Search

Soil nutrient constraints coupled with erratic rainfall have led to poor crop yields and occasionally to crop failure in sole cropping in the Guinea savanna of West Africa. We explored different maize-grain legume diversification and intensification options that can contribute to mitigating risks of crop failure, increase crop productivity under different soil fertility levels, while improving soil fertility due to biological N2-fixation by the legume. There were four relay patterns with cowpea sown first and maize sown at least 2 weeks after sowing (WAS) cowpea; two relay patterns with maize sown first and cowpea sown at least 3 WAS maize in different spatial arrangements. These were compared with groundnut-maize, soybean–maize, fallow-maize and continuous maize rotations in fields high, medium and poor in fertility at a site each in the southern (SGS) and northern (NGS) Guinea savanna of northern Ghana. Legumes grown in the poorly fertile fields relied more on N2-fixation for growth leading to generally larger net N inputs to the soil. Crop yields declined with decreasing soil fertility and were larger in the SGS than in the NGS due to more favourable rainfall and soil fertility. Spatial arrangements of relay intercrops did not have any significant impact on maize and legume grain yields. Sowing maize first followed by a cowpea relay resulted in 0.18–0.26 t ha−1 reduction in cowpea grain yield relative to cowpea sown from the onset. Relaying maize into cowpea led to a 0.29–0.64 t ha−1 reduction in maize grain yield relative to maize sown from the onset in the SGS. In the NGS, a decline of 0.66 and 0.82 t ha−1 in maize grain yield relative to maize sown from the onset was observed due to less rainfall received by the relay maize. Groundnut and soybean induced 0.38–1.01 t ha−1 more grain yield of a subsequent maize relative to continuous maize, and 1.17–1.71 t ha−1 more yield relative to relay maize across both sites. Accumulated crop yields over both years suggest that sowing maize first followed by cowpea relay is a promising ecological intensification option besides the more common legume–maize rotation in the Guinea savanna, as it was comparable with soybean–maize rotation and more productive than the other treatments.

Continuous cereal-based cropping has led to a rapid decline in soil fertility in the Guinea savanna agro-ecological zone of northern Ghana with corresponding low crop yields. We evaluated the effects of cropping system and soil fertility status on grain yields and N2-fixation by grain legumes and net N contribution to soil fertility improvement in contrasting sites in this agro-ecological zone. Maize was intercropped with cowpea, soybean and groundnut within a row, with a maize stand alternated with two equally spaced cowpea or groundnut stands and in the maize-soybean system, four equally spaced soybean stands. These intercrops were compared with sole crops of maize, cowpea, soybean and groundnut in fertile and poorly fertile fields at sites in the southern (SGS) and the northern (NGS) Guinea savanna. The proportion of N derived from N2-fixation (%Ndfa) was comparable between intercrops and sole crops. However, the amount of N2-fixed was significantly larger in sole crops due to a greater biomass accumulation. Legumes in poorly fertile fields had significantly smaller shoot δ 15N enrichment (-2.8 to +0.7‰) and a larger %Ndfa (55-94%) than those in fertile fields (-0.8 to +2.2‰; 23-85%). The N2-fixed however was larger in fertile fields (16-145kgNha-1) than in poorly fertile fields (15-123kgNha-1) due to greater shoot dry matter and N yields. The legumes grown in the NGS obtained more of their N requirements from atmospheric N2-fixation (73-88%) than legumes grown in the SGS (41-69%). The partial soil N balance (inkgha-1) was comparable between intercrops (-14 to 21) and sole legumes (-8 to 23) but smaller than that of sole maize receiving N fertiliser (+7 to +34). With other N inputs (aerial deposition) and outputs (leaching and gaseous losses) unaccounted for, there is uncertainty surrounding the actual amount of soil N balances of the cropping systems, indicating that partial N balances are not reliable indicators of the sustainability of cropping systems. Nevertheless, the systems with legumes seem more attractive due to several non-N benefits. Our results suggest that soybean could be targeted in the SGS and cowpea in the NGS for greater productivity while groundnut is suited to both environments. Grain legumes grown in poorly fertile fields contributed more net N to the soil but growing legumes in fertile fields seems more lucrative due to greater grain and stover yields and non-N benefits.

