The effects of Bradyrhizobium inoculation on soybean growth and productivity are well known, but plant responses to consortia of other beneficial microbes and microbial molecules have not yet been well explored. Therefore, the main aim of this study was to evaluate the effect of different combinations of beneficial bacteria with and without microbial secondary metabolites (MSM) on two soybean cultivars in three cropping seasons under tropical field conditions. The bacterial consortia consisted of Bradyrhizobium japonicum (strain SEMIA 5079) plus Bradyrhizobium diazoefficiens (strain SEMIA 5080) inoculated with different combinations of Bacillus subtilis (strain QST 713), Azospirillum brasilense (strains Ab-V5 and Ab-V6), and MSM (metabolites enriched in lipo-chitooligosaccharides (LCOs) extracted from B. diazoefficiens (strain USDA 110) and from Rhizobium tropici (strain CIAT 889)). Standard inoculation of Bradyrhizobium combined with Azospirillum brasilense and microbial secondary metabolites increased leaf total N (7.1%), total P (11.1%), and N-ureide (16.5%); nodule number (NN, 26%) and dry weight (NDW, 22%); root (RDW, 15.4%) and shoot dry weight (SDW, 6%); 100-seed weight (3.7%); grain yield (up to 516 kg ha −1 ); grain crude protein concentration (2.4%); and the agronomic efficiency index (AEI) (11%). Inoculation with bacterial consortia and metabolites increased grain yield and quality, representing a promising technology for sustainable soybean cropping in tropical regions.

The aim of the present study was to evaluate the effect of magnesium (Mg 2+) supply on the nutritional status and carbohydrate partitioning of sugarcane plants. The treatments consisted of two Mg 2+ levels in nutrient solution (2 mg L −1 and 10 mg L −1). The following parameters were evaluated: leaf chlorophyll content, root morphological parameters, dry matter partition, nutritional composition, partition of carbohydrates, and soluble sugars. All plant growth parameters were influenced by Mg 2+ concentrations, except stalk dry matter. Regarding the dry matter apportioning, Mg control plants presented higher dry matter in leaves than those under Mg deficiency. Plants malnourished with Mg presented higher concentration of K + but not total dry matter accumulation. In addition, photosynthetic pigments production was lowered by Mg deficiency. The concentration of reducing sugars in leaves or roots were not affected by magnesium levels. However, in the stalks, the sucrose concentration was higher in Mg 2+ well-nourished plants. Although the dry matter in stalks was not affected by Mg supply, Mg control plants had higher sucrose accumulation in stalks compared to Mg-deficient. Therefore, Mg fertilization seems to be a key to increase sugar yield in sugarcane fields, mainly in those with high K input.

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(1) Background: The aim of this study was to explore whether supplementary magnesium (Mg) foliar fertilization to soybean and maize crops established in a soil without Mg limitation can improve the gas exchange and Rubisco activity, as well as improve antioxidant metabolism, converting higher plant metabolism into grain yield. (2) Methods: Here, we tested foliar Mg supplementation in soybean followed by maize. Nutritional status of plants, photosynthesis, PEPcase and Rubisco activity, sugar concentration on leaves, oxidative stress, antioxidant metabolism, and finally the crops grain yields were determined. (3) Results: Our results demonstrated that foliar Mg supplementation increased the net photosynthetic rate and stomatal conductance, and reduced the sub-stomatal CO2 concentration and leaf transpiration by measuring in light-saturated conditions. The improvement in photosynthesis (gas exchange and Rubisco activity) lead to an increase in the concentration of sugar in the leaves before grain filling. In addition, we also confirmed that foliar Mg fertilization can improve anti-oxidant metabolism, thereby reducing the environmental stress that plants face during their crop cycle in tropical field conditions. (4) Conclusions: Our research brings the new glimpse of foliar Mg fertilization as a strategy to increase the metabolism of crops, resulting in increased grain yields. This type of biological strategy could be encouraged for wide utilization in cropping systems.

Production of soybean seeds enriched with molybdenumThe objective was to evaluate the production of seeds enriched by the application of foliar molybdenum (Mo) doses and the growth and yield of plants resulting from the seeds obtained in this cultivation. We used the cultivar BRS Valiosa RR and in the first year, we used three doses of molybdenum (0, 400, and 800 g ha -1 ), with four replications. With the harvested seeds, three lots of seeds with different Mo contents were formed (9.27; 51.56, and 65.43 mg kg -1 of Mo). In the second year, using the seeds produced, two experiments were set, conducted in parallel. The first experiment was arranged in a randomized block design in a 3 × 3 scheme with four replications -three application methods (without application, at sowing, and foliar in the V 4 stage at the dose of 25 g ha -1 Mo) and the three lots of seeds from the previous year. The second experiment was arranged in a randomized block design in a 4 × 4 × 3 scheme with four replications -four application stages (V 4 , in pre-flowering, in R 3 , and R 5 ) × four foliar Mo doses (0, 25, 50, and 100 g ha -1 ) × three batches of seeds enriched with different Mo contents from the previous year. The protein content in seeds was 9% higher in the presence of Mo, regardless of how this was provided. The use of Mo is positive for soybean yield, when provided by the use of seeds enriched with a level of up to 51.56 mg kg -1 or by foliar application at doses between 25 and 50 g ha -1.

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