Mineral nitrogen impairs the biological nitrogen fixation in soybean of determinate and indeterminate growth types

Soybean (Glycine max Merrill) crop production in Brazil relies mainly on biological nitrogen fixation (BNF) for nitrogen (N) supply. Recent adoption of indeterminate growth-type genotypes has raised doubts on the need for supplemental mineral N that might negatively affect the BNF. We assessed the effects of mineral N on BNF attributes of soybean genotypes grown in central and southern Brazil. Genotypes were inoculated with Bradyrhizobium sp. and/or received mineral N in three sets of experiments. In the first set, two genotypes received increasing rates of mineral N in nutrient solution, which consistently reduced the BNF. In the second set, mineral N applied at sowing and/or topdressing reduced nodulation and ureides-N in determinate and indeterminate growth-type genotypes. In the third set, mineral N applied at R5.3 stage, foliar or as topdressing, did not increase grain yield in four field experiments. Mineral N impaired BNF irrespective of the growth type and had no effect on grain yield.     

Effect of Mn on growth,modulation, and nitrogen fixation by soybeans grown in the greenhouse

Abstract

Soybean (Glycine max (L.) Merr. cv Bragg) plants were grown in the greenhouse using a low‐Mn Leefield sand amended with 0, 2.5, 5, 20 and 50 yg Mn/g. The plants were inoculated and were primarily dependent on symbiotically fixed N. Measurements of DTPA‐extractable soil Mn, soil pH, leaf tissue Mn, top weight, top N content, and nodule weight, volume and number were made at 27, 42, 56, 63 and 69 days after planting. The DTPA extrac‐tant was a good predictor of leaf tissue Mn giving a highly significant (P = 0.01) overall correlation coefficient of 0.704 for this comparison. Because of an unexpected decline in soil pH from 6.8 to 6.0 and an associated increase in DTPA‐extractable Mn from 0.14 to 0.24 yg/g during preparation and handling prior to the first harvest time, Mn in the leaf tissue of the controls was never less than 21 yg/g. Since this concentration of Mn is above the deficient level, no significant responses in top growth, nitrogen fixation or nodule measurements were obtained from the addition of low rates of Mn. The highest Mn rate was only mildly toxic in terms of top growth and top N content, producing leaf tissue having Mn concentrations ranging from 171 to 180 yg/g at the last three harvest periods.     

Nutrient concentration and yield variation within southern soybean germplasm grown on acid Norfolk soil

Abstract

Seventy‐one soybean genotypes were grown in the field on an acid Norfolk loamy sand to evaluate growth, seed yield, and nutrient concentrations in aerial plant fractions. The pH values in the Ap, A2, and B horizons were 4.6, 4.4, and 4.4, respectively. Cation exchange capacities (CEC) were 2.1, 0.9, and 2.8 me/100 g with an Al saturation of 34, 49, and 40%, respectively. Very few visual toxicity or deficiency symptoms were found among the genotypes. Analyses of aerial plant fractions collected when the genotypes were in bloom or early pod fill showed some significant differences, but In general P, K, Ca, and Mg concentrations were adequate, while Al, Fe, Mn, and Zn concentrations were very high. Average yields of genotypes in maturity groups IV, V, VI, VII, and VIII were 2.7, 2.7, 2.6, 2.4, and 2.2 t/ha, respectively. There were significant differences in seed yield among genotypes in maturity groups IV and VIII, but differences among genotypes in the other maturity groups were nonsignificant. Correlations between yield and nutrient concentration showed some significant relationships, but in general, this technique did not differentiate genotypes according to their tolerance to acid soil conditions.     

