Abstract
Improving soil water holding capacity (WHC) through conservation agriculture (CA)-practices, i.e., minimum mechanical soil disturbance, crop diversification, and soil mulch cover/crop residue retention, could buffer soil resilience against climate change. CA-practices could increase soil organic carbon (SOC) and alter pore size distribution (PSD); thus, they could improve soil WHC. This paper aims to review to what extent CA-practices can influence soil WHC and water-availability through SOC build-up and the change of the PSD. In general, the sequestered SOC due to the adoption of CA does not translate into a significant increase in soil WHC, because the increase in SOC is limited to the top 5–10 cm, which limits the capacity of SOC to increase the WHC of the whole soil profile. The effect of CA-practices on PSD had a slight effect on soil WHC, because long-term adoption of CA-practices increases macro- and bio-porosity at the expense of the water-holding pores. However, a positive effect of CA-practices on water-saving and availability has been widely reported. Researchers attributed this positive effect to the increase in water infiltration and reduction in evaporation from the soil surface (due to mulching crop residue). In conclusion, the benefits of CA in the SOC and soil WHC requires considering the whole soil profile, not only the top soil layer. The positive effect of CA on water-saving is attributed to increasing water infiltration and reducing evaporation from the soil surface. CA-practices’ effects are more evident in arid and semi-arid regions; therefore, arable-lands in Sub-Sahara Africa, Australia, and South-Asia are expected to benefit more. This review enhances our understanding of the role of SOC and its quantitative effect in increasing water availability and soil resilience to climate change.
Highlights
Matching food production with the rapid population growth using sustainable and environmentally friendly approaches represents a big challenge, under the changing climate [1,2,3,4,5,6]
Given that soil water holding capacity (WHC) responds to agronomic management, in this study, we focused on the assessment of the main conservation agriculture (CA)-practices, i.e., minimum soil disturbance, crop diversification, and crop residue retention (CRR), that could enhance soil WHC and available water holding capacity (AWHC)
The enhanced macro-porosity pores continuity and the increased number of bio-pores likely increase water infiltration, not soil WHC. This conclusion was supported by numerous short- and long-term studies (Table 2) in which soil water retention (SWR) or soil WHC was not affected by CA-practices
Summary
Matching food production with the rapid population growth using sustainable and environmentally friendly approaches represents a big challenge, under the changing climate [1,2,3,4,5,6]. Conservation agriculture and its components have been associated with many benefits, including carbon (C) storing in the soil [22,26,49,53,58,59,60,61,62,63,64], improved soil quality [26,57,65,66,67,68,69,70,71], decreasing runoff and soil erosion [2,72,73,74,75], increasing water productivity [6,52,69,76,77], energy use efficiency [78,79], and, in some cases, higher yield and profitability [6,80,81,82]. It is deserving to refine our understanding of if, how, and to what extent CA-practices affect soil WHC and water-saving and availability
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