Methods of converting yield data from experimental plot to hectrage un
its are proposed to enable reliable estimation of yield potentials of
crop varieties. Conventional direct linear extrapolation method of con
version gives too high estimates of yield per hectare. The proposed me
thods take into account the variability inherent in experimental mater
ials and cultural practices as well as different levels of management
skills of farmers, and make use of Smith's index of soil heterogeneity
. Two models are described for the estimation of the management index,
which may further be partitioned into low, medium and high management
levels. An example is given to illustrate the method and possible imp
lications discussed.