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.

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.

Sustainable management strategies are needed to improve agronomic efficiency and cereal yield production under harsh abiotic climatic conditions such as in tropical Savannah. Under these environments, field-grown crops are usually exposed to drought and high temperature conditions. Silicon (Si) application could be a useful and sustainable strategy to enhance agronomic N use efficiency, leading to better cereal development. This study was developed to explore the effect of Si application as a soil amendment source (Ca and Mg silicate) associated with N levels applied in a side-dressing (control, low, medium and high N levels) on maize and wheat development, N uptake, agronomic efficiency and grain yield. The field experiments were carried out during four cropping seasons, using two soil amendment sources (Ca and Mg silicate and dolomitic limestone) and four N levels (0, 50, 100 and 200 kg N ha⁻¹). The following evaluations were performed in maize and wheat crops: the shoots and roots biomass, total N, N-NO₃⁻, N-NH₄⁺ and Si accumulation in the shoots, roots and grain tissue, leaf chlorophyll index, grain yield and agronomic efficiency. The silicon amendment application enhanced leaf chlorophyll index, agronomic efficiency and N-uptake in maize and wheat plants, benefiting shoots and roots development and leading to a higher grain yield (an increase of 5.2 and 7.6%, respectively). It would be possible to reduce N fertilization in maize from 185–180 to 100 kg N ha⁻¹ while maintaining similar grain yield with Si application. Additionally, Si application would reduce N fertilization in wheat from 195–200 to 100 kg N ha⁻¹. Silicon application could be a key technology for improving plant-soil N-management, especially in Si accumulator crops, leading to a more sustainable cereal production under tropical conditions.

Inoculation with Azospirillum brasilense has promisingly increased plant yield and nutrient acquisition. The study aimed to estimate the dose of A. brasilense that increases yield, gas exchange, nutrition, and foliar nitrate reduction. The research was carried out in a greenhouse at Ilha Solteira, in a hydroponic system in randomized blocks with four replicates. The treatments consisted of doses of inoculation with A. brasilense strains AbV5 and AbV6 via nutrient solution (0, 8, 16, 32, and 64 mL 100 L⁻¹). Inoculation with A. brasilense at calculated doses between 20 and 44 mL provided the highest fresh and dry mass of shoots and roots, number of leaves, and leaf yield. In addition, the calculated doses of inoculation with A. brasilense increased the accumulation of N, P, K, Ca, Mg, S, B, Fe, Mn, and Zn in shoots and roots, except the accumulation of Ca in roots. It also increased cell membrane integrity index (15%), relative water content (13%), net photosynthesis rate (85%), intracellular CO₂ concentration (15%), total chlorophyll (46%), stomatal conductance (56%), transpiration (15%), and water use efficiency (59%). Hence, inoculation with A. brasilense at doses between 20 and 44 mL 100 L⁻¹ is considered the best approach for increasing the growth, yield, accumulation of nutrients, and gas exchange of hydroponically grown iceberg lettuce.

This study was designed to investigate the effects of Azospirillum brasilense and Bradyrhizobium sp. co-inoculation coupled with N application on soil N levels and N in plants (total N, nitrate N-NO₃⁻ and ammonium N-NH₄⁺), photosynthetic pigments, cowpea plant biomass and grain yield. An isotopic technique was employed to evaluate ¹⁵N fertilizer recovery and derivation. Field trials involved two inoculations—(i) single Bradyrhizobium sp. and (ii) Bradyrhizobium sp. + A. brasilense co-inoculation—and four N fertilizer rates (0, 20, 40 and 80 kg ha⁻¹). The co-inoculation of Bradyrhizobium sp. + A. brasilense increased cowpea N uptake (an increase from 10 to 14%) and grain yield (an average increase of 8%) compared to the standard inoculation with Bradyrhizobium sp. specifically derived from soil and other sources without affecting ¹⁵N fertilizer recovery. There is no need for the supplementation of N via mineral fertilizers when A. brasilense co-inoculation is performed in a cowpea crop. However, even in the case of an NPK basal fertilization, applied N rates should remain below 20 kg N ha⁻¹ when co-inoculation with Bradyrhizobium sp. and A. brasilense is performed.

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%).