At Level C, plant/environment data have been gathered for land evaluation,
but the most prominent activities in this area offer little guidance on how to
gather data for large numbers of lesser-known plants. Since land evaluation
has mostly focused on the major crops, data-sets at Level C have largely
been prepared by making generalisations from Level D information (see
Doorenbos and Kassam 1979 for good products of this process). Where
interest has been given to lesser-known species, workers concerned with land
evaluation have merely picked up scraps of information wherever they
could find them. Unfortunately, funding for land evaluation projects has
not included sums for research into how information about lesser-known
species can be cheaply generated, and since plant science has taken almost
no interest in the scientific problems raised by land evaluation [16], no
serious thought has emerged about how to obtain Level C ecophysiological
information for species for which there are no Level D descriptions.