The ‘N2Africa Review of policies relating to legume intensification in N2Africa counties’ showed that governments in N2Africa countries acknowledge the importance of legume intensification and its significant potential to contribute to improving food security and health, especially for poor families. At global level, the seventeen Sustainable Development Goals (SDGs) of the 2030 Agenda for Sustainable Development developed by the United Nations (UN) aim to end all forms of poverty, fight inequalities and tackle climate change, while ensuring that no one is left behind. The SDGs recognize that ending poverty must go hand-in-hand with strategies that build economic growth and addresses a range of social needs including education, health and job opportunities, amongst others. Governments are expected to take ownership and establish national frameworks for the achievement of the seventeen goals. Particularly, SDG2 ‘End hunger achieve food security and improved nutrition and promote sustainable agriculture’ seeks sustainable solutions to end hunger in all its forms and to achieve food security. It entails improving the productivity and incomes of small-scale farmers by promoting equal access to land, technology and markets, sustainable food production systems and resilient agricultural practices. The Comprehensive Africa Agriculture Development Programme (CAADP) is the pan-African policy framework for agricultural transformation, wealth creation, food security and nutrition, economic growth and prosperity for all. The CAADP Results Framework 2015 – 2025 is prepared by the Food and Agriculture Organisation (FAO) of the UN in cooperation with the New Partnership for Africa’s Development (NEPAD) Steering Committee. It recognizes the importance of increasing yield of food grains, tubers and legumes to catalyse transformation of Africa’s agricultural systems and presents critical actions required to achieve agricultural development agenda targets. Furthermore, the Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) serves as a platform for promoting regional research and in the sharing of benefits and spillovers that derive from such research. The association focuses on four thematic areas that are well aligned to the major ongoing regional and continental initiatives. These include (i) Integrated capacity strengthening, (ii) Development and scaling up of technologies and innovations, (iii) Policy advocacy, market analysis and institutional arrangement, (iv) Knowledge and information management. High yielding climbing bean varieties and training on different staking options are included in ASARECA projects that scale up best practices to address farmers’ needs.National governments in the N2Africa countries all developed national policies aimed at increasing agricultural productivity, improving food security, diversifying food production to improve nutrition, and increasing agricultural incomes of the rural people. All national policies refer to legumes, mostly indirectly (e.g. intercropping practices, as measure for soil fertility, amongst others). Table 1 presents the N2Africa target legumes mentioned in national policies per N2Africa country.All national policies aim at increasing the production and productivity of various legumes by various strategies, such as (i) adopting modern production techniques, (ii) strengthening coordination, institutional capacity and skills across the key actors, (iii) providing timely and appropriate market entry support for effective market development and (iv) scaling up production and trade, amongst others. Rhizobia are only referred to in a few national policies (e.g. Ethiopia, Kenya, Malawi and Rwanda). The Tanzanian government is the only government that developed an explicit policy tool to promote the pulses sector (e.g. common bean, cowpea, pigeonpea, green gram and chickpea, mung bean and Bambara nut).The study results will be completed and used to provide recommendations to governments about best-fit legume technologies, how to increase production and productivity of various legumes and how to stimulate farmers’ use.

