The supplementation of nitrogen can be increased by the use of nitrogen-fixing, diazotrophic bacteria such as Azospirillum brasilense. These bacteria can act to promote plant growth in various plant species, including corn (Zea mays L.). However, there is a need to understand the behavior of these bacteria in different agricultural systems. The objective of this study was to evaluate the effect on the growth and yield of corn inoculated with A. brasilense, and to identify the type of farming system which benefited most from the use of A. brasilense-based inoculants. The experiment conducted over two corn crop seasons was arranged in a 6 × 2 factorial scheme, consisting of six farming systems and the presence or absence of inoculation with the bacteria A. brasilense. The farming systems were derived from a long-term experiment with different fertilization systems that has been conducted since 1984. Among these systems, there were three conventional systems (CNT1: conventional no-till without fertilizer; CNT2: conventional no-till with 150 kg ha−1 of mineral fertilizer + 50 kg ha−1 of urea; CNT3: conventional no-till with 300 kg ha−1 of mineral fertilizer + 100 kg ha−1 of urea), and three organic systems (ONT1: organic no-till with 40 m3 ha−1 of organic compost; ONT2: organic no-till with 20 m3 ha−1 of organic compost; ONT3: organic no-till with 40 m3 ha−1 of organic compost and intercropped with Canavalia ensiformis). Although the Azospirillum population in the soil before planting was the same for all six systems, the count in the rhizospheric soil was higher in the organic systems, and there was no increase in that count due to inoculation. In this study, the only difference observed was within the CNT1 system, between the inoculated (CNT1-I) and uninoculated (CNT1-NI) treatments. In this system, inoculation resulted in an increase in plant height, in addition to higher concentrations of foliar N and P, and a higher plant survival rate, which culminated in higher yield. Corn inoculated with A. brasilense in the CNT1-I treatment showed a significant increase in yield—2839 kg ha−1 higher than that recorded for CNT1-NI. This study shows that, in the conventional low input treatment CNT1-I, inoculation with A. brasilense resulted in an increase in corn growth and yield.

Microorganisms play a crucial role in plant growth and development. Nitrogen-Fixing Bacteria (NFB), for instance, are essential to nitrogen nutrition. However, few studies have focused on this important community of coffee agrosystems. Therefore, this study aims to evaluate the diversity of NFB in soil and fruits from eight coffee farms. After DNA extraction, the V4 hypervariable region of 16S rDNA was amplified and sequenced in Illumina MiSeq sequencer. The prediction of potential nitrogen-fixing bacteria was performed by PICRUSt2. One hundred and eighteen ASVs were predicted as potential nitrogen-fixing. While 115 ASVs were detected in fruits, only four were found in fruits. The most abundant phylum was Proteobacteria (71 %), followed by Firmicutes (23 %). The relative abundance of the NFB concerning the whole bacterial community ranged from three to almost six percent. Only one ASV of the Rhizobiaceae family was found, simultaneously, in fruits and soil. The Bradyrhizobium genus was found in all soil samples. We conclude that important NFB are part of the microbiota present in the soil and coffee fruit and that there is a sharing between them. There is evidences that Bradyrhizobium genus can be considered a significant component of the core microbiota in coffee soil.

Effective microorganisms (EM) are inoculants used by farmers on various crops, and the actual efficiency of EM and their composition have been widely discussed. The objective of this study was to analyze the profile of the microbial community in soils after applying 3 EM inoculants from different origins with and without manure and to determine the impacts on growth and chemical composition of Urochloa brizantha (palisade grass). We showed, by PCR-DGGE technique, that the community structure of the fungi and bacteria in soil differed with EMs from different sources and that adding manure to the soil also significantly altered the bacterial and fungal profile. We also found that adding manure to soil resulted in a pronounced increase in both dry matter yield and crude protein concentration in palisade grass, while benefits of applying EM were largely restricted to a farmer-produced inoculant, where CP% was increased and NDF% was reduced when applied along with manure.