The use of plant growth promoting bacteria (PGPB) that can solubilize phosphorus (P) has shown potential to improve nutrient availability in grass crops such as corn (Zea mays L.) This study was developed to investigate if inoculation with Azospirillum brasilense, Bacillus subtilis or Pseudomonas fluorescens associated with P 2 O 5 rates can improve phosphorus use efficiency (PUE) reflecting on greater corn development and yield. The field trial was set up in a Rhodic Hapludox under no-till system under Savannah conditions, in a completely randomized block design with four replicates. Treatments were tested in a full factorial design and included: (i) five P 2 O 5 rates (0 to 105 kg ha −1) and (ii) four PGPB seed inoculation (Control-without inoculation, A. brasilense, B. subtilis or P. fluorescens). Inoculation was found to increase grain yield by 39.5, 29.1, and 15.9% when B. subtilis was inoculated in the absence of P 2 O 5 rates and associated with 17.5 and 70 kg P 2 O 5 ha −1 and by 34.7% when A. brasilense was inoculated with application of 105 kg P 2 O 5 ha −1. In addition, inoculation with B. subtilis and A. brasilense were found to increase P uptake, benefiting productive components development, leading to an improved PUE, and greater corn grain yield. The results of this study showed positive improvements in P uptake as a result of B. subtilis and A. brasilense inoculation, with an increase of 100.5 and 54.6% on PUE, respectively; while the P. fluorescens inoculation were less evident. Further research should be conducted under biotic or/and abiotic conditions such as attack of pathogens and insects, drought, salinity, water flooding, low and high temperature to better understand the role of PGPB, inoculated alone or in combination as the co-inoculated method.

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Enrichment of staple food with zinc (Zn) along with solubilizing bacteria is a sustainable and practical approach to overcome Zn malnutrition in human beings by improving plant nutrition, nutrient use efficiency, and productivity. Common bean (Phaseolus vulgaris L.) is one of a staple food of global population and has a prospective role in agronomic Zn biofortification. In this context, we evaluated the effect of diazotrophic bacterial co-inoculations (No inoculation, Rhizobium tropici, R. tropici + Azospirillum brasilense, R. tropici + Bacillus subtilis, R. tropici + Pseudomonas fluorescens, R. tropici + A. brasilense + B. subtilis, and R. tropici + A. brasilense + P. fluorescens) in association with soil Zn application (without and with 8 kg Zn ha−1) on Zn nutrition, growth, yield, and Zn use efficiencies in common bean in the 2019 and 2020 crop seasons. Soil Zn application in combination with R. tropici + B. subtilis improved Zn accumulation in shoot and grains with greater shoot dry matter, grain yield, and estimated Zn intake. Zinc use efficiency, recovery, and utilization were also increased with co-inoculation of R. tropici + B. subtilis, whereas agro-physiological efficiency was increased with triple co-inoculation of R. tropici + A. brasilense + P. fluorescens. Therefore, co-inoculation of R. tropici + B. subtilis in association with Zn application is recommended for biofortification and higher Zn use efficiencies in common bean in the tropical savannah of Brazil.

Phosphorus (P) is a critical nutrient for high sugarcane yields throughout its cultivation cycles, however, a higher amount of P becomes rapidly unavailable to plants due to its adsorption to soil colloids. Some plant growth-promoting bacteria (PGPBs) may be able to enhance P availability to plants and produce phytohormones that contribute to crop development, quality, and yield. Thus, this study aimed to evaluate leaf concentrations of nitrogen (N) and P, yield, and technological quality of sugarcane as a function of different levels of phosphate fertilization associated with inoculation of PGPBs. The experiment was carried out at Ilha Solteira, São Paulo—Brazil. The experimental design was randomized blocks with three replications, consisting of five phosphorus rates (0, 25, 50, 75, and 100% of the recommended P2O5 rate) and eight inoculations, involving three species of PGPBs (Azospirillum brasilense, Bacillus subtilis, and Pseudomonas fluorescens) which were applied combined or in a single application into the planting furrow of RB92579 sugarcane variety. The inoculation of B. subtilis and P. fluorescens provided a higher concentration of leaf P in sugarcane. The P2O5 rates combined with inoculation of bacteria alter technological variables and stalk yield of sugarcane. The excess and lack of phosphate fertilizer is harmful to sugarcane cultivation, regardless of the use of growth-promoting bacteria. We recommend the inoculation with A. brasilense + B. subtilis associated with 45 kg ha−1 of P2O5 aiming at greater stalk yield. This treatment also increases sugar yield, resulting in a savings of 75% of the recommended P2O5 rate, thus being a more efficient and sustainable alternative for reducing sugarcane crop production costs.

