The study has clearly demonstrated the ability of both Gamba
and Stylosanthes to grow on these acid infertile sandy soils under
rainfed conditions. Their deep rooted nature permitted the production
of green forage throughout the year that constitutes an
important source of livestock feed in this semi-arid environment
and resulted in greater stored water utilization. In addition, Gamba
responds positively to nitrogen fertilization. Whilst the ability of
these species to grow and produce high quality livestock feed holds
potential opportunities in overcoming soil chemical constraints,
there is a negative impact that needs to be considered when
recommending these species for use on these soils. Accelerated
soil acidification to depths below 110 cm should be of great concern
to land managers as remedial applications of lime to counter
the acidity generated will be relatively ineffective. It may be argued
that the treatments imposed, namely the application of NH4 based
fertilizers and the exploitive cut and carry system, was extreme.
However, it does represent the type of production system that small
scale farmers routinely use in the region or for that matter a cut and
bale system common to highly industrialized feed production
systems. It is suggested that extreme caution should be taken when
considering such a production system. Certainly, the use of NO3
based fertilizers at rates considerably higher than those applied in
the current study along with grazing would significantly reduce the
risk of acidification of surface soil horizons. However, it is argued
that such a strategy would not significantly alter the dynamics of
pH changes at depth in the profile.