Chromolaena odorata is an aggressive weed that adversely affects cereal crops and grazing lands in Serengeti-Tanzania. This study investigated allelopathic. Allelopathic Effects of Chromolaena odorata (L.) King & Robinson on Seed Germination and Seedlings Growth of Paddy and Barnyard Grass. Fulltext – Effect of Chromolaena odorata on the Growth and Biomass Allelopathy is defined as the direct or indirect harmful or beneficial effect of one plant on.

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Adetayo 1O. Lawal 2B.

Alabi 1 and O. Siam weed plants comprising of leaves and stems were cut, pounded with pestle and mortal. Five kg of the product was soaked in 20 litres of distilled water for a period of four days 96 allelopatuic. Seeds of three crops — corn maize var. Ife brown and soybean var. Tax E and two weeds — Siam weed and tridax Tridax procumbens L. The seeds were tested for germination with or without extract.

Weed and crop seedlings were also established in extract treated or distilled water medium and their growth was monitored. Weed seed germination was inhibited by siam weed extract more than crop seed germination.

Maize seed germination was not hindered by siam weed extract while on cowpea and soybean, 14 and 8 percent reduction in seed germination, respectively was recorded when compared with the untreated control.

Siam weed extract had some inhibitory effect on soybean growth at the later stage of crop growth, while the growth of maize, cowpea, tridax and siam weed itself was stimulated by siam weed extract. Siam weed extract inhibited seed germination of weeds and crops and stimulated the growth of certain crops. allelooathic

Siam weed Chromolaena odorata L King and Robinsona perennial weed belongs to the family Asteraceae. It easily takes over plantations of cocoa, plantain, oil palm, rubber and other long season crops. Observations reveal that in areas where siam weed grows, growth of other plants is always hampered Akobundu It is not yet clear whether allelopathy is responsible for such a growth behaviour.

Many of the allelochemicals are water soluble substances released into the environment through leaching, root exudation, volatilization and decomposition of plant residues and are affected by several environmental factors Reigosa et al. According to Maciasthe application of naturally occurring allelopathic substances which are ecologically friendly to agricultural practice is a promising method to control weeds.

Allelopathy was used by Chung et al.

Ahn and Chung and Chuo used allelopathy as an ecological control tool against several weeds in rice. The objective of this allekopathic was therefore xhromolaena determine the effect of siam weed extract on the germination and seedling performance of some crop and weed species.

Laboratory and greenhouse experiments were conducted at I. Tax E and two weeds — siam weed and tridax Tridax procumbens L. Water was used because most allelochemicals are water soluble Reigosa et al.

The composition was sieved and the chrojolaena was kept in a refrigerator at 5 o C for subsequent experiments. Seeds of the five plants, either treated with siam weed extract or untreated comprised the treatments.


A Petri dish was lined with sterilized filter paper for each treatment. Four replicates of each dish were made. Twenty five seeds of each of allelopzthic three crop plants were placed in respective Petri dishes because of larger crop seed size while 50 seeds of each weed were placed in respective Petri dishes. Treated Petri dishes were each supplied with 25 ml of extract while the untreated control was treated with 25 ml of distilled water.

Germinated seeds defined as emergence of radicle were counted 4 days after onset of the experiment and this was continued for a period of seven days thereafter. The greenhouse experiment was to determine the effect of siam weed extract on the germination and growth of the seeds of the crop and weed species in a soil medium. Seeds of the five plants, either treated with siam weed extract or untreated were used as treatments.

Five replications of each treatment were made. Five kg capacity polyethylene bags were filled with air-dried loamy soil. Twenty five weed seeds were planted approximately 1cm deep, while fifty crop seeds were planted 3 cm deep. Extract solution ml was added to treated pots, while distilled water was used as control.

