Understanding the Relations between Soil Biochemical Properties and N2O Emissions in a Long-Term Integrated Crop-Livestock System.

Edaphoclimatic conditions influence nitrous oxide (N2O) emissions from agricultural systems where soil biochemical properties play a key role. This study addressed cumulative N2O emissions and their relations with soil biochemical properties in a long-term experiment (26 years) with integrated crop-livestock farming systems fertilized with two P and K rates. The farming systems consisted of continuous crops fertilized with half of the recommended P and K rates (CCF1), continuous crops at the recommended P and K rates (CCF2), an integrated crop-livestock system with half of the recommended P and K rates (ICLF1), and an integrated crop-livestock at the recommended P and K rates (ICLF2). The ICLF2 may have promoted the greatest entry of carbon into the soil and positively influenced the soil's biochemical properties. Total carbon (TC) was highest in ICLF2 in both growing seasons. The particulate and mineral-associated fractions in 2016 and 2017, respectively, and the microbial biomass fraction in the two growing seasons were also very high. Acid phosphatase and arylsulfatase in ICLF1 and ICLF2 were highest in 2016. The soil properties correlated with cumulative N2O emissions were TC, total nitrogen (TN), particulate nitrogen (PN), available nitrogen (AN), mineral-associated organic carbon (MAC), and microbial biomass carbon (MBC). The results indicated that ICLF2 induces an accumulation of more stable organic matter (OM) fractions that are unavailable to the microbiota in the short term and result in lower N2O emissions.

Brief history of biofertilizers in Brazil: from conventional approaches to new biotechnological solutions.

Brazil has a long history of research with rhizobia and plant growth-promoting rhizobacteria (PGPR). Currently, the use of bio-based products in Brazil, containing microorganisms that are effective in promoting plant growth through various mechanisms, is already a consolidated reality for the cultivation of several crops of agricultural interest. This is due to the excellent results obtained over many years of research, which contributed to reinforce the use of rhizobia and PGPR by farmers. The high quality of the products offered, containing elite strains, allows the reduction and prevention in the use of mineral fertilization, contributing to low-cost and sustainable agriculture. Currently, research has turned its efforts in the search for new products that further increase the efficiency of those already available on the market and for new formulations or inoculation strategies that contribute to greater productivity and efficiency of these products. In this review, the history of biological products for main crops of agricultural interest and the new biotechnologies and research available in the agricultural market are discussed.

Enzyme activities in a sandy soil of Western Bahia under cotton production systems: short-term effects, temporal variability, and the FERTBIO sample concept.

Enzyme activities (EAs) and the FERTBIO sample concept have been increasingly adopted as a novel approach to estimate the soil quality in Brazil. However, the performance of this strategy in sandy soils of the Cerrado biome remains unclear. During 2 years, in a Cerrado's sandy soil, the short-term effects of ten different cropping systems (conventional tillage or no-tillage associated with monoculture, rotations, and/or successions) on the activities of ß-glucosidase, acid phosphatase, and arylsulfatase were studied. Issues related to annual variability and the feasibility of using the FERTBIO sample concept for soil enzymes activities were also evaluated. Soil samples were collected at three different depths (0-10 cm, 10-20 cm, and 20-40 cm) in March 2017 and February 2018. Five years since the beginning of the experiment, the presence of cover crops and no-till promoted improvements in EAs evidencing the importance of regenerative management practices for the sustainability of agroecosystems in sandy soils. Regardless of the cropping systems and depths evaluated, soil organic carbon and EAs showed low temporal variation during the 2 years of monitoring. Our results also showed that it is possible to use the FERTBIO sample concept for the Quartzipsament soils of Western Bahia, Brazil.

Correction to: Identification of soybean Bradyrhizobium strains used in commercial inoculants in Brazil by MALDI-TOF mass spectrometry.

The original version of this article unfortunately contained a mistake. The presentation of Fig. 1was incorrect. The correct version is given below.

Identification of soybean Bradyrhizobium strains used in commercial inoculants in Brazil by MALDI-TOF mass spectrometry.

Biological nitrogen fixation (BNF) with the soybean crop probably represents the major sustainable technology worldwide, saving billions of dollars in N fertilizers and decreasing water pollution and the emission of greenhouse gases. Accordingly, the identification of strains occupying nodules under field conditions represents a critical step in studies that are aimed at guaranteeing increased BNF contribution. Current methods of identification are mostly based on serology, or on DNA profiles. However, the production of antibodies is restricted to few laboratories, and to obtain DNA profiles of hundreds of isolates is costly and time-consuming. Conversely, the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS technique might represent a golden opportunity for replacing serological and DNA-based methods. However, MALDI-TOF databases of environmental microorganisms are still limited, and, most importantly, there are concerns about the discrimination of protein profiles at the strain level. In this study, we investigated four soybean rhizobial strains carried in commercial inoculants used in over 35 million hectares in Brazil and also in other countries of South America and Africa. A supplementary MALDI-TOF database with the protein profiles of these rhizobial strains was built and allowed the identification of unique profiles statistically supported by multivariate analysis and neural networks. To test this new database, the nodule occupancy by Bradyrhizobium strains in symbiosis with soybean was characterized in a field experiment and the results were compared with serotyping of bacteria by immuno-agglutination. The results obtained by both techniques were highly correlated and confirmed the viability of using the MALDI-TOF MS technique to effectively distinguish bacteria at the strain level.

Microbiological functioning, diversity, and structure of bacterial communities in ultramafic soils from a tropical savanna.

Ultramafic soils are characterized by high levels of metals, and have been studied because of their geochemistry and its relation to their biological component. This study evaluated soil microbiological functioning (SMF), richness, diversity, and structure of bacterial communities from two ultramafic soils and from a non-ultramafic soil in the Brazilian Cerrado, a tropical savanna. SMF was represented according to simultaneous analysis of microbial biomass C (MBC) and activities of the enzymes ß-glucosidase, acid phosphomonoesterase and arylsulfatase, linked to the C, P and S cycles. Bacterial community diversity and structure were studied by sequencing of 16S rRNA gene clone libraries. MBC and enzyme activities were not affected by high Ni contents. Changes in SMF were more related to the organic matter content of soils (SOM) than to their available Ni. Phylogeny-based methods detected qualitative and quantitative differences in pairwise comparisons of bacterial community structures of the three sites. However, no correlations between community structure differences and SOM or SMF were detected. We believe this work presents benchmark information on SMF, diversity, and structure of bacterial communities for a unique type of environment within the Cerrado biome.