This study examines the adoption of sustainable agricultural intensification practices— particularly cereal-legume intercropping—by smallholder farming households in Malawi. The focus of the study is on how spatial variation in key factors related to agricultural production and marketing influences farming households’ decision-making processes under risk. Separate analyses are done for six distinct agroecological zones in Malawi to evaluate how resource and market constraints affect farming households’ decisions to employ intercropping practices on their cropland and how the variations in these constraints have differing impacts on adoption of intercropping across different regions. This study provides valuable insights into the complexities of smallholder farming choices in diverse geographic contexts.

Food security is a critical issue in the Guinea savanna of Ghana where about 60% of the rural population, mostly smallholder farmers are food insecure. Food insecurity results from poor crop yields due to low soil fertility compounded by erratic unimodal rainfall and the inability of households to purchase required supplemental food. Rapid population growth means that the numbers of food insecure people are likely to increase, necessitating sustainable intensification and diversification to increase crop production per unit area of land. This thesis focused on testing spatial and temporal intensification and diversification options suitable for the variable biophysical and socio-economic conditions of smallholder farming systems in the Guinea savanna to increase productivity, mitigate the risk of crop failure, and thus to increase food self-sufficiency. One site in the southern Guinea savanna and one in the northern Guinea savanna were selected which differed in biophysical and socio-economic resources. In each site, field experiments were conducted on three fields differing in soil fertility (fertile, medium fertile, poorly fertile) to quantify: N2-fixation and N contribution to soil fertility by grain legumes in sole and intercropping; impact of replacement intercropping on increasing resource use efficiency and crop productivity; and productivity of relay (additive) intercropping and rotation of grain legumes with maize. Scenario analysis was performed with data from the N2Africa Ghana project supplemented with data from the on-farm experiments and literature to test the impacts of intensification and diversification options on household food self-sufficiency. Sole legumes fixed larger amounts of N2 than under intercropping. The soil N balance was generally positive and similar between intercrops and sole crops suggesting that both systems could be sustainable intensification and diversification options. Poor fields stimulated grain legumes to rely on atmospheric N2 for growth leading to more positive soil N balances than in fertile fields. Consequently, legumes in poor fields were more competitive with maize and led to greater intercrop yield advantage than in fertile fields. Across all fields and sites, intercropping enhanced the efficiency in resource use resulting in a 26% to 46% yield advantage over sole cropping. Intercrops were more efficient and productive in the drier northern Guinea savanna than in the wetter southern Guinea savanna. Yet the absolute larger grain yields achieved in fertile fields and in the southern Guinea savanna with more favourable soil fertility and rainfall resulted in greater net benefits. This suggests that intercropping is beneficial both in poorly fertile and fertile fields though the benefits take different dimensions. Legume-cereal rotation was superior in increasing the yield of maize without N fertiliser ranging from 0.38 t ha-1 in NGS to 1.01 t ha-1 in SGS due to residual N and non-N benefits compared with continuous maize cropping. Sowing cowpea first and relaying maize decreased maize grain yield substantially from 0.29 t ha-1 (14%) in SGS to 0.82 t ha-1 (83%) in NGS, representing 14% and 83% grain yield reductions relative to maize sown at the beginning of the season. These grain yield reductions were due to inadequate rainfall received by the relay maize. When maize was sown from the onset of the season and the cowpea relayed, the cowpea grain yield reduction was relatively smaller compared with that of maize. Such cowpea grain yield decline was similar between the SGS and NGS and ranged from 28% (0.18 t ha-1) to 47% (0.26 t ha-1) relative to the cowpea sown from the onset of the season. The cumulative grain yield of this relay system over two seasons was similar to that of the legume-cereal rotations even with cowpea failing to yield in the first season. The scenario analysis revealed a high incidence of food insufficiency among smallholder farm households in the Guinea savanna of Ghana. This ranged from 56% in the Northern region with relatively favourable rainfall, soil fertility and larger land area cropped per farm to 45% in the Upper East and Upper West regions with comparatively less rainfall, poor soils and smaller land area cropped. In addition, 21% of households in the Northern region and 37% in the Upper East and Upper West regions could only survive on their own food production for six months or less. However, the scenario analysis suggested that through intensification and diversification with grain legumes, the proportion of food self-sufficient households in the Guinea savanna could increase by 25 – 43% and those self-sufficient for a maximum of half a year decreased to 3 – 15%. Households could also generate substantial marketable surpluses to earn income. However, the total size of land cropped by a farm household matters, and improved access to markets and credit are needed to acquire the relevant inputs. Also, multi-year analysis using modelling would be relevant in providing insights on long-term nutrient balances, especially of N and soil organic matter to understand the long-term sustainability of the various options.

Continued population growth, rapidly changing consumption patterns and the impacts of climate change and environmental degradation are driving limited resources of food, energy, water and materials towards critical thresholds worldwide. These pressures are likely to be substantial across Africa, where countries will have to find innovative ways to boost crop and livestock production to avoid becoming more reliant on imports and food aid. Sustainable agricultural intensification - producing more output from the same area of land while reducing the negative environmental impacts - represents a solution for millions of African farmers. This volume presents the lessons learned from 40 sustainable agricultural intensification programmes in 20 countries across Africa, commissioned as part of the UK Government's Foresight project. Through detailed case studies, the authors of each chapter examine how to develop productive and sustainable agricultural systems and how to scale up these systems to reach many more millions of people in the future. Themes covered include crop improvements, agroforestry and soil conservation, conservation agriculture, integrated pest management, horticulture, livestock and fodder crops, aquaculture, and novel policies and partnerships.

Forward. A call for integrated soil fertility management in Africa. Introduction. ISFM and the African farmer. Part I. The principles of ISFM: ISFM as a strategic goal, Fertilizer management within ISFM, Agro-minerals in ISFM, Organic resource management, ISFM, soil biota and soil health. Part II. ISFM practices: ISFM products and fields practices, ISFM practice in drylands, ISFM practice in savannas and woodlands, ISFM practice in the humid forest zone, Conservation Agriculture. Part III. The process of implementing ISFM: soil fertility diagnosis, soil fertility management advice, Dissemination of ISFM technologies, Designing an ISFM adoption project, ISFM at farm and landscape scales. Part IV. The social dimensions of ISFM: The role of ISFM in gender empowerment, ISFM and household nutrition, Capacity building in ISFM, ISFM in the policy arena, Marketing support for ISFM, Advancing ISFM in Africa. Appendices: Mineral nutrient contents of some common organic resources.

Pulses have a long history in sub-Saharan Africa due to their multiple benefits. Pulses, and legumes in general, can play an important role in agriculture because of their ability to biologically fix atmospheric nitrogen and to enhance the biological turnover of phosphorus; thus they could become the cornerstone of sustainable agriculture in Africa. In this sense, there is a body of literature that points to diversification of existing production systems – particularly legumes species, which provide critical environmental services, including soil erosion control and soil nutrient recapitalization. This publication is a review of some of the promising strategies to support the cultivation and utilization of pulses on smallholder farms in sub-Saharan Africa. The review is part of the legacy of the International Year of Pulses (IYP), which sought to recognize the contribution that pulses make to human well-being and the environment.