The African Millennium Villages

We describe the concept, strategy and initial results of the Millennium Villages Project (MVP) and implications regarding sustainability and scalability. Our underlying hypothesis is that the interacting crises of agriculture, health, and infrastructure in rural Africa can be overcome through targeted public-sector investments to raise rural productivity, and thereby to increased private-sector saving and investments. This is carried out by empowering impoverished communities with science-based interventions. 78 Millennium Villages have been initiated in 12 sites in 10 African countries, each representing a major agroecological zone In early results, the research villages in Kenya, Ethiopia and Malawi have reduced malaria prevalence, met caloric requirements, generated crop surpluses, enabled school feeding programs, and provided cash earnings for farm families

Effect of soil amendments on bacterial wilt incidence and yield of potatoes in southwestern Uganda

Potato bacterial wilt caused by Ralstonia solanacearum is a major threat to potato production in Sub-Saharan Africa. It is believed that yield losses due to bacterial wilt increase with decreasing soil fertility. A soil amendment experiment was therefore conducted for 3 consecutive seasons, 1998A, 1998B and 1999A at Kachwekano at an altitude of 2200 meters) in southwestern Uganda. Organic materials: Sesbania sesban (S) and Leucaena diversifolia (L.) were applied in amounts sufficient to supply 100 kg N ha-1 either singly or combined with P and PK. Also added were NP and NPK from inorganic sources. The organic materials were incorporated into soil one week before planting, while the inorganic fertilisers were side-dressed at planting all at rates that would supply 100 kg ha-1 of N, P and K. Nitrogen in the form of urea was split-applied at planting and one month after. Bacterial wilt incidence differed with treatments and seasons. Disease incidence was lowest with treatments NP and S+ PK and highest with the control. Application of organic manures alone did not necessarily result in reduced wilt incidence except in a few cases. Both marketable and total tuber yields were consistently highest with S + PK and differed significantly from the control in all seasons. A combined analysis over the three seasons showed that the treatment S + PK gave a significantly higher yield (20.8 ha-1) than all other treatments, while the control yielded significantly lower (9.7 ha-1) than the other treatments. Sesbania as an organic manure performed better than Leucaena and potassium was found to be a useful nutrient for crop performance. When K was applied with NP, LP and SP, it brought about marketable yield increases of 11, 23 and 37%, respectively. Generally, the rate of wilt development, expressed in wilt incidence per unit time, was highest at early stage of growth, thereafter, it declined and stabilised during much of the tuber bulking stage The interaction between soil fertility and bacterial wilt incidence merits further studies in different environments. Key Words: Organic materials, inorganic fertilisers, polyphenols, ware yields, wilt incidence (African Crop Science Journal 2001 9(1): 267-278

Trees improve water storage and reduce soil evaporation in agroforestry systems on bench terraces in SW Uganda

The success of agroforestry in semi-arid areas depends on efficient use of available water and effective strategies to limit tree/crop competition and maximise productivity. On hillsides, planting improved tree fallows on the degraded upper section of bench terraces is a recommended practice to improve soil fertility while cropping continues on the lower terrace to maintain food production. This study examined the influence of tree fallows on soil water content (θ w ) and evaporation (E s ). Alnus acuminata Kunth (alnus), Calliandra calothyrsus Meissner (calliandra), Sesbania sesban L. (sesbania), a mixture of all three species, or sole crops (beans (Phaseolus vulgaris L.) or maize (Zea mays L.)) were grown on the upper terrace. The same sole crops were grown on the lower terrace. Four management regimes (unpruned, root, shoot and root + shoot pruned) were applied to the tree rows adjacent to the cropping area. Neutron probe and microlysimeter approaches were used to determine θ w and E s when the trees were c. 3.5 years old. Sesbania and alnus increased θ w by 9–18 % in the cropping area on the lower terrace but calliandra reduced θ w by 3–15 %. After heavy rain, E s comprised 29–38 % of precipitation in the tree-based treatments and 53 % under sole crops. Absolute values declined as rainfall decreased, but E s as a proportion of rainfall increased to 39–45 % in the tree-based treatments and 62 % for sole crops. Root + shoot pruning of alnus and the tree mixture increased θ w in the cropping area but had no significant effect in the other tree-based treatments. The results suggest that sesbania and alnus can be planted on smallholdings without compromising water supply to adjacent crops, whereas calliandra decreased water availability despite reducing E s . These results provide a mechanistic understanding of reported effects on crop yield in the same site

