Effects of Rotation with Trap Crops on Striga (Striga hermonthica Del. Benth) Incidence, its Seed Bank and Sorghum Growth and Yield

Abstract

A trial was conducted for three consecutive seasons (2006/07,
2007/08 and 2008/09) in a field artificially infested by Striga hermonthica
in the Experimental Farm of the Faculty of Agriculture, University of
Sinnar. The effects of a two seasons’ crop rotation on striga incidence, its
seed bank and growth and yield of subsequent sorghum crop were
investigated. The rotation comprised the trap crops, cowpea (Vigna
unguiculata), millet (Pennisetum glaucum), sesame (Sesamum indicum),
sunflower (Helianthus annuus) and fallows, in assorted combinations. A
sorghum monoculture, for the three seasons, was included as a control.
All treatments reduced striga emergence significantly in comparison to
sorghum monoculture. Sunflower and sesame grown for two consecutive
seasons caused the maximum reductions (80%), while a fallow followed
by sorghum resulted in the least reduction (42%). Significant reduction in
striga capsules (37%) was caused by two consecutive sesame crops. In the
second season, all treatments significantly reduced striga seed bank,. Two
consecutive fallows and two consecutive crops each of cowpea, millet and
sunflower resulted in the highest reductions in striga incidence (80% -
92%), while a fallow followed by sorghum exhibited the least reduction
(51-65%). None of the treatments had adverse effects on sorghum stand
early in the season; however, at harvest significant reduction was
observed. Sorghum monoculture resulted in the lowest stand, while
sunflower planted subsequent to a fallow and two successive sunflower
crops affected the highest stands. Among all treatments, sorghum