Influence of Edaphic, Climatic, and Agronomic Factors on the Composition and Abundance of Nitrifying Microorganisms in the Rhizosphere of Commercial Olive Crops

Abstract

The microbial ecology of the nitrogen cycle in agricultural soils is an issue of major interest. We hypothesized a major effect by farm management systems (mineral versus organic fertilizers) and a minor influence of soil texture and plant variety on the composition and abundance of microbial nitrifiers. We explored changes in composition (16S rRNA gene) of ammonia-oxidizing archaea (AOA), bacteria (AOB), and nitrite-oxidizing bacteria (NOB), and in abundance of AOA and AOB (qPCR of amoA genes) in the rhizosphere of 96 olive orchards differing in climatic conditions, agricultural practices, soil properties, and olive variety. Majority of archaea were 1.1b thaumarchaeota (soil crenarchaeotic group, SCG) closely related to the AOA genus Nitrososphaera. Most AOB (97%) were identical to Nitrosospira tenuis and most NOB (76%) were closely related to Nitrospira sp. Common factors shaping nitrifiers assemblage composition were pH, soil texture, and olive variety. AOB abundance was positively correlated with altitude, pH, and clay content, whereas AOA abundances showed significant relationships with organic nitrogen content and exchangeable K. The abundances of AOA differed significantly among soil textures and olive varieties, and those of AOB among soil management systems and olive varieties. Overall, we observed minor effects by orchard management system, soil cover crop practices, plantation age, or soil organic matter content, and major influence of soil texture, pH, and olive tree variety.

Differential characterization of physiological and biochemical responses during drought stress in finger millet varieties

“…Drought stress induces different physiological, genetic and metabolic responses among several species of plant and varieties. These responses are also influenced by edaphic, climatic and agronomic factors (Caliz et al, 2015). Vulnerability of plants to drought stress differentially varies in depending on stress severity, interactions among stressors, plant species and stages of their development (Demirevska et al, 2009).…”

Impact of Cover Crops on the Soil Microbiome of Tree Crops

“…These changing soil conditions and increased organic inputs likely drive the increased microbial diversity found in soils of perennial systems planted with cover crops [11,14,58]. This increased soil microbial diversity is positively correlated with nearly all of the benefits of cover crops to production systems, including increased soil organic carbon (SOC) and total N (TN) contents and, ultimately, tree production [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] (Table 1). Changes can persist throughout the long-term management of a perennial system, as 10 and 22 years of planting a monoculture cover crop of F. macrophylla in rubber (E. urophylla) orchards increased bacterial gene abundance and diversity down to a depth of 60 cm within the soil profile compared with the no-cover-crop control treatment [35].…”

Culture-Dependent and Culture-Independent Characterization of the Olive Xylem Microbiota: Effect of Sap Extraction Methods

“…With olive, most microbiome studies have focused on determining the microbial composition of the rhizosphere (Mercado-Blanco et al, 2004;Berg and Hallmann, 2006;Mendes et al, 2007;Aranda et al, 2011;Prieto et al, 2011;Montes-Borrego et al, 2013;Caliz et al, 2015;Gómez-Lama Cabanás et al, 2018), whereas only a few studies have focused on the endosphere or xylem microbiomes (Müller et al, 2015;Fausto et al, 2018;Sofo et al, 2019). Unraveling the microbiome of the olive xylem sap should provide a better understanding of the microbes that systemically move throughout the plant or are horizontally transmitted from plant to plant during vegetative propagation.…”