Hedging eroding slopes in Malawi – Can the integration of contour bunds and perennial forages improve Malawian mixed farming system productivity?

In Malawi’s wet season, reaching from December to April, only a fraction of rainfall is plant accessible. Large parts evaporate and widespread impermeable hoe pans hinder remaining water to infiltrate into the soil (Daamen et al., 1995; Douglas et al., 1999; World Bank, 2021). Additionally, Malawi’s common sloping topography causes up to 30% of rainfall to run off arable land before it can infiltrate (Swai et al., 2007). Soil covering and protecting plant biomass, which would slow down water flow, is rare due to progressing deforestation and inadequate farm management (Omuto & Vargas, 2019). Stronger and shorter rainfall events further reduce time for soil infiltration and worsen soil erosion (Vargas & Omuto, 2016). Whilst climate change progresses, rainfall events decrease in frequency, but increase in intensity, which causes dry spells and floods during the cropping season (IPCC, 2023; Muthoni et al., 2019; Prein et al., 2017). As such Malawi is currently facing the effects of El Niño, which is projected to cause a 22% reduction in produced maize, the country’s main staple crop (Duchoslav et al., 2024). In the face of these factors, which threaten crop yields, water conservation measures are urgently needed (Gondwe, 2023). Malawi’s arable land is degrading from long-term inorganic nitrogen (N) fertilizer-dominant maize monocropping. But the country is in a paradoxical dependency, as fertilizer demand is increasing to maintain yields (Bekunda et al., 1997; Burke et al., 2022a). Malawian farm systems rely on artificial fertilizer imports, mainly Urea and NPK, which historically the government provides to smallholders at subsidised rates through agricultural input programs (Duchoslav & Rusike, 2021). Soil water erosion is a main driver for water and soil nutrient losses, as the runoff contains considerable amounts of soil organic matter, mineral particles and nutrients (Omuto & Vargas, 2019). About three-quarters of Malawian soils are prone to erosion, with national annual soil loss numbered at 29 Mg ha 1 in 2014 (Vargas & Omuto, 2016). Soil erosion susceptibility depends on precipitation, topography, soil texture, soil cover and management (Omuto & Vargas, 2019). While precipitation cannot be changed, soil and water conservation structures (SWC) can modify field’s slope, create barriers and water catchments, while management practices influence soil cover and soil amendments, changing soil texture over time. Soil and water conservation measures have been demonstrated to effectively control erosion and increase farm system yields by improving soil fertility and water availability (Kizito et al., 2022; Liniger et al., 2011; Saiz et al., 2016). There are several structures commonly constructed on contour: simple ridges across the slope, box ridges (perpendicular connected ridges, creating micro-catchment “boxes”), grass strips, Vetiver grass (Chrysopogon zizanioides) stabilized bunds and large fanya juu or fanya chini bunds (a dug trench, with the soil deposited up-slope “juu” or down-lope “chini”) (Kizito et al., 2022; Liniger et al., 2011). Improved, multipurpose forages, which consist of selected fast-growing grasses and leguminous groundcovers, shrubs and trees, increase animal as well as crop productivity and can replace livestock unpalatable species (Kizito et al., 2022; Notenbaert et al., 2021). Their benefits range from pollen supply, medicinal properties, and fuelwood to large biomass quantities, which are usable as animal fodder, or mulch and compost for crop production (Jansen et al., 2020; Mokgolodi et al., 2011; Sibale et al., 2013). Deep-rooting, drought-resistant species supply harvestable products during the dry season (Baruch, 1994; Hanum & Maesen, 1997; Shelton, 2000; Sibale et al., 2013). Improved forage hedge integration on contour and the effects of erosion control structures on smallholder farm systems have mostly been explored separately in the last decades (Akinnifesi et al., 2010; Mangisoni, 2004; Mutegi et al., 2008; Shelton & Brewbaker, 1994; Tenge et al., 2005). Only few studies investigated the combination (Kizito et al., 2022; Liniger et al., 2011, p. 122; Menashe, 2001). The core problem is that depending on socioeconomic and biophysical context, specifically mixed farming system trade-offs and synergies between components are difficult to predict. Therefore, technological innovations need be tailored to individual locations. This difficulty might explain why contour bund and forage hedge adoption is neither widely spread among Malawian smallholders, nor a prioritized technology promoted by state or private organizations. Therefore, this research applies a participatory systems approach to fill the knowledge gap for which mixed-farming system context in Malawi contour bund and forage integration is most effective. This is addressed by the following research objectives. The main objective of this research was to quantify the effect of establishing contour bunds in combination with mixed perennial forage crops on farm-context specific smallholder farm productivity and assess how landowners evaluate this technology. To address this, four research questions were answered: i. What are the key characteristics of the current smallholder production system, especially regarding contour bund utilisation and forage species cultivation? ii. How does the integration of contour structures and forage species affect farm system productivity?a. What are the technical details of the contour structure and forage species? b. Which forage species combination would be optimal, given site-specific socioeconomic and biophysical constraints? c. How is current farm system productivity impacted by the redesign? iii. How does the implementation affect present day farm system productivity in terms of income, labour input, and soil fertility, given farm type specific forage biomass utilisation? Three scenarios will explore forage biomass allocation to: a) livestock production, b) composting and input for crop cultivation, c) forage sales. iv. How do farmers evaluate the redesign?