Glyphosate effects on photosynthesis,nutrient accumulation,and nodulation in glyphosate‐resistant soybean

Previous greenhouse studies have demonstrated that photosynthesis in some cultivars of first‐ (GR1) and second‐generation (GR2) glyphosate‐resistant soybean was reduced by glyphosate. The reduction in photosynthesis that resulted from glyphosate might affect nutrient uptake and lead to lower plant biomass production and ultimately reduced grain yield. Therefore, a field study was conducted to determine if glyphosate‐induced damage to soybean (Glycine max L. Merr. cv. Asgrow AG3539) plants observed under controlled greenhouse conditions might occur in the field environment. The present study evaluated photosynthetic rate, nutrient accumulation, nodulation, and biomass production of GR2 soybean receiving different rates of glyphosate (0, 800, 1200, 2400 g a.e. ha^–1) applied at V2, V4, and V6 growth stages. In general, plant damage observed in the field study was similar to that in previous greenhouse studies. Increasing glyphosate rates and applications at later growth stages decreased nutrient accumulation, nodulation, leaf area, and shoot biomass production. Thus, to reduce potential undesirable effects of glyphosate on plant growth, application of the lowest glyphosate rate for weed‐control efficacy at early growth stages (V2 to V4) is suggested as an advantageous practice within current weed control in GR soybean for optimal crop productivity.     

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。     

Effect of soil potassium availability on soybean root and shoot growth under unrestrained rooting conditions 1

The development of soybean (Glycine max (L.) Merr.) root systems was Investigated in two greenhouse pot experiments utilizing a modified cage technique. One soil at two levels of K availability was used to observe the effect of soil K fertility level on root weight and root length in 3 cm depth Increments to 24 cm. Experiments were terminated prior to restraint of root growth by the containers. Shoot mineral accumulation and dry matter partitioning between root and shoot components were Investigated.

High K plants were shorter and had a greater root:shoot mass ratio than low K plants. A trend for greater root dry matter production in soil layers below 12 cm under high K conditions was observed. There were no differences in root length between the treatments at any depth. Tissue K content was greater in the high K treatments and this Increase was equivalents offset by decreased tissue Mg concentrations. The taller low K plants had a greater leaf area and a lower specific leaf weight, resulting in part from decreased starch content. Daily evapotranspirational water losses per pot tended to be greater under the low K availability regime. This Information led to the speculation that under low K conditions, the soybean plant may increase K accumulation by promoting transpirational water use, aiding soil K acquisition by mass flow and diffusion. Tissue carbohydrate analyses suggest greater translocation of photosynthate out of the leaf in the low K plants for use in root absorption metabolism, rather than for production of increased root dry matter and/or increased root length.     

Effect of inoculum,variety, nitrogen,phosphorus, and potassium on yield,protein and oil content of soybeans at jabalpur,M.P. India

Abstract

Regardless of inoculum or fertility rate Bragg outyielded Clark 63 soybeans. Yields of Bragg and Clark 63 were increased about 1000 kg per ha by treatment with inoculum at the rate of approximately 313, 000 bacteria per seed. At the highest rate of applied N, yields of uninoculated soybeans, were lower than the inoculated soybeans at the lowest applied N rate. Phosphorus fertilizer increased yields at a decreasing rate and yields were decreased at the highest rate of applied P. Potassium fertilizer had a negative effect on soybean yields and did not significantly effect the protein or oil content of soybean seed. With increasing P fertilizer rates, there was a decrease in oil content and in increase in protein content of soybean seed.     

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.     

Effect of supplying P to a portion of the soybean root system on root growth and P uptake kinetics 1

Abstract

Knowledge of the effect of supplying P to portions of the soybean (Glycine max L. Merr) root system on P influx kinetics and root growth is important in developing P fertilizer placement practices for efficient fertilizer use. The objective of this research was to determine the effect of restricting P supply to portions of the root system on plant P status, root growth, and P influx kinetics. Two solution experiments were conducted in a controlled climate chamber. Phosphorus influx kinetics were determined on 25‐day‐old soybean plants that had been grown with 100, 75, 50, 25, and 12.5% of their roots initially exposed to P. Phosphorus influx kinetics were also measured on 25‐day‐old plants that had been P‐starved for the last 1, 2, 4, and 6 days prior to the determining P influx kinetics in order to relate plant P status to P influx kinetics.