Given the hypothesis that co-inoculation with plant growth-promoting bacteria (PGPB) enhances the beneficial effects of Rhizobium tropici with greater mineral nutrition, optimizes biological nitrogen fixation and reduces use of fertilizers in bean plants, the objective of this research was to evaluate the synergistic effects of Rhizobium tropici associated with Azospirillum brasilense, Bacillus subtilis, Pseudomonas fluorescens and their combinations, on increasing the efficiency of NPK fertilization to obtain high winter yields of the (irrigated) common bean in the Cerrado region. The experiment was carried out in the field over two years in a Rhodic Hapludox under a no-till system in Selvíria, Brazil. The experimental design comprised complete randomized blocks with four replications in a 3 × 7 factorial scheme. The treatments consisted of three doses of NPK fertilizer (control—0 kg ha−1 (control); 50% of the recommended dose; 100% of the recommended dose in two parts) and seven doses of inoculation or co-inoculation (control; Rhizobium tropici; R. tropici + Azospirillum brasilense; R. tropici + Bacillus subtilis; R. tropici + Pseudomonas fluorescens; R. tropici + A. brasilense + B. subtilis; R. tropici + A. brasilense + P. fluorescens). The PGPB in the co-inoculations increased the hundred-grain weight, the grain pod−1, the grain plant−1 and the grain yield following the NPK doses. The grain yield of the common bean was increased by co-inoculation with R. tropici + A. brasilense + P. fluorescens without NPK treatments, co-inoculation with R. tropici + P. fluorescens and R. tropici + A. brasilense + B. subtilis with the 50% dose of NPK and co-inoculation with R. tropici + B. subtilis with the recommended dose of NPK fertilizer (100%).

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Confinement of dairy cows in Brazil is significant, with the compost badded pack barn being the most used model, generating a large amount of good quality organic compost that can be used as a fertilizer in the pastures of the farms, reducing the use of industrialized fertilizers and mitigating the environmental impacts of dairy activity. An experiment was carried out in pots under greenhouse conditions to evaluate the effect of compost doses on the production, morphology and chemical-bromatological characteristics of Urochloa brizantha cv. Marandu A completely randomized design with 3 replications and 6 treatments consisting of 6 doses of the compost: 0; 50; 10; 20; 40 and 80 g.vaso-1. Increasing compost doses resulted in higher dry matter yield, higher tillers density and higher potassium and phosphorus contents in the forage. Dairy cow compost can be used for pasture fertilization, partially replacing industrialized fertilizers.

Background and aims Nano-zinc (Zn) fertilizer is an easily adaptable and environmentally safe alternative option that can effectively improve growth, yield and biofortification of common bean. Plant growth-promoting bacteria (PGPBs) could promote plant growth and nutrients availability in sustainable manner. Therefore, this study aimed to investigate the influence of foliar nano-Zn application in association with seed co-inoculations of PGPBs on growth, yield, biofortification and Zn use efficiencies in common bean cultivation. Two field experiments were performed with seven co-inoculations of PGPBs and three foliar nano-Zn doses applied 50% at R5 and 50% at R8 stages of common bean to determine plant height, shoot dry matter, grain yield, Zn concentration and uptake in shoot and grains, Zn partitioning index, daily Zn intake and Zn use efficiencies for agronomic biofortification. Results The combined foliar nano-Zn application and co-inoculation of R. tropici + B. subtilis enhance grain yield, leaf chlorophyll index, total protein content, grain Zn concentration and uptake, daily Zn intake, Zn use efficiency, applied Zn recovery and Zn utilization efficiency in common beans in 2019 and 2020 cropping seasons. Foliar nano-Zn application at a dose of 1.5 kg ha−1 increased plant height, shoot dry matter, shoot Zn uptake, Zn partitioning and agro-physiological efficiency under co-inoculation with R. tropici + B. subtilis in both cropping years. Conclusions The treatments with foliar nano-Zn application at a dose of 1.5 ha−1 and co-inoculation with R. tropici + B. subtilis improved performance, chlorophyll index, protein content, grain yield, and Zn efficiencies that can lead to better biofortification of common bean in tropical savannah. Therefore, it is recommended that applying nano-Zn via foliar along with co-inoculation of PGPBs could be the better option for productivity and biofortification of common bean. Graphical Abstract