Toward greater sustainability: how investing in soil health may enhance maize productivity in Southern Africa

Abstract

Climate change and soil fertility decline are major threats to smallholder farmers' food and nutrition security in southern Africa, and cropping systems that improve soil health are needed to address these challenges. Cropping systems that invest in soil organic matter, such as no-tillage (NT) with crop residue retention, have been proposed as potential solutions. However, a key challenge for assessing the sustainability of NT systems is that soil carbon (C) stocks develop over long timescales, and there is an urgent need to identify trajectory indicators of sustainability and crop productivity. Here we examined the effects of NT as compared with conventional tillage without residue retention on relationships between soil characteristics and maize (Zea mays L.) productivity in long-term on-farm and on-station trials in Zimbabwe. Our results show that relationships between soil characteristics and maize productivity, and the effects of management on these relationships, varied with soil type. Total soil nitrogen (N) and C were strong predictors of maize grain yield and above-ground biomass (i.e., stover) in the clayey soils, but not in the sandy soils, under both managements. This highlights context-specific benefits of management that fosters the accumulation of soil C and N stocks. Despite a strong effect of NT management on soil C and N in sandy soils, this accrual was not sufficient to support increased crop productivity in these soils. We suggest that sandy soils should be the priority target of NT with organic resource inputs interventions in southern Africa, as mineral fertilizer inputs alone will not halt the soil fertility decline. This will require a holistic management approach and input of C in various forms (e.g., biomass from cover crops and tree components, crop residues, in combination with mineral fertilizers). Clayey soils on the other hand have greater buffering capacity against detrimental effects of soil tillage and low C input.

Understanding the interactions of genotype with environment and management (G×E×M) to maize productivity in Conservation Agriculture systems of Malawi

“…A recent study by Mhlanga et al [ 22 ] showed that mulching is important in cropping systems of southern Africa as it serves as a source of organic matter for increased microbial activity as well as conserving moisture. This was also confirmed by Thierfelder et al [ 53 ]. Since the CPM-L system had no mulch, organic matter build-up, moisture conservation and soil temperature regulation in this system were not enhanced as compared to the CA-based systems.…”

A talajkímélő művelési rendszerek áttekintése az éghajlatváltozás hatásához alkalmazkodni képes talajok kialakítása és fenntartása céljából a szubszaharai Afrikában

“…However, pH was high under CT relative to CA practices (NT, MT, and RT). (NIGUSSIE et al, 2021a;SITHOLE -MAGWAZA, 2019) obtained low TN under CT relative to MT and a low C: N ratio under MT compared to CT. High NO -3 -N, C: N ratio, TN, and NH + -N were observed under NT compared to CT (CHAUKE et al, 2022;THIERFELDER et al, 2022).…”

“…SOC has been widely cited as a key indicator of soil quality (THIERFELDER et al, 2022). It is the earliest soil component to succumb to erosion and strangely the most difficult to restore, presenting significant challenges to modern farming (CHOWANIAK et al, 2020).…”

Exploiting crop genotype-specific root-soil interactions to enhance agronomic efficiency

“…Saharan Africa (SSA) is on the frontline of climate change, and technologies are urgently needed for this region that couple sustainable crop production combined with greater soil fertility and continuous protection of the soil resource, with enhanced resilience to climate induced changes in local conditions (3). Soils supporting food production in this region are often degraded, with 25% (350 million ha) of the total land area falling under this category (4), and characterised by poor structure, light texture and low (and declining) soil organic matter (SOM) content, often resulting from continuous conventional agriculture practices (tillage, crop residue removal, mono-cropping) (5,6).…”