ABSTRACT
Due to lack of information, a phyto-sociological survey was conducted
in wastelands of Raipur district during kharif 1996 to 1998. The survey revealed that
about 27 weed species were found associated with Parthenium hysterophorus during
rainy season. Among all weeds, Parthenium hysterophorus and Cassia tora had high
degree of sociability and formed into large colonies under arable soil habitats. The data
on distribution pattern revealed that Parthenium hysterophorus, Cassia tora and
Achyranthes aspera recorded higher Importance Value and were found dominant. The high
relative dominance of Parthenium was attributed to its high frequency,
aggressiveness and allelopathic effects on neighbouring plants. The study suggested that
there is strong need to start an Integrated Parthenium Management Programme in district.
INTRODUCTION
"A weed is a plant growing where it is not desired" Jethro
Tull (1731) was the first person to use the word weed in this sense in literatures in his
famous writing on ‘Horse Hoeing Husbanbandry’. This definition of weed, does not
identify a particular portion of plant kingdom as weedy. Rather, it tags the weedy nature
of a plant to the situation in which it occurs and the human attitude towards it ( Gupta,
1984). In general,weeds are considered as unwanted plants. Weeds compete with crops for
light, moisture and nutrients and harbour diseases and pests harmful to crops ( Oudhia et
al., 1999). Parthenium hysterophorus, locally known as Gajar ghas or Congress weed,
is one of the common wasteland weeds of Chhattisgarh( Oudhia, 1998). Parthenium
causes severe human health problems as well as agricultural losses. Parthenium and
related genera contain sesquiterpene lactones which induce severe allergic dermatitis and
other symptoms. In India, Parthenium weed causes yield losses upto 40 per cent in
several crops ( Adkins et al., 1998). Lethal allelopathic effects of Parthenium on
many agricultural crops including chickpea ( Oudhia et al., 1997a), kodo, mustard(Oudhia
and Tripathi, 1998), linseed ( Oudhia et al., 1997b) etc., have been reported.
Chhattisgarh is rich in bio-deversity ( Oudhia and Tripathi, 1999). Parthenium is
becoming a curse for this bio-diversity. Due to non-availability of any information, a
phyto-sociological survey of rainy season wasteland weeds with special reference to Parthenium
was conducted by Department of Agronomy, Indira Gandhi Agricultural University, Raipur
(India) during 1996-98.
MATERIALS AND METHODS
A detailed floristic survey using multistage random sampling was
conducted during rainy seasons in Raipur districts. Raipur is situated at 21. 160 N latitude and 81.360 E longitude with an altitude of
289.56 m above the mean sea level in the South-Eastern part of Madhya Pradesh (India). The
annual rainfall in this region ranges from 1200 to 1400 mm. Weed studies were made
following list count method suggested by Raju and Reddy (1998) using 50x50 cm quadrate.
Sampling was done randomly at 70 spots in various situations. The compiled data were
analysed for quantitative and qualitative studies using Following formulae:
|
1. Absolute
density |
= Total no.of individuals of a species in all quadrates |
Total no. of quadrates
employed |
|
2. Relative
density ( %) |
= Absolute density for a given species x 100 |
Total absolute density for
all species |
|
3. Absolute
frequency (%) |
= AQuadrates in which species occurs x 100 |
Total no. of quadrates
employed |
|
4. Relative
frequency (%) |
= Absolute frequency value for a species x 100 |
Total absolute frequency
values for all species |
|
5. Importance
value (IV) |
Relative density + Relative frequency |
|
|
6. Summed
Dominance Ratio ( SDR) |
Importance
value |
| 2 |
|
|
RESULTS AND DISCUSSION
The study revealed that more than 28 weed species ( belong to more than
8 families ) grow naturally during rainy season in wastelands of Raipur district. Data
presented in Table 1 reveal that Parthenium hysterophorus and Cassia tora
have high degree of sociability and formed into large colonies under arable soil habitats.
Several large sized weeds like Datura stramonium, Jatropha glandulitera and Calotropis
gigantea were found as isolated individuals in weed community. Data portrayed in Table
2 on the distribution pattern revealed that Parthenium hysterophorus, Achyranthes
aspera and Cassia tora recorded higher importance values and were found
dominant. It is clear from the data ( Table 2) on summed dominance ratio that Parthenium
hysterophorus registered the maximum value followed by Achyaranthes aspera and Cassia
tora. The high relative dominance of Parthenium hysterophorus was attributed to
its high frequency, aggressiveness and allelopathic effects on neighbouring plants. The
small statured weeds like Parthenium hysterophorus and Paspalidium punctatum
had lower Importance Values.
Wastelands are a potential source of naturally growing medicinal
plants. The increasing infestation of Parthenium in wasteland as observed during
the study, is smothering and inhibiting the useful native flora. It was also observed that
heavy Parthenium infestation inwasteland is serving as year round seed bank for
adjacent agricultural fields. The study suggested that there is a strong need to start an
Integrated Parthenium Management Programme (IPMO) in order to root out the Parthenium
weed, a curse for bio-diversity, from the wastelands of Raipur distict.
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