Soil and crop management practices and the water regulation functions of soils: a qualitative synthesis of meta-analyses relevant to European agriculture

Abstract

Abstract. Adopting soil and crop management practices that conserve or enhance soil structure is critical for supporting the sustainable adaptation of agriculture to climate change, as it should help maintain agricultural production in the face of increasing drought or water excess without impairing environmental quality. In this paper, we evaluate the evidence for this assertion by synthesizing the results of 34 published meta-analyses of the effects of such practices on soil physical and hydraulic properties relevant for climate change adaptation in European agriculture. We also review an additional 127 meta-analyses that investigated synergies and trade-offs or help to explain the effects of soil and crop management in terms of the underlying processes and mechanisms. Finally, we identify how responses to alternative soil–crop management systems vary under contrasting agro-environmental conditions across Europe. This information may help practitioners and policymakers to draw context-specific conclusions concerning the efficacy of management practices as climate adaptation tools. Our synthesis demonstrates that organic soil amendments and the adoption of practices that maintain “continuous living cover” result in significant benefits for the water regulation function of soils, mostly arising from the additional carbon inputs to soil and the stimulation of biological processes. These effects are clearly related to improved soil aggregation and enhanced bio-porosity, both of which reduce surface runoff and increase infiltration. One potentially negative consequence of these systems is a reduction in soil water storage and groundwater recharge, which may be problematic in dry climates. Some important synergies are reductions in nitrate leaching to groundwater and greenhouse gas emissions for nonleguminous cover crop systems. The benefits of reducing tillage intensity appear much less clear-cut. Increases in soil bulk density due to traffic compaction are commonly reported. However, biological activity is enhanced under reduced tillage intensity, which should improve soil structure and infiltration capacity and reduce surface runoff and the losses of agro-chemicals to surface water. However, the evidence for these beneficial effects is inconclusive, while significant trade-offs include yield penalties and increases in greenhouse gas emissions and the risks of leaching of pesticides and nitrate. Our synthesis also highlights important knowledge gaps on the effects of management practices on root growth and transpiration. Thus, conclusions related to the impacts of management on the crop water supply and other water regulation functions are necessarily based on inferences derived from proxy variables. Based on these knowledge gaps, we outlined several key avenues for future research on this topic.

Interactive effects of long-term management of crop residue and phosphorus fertilization on wheat productivity and soil health in the rice–wheat

“…Conservation tillage + residue retention improved the infiltration rate over residue removal treatment 32 . The improved aggregate stability and moisture retention could explain the enhanced infiltration rates.…”

Crop rotational diversity can mitigate climate‐induced grain yield losses

“…Increasing CRD could improve soil structure and soil organic matter content, facilitating the retention of water and nutrients in several field experiments (Kremen & Miles, 2012; Schmer et al., 2020; Sprunger et al., 2020). Nevertheless, trade‐offs might occur if the added crops increase water demands, as observed in some experiments (Blanchy et al., 2023), in the absence of sufficient soil water recharge outside the growing season. Improved soil water retention could reduce water stress under low precipitation and limit nutrient leaching under high precipitation (Renwick et al., 2019).…”

“…The benefits of CRD to grain yields under warming likely resulted from a combination of mechanisms. By enhancing soil structure and, hence, water availability (Blanchy et al., 2023; Kremen & Miles, 2012; Schmer et al., 2020; Sprunger et al., 2020), CRD might reduce water stress and increase evaporative cooling, which mitigates heat stress (Sadok et al., 2021). Similarly, preceding crops with large and deep rooting systems can create biopores, that is, pathways in the soil that facilitate root growth of the following crop, and hence deeper water uptake (Han et al., 2015), buffering against soil water fluctuations.…”

Interactions between soil structure dynamics, hydrological processes, and organic matter cycling: A new soil‐crop model

“…The structure of agricultural soils is also dynamic at time scales ranging from seconds (e.g., tillage and compaction) to seasons and decades (e.g., root growth and the activity of soil biota; Meurer, Barron, et al, 2020). Soil structure dynamics triggered by changes in soil and crop management practices or climate (i.e., the critical external drivers) lead to feedbacks in the soil–plant system, which may result in the long term in either soil physical degradation or restoration (Henryson et al, 2018; Blanchy et al, 2023; Figure 1).…”