Complementary practices supporting conservation agriculture in southern Africa. A review

Abstract

Conservation agriculture (CA)-the simultaneous application of minimum soil disturbance, crop residue retention, and crop diversification-is a key approach to address declining soil fertility and the adverse effects of climate change in southern Africa. Applying the three defining principles of CA alone, however, is often not enough, and complementary practices and enablers are required to make CA systems more functional for smallholder farmers in the short and longer term. Here, we review 11 complementary practices and enablers grouped under six topical areas to highlight their critical need for functional CA systems, namely: (1) appropriate nutrient management to increase productivity and biomass; (2) improved stress-tolerant varieties to overcome biotic and abiotic stresses; (3) judicious use of crop chemicals to surmount pest, diseases, and weed pressure; (4) enhanced groundcover with alternative organic resources or diversification with green manures and agroforestry; (5) increased efficiency of planting and mechanization to reduce labor, facilitate timely planting, and to provide farm power for seeding; and (6) an enabling political environment and more harmonized and innovative extension approaches to streamline and foster CA promotional efforts. We found that (1) all 11 complementary practices and enablers substantially enhance the functioning of CA systems and some (e.g., appropriate nutrient management) are critically needed to close yield gaps; (2) practices and enablers must be tailored to the local farmer contexts; and (3) CA systems should either be implemented in a sequential approach, or initially at a small scale and grow from there, in order to increase feasibility for smallholder farmers. This review provides a comprehensive overview of practices and enablers that are required to improve the productivity, profitability, and feasibility of CA systems. Addressing these in southern Africa is expected to stimulate the adoption of CA by smallholders, with positive outcomes for soil health and resilience to climate change.

Innovative Pro-Smallholder Farmers’ Permanent Mulch for Better Soil Quality and Food Security Under Conservation Agriculture

“…Soil degradation is a global challenge that threatens agricultural food production and food security [17]. According to Vaezi et al [18], soil degradation is a consequence of the bare or scarcely covered soils in semi-arid lands.…”

The Ability of Conservation Agriculture to Conserve Soil Organic Carbon and the Subsequent Impact on Soil Physical, Chemical, and Biological Properties and Yield

“…Conservation agriculture is defined as a system that combines minimum or no tillage (NT) with permanent soil cover (that leaves at least 30% of the soil covered between harvest and planting) and diversified crop species that include legumes (FAO, 2019). Other companion practices, such as integrated pest and nutrient management, are also often incorporated into the CA system on a site specific basis to help ensure its success (Lal, 2015a;Thierfelder et al, 2018). Overall, CA is a farming system designed to enhance the sustainability of agricultural production by conserving and protecting soil, water and biological resources so that external inputs can be kept to a minimum (Figure 1).…”

Sustainable Weed Management for Conservation Agriculture: Options for Smallholder Farmers

“…In addressing weed control challenges, scientific studies have provided evidence that minimum and no-tillage induce shifts of weed population particularly towards perennial weeds, thus creating a long-lasting weed problem [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Moreover, annual weeds such as Kochia (Kochia scoparia (L.) Schrad.)…”