Abstract
Sub-Saharan Africa (SSA) faces climate change and food insecurity challenges, which require action to create resilient farming systems. Conservation agriculture (CA) is widely promoted across SSA but the impacts on key soil physical properties and functions such as soil structure and hydraulic properties that govern water storage and transmission are not well understood. The aim of this study was to assess the impacts of long term (10–12 years) maize-based CA on soil hydraulic conductivity, water retention and pore size distribution. Root zone (0–30 cm depth) soil total porosity, pore size distribution, saturated hydraulic conductivity (Ksat) and plant available water capacity (PAWC) of conventional maize monocrop farming systems (CP) are compared with those of adjacent CA trials with either sole maize or maize intercrop/rotation with cowpea (Vigna unguiculata L.), pigeon pea (Cajanus cajan L.) or velvet bean (Mucuna pruriens L) in trial locations across central and southern Malawi. Results show that maize-based CA systems result in significant changes to soil hydraulic properties that correlate with improved soil structure. Results demonstrate increases of 5–15 % in total porosity, 0.06−0.22 cm/min in Ksat, 3–7 % in fine pores for water storage and 3–6 % in PAWC. Maize monocrop CA had similar effect on the hydraulic properties as the maize-legume associations. The values of Ksat for CA systems were within optimum levels (0.03–0.3 cm/min) whereas PAWC was below optimum (<20 %). There was no significant build-up in soil organic matter (OM) in the CA systems. The results lead to a recommendation that crop residue management should be more pro-actively pursued in CA guidance from agricultural extension staff to increase soil OM levels, increase yields and enhance climate resilience of sub-Saharan African farming systems.
Highlights
Climate change, climate extremes, soil fertility decline and food insecurity are significant challenges facing sub-Saharan Africa (SSA), with 23 % of the population being undernourished and over 35 million people expected to be food insecure by 2050 (FAO and ECA, 2018)
This study investigated the impacts of long term (10–12 years) Conservation agriculture (CA) trials in central and southern Malawi on soil hydraulic properties at three trial locations
There was no significant difference in plant available water capacity (PAWC) between the surface and sub-surface soil layers in all the three sites
Summary
Climate extremes, soil fertility decline and food insecurity are significant challenges facing sub-Saharan Africa (SSA), with 23 % of the population being undernourished and over 35 million people expected to be food insecure by 2050 (FAO and ECA, 2018). The climate resilience of farming systems depends on soil attributes such as structure, nutrient content, organic matter (OM) and biota (Lal, 2011; Cardoso et al (2013)). Understanding the structural characteristics of soils (e.g. pore size distribution and geometry, hydraulic conductivity and water retention capacity) under different agricultural systems provides insight into the resilience of such systems to changing environmental conditions. Maize-based CP systems are characterised by: the formation of a compact layer at about 25 cm below the soil surface which impedes water infiltration as well as root penetration and distribution within the rhizosphere (Materechera and Mloza-Banda, 1997); inefficient soil water conservation during dry periods (Thierfelder et al, 2013); disruption of continuous soil pores resulting in lower infiltration and transmission of rain water to plant roots (Thierfelder et al, 2005); increased susceptibility of soils to drying and moisture loss when ridges are not covered with mulch (Thierfelder and Wall, 2009); and the tendency for plant roots and associated mycorrhizal fungi to be disturbed and cut during weeding and reconstruction of ridges (Thierfelder et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
