This study aimed to estimate genetic and phenotypic parameters and provide knowledge for breeding programs aiming at the selection of the main characters of assessment in soybeans. The experiment was installed in Sabia farm, located at ‘Serra das Laranjeiras” , in the municipality of Currais, Piaui, Brazil, during the 2011/2012 crop year using a randomized block design with 27 genotypes and three repetitions. The evaluated variables were: height at flowering (APF), height at maturity (APM), pod insertion height (AIV), grain yield (PG), number of nodes (NN) and number of pods (NV). The obtained heritability coefficients were from medium to high, for all evaluated characters, ranging from 0.53 to 0.94, for grain yield and plant height at flowering, respectively. These high heritability were confirmed by the high degree of genetic variation and the CVg/CVe ratio, indicating a high prospect of success for the phenotypic selection. The higher positive genetic correlations and the significant (P <0.01) were observed between grain yield and the variables number of nodes (0.807**) and number of pods (0.781**), indicating that the selection of plants with higher number of nodes and pods could result in more productive plants. The Williams-based index presented the highest percentage of gain with the selection offor the grain yield (21.84%) variable.

Plant growth-promoting bacteria (PGPB) are found in plant tissues and promote plant growth by secretion of hormones and enzymes, or by facilitating the nutrient uptake. This study assessed forty PGPB isolates to determine their effects on maize and sorghum growth. These isolates were also compared with uninoculated plants, as negative (-N; without N fertilization) and positive (+N; with N fertilization) controls. Plant height, stem diameter, shoot and root dry mass, leaf N accumulation and chlorophyll content were evaluated. For both the maize and sorghum, the height, stem diameter and shoot dry mass in plants inoculated with PGPB were similar to those of uninoculated plants supplied with N, and the responses for root mass were higher than in plants supplied with N. However, the PGPB isolates did not promote N accumulation and chlorophyll content similar to those of uninoculated plants supplied with N. The IPACC26 and IPACC30 isolates, both identified as Bacillus subtilis, resulted in better responses for plant growth and N accumulation than the other isolates.

Silicon (Si) fertilization is widely recognized to improve the development of crops, especially in tropical soils and cultivation under dryland management. Herein, our working hypothesis was that Si stoichiometry favors the efficient use of carbon (C), nitrogen (N), and phosphorus (P) in sugarcane plants. Therefore, a field experiment was carried out using a 3 × 3 factorial scheme consisting of three cultivars (RB92579, RB021754 and RB036066) and three forms of Si application (control without Si; sodium silicate spray at 40 mmol L⁻¹ in soil during planting; sodium silicate spray at 40 mmol L⁻¹ on leaves at 75 days after emergence). All Si fertilizations altered the elemental C and P stoichiometry and sugarcane yield, but silicon-induced responses varied depending on sugarcane cultivar and application method. The most prominent impacts were found in the leaf Si-sprayed RB92579 cultivar, with a significant increase of 7.0% (11 Mg ha⁻¹) in stalk yield, 9.0% (12 Mg ha⁻¹) in total recoverable sugar, and 20% (4 Mg ha⁻¹) in sugar yield compared to the Si-without control. In conclusion, our findings clearly show that silicon soil and foliar fertilization alter C:N:P stoichiometry by enhancing the efficiency of carbon and phosphorus utilization, leading to improved sugarcane production and industrial quality.