Understanding farmer knowledge and site factors in relation to soil-borne pests and pathogens to support agroecological intensification of smallholder bean production systems

Introduction

Pests and diseases limit common bean (Phaseolus vulgaris) production in intensifying smallholder farming systems of sub-Saharan Africa. Soil-borne pests and diseases (SPD) are particularly challenging for farmers to distinguish and manage in cropping systems that vary in terms of soils, farmer knowledge, and management factors. Few studies have examined soil drivers of SPD in smallholder systems, integrated with farmers' perceptions and management practices.

Methods

In Kilimanjaro, Tanzania, we assessed farmer knowledge and SPD management for common bean alongside soil type and soil quality. Focus group discussions and field survey findings including farmer observations and soil nutrient balances were integrated with soil analyses of farmers' fields. Multiple correspondence analysis (MCA) and principal component analysis (PCA) assessed relationships among farmer demographics, pests and diseases, soil characteristics, and management practices.

Results and discussion

Surveys revealed that 100% of farmers knew of the bean foliage beetle (Ootheca bennigseni) but few recognized the soilborne pest Ophiomyia spp. or bean fly despite it being more destructive. About a third of farmers knew of root rot diseases caused by Pythium spp. and Fusarium spp. Synthetic pesticides were used by 72% of farmers to control pests, while about half that (37%) used pesticidal plants, particularly Tephrosia vogelii extracts sprayed on foliage. Regarding SPD, 90% of farmers reported that their management practices were ineffective. Meanwhile, synthetic fertilizers were used by nearly all farmers in beans intercropped with maize (Zea mays), whilst very few farmers used manure or compost. Soil available phosphorus was lowbut showed a balance between inputs and outputs regardless of whether fields were owned. Field nitrogen balances were more negative when fields were owned by farmers. An MCA showed that older farmers employed a greater number of pest control practices. The PCA showed that field variability was dominated by soil organic matter, elevation, and soil pH. Higher organic matter levels were also associated with less stunting and wilting of beans observed by farmers. Our results suggest that research and farmer learning about SPD ecology are key gaps, alongside recycling of organic residues to soils. Cost-effective and sustainable practices to manage bean SPDs for smallholders are also needed.

Organic Nutrient Source Allocation and Use in Smallholder Farming Communities: What Are We Missing?

Organic nutrient sources (ONS) are managed as a key resource by smallholder farmers to maintain the productivity of soils. Recycling of ONS by applying them to soils is a globally dominant strategy of ecological nutrient management. Understanding how ONS produced on-farm are allocated and what drives farmer decision making around their use is critical for sustainable nutrient management in smallholder agroecosystems. Using focus group discussions and a survey of 184 farming households, we studied socio-economic, socio-cultural, and environmental drivers of ONS allocation and use at the farm scale in three contrasting agroecological zones of western Kenya. Farm typologies of ONS management were also developed using cluster analysis based on resource endowment and the connectedness of farmers, management norms, and interaction with extension. Our findings suggest that the more resource endowed a farmer is, the more ONS are allocated to the main plot within the farm. We also observed that farmers preferred allocating more resources to plots that were considered more fertile. Land tenure had an important influence, in that main plots not owned by farmers were more likely to retain ONS such as crop residues. Management of residues is dependent on farmer gender, for instance, female farmers tended to burn legume residues in particular, which is notable since these higher quality residues are often considered key to sustainable soil nutrient management. Farm typologies featured different allocation patterns of ONS and were associated with resource endowment and farmer networks, including external ties to extension agents and internal ties to other farmers. Finally, there was a strong overarching influence of agroecological zone that often escapes characterization on the allocation of ONS. As research and development organizations continue to engage with smallholder farmers to reduce the burden of global food insecurity, the insights gained by this research will allow better anticipation of drivers and obstacles to improved nutrient management in these farming landscapes and communities.

