Over the past half-century, agricultural production gains have provided a platform for rural and urban economic growth worldwide. In African countries, however, agriculture has been widely assumed to have performed badly. Foresight commissioned analyses of 40 projects and programmes in 20 countries where sustainable intensification has been developed during the 1990s–2000s. The cases included crop improvements, agroforestry and soil conservation, conservation agriculture, integrated pest management, horticulture, livestock and fodder crops, aquaculture and novel policies and partnerships. By early 2010, these projects had documented benefits for 10.39 million farmers and their families and improvements on approximately 12.75 million ha. Food outputs by sustainable intensification have been multiplicative—by which yields per hectare have increased by combining the use of new and improved varieties and new agronomic—agroecological management (crop yields rose on average by 2.13-fold), and additive—by which ...

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Sustainable intensification in African agriculture

Sustainable intensification in agricultural systems

Agriculture and fishing are the primary source of almost all our food, as well as of many other products, so remain vital activities even though their share in the economy is small and in continuous decline. Partly for this reason public policy in these areas is almost entirely integrated at European level in the Common Agricultural Policy (CAP) and Common Fisheries Policy (CFP). Forestry policies are also heavily affected by EU-level decision-making. As agriculture dominates in terms of direct contribution to GDP and numbers of people engaged in it, as well as accounting for the largest amount of public support expenditure, it is agriculture that will receive the greatest attention here.

Agriculture, Forestry and Fisheries

Tithonia diversifolia, a shrub in the family Asteraceae, is widely distributed along farm boundaries in the humid and subhumid tropics of Africa. Green biomass of tithonia has been recognized as an effective source of nutrients for lowland rice (Oryza sativa) in Asia and more recently for maize (Zea mays) and vegetables in eastern and southern Africa. This paper reviews the potential of tithonia green biomass for soil fertility improvement based on recent research in western Kenya. Green leaf biomass of tithonia is high in nutrients, averaging about 3.5% N, 0.37% P and 4.1% K on a dry matter basis. Boundary hedges of sole tithonia can produce about 1 kg biomass (tender stems + leaves) m−1 yr−1 on a dry weight basis. Tithonia biomass decomposes rapidly after application to soil, and incorporated biomass can be an effective source of N, P and K for crops. In some cases, maize yields were even higher with incorporation of tithonia biomass than with commercial mineral fertilizer at equivalent rates of N, P and K. In addition to providing nutrients, tithonia incorporated at 5 t dry matter ha−1 can reduce P sorption and increase soil microbial biomass. Because of high labor requirements for cutting and carrying the biomass to fields, the use of tithonia biomass as a nutrient source is more profitable with high-value crops such as vegetables than with relatively low-valued maize. The transfer of tithonia biomass to fields constitutes the redistribution of nutrients within the landscape rather than a net input of nutrients. External inputs of nutrients would eventually be required to sustain production of tithonia when biomass is continually cut and transferred to agricultural land.

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Tithonia diversifolia as a green manure for soil fertility improvement in western Kenya: A review

Integrated Pest Management (IPM) is a leading complement and alternative to synthetic pesticides and a form of sustainable intensification with particular importance for tropical smallholders. Global pesticide use has grown over the past 20 years to 3.5 billion kg/year, amounting to a global market worth $45 billion. The external costs of pesticides are $4–$19 (€3–15) per kg of active ingredient applied, suggesting that IPM approaches that result in lower pesticide use will benefit, not only farmers, but also wider environments and human health. Evidence for IPM’s impacts on pesticide use and yields remains patchy. We contribute an evaluation using data from 85 IPM projects from 24 countries of Asia and Africa implemented over the past twenty years. Analysing outcomes on productivity and reliance on pesticides, we find a mean yield increase across projects and crops of 40.9% (SD 72.3), combined with a decline in pesticide use to 30.7% (SD 34.9) compared with baseline. A total of 35 of 115 (30%) crop combinations resulted in a transition to zero pesticide use. We assess successes in four types of IPM projects, and find that at least 50% of pesticide use is not needed in most agroecosystems. Nonetheless, policy support for IPM is relatively rare, counter-interventions from pesticide industry common, and the IPM challenge never done as pests, diseases and weeds evolve and move.

