Microbial community responses to soil tillage and crop rotation in a corn/soybean agroecosystem

Abstract

The acreage planted in corn and soybean crops is vast, and these crops contribute substantially to the world economy. The agricultural practices employed for farming these crops have major effects on ecosystem health at a worldwide scale. The microbial communities living in agricultural soils significantly contribute to nutrient uptake and cycling and can have both positive and negative impacts on the crops growing with them. In this study, we examined the impact of the crop planted and soil tillage on nutrient levels, microbial communities, and the biochemical pathways present in the soil. We found that farming practice, that is conventional tillage versus no‐till, had a much greater impact on nearly everything measured compared to the crop planted. No‐till fields tended to have higher nutrient levels and distinct microbial communities. Moreover, no‐till fields had more DNA sequences associated with key nitrogen cycle processes, suggesting that the microbial communities were more active in cycling nitrogen. Our results indicate that tilling of agricultural soil may magnify the degree of nutrient waste and runoff by altering nutrient cycles through changes to microbial communities. Currently, a minority of acreage is maintained without tillage despite clear benefits to soil nutrient levels, and a decrease in nutrient runoff—both of which have ecosystem‐level effects and both direct and indirect effects on humans and other organisms.

Legacy of land use history determines reprogramming of plant physiology by soil microbiome

“…However, agricultural practices can drive the composition of plant-associated microbiomes to adapt the plant to biotic and abiotic stresses [4]. It has been shown that application of herbicides, pesticides, and tillage practices can lead to shifts in the rhizosphere microbial community compositions [5][6][7][8][9], with possible consequences for crop performance [4,10,11]. In a comparison of plants grown in monocultures and mixtures, it was found that the former had the lowest microbial diversity [12].…”

Asymbiotic nitrogen fixation is greater in soils under long-term no-till versus conventional tillage

“…Although several studies have indicated that greater asymbiotic N fixation is possible under no-till (Gupta and Roper, 2010; Smith et al, 2016) this is the first study to indicate that greater asymbiotic N is produced in soils under long-term no-till management. This study will hopefully lead to more careful examination of paired fields, or carefully constructed tillage experiments.…”

“…Long-term no-till fields generally have a greater supply of C and more diverse C sources compared to a conventional-tilled soil (Awale et al, 2013; Smith et al, 2016). Also, the greater stable aggregation in a no-till soil would provide a habitat for N-fixers and protect them from biocides that they might otherwise encounter (Gupta and Roper, 2010).…”

“…Microbial communities found in stable aggregates under no-till have a greater range of soil organic matter cycling-process rates than similar microbes in conventional systems where aggregates are disturbed or destroyed. No-till management systems are associated with greater number of N-fixing genes compared to soil from conventional-till fields (Smith et al, 2016).…”

Soil biodiversity and biogeochemical function in managed ecosystems

“…A majority of studies demonstrate higher soil microbial biomass under notill versus conventional tillage systems (Wardle 1995;D'Hose et al 2018). Soils under reduced or no-till systems also exhibit altered microbial communities in comparison to conventional tillage (Helgason et al 2009;Kuntz et al 2013;Smith et al 2016). These shifts in microbial diversity can change the functional capacity of the communities (Mangalassery et al 2015;Nivelle et al 2016).…”