Reducing the portion of the roots supplied with P reduced P uptake. This resulted in a reduction in plant P concentration and was related to a 3.41‐fold increase in maximum P influx measured on 25‐day‐old plants. Restricting the proportion of roots supplied with P had no significant effects on the Michaelis‐Menten constant or on the concentration in solution where net influx was zero. Root growth rate of the roots in the P containing solution was not significantly different from those in the ‐P solution.

Phosphorus uptake was correlated with final root surface area exposed to P (r² = 0.88??). Starving the plants for P reduced P concentration in the shoot and root and this resulted in as much as a 1.68‐fold increase in maximum influx.     

Effect of elevated carbon dioxide on growth,nutrient partitioning,and uptake of major nutrients by soybean under varied nitrogen application levels

Rising carbon dioxide (CO₂) concentration causes fertilization effects resulting in enhanced crop biomass and yields and thus likely enhances nutrient demand of plants. Hence, this field study was carried out to investigate the effects of elevated CO₂ and N on biomass yield, nutrient partitioning, and uptake of major nutrients by soybean (Glycine max L.) using open‐top chambers (OTCs) of 4 m × 4 m size. Soybean was grown in OTCs under two CO₂ [ambient and elevated (535 ± 36.9 mg L^?1)] and four N levels during July to October 2016. The four N levels were N₀, N₅₀, N₁₀₀, and N₁₅₀ referring to 0, 50, 100, and 150% recommended dose of N. Both CO₂ and N significantly affected biomass and grain yield, though the interaction was non‐significant. CO₂ enrichment produced 30–65% higher biomass and 26–59% higher grain yield under various N levels. As compared to the optimum N application (N₁₀₀), the CO₂‐mediated increment in biomass yield decreased with either lower or higher N application, with the response being lowest at N₁₅₀. As compared to ambient concentration, elevated CO₂ resulted in significant reduction of seed P concentration at all N application levels but at N₁₅₀, an opposite trend was observed. The decrease in seed P was maximum at N₀ and N₅₀ (7–9%) and by 3% at N₁₀₀, whereas there was a gain of 7.5% at N₁₅₀. The seed N and K concentrations were not affected either by CO₂ or N application. Total N, P, and K uptake at harvest were significantly affected by CO₂ and N, but not by CO₂ × N interaction. Elevated CO₂ resulted higher uptake of N by 18–61%, P by 23–62%, and K by 22–62% under various N treatments.     

Effects of foliar fertilization on yield,protein, oil and elemental composition of two soybean varieties

Abstract

The effects of foliar fertilization on the yield and seed composition of two soybean (Glycine max L. Merrill) varieties were investigated under mid‐Missouri conditions over a 2‐year period. The foliar fertilizer treatments consisted of (i) 80–8–24–4 (NPKS) kg/ha, (ii) 40–4–12–2 (NPKS) kg/ha, and (in) control (no foliar treatment) with the optimum proportion of N:P:K:S in the solution 10:1:3:0.5 respectively. Nutrient sources were urea, potassium polyphosphate, and potassium sulfate. Water solutions of fertilizers (pH 6.9) containing 0.1% Tween 80 (v/v) were sprayed on the plants using a CO₂ ‐ pressurized back‐pack sprayer. Foliar fertilizer was split between four equal applications during the seed filling period. The variety Mitchell at the higher rate and the variety Williams at the lower fertilizer application rate produced slight, though statistically insignificant, yield increases. At the higher rate of application, the seed protein contents of both varieties increased, while the oil contents decreased. The concentrations of P and K in the seeds were not affected by foliar fertilization, but at the higher rate, there was a small decrease in S content of Williams variety.     

