Abstract:
Plant-soil feedback can influence aboveground interactions between plants and
herbivores by affecting plant chemistry. Such interactions can be utilized in pest
management. However, cropping systems such as maize-legume intercropping
(MLI) can influence these interactions which is not well understood. In this study,
we explored effects of MLI systems on soil physico-chemical properties, maize
growth, larval feeding and development of fall armyworm (Spodoptera
frugiperda). We used sterile soil and soil conditioned by different MLI and
maize-monoculture cropping systems to explore these interactions. Soil
samples that included soil conditioned by different MLI and maizemonoculture
cropping systems were collected from smallholder farmer fields
in eastern Kenya, where different MLI and maize-monoculture cropping systems
were being practiced. These soil samples were compared with sterile soils for
physico-chemical properties using black oxidation and Walkley methods. Threeweeks-
old maize plants grown in the different soil treatments in the greenhouse
were used for larval feeding and development assays. Neonate S. frugiperda
larvae were allowed to feed on maize leaf discs for 24 hours and another set of
plants were inoculated with the neonates for 15 days and the larval survival and
development monitored. Soil obtained from different maize-edible legume
intercropping systems had a higher pH, electrical conductivity, nitrogen,
organic carbon, potassium, phosphorus, calcium, magnesium, exchangeable
acidity, copper, clay and silt compared to maize-monoculture and sterile soil.
Maize plants grown in MLI soil had better growth parameters compared to those
in maize-monoculture and sterile soils. A high correlation was found between pH
and plant biomass, while no significant correlation with other physico-chemical
properties was noted. There were significant differences in larval feeding by S.
frugiperda neonates when exposed to constitutive and induced maize leaf discs
with more leaf tissue fed on maize grown in maize-monoculture and sterile soil. When allowed to feed for 15 days, S. frugiperda larval weight and length were
significantly lower on maize plants grown in soils conditioned by MLI than those
grown in soil conditioned by maize-monoculture and sterile soils. Findings from this study show how conditioning soil by MLI systems improve soil health, maize
growth and reduces S. spodoptera larval feeding and development.
