Gudeta W. Sileshi

Fertiliser trees for sustainable food security in the maize-based production systems of East and Southern Africa. A review

The negative effects of soil fertility depletion on food security, especially among smallholder farmers in Africa, is of economic importance, and may be worsened by climate change and rising global fertiliser prices. Substantial efforts and investment have gone into development of alternative soil fertility management options. These include vigorous research and development of N-fixing plants or “fertiliser trees”, that has been on-going in the last two decades in East and Southern Africa. In this paper, we review several studies conducted both on-station and on-farm and synthesise the results in terms of improvements in soil physical, chemical and biological properties, and crop yield in response to fertiliser trees. Our major findings are that (1) fertiliser trees add more than 60 kg N ha−1 per year through biological nitrogen fixation (BNF); (2) nutrient contributions from fertiliser tree biomass can reduce the requirement for mineral N fertiliser by 75%, translating to huge savings on mineral fertilisers; (3) fertiliser trees were also shown to substantially increase crop yield. A meta-analysis has further provided conclusive evidence that with good management, fertiliser trees can double maize yields compared with local farmer practices of maize cultivation without addition of external fertilisation. (4) Financial analyses showed that fertiliser tree systems are profitable and also have higher net returns than the farmers’ de facto practice, i.e. continuous maize cropping without fertiliser. We conclude that widespread adoption and scaling up of fertiliser trees can reduce the amount of mineral fertiliser needed, maintain the soil ecosystem, and positively impact on the livelihoods of farm households in southern Africa.

Farmers' insect pest management practices and pesticidal plant use in the protection of stored maize and beans in Southern Africa

Storage losses due to pests threaten livelihoods of farmers across Africa. Synthetic pesticides provide effective control when used correctly but resource-poor farmers cannot afford them. A survey of farmer ethno-ecological knowledge of pests of stored maize and bean, and their pest management practices including pesticidal plant use, was conducted in eastern Zambia and northern Malawi. Almost all respondents reported serious pest damage, with bruchids (Callosobruchus maculatus) and grain weevils (Sitophilus spp.) being major pests in beans and maize, respectively. The larger grain borer (Prostephanus truncatus) was reported more widely in Malawi. In Zambia, 50% of farmers used synthetic pesticides during storage, while nearly all did so in Malawi. Despite differences in storage methods between Malawi and Zambia, farmers in both countries were familiar with pesticidal plants, where Tephrosia vogelii was the most frequently reported. Surprisingly few farmers actually used pesticidal plants, highlighting a promotion opportunity. Our results provide a foundation for optimizing the use of pesticidal plants and enhancing their value to resource-poor farmers, across Africa.

Applications of phytochemical and in vitro techniques for reducing over-harvesting of medicinal and pesticidal plants and generating income for the rural poor

Plants provide medicine and pest control resources for millions of poor people world-wide. Widespread harvesting of medicinal and pesticidal plants puts pressure on natural populations, thus severely compromising their contribution to the income and well-being of traders and consumers. The development of in vitro propagation techniques appropriate for developing countries will provide a robust platform for effective propagation and cultivation of endangered plants. This review focuses on advances in the application of phytochemical and in vitro tools to identify and rapidly propagate medicinal and pesticidal plants. Problems of over-harvesting can be alleviated and ex situ cultivation in agroforestry systems can be facilitated through improving seed germination, in vitro cloning and the use of mycorrhizal fungi. We also present a case for effective use of phytochemical analyses for the accurate identification of elite materials from wild stands and validation of the desired quality in order to counter loss of efficacy in the long run through selection, propagation or ex situ management in agroforestry systems. Future prospects are discussed in the context of medicinal activity screening, sustainable propagation, on-farm planting, management and utilization.

Biodiversity of the urban homegardens of São Luís city, Northeastern Brazil

There is a widely held notion that the increasing trend of urbanization accelerates loss of biodiversity and displaces native species. This study assessed the validity of this notion in the city of São Luís the capital of the state of Maranhão in the northeastern Brazil. The specific objectives of the study were to (1) assess plant and animal diversity of urban homegardens, (2) compare the diversity of homegardens in terms of origin of these species (exotic or indigenous to Brazil). We conducted a biodiversity survey in 40 randomly selected ‘quintais’ (hereafter called homegardens) from ten locations in the city of São Luis. We evaluated the species richness and diversity of various use categories of plant and animal species indigenous to Brazil as well as exotic species. A total of 186 species of plants in 68 families were recorded in the sampled homegradens. A total of 63 fruit tree species representing 34% of all tree species were found. Of these species, those indigenous to Brazil accounted for 58% of the cases, and this was significantly higher than the exotic species. Most of the species (60%) were indigenous to Brazil (wild and semi-wild domesticates), while the rest (40%) were exotic. A total of 42 species of vertebrates (mainly reptiles, birds and mammals) were also found in the homegardens, of which 47% were indigenous to Brazil. Some of the plant and animal species found in the homegardens are endangered species in their native habitats, suggesting that homegardens could provide a unique opportunity for their conservation and sustainable use. These species continue to play a vital role in the socioeconomic and ecological landscape of the city.

Labour inputs and financial profitability of conventional and agroforestry-based soil fertility management practices in Zambia

Abstract Several agro-ecological practices have been developed to increase the range of soil fertility management options available to farmers, but little information is available on their labour input requirement and profitability relative to conventional practices. This study used a multiple visit cost-route method to estimate labour inputs and financial profitability of agroforestry-based and conventional (with and without fertiliser) soil fertility management practices in eastern Zambia. Results show that aggregated over a five-year cycle, labour inputs used under agroforestry practices were lower than fertilised maize fields but higher than non-fertilised continuous cropped maize. Agroforestry practices were more profitable (NPV ranging between

Farmers' perceptions of tree mortality, pests and pest management practices in agroforestry in Malawi, Mozambique and Zambia

233 and

POTENTIAL OF BIOMASS TRANSFER TECHNOLOGIES IN SUSTAINING VEGETABLE PRODUCTION IN THE WETLANDS ( DAMBO S) OF EASTERN ZAMBIA

327 ha-1) than unfertilised maize fields (NPV of

A critique of current trends in the statistical analysis of seed germination and viability data

130 ha-1) but less profitable than fertilised maize fields. The NPV for the latter is

Carbon Sequestration Potential of Agroforestry Systems in Africa

499 ha-1 under a 50% government subsidy on fertiliser but, it fell to

Occupancy-abundance models for predicting densities of three leaf beetles damaging the multipurpose tree Sesbania sesban in eastern and southern Africa.

349 ha-1 when the subsidy effect is removed. In terms of return per unit investment cost, agroforestry practices performed better with a benefit to cost ratio ranging between 2.77 to 3.13 in contrast to 2.65 (subsidised fertiliser) and 1.77 (non-subsidised fertiliser). The returns to labour per person day was