Comparison of water stress effects on growth,leaf water status,and nitrogen fixation activity in tropical pasture legumes siratro and desmodium with soybean

Siratro (Macroptilium atropurpureum), desmodium (Desmodium intortum), and soybean (Glycine max) were grown in pots with or without irrigation for 20 d at the vegetative growth stage in order to examine the effects of water stress on the leaf water potential, stomatal conductance, biomass production, biological nitrogen fixation, and nitrogen accumulation. Whole plant weight decreased under water stress conditions and the decrease was less pronounced in siratro than in desmodium and soybean. Decrease in total leaf area was the largest and dry matter partition to stem and petioles was the highest in siratro. Decrease in leaf water potential was lower in desmodium and soybean than in siratro. Although water stress decreased biological nitrogen fixation in all the species, the decrease was relatively less pronounced in siratro than in desmodium and soybean. Whole plant nitrogen concentration was higher in siratro than in soybean and desmodium. The results indicated that siratro is more tolerant to water stress than soybean and desmodium. This could be partially attributed to the maintenance of a higher water potential and higher biological nitrogen fixation by siratro under water stress conditions.     

Evaluation of the field performance,nitrogen fixation efficiency and competitive ability of pea landraces grown under organic and conventional farming systems

In the present study, three pea Greek landraces Schinousa (AUASCHIN001), Andros (AUAANDRO001), and Amorgos (AUAAMORG001), and the commercial variety Onward were grown following either conventional or organic farming practices. The main objective of the study was to assess the suitability of these three landraces for organic cultivation as compared with a standard commercial variety. The total fresh pod yield produced by AUASCHIN001 and AUAAMORG001 was significantly lower than that obtained from ‘Onward’ and AUAANDRO001. Furthermore, the three landraces exhibited a higher competition to weeds than the commercial variety. Under organic farming conditions, AUASCHIN001 and AUAAMORG001 produced appreciably less shoot biomass than ‘Onward’ and this resulted in commensurate decreases in the total amount of BNF (biological nitrogen fixation) in their plant tissues, although the percentage of nitrogen (N) fixed from the atmosphere was significantly lower in ‘Onward’. AUAANDRO001 rendered the highest amounts of BNF in the organic farming systems, which was similar to that produced by ‘Onward’ in the conventional system. These results indicate that the tested landraces and especially AUAANDRO001 are more adaptable to low soil N levels and high weed competition, and thus they are more suitable for organic cultivation than ‘Onward’ which performs best in conventional cropping systems.     

Cadmium‐ and barium‐toxicity effects on growth and antioxidant capacity of soybean (Glycine max L.) plants,grown in two soil types with different physicochemical properties

The pollution of agricultural soils by metals is of growing concern worldwide, and is increasingly subject to regulatory limits. However, the effect of metal pollutants on the responses of plants can vary with soil types. In this study, we examined the growth and antioxidant responses of soybean plants exposed to contrasting soils (Oxisol and Entisol), which were artificially contaminated with cadmium (Cd) or barium (Ba). Cadmium reduced plant growth at concentrations higher than 5.2 mg (kg soil)^–1, while Ba only affected plant growth at 600 mg kg^–1. Such levels are higher than the limits imposed by the Brazilian environmental legislation. Lipid peroxidation was increased only at a Cd concentration of 10.4 mg kg^–1 in the Oxisol, after 30 d of exposure. Twelve superoxide dismutase (SOD; EC 1.15.1.1) isoenzymes were evaluated, most of which were classified as Cu/Zn forms. The SOD activity in the leaves of plants grown in the Oxisol decreased over time, whilst remaining high in the Entisol. Catalase (CAT; EC 1.11.1.6) activity in the leaves exhibited little response to Cd or Ba, but increased over time. Glutathione reductase (GR; EC 1.6.4.2) activity was reduced over time when exposed to the higher Cd concentrations, but increased following Ba exposure in the Oxisol. The enzyme‐activity changes were mainly dependent on soil type, time of exposure and, to a lesser extent, the metal concentration of the soil. Soybean plants grown in a sandy soil with a low buffering capacity, such as Entisol, suffer greater oxidative stress than those grown in a clay soil, such as Oxisol.     

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.     

