Abstract
Food insecurity is a chronic problem in Africa and is likely to worsen with climate change and population growth. It is largely due to poor yields of the cereal crops caused by factors including stemborer pests, striga weeds and degraded soils. A platform technology, ‘push–pull’, based on locally available companion plants, effectively addresses these constraints resulting in substantial grain yield increases. It involves intercropping cereal crops with a forage legume, desmodium, and planting Napier grass as a border crop. Desmodium repels stemborer moths (push), and attracts their natural enemies, while Napier grass attracts them (pull). Desmodium is very effective in suppressing striga weed while improving soil fertility through nitrogen fixation and improved organic matter content. Both companion plants provide high-value animal fodder, facilitating milk production and diversifying farmers’ income sources. To extend these benefits to drier areas and ensure long-term sustainability of the technology in view of climate change, drought-tolerant trap and intercrop plants are being identified. Studies show that the locally commercial brachiaria cv mulato (trap crop) and greenleaf desmodium (intercrop) can tolerate long droughts. New on-farm field trials show that using these two companion crops in adapted push–pull technology provides effective control of stemborers and striga weeds, resulting in significant grain yield increases. Effective multi-level partnerships have been established with national agricultural research and extension systems, non-governmental organizations and other stakeholders to enhance dissemination of the technology with a goal of reaching one million farm households in the region by 2020. These will be supported by an efficient desmodium seed production and distribution system in eastern Africa, relevant policies and stakeholder training and capacity development.
Highlights
Africa faces serious challenges in feeding its population, having reverted from being a net exporter of agricultural commodities to being a net importer of the same for the last three decades
Despite land being perceived to be lost to trap cropping, the resultant benefits from push–pull technology through maize yield increase and the extra income from sale or utilization of Napier grass and desmodium were more than sufficiently high to cover all the initial capital costs and still make a substantial margin, yet the low investments associated with the other compared technologies were generally not justified by the revenue recovered
In the adapted push–pull technology, which is currently practiced by about 10 000 farmers in Kenya, Tanzania and Ethiopia, brachiaria cv mulato is used as a trap plant while D. intortum is used as an intercrop, with field trials conducted in relatively drier areas of western Kenya with mean annual rainfall of more than 700 mm and mean daily temperatures more than 258C, indicating effective control of cereal stemborers and striga, with concomitant increases in grain yields in both sorghum and maize
Summary
Africa faces serious challenges in feeding its population, having reverted from being a net exporter of agricultural commodities to being a net importer of the same for the last three decades. Human population more than tripled in the second half of the twentieth century, from 230 million to 811 million [2] In spite of this rapid surge in human population, average growth in food production in the continent has at best stagnated, with reports indicating decline in crop yields over the last few decades in several places within the continent [3]. One of the main causes of the chronic food insecurity witnessed in Africa is poor crop yields, largely caused by insect pests, weeds and degraded soils. This is complicated further by the increasingly hot and dry weather conditions associated with climate change [4,5]. The efficient production of cereals, per unit of input, is central to the food security challenge
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