speargrass rhizome biomass in gliricidia plots throughout the sampling period
irrespective of moisture conditions. This would suggest that speargrass shoots
in the alley crop plots were not able to supply enough assimilates to support
rhizome growth. This is to be expected since speargrass shoot biomass has
been shown to be adversely affected by gliricidia hedgerows. Speargrass
rhizome biomass was reduced by 96% and 90% in gliricidia and leucaena
hedgerow species respectively, 12 months after sampling was started. The
fact that rhizome biomass declined in the hedgerow plots where speargrass
was shaded, but increased steadily throughout the rainy reason in the control
(Fig. 4), plot strongly implicates light as a growth factor that was limiting and
contributing to the decline in speargrass rhizome biomass. Rhizomes of
speargrass in both gliricidia and leucaena plots had longer internodes than
speargrass in control plots, possibly as a result of shading by hedgerows.
Soerjani [1970] observed a similar response of speargrass rhizomes to light
stress.