The assessment of soil aggregate stability to raindrop impact for some tropical soils material, with particular reference to iron
Soil aggregate stability to raindrop impact is df fundamental
importance to many aspects of the soil system, in particular
rainsplash erosion. This stability has been measured by use of
single drop rainfall simulators, the characteristics and operation of
which have, in the past, shown considerable variation. The drop
sizes, impact frequency, drop fall height, chemistry of drop-forming
liquid, aggregate pretreatment, and definition of breakdown affect
the way in which the the apparatus can be used to define stability.
In this thesis an apparatus is developed that is believed to give
results with increased consistency and replicability.
An index of stability (F) is evolved from data collected using the
raindrop simulator which is then used to characterise a set of iron
rich, tropical soils from Kenya and Mo~ambique. Information about
the iron, textural, chemical and magnetic status of each soil sample
is also collected and used to try to predict the stability index
through a process of statistical modelling. Models for highly
stable and poorly stable soils are developed and finally a
definitive model that can be used for all the soils.
The last section of this investigation attempts to try and explain
the results in terms of the processes that might be operating in
the soil. Specific reference is made to the iron content of the
soils because of its natural abundance in the samples considered.
The possible contributions of total iron, crystalline iron, amorphous
iron and organic iron to aggregate stability are discussed.