The pots were watered every other day with ml distilled water. Record of germination percentage was taken for each seed type. Seedlings were thinned to 4 plants per pot 3 weeks after planting WAP. Data on crop plant height and number of leaves were taken at weekly intervals from 3 to 6 WAP. Data on weeds could not be taken at this period because weed growth was slow. At 4 and 6 WAP for seedlings and 8 and 10 WAP for weed seedling, samples were randomly harvested, dried and weighed to determine dry matter content.

Separate T-tests were chromloaena on the treated and untreated plants, according to the type of plant. Crop seed germination was generally less affected by siam weed extract than was weed seed germination Table 1. In the Laboratory, maize seed germination was not hindered by siam weed extract. On cowpea and soybean, 14 and 8 percent reduction in seed germination, respectively was recorded when compared with the untreated control.

Germination of tridax was poor and therefore the effect of the treatment could not be ascertained. The same trend of germination was maintained in the greenhouse except that the weed seed chgomolaena better chromllaena in the laboratory. Various biological, chemical and physical components may be responsible. Akobundu listed factors such as soil temperature, soil moisture regime, alternate wetting and drying of soil, soil nitrate level among others as those that affect seed germination.

Although, the effect was slight on crop seeds and more on weed seeds, this report is alleelopathic by the findings of Oke that siam weed extract inhibited the germination of seeds of cowpea, soybean and tridax.

The inhibitory effect of siam weed extract on germination of its seed is in agreement with the findings of Bhowmik and Doll and Johnson and Harold who observed that many weed species exhibit allelopathic autotoxic effects on the germination of their own seeds. Time Weeks After Planting. Weed growth in terms of height and number of leaves could not be assessed because the weeds generally had slow growth and were too tiny to be handled up till 6 weeks of growth assessment.


This could not be attributed to the detrimental effect of siam weed extract as the untreated plants were equally affected but to the growth characteristic of the weeds.

Alabi had indicated that the stem girth and number of branches in thorny mimosa Mimosa invisa Mart could not be assessed until 6 weeks after establishment due to small plant size. Results of weed dry weight assessed at 8 and 10 WAP Table 4show that the growth of tridax and siam weed was stimulated by the extract of siam weed from 8 and 10 WAP and after, respectively.

Journal of Applied Sciences and Environmental Management

However, this stimulatory effect of siam weed extract would not benefit weeds which germination has been marked prevented Table 1. The domination of a habitat by siam weed therefore, may be mainly due to weed seed population reduction. Leather gave a similar report that sunflower Helianthus annuus L.

Soybean plant height and number of leaves were not affected by siam weed extract Tables 2 and 3. However, the crop dry weight at 10 WAP was markedly inhibited by the extract Table 4. Maize height and number of leaves in cowpea were stimulated from 5 WAP by siam weed extract. Cowpea dry weight assessment at 10 WAP also shows that the crop growth was stimulated by siam weed extract.

These observations agree with the findings of Rahman and Sabagyowho obtained a stimulated growth of rice plants on soil containing allelopathkc spear grass Imperata cylindrica Anderss. Allelopathic potential of rice hulls on germination and seedling growth of barnyard grass. Agronomy Journal 99, Thesis, University doorata Ibadan.

Weed Science in the tropics: John Whiley and Sons; pp. Corn and Soybean response to allelopathic effects of weed and residues. Agronomy Journal 74, Allelopathy and Sustainable Agriculture. ACS symposium series American chemical society, Washinton, DC. Assessment of Allelopathic potential of barnyard grass Echinochloa crus-galli on rice oryza sativa L. Crop Protection 20— Effect of three weed residues on weed and crop growth.

Weed Science 34 Sunflowers Helanthus annus are allelopathic to weeds. Weeds Science 31, Allelopathy in the search for natural herbicide model. The allelopathic potential of Chromolaena odorata on seed germination and seedling allelpoathic of vigina unguiculata var.

July | Australian Journal of Crop Science

Rahman M and Subagyo T The effects of alang-alang Imperata Cylingrica L. Ecological approach in allelopathy. Critical Review in Plant Science 18, Log In Sign up!

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