The effects of several crop management factors on bread wheat yields in the Ethiopian highlands

Abstract

Crop management (CM) research conducted in Ethiopia has tended to quantify yield gains and losses associated with single management factors, making it difficult to determine the relative importance of main effects and interactions among factors. During 1987 and 1988, exploratory trials examining several CM factors for bread wheat (Triticum aestivum) production were conducted at four research centres situated in the priority wheat production zones of Ethiopia. In the two cropping seasons of 1990, five similar trials were executed in south-eastern Ethiopia to examine the differential responses to four CM factors between farmers' fields and a research site. All 13 trials examined differences between local and improved bread wheat varieties, and response to fertiliser and hand weeding. A fourth factor of local significance such as fungicide, insecticide, or sowing date was added at each site to complete a 24 design. Treatment main effects exerted the predominant influence on grain yield (GY). Relative to unimproved traditional germplasm, GY increments from modern varieties ranged from 13 to 315%. Fertiliser application reduced GY by 9% in one trial due to enhanced lodging, but, in nine others, increased yield from 20 to 88%. Hand weeding increased GY in nine trials; the increases ranged from 17 to 94%. Fungicide increased GY by 5% in two trials, primarily by increasing the yield of a susceptible semi-dwarf variety under a heavy epidemic of stripe rust (Puccinia striiformis). Seed treatment with insecticide for control of shoot fly (Delia arambourgi) increased GY by 13 to 46% in four trials. Two way interactions involving variety emphasised the greater responsiveness of modern varieties to improved management and higher levels of inputs. Overall, the interactions demonstrated the beneficial impact of combining improved production practices in one cultural package. From the comparison of on-farm and on-station results, it was apparent that station conditions differ dramatically from farmers' circumstances in terms of heat crop response to hand weeding, fertiliser application and insecticidal seed treatment. This has obvious implications for the extrapolation of research results generated on station to the surrounding small-scale farming community.