Agron. Sustain. Dev. 27 (2007) 197-208
DOI: 10.1051/agro:2007003

Ecological and agro-economic study of small farms in sub-Saharan Africa

D.D. Onduru^a and C.C. Du Preez<sup>b

a</sup>  ETC-East Africa, PO Box 76378-00508 Yaya, Nairobi, Kenya
^b  Department of Soil, Crop and Climate Sciences, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa

(Accepted 12 December 2006; published online 7 March 2007)

Abstract - Land degradation, rising population and poverty in sub-Saharan Africa threatens the agricultural sustainability and productivity, quality of the environment and socio-economic wellbeing of rural populations. We studied farm ecological, economic and social sustainability, productivity and production risks in the Mbeere District of Eastern Kenya. We used a soil nutrient monitoring methodology to collect data from 30 households. Ecological sustainability was threatened by soil nutrient decline at rates of 1.7 kg P and 5.4 kg K ha^-1 half year^-1 while N was nearly balanced in soils. Soil phosphorus and potassium stocks, in the cultivated soils, declined at rates of 0.3% and 0.1% half year^-1, respectively. Farm economic returns were positive, albeit low, and could not sustain the livelihoods of the households. All the 30 households were living below the poverty line of 1 US dollar a day. Farm productivity was low, with livestock and yields of major staple food crops below on-farm target yields. To spread out the risks of production, farming households were cultivating an average of 4.7 crop fields, keeping more than two types of livestock and practising intercropping systems. Intercropping maize-beans reduced nutrient decline and raised household incomes compared with monocropping of either of the two crops. Despite the low rates of nutrient decline, high risks of production and the low crop yields, the livestock productivity and farm economic performance put the sustainability of these farming systems into question. The low levels of nutrient decline in small farms averaging at 1.7 kg P and 5.4 kg K ha^-1 half year^-1 contrasts with the high nutrient depletion rates on macro-scale levels, e.g. 20-40 N, 3.5-6.6 kg P and 20-40 kg K ha^-1 year^-1 for Eastern African countries and 22 kg N, 2.5 kg P and 15 kg K ha^-1 year^-1 for sub-Saharan Africa. These findings indicate that the extent of nutrient decline and conservation differs across sub-Saharan Africa. The positive contribution of intercropping to nutrient balances suggests the need to encourage farmers to adopt such systems rather than monocropping.

Key words: agro-ecological sustainability / drylands / production risks / socio-economic sustainability / sustainable agriculture

Corresponding author: d.onduru@etc-eastafrica.org

© INRA, EDP Sciences 2007