Fertiliser effects on sustainability in the wheat-based small-holder farming systems of southeastern Ethiopia
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On-farm trials were conducted over three seasons throughout the highlands of Ethiopia to examine the sustainability of increased nitrogen and phosphorus fertilizer application on bread wheat in the peasant farming sector. Nitrogen fertiliser decreased soil pH by 0.2 to 0.3 units over one crop season. Nitrogen rates as low as 20.5 kg ha-1 significantly increased the density of wild oats in the wheat crop; the response to N was quadratic, attaining a maximum of 246 wild oat panicles M-2 at 41 kg ha-1 relative to 191 panicles M-2 for the 0 N treatment. Broadleaf weed densities and the labour requirement for hand weeding the wheat crop were also significantly increased by fertiliser N. The incidence of stripe rust on wheat foliage was increased by 18% on a susceptible bread wheat cultivar with the application of 82 kg N ha-1. Phosphorus fertiliser increased the incidence of stripe rust by 14% with the application of 40 kg P ha-1. In contrast, P significantly decreased the density of wild oats and broadleaf weeds, presumably affecting both characters through an enhancement of crop biomass production. To have a sustainable impact on wheat grain yields in Ethiopia, increased fertiliser usage should be accompanied by the provision of other essential farm-level inputs such as herbicide and seed of rust-resistant cultivars.
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