Biotechnologie, Agronomie, Société et Environnement (Jan 2006)
Yield trends in the long-term crop rotation with organic and inorganic fertilisers on Alisols in Mata (Rwanda)
Abstract
A crop rotation system with various species was established on «Alisols» at Mata grassland site, oriental side of Zaire-Nile Watershed Divide (CZN), Rwanda. Inorganic and organic fertilisers were applied in various plots led in randomised complete blocs with three replicates. Crop yield data were each season recorded over a 9-year period. Results showed that there was very low or no harvest in plots without fertilisers. Where fertilisers were applied, the yield generally increased but remained relatively low: only few crops and varieties adapted to the Mata ecology such as potatoes and fi nger millet responded well to fertilisers. Liming was absolutely necessary to get any acceptable crop yield improvement with NPK. High rate of rich farmyard manure was effi cient alone and its effect was seen up to 4 seasons after its four regular seasonal applications. Mata compost (C/N>25, 0,3 g P.kg-1) had little benefi cial effect. One, four and half, and eight tons of lime per ha applied 3 times in 8 years increased soil pH (in water) but not up to 6,5. It is then concluded that to succeed improving food production at the CZN area, selection of crops and varieties to fi t ecological conditions and amending soils to fi t crops be combined, but not opposed.
