The Bacterial Community Structure and Microbial Activity in a Traditional Organic Milpa Farming System Under Different Soil Moisture Conditions

Abstract

Agricultural practices affect the bacterial community structure, but how they determine the response of the bacterial community to drought, is still largely unknown. Conventional cultivated soil, i.e., inorganic fertilization, tillage, crop residue removal and maize (Zea mays L.) monoculture, and traditional organic farmed soil “milpa,” i.e., minimum tillage, rotation of maize, pumpkin (Cucurbita sp.) and beans (Phaseolus vulgaris L.) and organic fertilization were sampled. Both soils from the central highlands of Mexico were characterized and incubated aerobically at 5% field capacity (5%FC) and 100% field capacity (FC) for 45 days, while the C and N mineralization, enzyme activity and the bacterial community structure were monitored. After applying the different agricultural practices 3 years, the organic C content was 1.8-times larger in the milpa than in the conventional cultivated soil, the microbial biomass C 1.3-times, and C and N mineralization 2.0-times (mean for soil incubated at 5%FC and FC). The dehydrogenase, activity was significantly higher in the conventional cultivated soil than in the milpa soil when incubated at 5%FC, but not when incubated at FC. The relative abundance of Gemmatimonadetes was larger in the conventional cultivated soil than in the milpa soil in soil both at 5%FC and FC, while that of Bacteroidetes showed an opposite trend. The relative abundance of other groups, such as Nitrospirae and Proteobacteria, was affected by cultivation technique, but controlled by soil water content. The relative abundance of other groups, e.g., FBP, Gemmatimonadetes and Proteobacteria, was affected by water content, but the effect depended on agricultural practice. For soil incubated at FC, the xenobiotics biodegradation and metabolism related functions were higher in the milpa soil than in the conventional cultivated soil, and carbohydrate metabolism showed an opposite trend. It was found that agricultural practices and soil water content had a strong effect on soil characteristics, C and N mineralization, enzyme activity, and the bacterial community structure and its functionality. Decreases or increases in the relative abundance of bacterial groups when the soil water content decreased, i.e., from FC to 5%FC, was defined often by the cultivation technique, and the larger organic matter content in the milpa soil did not prevent large changes in the bacterial community structure when the soil was dried.

Pea (Pisum sativum l.) Plant Shapes Its Rhizosphere Microbiome for Nutrient Uptake and Stress Amelioration in Acidic Soils of the North-East Region of India

“…Similarly, nutrient and residue management practices such as the application of chemical fertilizers often influence the endogenous microbial communities (Fierer et al, 2007). However, soil bacterial diversity is known to be affected by the numerous environmental factors including soil pH (Lauber et al, 2009;Cho et al, 2016;Sánchez-Cañizares et al, 2017), the chemistry of soil organic matter (Lupatini et al, 2017), plant species grown in the soil (Yamamoto et al, 2018), secretion of different root exudates by the plant species (Sasse et al, 2018;Huang et al, 2019), and processing of the soil before the cultivation of the plants (Moreno-Espíndola et al, 2018). Plant root exudates primarily stimulate the microbial activity in the rhizosphere, resulting in increased microbial active biomass and abundance in the rhizosphere by several folds in comparison to surrounding bulk soil (Lugtenberg and Kamilova, 2009).…”

Changes on Bacterial and Fungal Soil Communities in Long-Term Organic Cropping Systems

“…Indeed, the impact of the cropping system is considered to be stronger than any potential spatiotemporal variations [74]. The effect of the different cropping systems was not reflected in the dominant bacterial phyla, contrary to that observed by Lupatini, et al [73] or Moreno-Espíndola et al [75]. Hartman et al [74] observed that differences in the bacterial community between organically farmed and conventionally managed soils under integrated fertilization were smaller.…”

Inoculation with mycorrhizal fungi and irrigation management shaped the bacterial and fungal communities and networks in vineyard soils

“…Under our experimental conditions, Actinobacteria and Chloro exi phylum increased in HI plots. Accordingly, it was previously reported Moreno-Espíndola et al [60] in an organic Milpa farm with different moisture, thus these authors suggested that phylotypes belonging to Actinobacteria and Chloro exi were enriched in dry conditions because their thick cell walls, lamentous growth and spore formation favor them under dry conditions [61]. In contrast, Vink et al [56] found little variation in Actinobacteria and Proteobacteria proportions between the different cultivars, the phenological stages and irrigation treatments.…”