Ecology of Some Weeds of Winter Crop Fields in Kathmandu Valley
Date
2021
Authors
Das Mallik, Baby Babita
Journal Title
Journal ISSN
Volume Title
Publisher
Department of Botany
Abstract
In Nepal, weeds cause yield loss up to 45% in the mustard (Brassica campestris L.)
field and 50% in wheat (Triticum aestivum L.), sometimes even more losses when the
weed population and density are higher. Usually, weeds are harmful but some may
have economic importance as organic compost, food or fodder, medicine, and
industrial uses. The use of invasive plants (like Ageratina adenophora (Spreng) King
& Rob. and Parthenium hysterophorus L.) and a native weed (Artemisia dubia Wall.
Ex. Besser), for preparing biofertilizer and their effect on weed and winter crops have
been investigated in the present study. The main objectives of the present study were
to understand the weed ecology in winter crop fields. Other important objectives were
to investigate the allelopathic effect of Artemesia dubia, Ageratina adenophora and
Parthenium hysterophorus to control selected weeds of winter crops by using aqueous
extract, compost extract, and their compost. The study was carried out at the wheat
and mustard fields of selected sites (Kirtipur, Bhaktapur, Godawari, Chapagaon,
Dharamsthali, and Shivapuri) during winter (Oct-March) in the year 2012-2014.
Based on the highest IVI value only four common weed species (Ageratum
conyzoides L., Bidens pilosa L., Cyperus rotundus L., and Galinsoga parviflora Cav.)
were selected for a further ecological studies like phenology, soil seed bank, seed
morphology, seed germination, and allelopathic effect. Altogether 40 plants of each
weed (Ageratum conyzoides, Bidens pilosa, Cyperus rotundus, and Galinsoga
parviflora) were randomly selected and their phenophase was carefully examined
from the germination stage to seed dispersal stage of plants using the phenological
index technique. The shape, color, and size (length and breadth) of the four common
weed seeds were measured under a compound microscope for weed seed morphology
study.
Seed germination experiment was conducted on environmental conditions like
moisture (content 3, 6, 9, 12, 15 ml), temperature (5, 10, 15, 20 and 25˚C), pH (value
4, 5, 6, 7, 8 and 9) and light (normal, red, yellow, blue, green and dark color). For the
crops, optimum moisture content (9 ml) was required. The experiments on seed
germination of moisture indicated that Cyperus rotundus and Galinsoga parviflora do
not require more moisture to germinate and grow. Seed germination of both crops
enhanced significantly at 15 to 20˚C treatments but all weed seeds were significantly
high at 10 to 15˚C. The percentage of seed germination of both crops Brassica
campestris and Triticum aestivum increased significantly in normal and green light. Seed germination of Ageratum conyzoides, Cyperus rotundus, and Galinsoga
parviflora was significantly different in normal, red, yellow, and green light.
Germination of all weed seeds was completely inhibited in blue and dark light. Seed
germination and seedling growth were higher in pH 5-7 in most cases. Seed
germination was also conducted with different concentrations (control, 1, 2.5, 5, 10%)
of chemical fertilizer solutions and different doses of fertilizer amended in soil
(control, 10, 20, 40, 50 g/kg soil). Seed germination of both crops and all the weeds
were mostly high in control and 1% of both urea and potash solution. The germination
of selected weed seeds reduced significantly with increasing concentrations of both
urea and potash in soil. The aqueous extracts vegetative parts of Ageratina
adenophora, Parthenium hysterophorus, and Artemisia dubia, their compost extract
(of the whole plant) of different concentration (control, 1, 2.5, 5, and 10%) and soil
amended with composts (of different doses 0, 10, 20, 40, and 50 g compost/kg soil)
were used to understand their effects on seed germination, seedling growth of crops
(Triticum aestivum, Brassica campestris) and the common weed. The aqueous and
compost extracts of Ageratina adenophora and Parthenium hysterophorus
significantly reduced seed germination and seedling length (shoot and root) with
increasing concentrations. The stem and leaf extracts of Ageratina adenophora
showed a more inhibitory effect on the seed germination of both winter crops and all
weeds as compared to root extract. In the soil amended with different amounts of
Ageratina adenophora and Parthenium hysterophorus compost showed more
reduction in seed germination among the weeds in comparison to both crop plants.
Seed germination of Cyperus rotundus was completely inhibited even at 1%
Parthenium compost extract and soil amended with 10 g/kg Parthenium compost. The
aqueous extract and compost extracts and compost of the native plant Artemisia also
significantly reduced seed germination, seedling length of both selected crops and
weeds, with increasing concentrations, but were less detrimental than the compost of
the other two invasive weeds. From this study, it was found that compost of Ageratina
adenophora and Parthenium hystrophorus at the rate of 20-40 g/kg soil was effective
to control the winter weeds. Hence the use of Ageratina adenophora and Parthenium
hysterophorus compost are suggested to use at low concentrations (20-40 g/kg soil) in
wheat or mustard fields, especially to control most of the common weeds. This
information suggests preparing compost from the invasive weeds which can act as
environmentally safe and cost-effective bio-herbicides along with an important
strategy for weed management.
Description
Keywords
Ecology, Winter Crop