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Integrated Pest Management for Sustainable Intensification of Agriculture in Asia and Africa

Composition and degradability of different fractions of Calliandra leaves, pods and seeds

Economic and social benefits of new forage technologies in Mindanao, Philippines and Tuyen Quang, Vietnam

There are opportunities for increasing milk production in central Kenya through the use of tree fodder, leading to higher farm income. Most research for intensive use of fodder trees has been carried out on exotic species, neglecting indigenous ones. The objectives of this study were to assess the potential of indigenous and naturalized fodder trees and shrubs (IFTS) in central Kenya, involving farmers in all phases of research in order to increase the adoption of so developed technologies. Formal surveys and feedback meetings were conducted. Farmers chose tree seedlings, planted them on-farm, and the performance was monitored. Farmers' assessments of qualities of IFTS were compared with laboratory nutritive analyses. Two feeding trials with dairy heifers were conducted involving seven fodder tree species. It was found that farmers used a total of 160 different IFTS. Their ratings on palatability for cattle and goats and milk production for goats differed significantly among tree and shrub species. On-farm assessment of planted IFTS provided useful information on preference of species, in addition to the survey results. There were strong relationships between laboratory nutritive analyses and farmers' assessment of quality of IFTS and useful characteristics of individual species were obtained through comparing the two methods. Dry matter intake by heifers was higher for some IFTS than for the popular exotic species Calliandra calothyrsus . Selective feeding behaviour of heifers caused an improvement of nutrient concentrations of consumed feed of up to 29 %. It was concluded that there is a large potential for intensive use of IFTS in central Kenya. Promising species for the subhumid zone are: Ficus thoningii, Lantana camara, Morus alba, Manihot glaziovii, Sapium ellipticum, Tithonia diversifolia, Trema orientalis, Triumfetta tomentosa and Vernonia lasiopus ; for the medium and semi-arid zone they are: Acacia ataxacantha, Aspilia mossambicensis, Crotalaria goodiiformis, Grewia tembensis, Indigofera lupatana, Lantana camara and Melia volkensii . Future research is needed on experiments with lactating cows, agronomic performance, protein quality and current mechanisms preventing toxicity of L. camara .

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The potential of indigenous and naturalized fodder trees and shrubs for intensive use in central Kenya

A 67-day feeding experiment was conducted to study the effects of inclusion of 5%, 7.5% or 10% leaf meal of Calliandra calothyrsus (calliandra) in the diets of laying hens on feed intake, egg production, egg weights, yolk colour and the birds' weights. While no significant effects were seen on either egg numbers or egg size, feed intake increased and the efficiency of feed utilization decreased with increasing inclusion of the foliage. Absolute initial and final body weights did not show significant treatment differences but live weight changes over the course of the experiments were statistically significant, weight gains decreasing with increasing calliandra levels. The strength of colour of the yolks increased within 3 days of offering the calliandra, irrespective of the level of inclusion. The persistence of the colour change after withdrawal of the leaf meal ranged from 3 days at the 5% inclusion to over 10 days at the 10% level. While it may be possible to include calliandra leaf meal in poultry rations along with other, local, low-cost components, there would appear to be little advantage in using it in conjunction with commercial layers meal at levels higher than those necessary to provide the desired pigmentation level in the yolks (5% or less).

R.L. Roothaert

Papers

Composition and degradability of different fractions of Calliandra leaves, pods and seeds

Economic and social benefits of new forage technologies in Mindanao, Philippines and Tuyen Quang, Vietnam

The potential of indigenous and naturalized fodder trees and shrubs for intensive use in central Kenya

The feeding of leaf meal of Calliandra calothyrsus to laying hens.

Feed intake and selection of tree fodder by dairy heifers