Unpicking the Inter-relationships Between Off-Farm Livelihood Diversification, Household Characteristics, and Farm Management in the Rural Andes

Rural households across the world are increasingly turning to off-farm sources of income to complement or replace farm income. A better understanding of these livelihood adaptations, their consequences, and the processes behind them will facilitate more effective rural development policies and projects. The objective of this research was to examine how off-farm income influences rural livelihoods, elucidate factors that determine different livelihood strategies, as well as understand how these livelihood strategies are associated with different approaches to farm management. Using data from 588 Rural Household Multi-Indicator Surveys (RHoMIS) in three rural Andean regions in Bolivia, Ecuador, and Peru, we identified a typology of farming household livelihood strategies, and assessed the differences among these household types with regard to household and farm level characteristics, and farm management. We found that among the household types that incorporated off-farm income into their livelihood strategies, there were significant differences in approaches to farm management. Specifically, we observed an increased use of industrialized farming techniques among one household type, a deintensification, or a stepping-out of farming activities in another household type, and a tendency toward livestock specialization in the other household type. Moreover, our findings revealed that household level characteristics (age and education level of head(s) of household, and household composition) played an important role in mediating which type of livelihood strategy the households employed. For example, “stepping-out” households generally had younger and more educated household heads. Location-specific factors such as access to markets, irrigation, and off-farm employment opportunities were also likely to be highly influential in terms of which pathways farming households adopted as their livelihood strategy. We conclude that rural development programmes and projects must be driven by the rural communities themselves taking into account this heterogeneity in household characteristics and livelihoods and engaging in the already advanced conversations around different approaches to farming and the conservation of common natural resources.

Global distribution of earthworm diversity

Soil organisms, including earthworms, are a key component of terrestrial ecosystems. However, little is known about their diversity, their distribution, and the threats affecting them. We compiled a global dataset of sampled earthworm communities from 6928 sites in 57 countries as a basis for predicting patterns in earthworm diversity, abundance, and biomass. We found that local species richness and abundance typically peaked at higher latitudes, displaying patterns opposite to those observed in aboveground organisms. However, high species dissimilarity across tropical locations may cause diversity across the entirety of the tropics to be higher than elsewhere. Climate variables were found to be more important in shaping earthworm communities than soil properties or habitat cover. These findings suggest that climate change may have serious implications for earthworm communities and for the functions they provide.

Land use as a driver of soil fertility and biodiversity across an agricultural landscape in the Central Peruvian Andes

Land use change and intensification in agricultural landscapes of the Andean highlands have resulted in widespread soil degradation and a loss in soil-based ecosystem services and biodiversity. This trend threatens the sustainability of farming communities in the Andes, with important implications for food security and biodiversity conservation throughout the region. Based on these challenges, we sought to understand the impact of current and future land use practices on soil fertility and biodiversity, so as to inform landscape planning and management decisions for sustainable agroecosystem management. We worked with local communities to identify and map dominant land uses in an agricultural landscape surrounding Quilcas, Peru. These land uses existed within two elevations zones (low-medium, 3200-3800 m, and high elevation, 3800-4300 m). They included three types of low-medium elevation forests (eucalyptus, alder, and mixed/native species), five pasture management types (permanent pasture, temporal pasture [in fallow stage], degraded pasture, high-altitude permanent pasture, and high-altitude temporal pasture [in fallow stage]) and six cropping systems (forage crops, maize/beans, and potato under four types of management). Soil fertility was evaluated in surface soils (0-20 cm) with soil physicochemical parameters (e.g., pH, soil organic matter, available nutrients, texture), while soil biological properties were assessed using the abundance and diversity of soil macrofauna and ground cover vegetation. Our results indicated clear impacts of land use on soil fertility and biological communities. Altitude demonstrated the strongest effect on soil physicochemical properties, but management systems within the low-mid elevation zone also showed important differences in soil biological communities. In general, the less-disturbed forest and pasture systems supported more diverse soil communities than the more intensively managed croplands. Degraded soils demonstrated the lowest overall soil fertility and abundance of soil macrofauna, but this may be reversible via the planting of alder forests. Our findings also indicated significant covariation between soil physicochemical parameters, soil macrofauna, and ground vegetation. This suggests that management for any one of these soil properties may yield unintended cascading effects throughout the soil subsystem. In summary, our findings suggest that shifts in land use across the landscape are likely to have important impacts on soil functioning and biodiversity.