Tropical and Subtropical Agroecosystems (Jan 2023)
FACTORS AFFECTING THE NITROGEN FIXATION IN THE Inga spp.-RHIZOBIA SYSTEM IN SHADE COFFEE PLANTATIONS
Abstract
Background. The results of a review on the factors that affect nitrogen fixation in the Inga-café system are presented. The nitrogen contribution that the Inga Miller tree genus provides to shade coffee plantations and the factors that affect its stability in biological nitrogen fixation are scarcely recognized. This work delves into the ecological factors and glyphosate herbicides that can affect the symbiosis of Inga spp. with diazotrophic bacteria in their roots (rhizobia), which form nodules and carry out biological nitrogen fixation. Methodology. Different information sources such as EBSCO, Scopus and Google Schoolar were reviewed, with logical or Boolean data search. 183 papers were used to address the factors that affect the symbiosis between trees of the Inga genus and rhizobia. The findings were organized in: Inga Miller taxonomy, shade coffee plantations with Inga spp., symbiosis between Inga spp. and Bradyrhizobium spp., ecological factors that affect the functioning of the Inga spp.-rhizobia symbiosis and the agrochemical factor: glyphosate herbicide. Results. The genus Inga is recognized as a clade Mimosoideae nested in the subfamily Caesalpinioideae. Shade coffee plantations with Inga are established below 23º N and 30º S, up to 3,100 m.a.s.l. and the symbiont genus is predominantly Bradyrhizobium spp. whose ecological limits of Inga spp-rhizobia were: altitude [988.7-1,381.5 m.a.s.l.], annual precipitation [2,048.4-2,064.36 mm], temperature [20.39-21.93 ºC] and soil pH [4.88-5.42 pH]. Glyphosated herbicides, as an external stimulus, can reduce the benefit of biological nitrogen fixation and erode the soil by keeping it devoid of vegetation. Additionally, some Bradyrhizobium spp. (thiO gene), which oxidizes glyphosate to aminomethylphosphonic acid (AMPA), could be a potential glyphosate degrader in the soil. Implications. Shade coffee plantations with 205-250 trees per hectare of Inga spp. allow fixing around 45 kg of N ha-1 year-1. This review may allow the adoption of new observational or experimental studies of the Inga spp.-rhizobia symbiosis, to approach the performance that favors the biological fixation of nitrogen in shade coffee plantations. Conclusions. The review indicates that there is a specific association between Inga spp. and Bradyrhizobium spp., that ecological factors, including the agronomic management with glyphosated herbicides can decrease nitrogen fixation performance during the symbiosis between Inga spp. and rhizobia. No systematic studies of the symbiosis-environment-agrochemical interaction in shade coffee plantations were found.
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