Protection of free-living nitrogen-fixing bacteria within the soil matrix

Seasonal variations in the diversity and abundance of diazotrophic communities across soils

“…Indeed, it has been shown that 70% of the free-living N-fixing bacteria are located in the clay fraction (Chotte et al, 2002). The availability of carbon is another factor that affects the level of N fixation in soils, the carbon becoming available from rhizodeposition or via retention of crop residues (Gupta & Roper, 2010). The results from our multiple regression analysis supported this latter conclusion, as soil pH was positively correlated with the overall nifH gene abundance at all four sampling times.…”

“…Interestingly, the effect of soil pH on the abundance of diazotrophs varied across the season, being stronger in June, when it explained almost half of the variation in nifH gene copy numbers. The availability of carbon is another factor that affects the level of N fixation in soils, the carbon becoming available from rhizodeposition or via retention of crop residues (Gupta & Roper, 2010). Indeed, in our work, soil DOC had an overall positive effect on nifH gene abundance, albeit to a lesser extent than pH.…”

“…Clay fractions in soils are important in imparting specific physical properties, forming micro-and macroaggregates (Gupta & Roper, 2010), and providing microaerophilic or anaerobic conditions that are favorable to N fixation. This knowledge is consistent with our findings, which showed higher abundances of nifH genes in the clay soils compared with the sandy ones.…”

Relationship between soil physicochemical characteristics and nitrogen-fixing bacteria in agricultural soils of the Atlántico department, Colombia

“…These problems are mainly related to the increase in soil salinity, decrease in soil pH (mostly of nitrogenous fertilizers exert an acidifying action on the soil), and the contamination of groundwater (Martínez-Mera et al, 2016;Iturri and Buschiazzo, 2016). At the same time, these alterations in the physicochemical characteristics of soils, depending on the climatic conditions of the zone, can bring changes in the distribution, diversity and abundance of soil microorganisms (Mahmood et al, 2006;Gupta and Roper, 2010). The identification of alternative sources of fertilization that reduce impacts on soils is necessary for the development of sustainable agriculture and sustainable soil management practices (Martínez-Mera et al, 2016).…”

Diversidade microbiana envolvida na ciclagem do nitrogênio em solos de cultivo de cana-de-açúcar no estado de São Paulo

“…A atividade e a diversidade microbiana são consideradas potenciais indicadores de degradação do solo, bem como da sua recuperação (LUNDQUIST et al, 1999;CALDERÓN et al, 2001;NANNIPIERI et al, 2003). Grupos microbianos funcionais, tais como os fixadores de nitrogênio e amônio-oxidantes, desempenham papeis fundamentais na ciclagem do nitrogênio em solos agricultáveis (HABTESELASSIE et al, 2013). O estudo destes grupos é muito importante, uma vez que a nitrificação, acoplada com a desnitrificação, constituem as maiores fontes de perda de N no solo (RACHID et al, 2012).…”