Long-term residue removal under tillage decreases amoA-nitrifiers and stimulates nirS-denitrifier groups in the soil

N Kim,C.W Riggins,S Rodríguez-Zas,M.C Zabaloy,M.B Villamil

doi:10.1016/j.apsoil.2020.103730

N Kim, C.W Riggins + Show 3 more

Open Access

https://doi.org/10.1016/j.apsoil.2020.103730

Copy DOI

Abstract

No-till in continuous corn (Zea mays L.) production helps to keep an important volume of residues on the soil surface, creating management challenges that could be alleviated by residue removal for bioenergy or animal use. Crop residues, however, are essential to stimulate microbial nutrient cycling in agroecosystems. Thus, both residue removal and tillage options need to be fully evaluated for their impacts on ecosystem services related to soil health, including microbial N cycling. We explored the main steps of the microbial N cycle in relation to soil properties by using targeted gene abundance as a proxy following over a decade of residue removal in continuous corn systems either under no-till or chisel tillage. We used real-time quantitative polymerase chain reaction (qPCR) for the quantification of phylogenetic groups and functional gene screening of the soil microbial communities, including genes encoding critical enzymes of the microbial N cycle: nifH (N2 fixation), amoA (nitrification – ammonia oxidation), nirK and nirS (denitrification – nitrite reduction), and nosZ (denitrification – nitrous oxide reduction). Our results showed that long-term residue removal and tillage decreased soil organic matter (SOM), water aggregate stability (WAS), and the relative abundance (RA) of ammonia-oxidizing bacteria (AOB) carrying nitrifying amoA genes. Denitrifiers carrying nirS genes decreased under no-till as crop residue was removed. In addition, our results evidenced strong correlations among soil properties and phylogenetic groups of bacteria, archaea, and fungi. Overall, this study demonstrated limited but definite impacts of residue management and tillage on the soil environment, which could be exacerbated under less resilient conditions.

Highlights

Soil degradation from anthropogenic sources, including conven tional intensive agriculture, threatens food production around the globe (FAO and ITPS, 2015)
The probability values and degrees of freedom associated with the ANOVA for the effects of residue removal, tillage, and their interaction are shown in the lower portion of Table 1 for each extracted principal components (PCs)
Results showed a statistically significant interaction effect (RR x T, Table 1) for PC2 (p < 0.0337). This interaction effect indicated that the soil vari ables represented by PC2 responded differently to residue removal depending on the tillage practices

Summary

Introduction

Soil degradation from anthropogenic sources, including conven tional intensive agriculture, threatens food production around the globe (FAO and ITPS, 2015). Soil chemical imbalance from excessive N fer tilizer input is one source of soil degradation (Belay et al, 2002; Khan et al, 2007; Schroder et al, 2011). Excessive fertilizer input im poses environmental and societal costs through eutrophication of water sources (Selman et al, 2008), elevated nitrate pollution in drinking water (Pennino et al, 2017; Zhang et al, 2018), and higher greenhouse gas (GHG) emissions (Fowler et al, 2013). A notable example of such impacts in the US is the seasonal hypoxic zone that forms in the Gulf of Mexico due in large part to excess N from the agricultural inputs that drain into the Mississippi River Basin (EPA, 2017). The Mid west region is a major contributor of N leaching into the Gulf of Mexico (White et al, 2014)

Methods

Results

Discussion

Conclusion