Abstract

A critical analysis of conventional water resources assessments and re-visiting the on-farm water balance suggests large scopes for water productivity improvements in small-holder rainfed farming systems in drought prone environments of Eastern and Southern Africa. The paper addresses key management challenges in trying to upgrade rainfed agriculture, and presents a set of field experiences on system options for increased water productivity in small-holder farming. Implications for watershed management are discussed, and the links between water productivity for food and securing of water flow to sustain ecosystem services are briefly analysed. Focus is on sub-Saharan Africa hosting the largest food deficit and water scarcity challenges.The paper shows that there are no agro-hydrological limitations to doubling on-farm staple food yields even in drought prone environments, by producing more "crop per drop" of rain. Field evidence is presented suggesting that meteorological dry spells are an important cause for low yield levels and it is hypothesised that this may constitute a core driver behind farmers risk aversion strategies. The dry spell induced risk perceptions contribute amongst others to soil nutrient mining due to insignificant investments in fertilisation. For many small-holder farmers in the semi-arid tropics it is simply not worth investing in fertilisation (and other external inputs) as long as the risk for crop failure remains a reality every fifth year with risk of yield reductions every second year, due to periodic water scarcity during the growing season (i.e., not necessarily cumulative water scarcity).Results are presented from field research on small-holder system innovations in the field of water harvesting and conservation tillage. Upgrading rainfed production systems through supplemental irrigation during short dry-spells is shown to dramatically increase water productivity. Downstream implications of increased upstream withdrawals of water for upgrading of rainfed food production are discussed.Finally it is argued that some of the most exciting opportunities for water productivity enhancements in rainfed agriculture are found in the realm of integrating components of irrigation management within the context of rainfed farming, e.g., supplemental or micro irrigation for dry spell mitigation. Combining such practices with management strategies that enhance soil infiltration, improve water holding capacity and plant water uptake potential, can have strong impact on agricultural water productivity. This suggests that it is probably time to abandon the largely obsolete distinction between irrigated and rainfed agriculture, and instead focus on integrated rainwater management. (C) 2002 Elsevier Science Ltd. All rights reserved.

Published in

Physics and chemistry of the earth
2002, Volume: 27, number: 11-22, pages: 949-959
Publisher: Elsevier {BV}

UKÄ Subject classification

Agricultural Science


Publication identifier

DOI: https://doi.org/10.1016/s1474-7065(02)00098-0

Permanent link to this page (URI)

https://res.slu.se/id/publ/102555