Soil fertility and land productivity: a guide for extension workers in the eastern Africa region

Traditional subsistence low-input low-yield agriculture can no longer adequately ca-ter for all food fibre cash industry and other human needs in sub-Saharan Africa.ëModerní or ëGreen Revolutioní market-oriented agriculture that relies on adequateuse of external inputs such as chemical fertilizers herbicides pesticides high-yielding varieties and farm mechanization (including irrigation) has resulted in dramatic agri- cultural yield increases in certain Third World countries especially in Asia in the last30ñ40 years. But Africa has been bypassed by these developments.Farmers in the eastern Africa region (defined here as Eritrea Ethiopia Kenya Uganda Tanzania Zambia and Malawi the seven countries which comprise RELMAís area of operation) are getting barely 25% of the yields that are attained at neighbour-ing research stations. The difference arises from the better supply maintenance andmanagement of plant nutrients as well as improved tillage practices and good soil-moisture management at research stations (Figure 1.1). Declining soil fertility low soil moisture soil salinity/sodicity soil compaction and the formation of hardpans are major causes of low land productivity which is itself manifested as low crop yields low farm incomes and deepening rural poverty. There are worsening food deficits in manyareas of the eastern African region. This has led to too much dependence on food aid (food grown in other countries using massive applications of fertilizers and crop-protec-tion chemicals). The current high poverty levels can be reduced through effective ac-tion to raise soil fertility to levels that will bring crop yields closer to the potential for each ecological zone.

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