; Knoth et al.
It was estimated that about 5. So, we speculate that the greater BNF activity would require greater photosynthesis more chlorophyll content since BNF is an energy-consuming process. It is possible that in Dongfu 4 and Heihe 38, a remarkable proportion of carbohydrates produced by photosynthesis was used for N 2 fixation. Another point in this study is the fact that the amounts of AN in the soil samples at harvest are similar across all treatments, despite the significant differences in N supply at the beginning, which is similar to the results in previous report Eickhout et al.
In the N0 treatments, the increase of AN in the soil might from the BNF by rhizobia for the nodulating cultivars Heihe 38 and Dongfu 4 and from BNF by other diazotrophic bacteria for the non-nodulating cultivar En Indeed, the abundances of diazotrophs Azoarcus , Azospira , Azospirillum , Azotobacter , and Azovibrio Supplementary Table S2 were greater in the rhizosphere of En and Heihe 38 than that of Dongfu 4. In the other treatments, the supplied N might be removed by plant absorption, NO 3 — leaching, denitrification, and NH 3 volatilizing as reported in fields of other crops Raun and Johnson, ; Eickhout et al.
Also, high N supply could decrease the utilization efficiency of N fertilizer by crops Raun and Johnson, ; Eickhout et al.
Considering the fact that the biomass of soybean was not significantly increased by the addition of N fertilizer for two nodulation cultivars and, in addition, an increase of height was obtained at N1 level and the height was not further increased at N2 and N3 levels, demonstrating that the symbiotic BNF might completely fit the N nutrient requirement of soybean growth, excessive supply of N fertilizer was not necessary, as reported in other studies Ju et al.
HW was the first and corresponding author of this article, who was responsible for the manuscript writing and organizing research. CG was mainly responsible for bioinformatics analyzing.
XL and CY were responsible for sample collection and processing. WL was responsible for linguistic modification.
SW was responsible for field management. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Liu, F. Soil indigenous microbiome and plant genotypes cooperatively modify soybean rhizosphere microbiome assembly. BMC Microbiol. Marschner, H. Mineral Nutrition of Higher Plants. The SNB strains found in the soil of Central Europe could also be promising candidates for the development of inoculants and already represent a contribution to the successful cultivation of soybeans in Central Europe.
Soybean Glycine max [L. In Europe, however, areas under soybean cultivation are still below 1 million ha, and the region depends largely on imports from North and South America to meet its protein demand Watson et al. The demand for soybeans from Europe is increasing, and there is a growing interest by farmers to experiment with the crop Reckling et al. There are studies to identify potent indigenous and commercial Bradyrhizobia inoculants suitable for European conditions Zimmer et al.
However, very little is known about the potential of soybeans in higher latitudes Lamichhane et al. The Bradyrhizobia are either indigenous and present in the soils along with the appropriate hosts or are introduced with a new host by seed inoculation Corman et al. In areas where soybeans were domesticated centuries ago, soybean-nodulating Bradyrhizobia SNB usually survive and are present in soils in high diversity, making the utilization of commercial inoculants less important Zhang et al.
In contrast, a soybean is a novel crop in Central Europe Shurtleff and Aoyagi, , and it has been shown that such soils lack native SNB Crozat et al. Thus, enhancing soybean expansion and productivity in Europe will also depend on effective inoculation, and farmers currently cultivate soybeans, using commercially available Bradyrhizobium inoculants Zhang et al.
Previous research in Central Europe has been mainly focused on the selection of the most efficient Bradyrhizobia strains from different inoculants under cold growing conditions Kadiata et al. These experiments tested the symbiotic performance of soybeans with inoculants in soils with no history of soybean cultivation. On the other hand, previously introduced strains, subsequently, might remain genetically isolated in soil or may undergo genetic changes to fit the local conditions Perrineau et al.
Indeed, inoculants are often applied to soils with soybean cultivation history and established SNB Obaton et al. Little is known about the possible influences of the previously introduced SNB on the symbiotic performance of commercial inoculants.
Research in the North and South America showed that the response of inoculation with commercial Bradyrhizobia inoculants differed in soils when soybean was included in previous rotations. This introduced SNB in the soil can either enhance, stay neutral or compete with the elite strain in the commercial inoculants Thies et al.
There is sufficient evidence regarding the presence of SNB in European soils at high latitudes with cold winters. The presence of indigenous bacteria can be seen as a chance for the SNB to adapt to European conditions. It may also cause a problem by escalating the competition between indigenous and inoculated strains. However, no information is available concerning the symbiotic performance of soybeans with the present SNB in the soil of Central Europe and their competition with commercial inoculants.
The objectives of this study were to i investigate the nodulation and symbiotic efficiency of indigenous SNB in soils from different soybean cropping intervals, and ii assess the response of a soybean to commercial inoculants in the presence of indigenous SNB in a pot experiment. Plants were grown from January to February for 40 days in tall and narrow 2.
At each location, soil samples were collected from five random spots at a depth of 0 to 20 cm. The main agronomic practices at both locations: The maize is amended with cattle manure in early spring; manure is immediately incorporated, using a chisel plow.
Grass-clover mix is mowed 2—3 times per year, and the biomass is raked and baled. Weeds are managed using rotary hoeing and row cultivation until crop canopy closure. Soybean cropping interval SCI refers to the year s since the last soybean cultivation. In the sampling sites with zero SCI, there is no history of soybean cultivation.
