Soil fertility status and Striga hermonthica infestation relationship due to management practices in Western Kenya
Striga hermonthica, a parasitic weed, has long been believed to be correlated with the
declining soil fertility status. However scientists have recently come to question this statement
since some recent studies have shown contradictive results. To investigate whether soil
fertility status and infestation of Striga hermonthica were correlated and the impact of it were
caused by farmer management, 120 farmers in Western Kenya, where Striga hermonthica
infestation is prone, participated in this study. In three districts with two sub-locations each,
farmers answered a structural questionnaire and identified two fields, one with high and one
with low soil fertility. These fields later came to be the basis for this study and soil were
therefore also sampled from them. Different soil variables such as: pH, ohlsen-P, texture, C,
N, and seed bank of Striga hermonthica, were then analyzed. The Striga seed bank differed
significantly between the districts, but there were no differences between the farms or the two
fields (high and low soil fertility) on each farm. pH, C and N gave significant results for the
amount of Striga seeds found in the soil. Soils with lower C:N ratio also contained fewer
Striga seeds, while fields with high pH had more Striga seeds present. In Nyabeda, one of the
sub-locations, trials were installed on the identified fields at 11 farms to measure actual Striga
emergence in the field. Local and IR-maize were planted, both with and without fertilization.
Variety was significant for both Striga emergence count and maize yield. Field status was
also significant for Striga emergence. Fertilisation played no significant role in Striga
emergence nor did it increase the yield. The local maize variety gave significantly higher
yields than the IR-maize did. Furthermore IR-maize resulted in significantly higher
emergence of Striga. Striga infestation seems to be correlated with soil fertility status, though
the impact of farmer management has not been fully investigated due to the limited amount of
time and data available. Further studies are needed to understand the impact of farmer
management practices on Striga infestation and soil fertility.