This index accounts for both abundance and evenness of the species
present. The proportion of species ‘i’ relative to the species richness
(pi) was calculated, and then multiplied by the natural logarithm
of this proportion (ln pi) [22].
H = −
S
i=1
Pi ∗ ln Pi
2.3.5. Evenness
The species evenness (E)is the relative abundance or proportion
of individuals among the species. This index is calculated by dividing
H by Hmax (here Hmax = ln S). Evenness values range between
0 and 1, with 1 being complete evenness [22].
E = H/Hmax = H/ ln S
2.3.6. Rank-abundance diagrams
The rank-abundance curve provides a means for visually representing
species richness and species evenness. Species richness
can be viewed as the number of different species on the chart i.e.
how many species were ranked. Species evenness is derived from
the slope of the line that fits the graph. A steep gradient indicates
low evenness as the high-ranking species have much higher abundances
than the low ranking species. A shallow gradient indicates
high evenness as the abundances of different species are similar.
2.3.7. Relative abundance
Relative abundance is the ratio (expressed as percent) of the
density of one species to the density of the weed community.
2.3.8. Weed smothering efficiency (WSE)
Weed smothering efficiency can be defined as:
WSE = (W1 − W2)/W1 × 100
Where,
W1: Weed population/biomass in sole baby corn
W2: Weed population/biomass in intercropping system
2.4. Statistical analysis
The information collected on different parameters was subjected
to suitable statistical analysis following the procedures
described by Gomez and Gomez [24]. The least square difference
(LSD/CD) was worked out where variance ratio (‘F’ test) was significant
at 5% confidence level for source of variances.