Crop residues exacerbate the negative effects of extreme flooding on soil quality

Abstract

Extreme flood events are predicted to have a negative impact on soil quality. Currently, there is a lack of information about the effect of agricultural practices on soil functioning and microbial processes under these events. We hypothesized that the impact of flooding on soil quality will be exacerbated when crop residues are present in the soil as they will induce more extreme anaerobicity. A spring extreme flood event (10°C, 9 weeks) was simulated in mesocosms containing an arable sandy-loam soil low in nutrients. The main treatments were (1) with and without flooding and (2) with and without maize residue addition (8 Mg ha −1 ). We monitored changes in soil chemical quality indicators (e.g. pH, salinity, Fe 3+ , P, C, NH 4 + , NO 3 − and organic N), greenhouse gas (GHG) emissions (CO 2 , CH 4 , N 2 O) and soil microbial community composition (PLFAs) during a prolonged flood period (9 weeks) and an 8-week Brecovery^period after flooding. In comparison to the other treatments, flooding in the presence of crop residues resulted in a dramatic drop in soil redox potential. This was associated with the enhanced release of Fe and C into solution and an increase in CH 4 emissions. In contrast, maize residues reduced potential nitrate losses and N 2 O emissions, possibly due to complete denitrification and microbial N immobilization. Both flooding and maize residues stimulated microbial growth and promoted a shift in microbial community composition. Following floodwater removal, most of the soil quality indicators returned to the levels of the control treatment within 5 weeks. After this short recovery phase, no major impact of flooding could be observed on plant growth (maize pot-grown). Overall, we conclude that both extreme flooding and management regime negatively impact upon a range of soil quality indicators (e.g. redox, GHG emissions); however, the soil showed high resilience and recovered quickly after floodwater removal. Further work is required to investigate the impact of repeated extreme flood events on soil quality and function over longer timescales.

Typology of extreme flood event leads to differential impacts on soil functioning

“…Alterations in the assessed gaseous emissions from the flooded mesocosms were also dependent on flood typology. Normally, very low emissions of CO 2 , CH 4 and N 2 O have been observed during flooding in previous experiments with this soil (Sánchez-Rodríguez et al, 2017). CH 4 emissions were, however, detected immediately after floodwater removal.…”

“…CH 4 emissions were, however, detected immediately after floodwater removal. We ascribe this to the release of CH produced during flooding, but which had become trapped within the soil pores until floodwater removal ( Moore and Roulet, 1993;Sánchez-Rodríguez et al, 2017). In our experiment, the prevailing conditions under flooding (-100 mV redox potential, high DOC, senescing vegetation) were ideal for CH 4 production (Hou et al, 2000).…”

“…Although some small N 2 O emissions from residual soil NO − at the start of flooding were detected in a similar previous experiment (Sánchez-Rodríguez et al, 2017), the most important emissions were measured during the soil recovery phase (Sánchez-Rodríguez et al, 2017. This is the reason why we focused our GHGs measurements on the soil recovery stage.…”

The impact of drought and rewetting on N2O emissions from soil in temperate and Mediterranean climates

“…Anthropogenic climate change is predicted to increase the intensity and frequency of extreme weather events such as flooding, storms and droughts (Stocker, 2014). This has implications for biogenic greenhouse gas emissions, as the hydrological regime of soil is increasingly likely to fluctuate (Sánchez-Rodríguez, Hill, Chadwick, & Jones, 2017). Long-term studies of N 2 O emissions from field sites have noted that emissions can suddenly increase by orders of magnitude above the average seasonal flux (Parkin & Kaspar, 2006;Scanlon & Kiely, 2003), with rapid changes in temperature and soil moisture often due to spring rains or winter thawing.…”

Flooding, Food Security and the Sustainable Development Goals in Nigeria: An Assemblage and Systems Thinking Approach

“…However, availability and access do not guarantee adequate utilization of the necessary nutrition from food (Zewdie 2014). Nutrient and soil loss occurs as a result of flooding (Sánchez-Rodríguez et al 2017). This subsequently reduces the nutritional composition of food cultivated on nutrient-poor soil, since degraded soil produces low-quality food (Lal 2009).…”