No-till and cover crops shift soil microbial abundance and diversity in Laos tropical grasslands

Abstract

Agricultural practices affect the physical and chemical characteristics of the soil, which in turn may influence soil microorganisms with consequences on soil biological functioning. However, there is little knowledge on the interactions between agricultural management, soil physicochemical properties, and soil microbial communities, notably in tropical ecosystems with few studies conducted in strongly weathered and acid soils. Here, we investigated the early effect of tillage and crop residues management on top soil physical, chemical, and microbial properties in an acid savannah grassland of northeastern Laos. We initiated a 3-year rotation of rice/corn/soybean under three no-till systems (NTs) distinguished by the cover crops associated prior to and with the main crops, and one conventional tillage-based system (CT). The effect of agricultural management was evaluated 2 years after land reclamation in reference to the surrounding natural pasture (PAS). Our results demonstrate that NTs improve soil physicochemical characteristics (aggregate stability, organic carbon, and cation exchange capacity) as well as microbial abundance (total biomass, bacterial and fungal densities). A significant discrimination of the genetic structure of soil bacterial community was also observed between NTs, CT, and PAS. Interestingly, bacterial abundance and diversity were differently influenced by soil environment changes: microbial density was affected by the quantity and diversity of crop residues, soil organic carbon, and exchangeable base contents, whereas soil bacterial genetic structure was mainly determined by exchangeable aluminum content, pH, cation exchange capacity, and C/N ratio. Altogether, our study represents one of the most complete environmental evaluations of agricultural practices in tropical agrosystems and leads to recommend no-till systems with high residue restitutions to improve the physical, chemical, and microbial properties of tropical acid soils and thus contribute to the sustainability of agriculture in these ecosystems.

Soil organic carbon fraction losses upon continuous plow-based tillage and its restoration by diverse biomass-C inputs under no-till in sub-tropical and tropical regions of Brazil

“…6). Additional research is needed to analyze the cumulative effects of a mixture of cover/relay crops under NT on root exudation, and changes in rhizospheric biological activities, which influence nutrients and C cycling by improving soil aggregation and physically protecting plant-derived SOC and microbially derived organic C. In an acid tropical grassland environment in Laos, Lienhard et al (2013) showed that high and diversified biomass-C inputs under NT induced significant modifications when compared with conventional plow-based tillage. NT increased aggregate stability and soil organic carbon content, enhanced nutrient availability and microbial biomass as a result of a simultaneous increase of fungal and bacterial densities.…”

Importance of cover crops in alleviating negative effects of reduced soil tillage and promoting soil fertility in a winter wheat cropping system

“…It is based on three fundamental principles: 1. diversification of crop rotation, 2. reduction of soil tillage and 3. permanent soil cover (FAO, 2017). Compared to classical plough tillage, reduced tillage has several advantages, such as reduction of fuel costs, decreased disturbance for soil organisms, preservation of soil fertility, higher soil macroporosity, better water retention (Holland, 2004;Lienhard et al, 2013;Mazzoncini et al, 2011;Murugan et al, 2014;Palm et al, 2014;Sapkota et al, 2012;Soane et al, 2012). In contrast, detrimental effects, such as increased soil density, reduction of mineralisation or slowing of soil warming, could be observed in reduced tillage systems, especially with direct seeding (Soane et al, 2012).…”

Soil quality, microbial functions and tomato yield under cover crop mulching in the Mediterranean environment

“…Among all soil properties, microbial biomass and soil enzyme activities prove to be sensitive indicators of soil quality as they are measurements which rapidly respond to changes due to different management and environmental factors (Alvear et al, 2005). Soil perturbations, such as tillage, can alter microbial processes, biogeochemical nutrient cycles (overall C stored) (Janzen et al, 1997) thus modifying the structural and functional diversities of the soil microbial communities (Lienhard et al, 2012). In fact, physical disturbance exposes Soil organic matter (SOM) to biological activity, thus facilitating the penetration of water at greater depths and accelerating its decomposition.…”