The Convergence of Sciences–Strengthening Innovation Systems (CoS–SIS) programme is based on the premise that the livelihood of the African smallholder farmer is constrained by the existence and/or performance of formal and informal institutions that are not conducive to small-farm development. CoS–SIS employs nine platforms in Ghana, Benin and Mali – “Concertation and Innovation Groups” (CIGs) – that aim to facilitate institutional change above the farm level (e.g. rules and regulations, bylaws, policies, interaction patterns in the value chain), in order to create a conducive environment for farm-level innovation, which is also often linked to technical innovation. Issues that should be taken into consideration when implementing an innovation platform include: conditions external to the platform, power relations within and outside the platform, role of research and development, capacity building of stakeholders, scaling up and sustainability. Lesson learnt include the need to: i) build motivation and manage expectations from the start; ii) get the right representation of actors on the platform; iii) invest in time; iv) manage power imbalances and mitigate power relations; v) create opportunities and seize them when they arise; vi) be sensitive to gender dynamics; vii) adjust platform membership when the need arises; viii) monitor external factors; and ix) embed critical platform functions in the existing structures. Some challenges encountered were: i) high expectations from platform members; ii) tight work schedules of some of the platform members, especially actors from the public sector; iii) how to sustain platform activities when funding ceases; and iv) influence of external factors such as government policy, political changes and changes in commodity price on platform activities.

The original entry point for this study was how to optimize long-term rotation strategies for addressing the problem of soil fertility decline inWenchi,Ghana. However, as the study progressed over time, it was realized that what we initially interpreted as soil fertility management strategies were closely intertwined with wider issues such as cropping systems, livelihood aspirations and land tenure relations. Exploration of farmers' soil fertility management practices revealed a link between tenure insecurity among migrant farmers especially, and limited attention for regeneration of soil fertility. The native farmers who own land tend to use rotations involving long-duration crops such as cassava and pigeonpea to improve their soils. In contrast, migrants who depend mostly on short-term rental or sharecropping arrangements, rely more on rotations with short- duration crops such as cowpea and groundnut to improve soil fertility. A study to examine diversity among farm households and their relevance and implications for orienting action research aimed at combating soil fertility decline revealed that historical, ethnic and gender dimensions of diversity provide additional insights in livelihood patterns and soil fertility management which are relevant for fine-tuning technical and social action research agendas. Relevant differences between farm households result from the interplay between structural conditions and the strategies of active agents. Five cowpea varieties were evaluated for their grain yield, Nsub>2 -fixation and their contribution to the productivity of subsequent maize crop grown in rotation. On both farmer and researcher-managed fields, there were no significant differences in grain yield among the different varieties. Using the 15 N natural abundance technique, the proportion of N 2 fixed by the different cowpea varieties ranged between 61 and 77%. On both farmer and researcher-managed fields, maize grain yield after cowpea without application of mineral N fertiliser was higher than maize after maize. Although farmers recognized the contribution of cowpea to soil fertility and yields of the subsequent maize crop, they did not consider this as an important criterion when selecting varieties for use in their own fields. The overriding criteria for selecting cowpea varieties were more related to their early harvest, seed quality in terms of taste and marketability and ease of production (low labour demand). The performance of maize under different cropping sequences was evaluated in both farmer and researcher-managed experiments. Yield of maize without N application was higher after cassava and pigeonpea compared to that after speargrass fallow, cowpea or maize in both researcher and farmer-managed experiments. A simple financial analysis performed to evaluate the profitability of the various rotational sequences showed cassava/maize rotation to be the most profitable rotational sequence while speargrass fallow/maize rotation was found to be the least profitable. Farmers' preferences for a particular practice were more related to accessibility to production resources and livelihood aspirations. An action research in the social realm was carried out to develop institutional arrangements beneficial for soil fertility. Initial efforts aimed at bringing stakeholders together in a platform to engage in a collaborative design of new arrangements were stranded mainly because conditions conducive for learning and negotiations were absent. The implementation of experimentation with alternative tenure arrangements initiated by individual landowners and tenant farmers too ran into difficulties due to intra-family dynamics and ambiguities regarding land tenure. Further investigations to find out how ambiguities could be tackled, revealed that the local actors themselves had worked towards institutional arrangements to reduce ambiguities. However, there is still considerable scope for further development of these self-organised innovations. The study stresses the need for continuous diagnosis and exploration in action research in order to steer research in a relevant direction.