Tree species and pruning regime affect crop yield on bench terraces in SW Uganda

Integration of trees on farms may exert complementary or competitive effects on crop yield. This four year study examined novel systems in which Alnus acuminata (alnus), Calliandra calothyrsus (calliandra), Sesbania sesban (sesbania) or a mixture of all three were grown on the degraded upper part of bench terraces in Uganda; beans or maize were grown on the more fertile lower terrace during the short and long rains. Three pruning treatments (shoot, root or shoot+root pruning) were applied to the tree rows adjacent to the crops; shoot prunings were applied as green manure to the woodlot from which they came. Pruning increased survival in calliandra and reduced survival in sesbania; alnus was unaffected. Pruning reduced tree height and stem diameter in alnus, but did not affect calliandra or sesbania. Maize yield adjacent to unpruned calliandra, alnus and sesbania or a mixture of all three was reduced by 48, 17, 6 and 24 % relative to sole maize. Shoot pruning initially sustained crop performance but shoot+root pruning became necessary when tree age exceeded two years; shoot+root pruning increased maize yield by 88, 40, 11 and 31 % in the calliandra, alnus, sesbania and tree mixture systems relative to unpruned trees. Bean yield adjacent to unpruned calliandra, alnus, sesbania and the tree mixture was 44, 31, 33 and 22 % lower than in sole crops and pruning had no significant effect on crop yield. The results suggest that sesbania fallows may be used on the upper terrace without reducing crop yield on the lower terrace, whereas pruning of alnus is needed to sustain yield. Calliandra woodlots appear to be unsuitable as crop yield was reduced even after pruning

Water Infiltration, Conductivity and Runoff under Fallow Agroforestry on Sloping Terraces

Appropriate management of available water supplies is essential to prolong the growing season and optimize the effectiveness with which rainfall is used for agricultural production. The present study examined the impact of planting tree fallows ( Alnus acuminata , Calliandra calothyrsus and Sesbania sesban) on the degraded upper sections of sloping terraces on water infiltration and subsequent runoff on a Haplic ferralsol in southwestern Uganda. Infiltration measurements, done by a tension infiltrometer, were conducted under 3-year old tree canopies, under maize stands grown adjacent to trees, and under sole maize ( Zea mays ). Runoff from confined plots of agroforestry (trees on upper and crops on lower terrace sections) and sole crop systems were measured by the tipping bucket method mounted with counters. Measurements of runoff was done during the long rains of 2003 and short rains of 2004. Infiltration was invariably higher under agroforestry systems (P <0.001) than sole cropping, particularly under Alnus and Calliandra systems. A similar pattern was observed for saturated hydraulic conductivity (Ksat), which was greater in all tree-based systems except Sesbania than in the sole crop (P <0.01). The Ksat values were 1.3, 2.2, 1.0 and 0.8 cm h-1 respectively under Alnus, Calliandra, Sesbania and sole crop systems. Of even greater significance is the ability of trees to reverse the typical gradient in soil hydraulic properties observed on sloping terraces. Saturated hydraulic conductivity was consistently higher on the upper terrace than the lower terrace in the tree-based systems (P <0.01), whereas the reverse was true for the sole cropping system. During rainfall events of <10 mm, runoff accounted for only <4% of total rainfall in all treatments. The reduction in runoff relative to the sole crop control was 64, 84 and 96 in the Alnus, Calliandra and Sesbania systems. During high rainfall events (>10 mm) the effect of agroforestry was more dramatic, reducing runoff relative to the sole crop by 92, 76 and 91, respectively under Alnus, Calliandra, and Sesbania systems. Results demonstrate the ability of trees to break loose the hard compacted soils on the upper terrace so as to increase infiltration. The resultant increase in infiltration coupled with physical barriers of ground litter combine to reduce runoff under agroforestry systems

Assessing nutritional diversity of cropping systems in African villages

Background: In Sub-Saharan Africa, 40% of children under five years in age are chronically undernourished. As new investments and attention galvanize action on African agriculture to reduce hunger, there is an urgent need for metrics that monitor agricultural progress beyond calories produced per capita and address nutritional diversity essential for human health. In this study we demonstrate how an ecological tool, functional diversity (FD), has potential to address this need and provide new insights on nutritional diversity of cropping systems in rural Africa. Methods and Findings: Data on edible plant species diversity, food security and diet diversity were collected for 170 farms in three rural settings in Sub-Saharan Africa. Nutritional FD metrics were calculated based on farm species composition and species nutritional composition. Iron and vitamin A deficiency were determined from blood samples of 90 adult women. Nutritional FD metrics summarized the diversity of nutrients provided by the farm and showed variability between farms and villages. Regression of nutritional FD against species richness and expected FD enabled identification of key species that add nutrient diversity to the system and assessed the degree of redundancy for nutrient traits. Nutritional FD analysis demonstrated that depending on the original composition of species on farm or village, adding or removing individual species can have radically different outcomes for nutritional diversity. While correlations between nutritional FD, food and nutrition indicators were not significant at household level, associations between these variables were observed at village level. Conclusion: This study provides novel metrics to address nutritional diversity in farming systems and examples of how these metrics can help guide agricultural interventions towards adequate nutrient diversity. New hypotheses on the link between agro-diversity, food security and human nutrition are generated and strategies for future research are suggested calling for integration of agriculture, ecology, nutrition, and socio-economics

The African Millennium Villages

We describe the concept, strategy, and initial results of the Millennium Villages Project and implications regarding sustainability and scalability. Our underlying hypothesis is that the interacting crises of agriculture, health, and infrastructure in rural Africa can be overcome through targeted public-sector investments to raise rural productivity and, thereby, to increased private-sector saving and investments. This is carried out by empowering impoverished communities with science-based interventions. Seventy-eight Millennium Villages have been initiated in 12 sites in 10 African countries, each representing a major agroecological zone. In early results, the research villages in Kenya, Ethiopia, and Malawi have reduced malaria prevalence, met caloric requirements, generated crop surpluses, enabled school feeding programs, and provided cash earnings for farm families