Effect of inoculum,variety, phosphorus,and potassium on certain attributes of two soybean varieties at Jabalpur,M.P., India

Abstract

An experiment to determine the effect of inoculum, N, P, and K on certain attributes of two soybean varieties was conducted in 1967 at JNKW. The experimental area had no prior history of soybean production and contained few, if any, soybean rhizobia.

Plant height, height to first pod, lodging, seed quality, and seed weight were affected by applied N. Applied P had a quadratic effect upon plant height, while plant height decreased linearly with increasing levels of applied K. The effect of N was linear and applied P curvilinear upon lodging. Uninoculated plants had seed with poorer seed quality scores and lower seed weights than inoculated plants. Applied P increased seed weight. Height to first pod was higher for Bragg than for Clark 63.     

The effect of lime levels on the growth of beans and maize and nodulation of beans in three tropical acid soils

Abstract

A study to investigate the effect of lime on dry matter yield of maize (Zea mays) and beans (Phaseolus vulgaris) and nodulation of beans grown in three tropical acid soils (two humic Nitosols and one humic Andosol) was carried out in a greenhouse. The soils ranged from 4.2 to 5.0 in pH; 1.74 to 4.56 in %C; 21.0 to 32.0 meq/100g in CEC; 5.10 to 8.10 meq/100g in exchange acidity; 0.60 to 3.20 meq/100g in exchangeable (exch.) Al and 0.13 to 0.67 meq/ 100g in exch. Mn.

Exchange acidity and exch. Al decreased with increasing levels of lime in the three soils. Exchangeable Al was reduced to virtually zero at pH 5.5 even in the soils which had appreciable initial amounts. Exchangeable Mn also decreased with increasing levels of lime in the two Nitolsos. Exceptional results, however, were obtained with the Andosol where exch. Mn increased ten‐fold with the first level of lime and then decreased with subsequent levels.

In all the soils, mean dry matter yield of beans and maize, and mean nodule dry weight of beans generally increased significantly with increasing lime levels up to pH value of 6.0. The dry matter yield of beans and maize, and nodule weight of beans, however, decreased progressively with increasing lime levels beyond pH 6.0 value. pH range of 5.5 to 6.0 was considered optimum for the growth of maize and beans, and nodulation of beans in these soils.     

Effects of prolonged flooding on soybean at the R2 growth stage. I. Dry matter and N and P accumulation

Prolonged flooding of soybean [Glycine max(L.) Merrill] reduce yields. One explanation for lower yields in legumes has been the reduction in N fixation associated with the reduction in 0₂ supply in the flooded soil. This work investigated the effects of prolonged flooding at the initiation of reproductive growth on the dry matter and N and P accumulation in soybean. The field study was conducted on a Crowley silt loam (Typic Albaquaif). Forrest soybean were flooded at R₂ for 7 consecutive days at a flood height of 2.5 cm. Dry matter accumulation and concentrations of N and P of the stems, leaves, branches, and pods were determined by nodes on both flooded and non‐flooded plants for six sampling periods of 0, 7, 14, 21, 36, and 62 days after flooding. The results showed that, in terms of concentration and total amounts accumulated, flooding at R₂ adversely affected N nutrition in soybean. The soybean recovered from this effect two weeks after the flood was removed. As compared to the non‐flooded soybean, flooding improved P nutrition. The flooded soybean had greater P concentrations and total amounts of P accumulated. Flooding also prolonged vegetative growth in the upper portion of the canopy.     

Effects of co-inoculation of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 on plant growth,nodulation, nitrogen fixation,nutrient uptake,and yield of soybean in a field condition