Similar agronomic practices were used in all sampled sites. Their particle size distribution categorizes the soil as slightly loamy sand. The field capacity lies between 9. Soil pH in water ranged from neutral pH 7. At both locations, the contents of double lactate extractable phosphorus, exchangeable potassium, and magnesium ranged from 1. Surface-sterilized, bold, and healthy seeds were sown two seeds per pot at a depth of 3 cm. There were two treatments: non-inoculation and inoculation with a commercial inoculant.
Each treatment was replicated six times. A trap host approach, described by Howieson et al. The soil temperatures in the pot were measured, using a soil thermometer. After 40 days, the aboveground plant growth parameters, such as the height and dry weight of the plant shoots, were determined. Afterward, roots were washed carefully with water over a metal sieve to ensure minimum nodule loss and to reduce possible shedding and rupturing of nodules.
The number of nodules and average weight of nodules per plant were determined. Nitrogen concentrations in the plant green tissues were measured according to the Kjeldahl method. Olympus AT auto analyzer was used to measure the nitrogen contents in shoots. Leghemoglobin in the soybean nodules was determined by using the modified method of Wilson and Reisenauer Each plant root system was washed and cleansed of soil particles. To evaluate the response of nodulation and symbiotic performance of SNB to a soybean cropping interval, separate data of each location from non-inoculated treatments were subjected to the variance analysis.
To evaluate the response of nodulation and symbiotic performance to inoculation, data collected from each location were divided into sites with and without soybean history. Meanwhile, the root system architecture traits divided the soil samples in Fehrow into two groups. The second group consists of soils with no soybean history, soils with 1-year SCI, and soils with 3-year SCI, which were statistically the same in all measured root system architecture traits.
Results of the nodulation rate, the average weight of nodules, leghemoglobin content, and nitrogen concentration in the green tissue were significantly different between locations and were analyzed separately. The nodule number formed on plants grown in soils with 1- and 2-year SCI was not significantly different from soils with 3- and 4-year SCI, and soils with no soybean history. However, plants grown in soils with 3-year SCI formed significantly more nodules than that with 4-year SCI and no soybean history.
The average weight of nodules was Table 2. Influence of soybean cropping interval on nodulation rate, average weight of nodules, content of leghemoglobin in nodules as well as nitrogen concentration in plant shoot at Fehrow. However, the leghemoglobin content of nodules in soil with no soybean history was The average weight of nodules ranged from Table 3. Tissue nitrogen content in soil with no legume history was 2.
Inoculation showed a significant influence on the nodulation rate in the soil with no soybean history. Relative to non-inoculation, the nodulation rate increased by In the soils with soybean history, the response to inoculation differed between the locations.
Figure 1. Influence of inoculation on nodulation rate, content of leghemoglobin in nodules as well as nitrogen concentration in plant shoot. Soybean was introduced in the soil with soybean history since 1—4 years or never introduced in the soil with no soybean history. The black bars represent the inoculated plant. Gray bars represent the non-inoculated plants. Numbers in brackets indicate the percentage difference mean, either higher or lower as shown, between inoculated and non-inoculated plants.
In Fehrow, the average weight of nodules reduced from Also, the average weight of nodules reduced from The leghemoglobin contents of soybean nodules did not increase significantly by inoculation. The shoot nitrogen concentration showed a positive response to the commercial inoculant tested in the soils with no soybean history at both locations, i. Soybean tissue nitrogen concentration increased in inoculated soils with no soybean history by 7.
The plant height, dry weight of shoot, and SPAD value as well as all root architecture traits did not show a positive response to the commercial inoculant tested in this experiment data not presented. In contrast, the dry weight of the shoot showed a significantly positive correlation with all root architecture traits r 2 from 0. A significant positive relationship existed among the root architecture traits: root length, a surface area, volume, a diameter, and tips r 2 ranged from 0.
No correlations were found for the nodulation rate and the following parameters: leghemoglobin content in the nodules, plant height, dry weight of shoot, and all root architecture traits.
The observed nodules had a very high leghemoglobin content Tables 2 and 3 , which suggests evidence of symbiotic nitrogen fixation Ott et al. It might be related to the ability of soybeans to establish symbiosis with other rhizobia, which has a broad range of host plants, confirming the results obtained in northeastern China Yan et al.
Yan et al. Yuan et al. This isolate is capable of forming nodules with soybeans more effectively than the commercial isolates. Vargas et al. However, at both locations in the present study, the nodulation rate of plants grown in soils with no soybean or legume history was lower than plants grown in soils with 1—4 years SCI and was accompanied by a high average nodule weight per plant and low shoot nitrogen concentration.
These observations support the assertion that SNB can be present in soils at low population densities Thies et al. The nodulation rate was high when the inoculated soybean seeds were grown in the soils from the sites with no soybean history, which was initially devoid of SNB or had it in low populations Figure 1.
The positive response to inoculation is consistent with the other experiments conducted under controlled conditions in growth chambers Kadiata et al. The higher nodulation rate was associated with a higher nitrogen concentration in the plant shoots Figure 1 , which was also found in other studies Koutroubas et al.
These observations indicate that the native or nonspecific soybean strains present in the soil are neutral and did not compete with the commercial inoculants Sinclair and Nogueira,
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