The conventional soil fertility evaluation methods are invariably non-small scale farmer friendly, owing to the costs involved, the complexity associated with the interpretation of the laboratory results and the patience required to access the necessary recommendations. Many plants especially weeds have been associated by small scale farmers with declining soil fertility. However, the reliability of this perception has not yet been extensively verified. Thus, an ethno-ecological study was conducted on fields under cultivation with intermittent fallows on Nitisols in Buikwe District, Central Uganda to establish the relationship between spear grass (Imperata cylindrica) population, residue burning and soil properties; and determine the reliability of the species as a soil fertility indicator. It is difficult to discern whether spear grass as a species prefers habitation of low fertility soils or is simply more competitive on low fertility soils than other plant species including crops. This is an issue that deserves further research involving deliberate enrichment of the soil with fertilizers to eliminate the competitive aspect.