ABSTRACT

Co-inoculation of nitrogen-fixing bacteria with plant growth-promoting bacteria has become more popular than single inoculation of rhizobia or plant-growth-promoting bacteria because of the synergy of these bacteria in increasing soybean yield and nitrogen fixation. This study was conducted to investigate the effects of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 co-inoculation on plant growth, nodulation, nitrogen fixation, nutrient uptake, and seed yield of the ‘Yezin-6’ soybean cultivar. Nitrogen fixation was measured using the acetylene reduction assay and ureide methods. Uptake of major nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] was also measured. This study showed that single inoculation of SAY3-7 significantly increased shoot biomass; nodulation; Relative Ureide Index (RUI %), percent nitrogen derived from N fixation (% Ndfa); N, P, K, Ca, and Mg uptakes; during the later growth stages (R3.5 and R5.5), compared with control. These observations indicate that SAY3-7 is an effective N-fixing bacterium for the plant growth, nodulation, and nitrogen fixation with an ability to compete with native bradyrhizobia. Co-inoculation of SAY3-7 and P4 significantly improved nodule number; nodule dry weight; shoot and root biomass; N fixation; N, P, K, Ca, and Mg uptake; at various growth stages and seed yield in ‘Yezin-6’ soybean cultivar compared with the control, but not the single inoculation treatments. Significant differences in plant growth, nodulation, N fixation, nutrient uptake, and yield between co-inoculation and control, not between single inoculation and control, suggest that there is a synergetic effect due to co-inoculation of SAY3-7 and P4. Therefore, we conclude that Myanmar Bradyrhizobium strain SAY3-7 and P4 will be useful as effective inoculants in biofertilizer production in the future.     

Bragg soybeans grown on a southern coastal plains soil i. dry matter distribution,nodal growth analysis,and sample variability

Yields of soybean [Glycine max (L.) Merr.] are affected by the manner in which available resources are partitioned into component plant parts. Little is known about these partitioning processes and much of what has been reported describes indeterminate cultivars or comes from other than field studies. A field investigation was conducted, therefore, on a Goldsboro loamy sand (Aquic Paleudult) to characterize in detail the growth and development of a determinate soybean cultivar ‘Bragg’. Soybean were grown in well watered field plots in four replications from each of which 4 nested samples of 0.3 m² each were combined at each sampling. Leaf area, dry matter production, internode length, and sample variability were determined nodally at 10‐ to 14‐day intervals from 7 July to 17 October. Plant components at each node were separated into stems, leaf blades, pods, and petioles. Primary and secondary branches were combined in the petiole fraction.

Maximum above ground plant dry weight achieved was 1027 g/m² and maximum combined nodal dry weight was 92 g/m² (at node 8), both occurring at the R7 growth stage. Canopy dry weight distribution over time was unique for each plant part. Growth analyses showed that RGR, NAR, LAR, and LWR declined with plant age at a rate that could be described with either linear or exponential models. A maximum CGR of 16.24 g/m²/day occurred at mid‐podfill and declined thereafter due to maturity. Leaf area per node peaked between nodes 7 and 12, decreasing uniformly toward the top of the canopy. Maximum nodal LAI was 0.79 at node 7 on 31 August.

Distribution of dry weight among parts varied with plant age and node position. Maximum dry weights of stems (276 g/m²), petioles (253 g/m²), and leaves (263 g/m²) were found during mid‐podfill. During mid‐August, the dry weights of the stems, petioles, and leaves were similar and approximately 250 g/m². Stem dry weights had the lowest coefficients of variation of all plant fractions once maximum dry weight was achieved. Internode length varied along the stem with the maximum at node 12. By bloom, expansion of the internodes lower than 12 had ceased; expansion of the eight higher internodes ceased three weeks later. During vegetative growth, the ratio of stem internodal dry weight to internodal length had peak values at the lowest and highest internodes. During reproductive growth, the ratio decreased linearly with internode number. Coefficients of variation (CV) for the combined weight of plant parts, and for stems, petioles, leaves, and pods were relatively constant during the season and were 24.8, 23.4, 38.2, 25.5, and 26.8%, respectively. The CV's for the combined weight of plant parts were somewhat higher at the lowest and uppermost nodes. This variability resulted from the abscission of petioles and leaves in the lower nodes and the initiation of leaves, petioles, and pods in the upper nodes where rapid growth and development was occurring. Time from node initiation to achievement of lowest stable CV was determined for each node and plant part. Plant node position and morphological part with the lowest CV was identified for each sampling date (and growth stage).