Efficient use of external inputs and water conservation are a prerequisite of sustainable agricultural productivity in semiarid West Africa. A field experiment was carried out during 3 years (2000–2002) at Saria in semiarid Burkina Faso (800 mm of annual rainfall, PET of 2000 mm per year) to assess the effects of stone rows or grass strips of Andropogon gayanus Kunth cv. Bisquamulatus (Hochst. Hack.) as soil and water conservation (SWC) measures, the sole application of an organic (compost-N) or mineral (urea-N) nitrogen and the combined use of SWC and compost-N or urea-N on N flows and balances. The trial was conducted on a Ferric Lixisol with 1.5% slope and comprised nine treatments in two replications. The SWC measures were put along contours lines. During the three consecutive years, all treatments induced negative annual N balances (75 to 24 kg N ha1 ). The main factors explaining these negative balances were N exports by sorghum biomass and soil erosion-induced N losses. Large amounts of N (7 kg N ha1 per year in 2000 and 44 kg N ha1 per year in 2002) were lost in the control treatment through runoff and eroded sediments, which corresponds respectively to about 10 and 43% of the total outflow of N. Sole stone rows and grass strips reduced erosion N losses to 8 and 12%, respectively, of the total annual loss. The combined application of SWC measures and nutrients inputs reduced erosion N losses to only 2–7% of the annual N loss. The application of urea-N or compost-N led to the lowest soil N mining over the 3 years, whereas the highest N mining was observed in plots without added N. We conclude that N mining in poor fertile soils of West Africa can be mitigated through an integration of local water and nutrient management practices.
Robert Zougmor Institute for Environment and Agricultural Research (INERA), Natural Resource Management, 04 BP 8645,
Ouagadougou 04, Burkina Faso
Abdoulaye Mandoc An International Centre for Soil Fertility and Agricultural Development, Africa-Division, BP 4483, Lome´, Togo
Leo Stroosnijderb Erosion and Soil and Water Conservation Group, Department of Environmental Sciences, Wageningen University,
Nieuwe Kanaal 11, 6709 PA Wageningen, The Netherlands
Serge Guillobez Centre International en Recherches Agronomiques pour le De´veloppement (CIRAD), BP 5035, 34032 Montpellier, France
Copyright:# 2004 Elsevier B.V. All rights reserved.