Sustainable intensification of cropping systems requires to increase productivity and nutrients use efficiency while reducing negative impacts of agricultural management practices on ecosystem and environment. Plant growth-promoting rhizobacteria (PGPR) inoculations are considered one of the most promising and safe strategy to alleviate environmental alterations in context of climatic extremes to improve plant nutrition while reducing dependency of nitrogen (N) fertilizer application. This study investigated the interactive effects of N levels and inoculation with A. brasilense on plant biomass, grain yield, agronomic efficiency (AE) of applied N, apparent N-fertilizer recovery (AFR) and N content in plant targeting economic feasibility of wheat production system. The field trial tested 4 N application levels applied in side-dressing (control, low, average and high; named 0, 50, 100 and 200 kg N ha−1) and two inoculations (without and with A. brasilense seed inoculation). The results exhibited that inoculation with A. brasilense enhanced AE, AFR and N uptake in wheat plants with increased root and shoot N accumulation and grain N accumulation under average and high N application levels. In addition, inoculation increased root and shoot biomass, leading to a yield increase of 10.3% compared with non-inoculated plants. Wheat plant inoculation associated with application of the average N level provided the greatest profitability. Furthermore, results showed that reducing N fertilization from 100 to 50 kg N ha−1 along A. brasilense inoculation led to an increase in operating profit of 10.5%. In view of low economic cost, ease of application, and high probability of a positive response by wheat crops, even associated with different N application levels, the inoculation with A. brasilense prone to be a key sustainable management practice to improve wheat production under tropical conditions. This practice has the potential to increase wheat grain yield, N use and uptake, and overall farm profitability.
This research was developed to investigate whether inoculation with Azospirillum brasilense in combination with silicon (Si) can enhance N use efficiency (NUE) in wheat and to evaluate and correlate nutritional and productive components and wheat grain yield. The study was carried out on a Rhodic Hapludox under a no-till system with a completely randomized block design with four replications in a 2 × 2 × 5 factorial scheme: two liming sources (with Ca and Mg silicate as the Si source and limestone); two inoculations (control - without inoculation and seed inoculation with A. brasilense) and five side-dress N rates (0, 50, 100, 150 and 200 kg ha−1). The results of this study showed positive improvements in wheat growth production parameters, NUE and grain yield as a function of inoculation associated with N rates. Inoculation can complement and optimize N fertilization, even with high N application rates. The potential benefits of Si use were less evident; however, the use of Si can favour N absorption, even when associated with A. brasilense. Therefore, studies conducted under tropical conditions with Ca and Mg silicate are necessary to better understand the role of Si applied alone or in combination with growth-promoting bacteria such as A. brasilense.
The use of biological techniques such as plant growth-promoting bacteria (PGPB) can represent a sustainable alternative for cereal growth in tropical areas. Research showing the potential for management practices which optimize PGPB inoculation is of utmost importance. This research was developed to investigate the potential use of Azospirillum brasilense in wheat cropping systems, as well as to assess the potential synergistic interactions between the beneficial use of silicon (Si), principally under abiotic and biotic conditions, and A. brasilense forms of application and how they impact crop development and wheat yield. The study was set up in a Rhodic Hapludox under a no-till system. The experimental design was a completely randomized block design with four replicates arranged in a factorial scheme with four inoculation forms (control, seed, groove, and leaf) and two soil acidity corrective sources (Ca and Mg silicate as Si source and dolomitic limestone). Seed inoculation was more effective in promoting wheat growth and development, with higher yield, showing an increase of 26.7% in wheat grain yield. Calcium and magnesium silicate application associated with foliar inoculation and without A. brasilense inoculation can increase wheat grain yield.
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