How different soil moisture levels affect the microbial activity

Abstract

The lowland soils are characterized by high susceptibility to water saturation. This anaerobic condition is usually reported in paddy fields and alters the decomposition process of soil organic compounds. The aim of this study was to evaluate the soil microbial and enzymatic activity of a lowland soil at different soil moisture contents. A poorly drained Albaqualf cultivated with irrigated rice was used to evaluate microbial and enzymatic activity in treatments with different levels of soil moisture, being: i) 60% of field capacity (FC) (60%FC); ii) 100% of FC (100%FC); iii) flooded soil with a 2 cm water layer above soil surface, and iv) soil kept at 60%FC with late flood after 29 days the incubation. The greater soil microbial activity was observed in the 100%FC treatment, being 41% greater than 60%FC treatment and only 2% higher than flooded treatment. The enzymatic activity data by fluorescein diacetate (FDA) hydrolysis corroborated the higher CO2 release in treatments with higher soil moisture content. Differently from the results reported, the main methodologies to evaluate microbial activity still recommend maintenance of the soil with a moisture content close to 60% of the FC. However, in lowland soil with history of frequent paddy fields, the maintenance of moisture close to 60% of the FC can limit the microbial activity. The soil respiration technique can be used to evaluate the microbial activity in flooded soil conditions. However, further studies should be conducted to understand the effect of the cultivation history on the microbial community of these environments.

Carbon emissions in hydromorphic soils from an estuarine floodplain forest in the Amazon River

“…For the floodplain environment, studies on CO 2 emission are incipient, but other authors have concluded that hydromorphic soils have greater microbial activity than drained soils (Acosta et al, 2019). This was also verified in a laboratory experiment when soils that were irrigated up to field capacity (100%) and those that were flooded and kept under flooding, with a water depth of 2 cm above the ground, were observed to be the ones with the highest accumulation of CO 2 emission in 64 days (Denardin et al, 2020). Therefore, a possible explanation is the increased respiration of microorganisms associated with high moisture levels and flooding of the soil in the floodplain environment.…”

“…Although soil moisture and periodic flooding favor microbial activity and, consequently, CO 2 emission (Denardin et al, 2020), in longer periods of flooding, such as in April and May, this relationship can become negative due to a long anoxia time without soil aeration. Sotta et al (2004) state that the formation of a water layer on the ground for a long period prevents the emission of CO 2 into the atmosphere when the area is flooded.…”

Rice Growth Performance, Nutrient Use Efficiency and Changes in Soil Properties Influenced by Biochar under Alternate Wetting and Drying Irrigation

“…Nevertheless, decreased activity of DHA and urease under AWD over CF might be due to soil drying intermittently, thereby reducing microbial activities. The reduced moisture levels decrease soil enzymatic activities, as reported by Denardin et al [35] and Zhao et al [36].…”

Effects of Abiotic Stress on Soil Microbiome

“…Furthermore, drought season has a pronounced effect on the soil microbiome, as moisture and temperature [15] are determinant effectors of microbial growth and activity as mentioned in our previous section. The moisture level influences soil microbiota and causes shifts in microbial activity and structural diversity [83,84]. Whereas, a rise in temperature due to drought season has detrimental impact on microbial biomass [84] and microbial population abundance [85].…”