Alelopatia Malezas

Crop Protection 21 (2002) 699–705

Allelopathic response of Phalaris minor to crop and weed plants
in rice–wheat system
Hari Om, S.D. Dhiman*, Sajjan Kumar, Hemant Kumar
CCS Haryana Agricultural University, Rice Research Station, Kaul, Kaithal 136 021, India
Received 17 April 2001; received in revised form 15 January 2002; accepted 24 January 2002

Abstract
Green manuring of sunflower anddhaincha reduced plant population of Phalaris minor 100 per cent under lab and 42 per cent and
15 per cent, respectively, under field conditions, thus, indicating the inhibitory role of allelo-chemicals. Grain yield of wheat was
significantly higher with the green manuring of sunflower and dhaincha before rice transplanting over summer fallow. The
allelopathic potential of broad-leaved weeds ofwheat in inhibiting germination of P. minor was in the order of Chenopodium
album = Medicago denticulata = Melilotus indica = Convolvulus arvensis (100 per cent inhibition)>Vicia hirsuta (86 per cent)>
Cirsium arvense (48 per cent) > Lathyrus aphaca (38 per cent) > Rumex acetosella (9 per cent). Exudates of rice cultivars HKR 126,
IR 64, Jaya and Haryana Basmati-1 registered >50 per centinhibition of germination of P. minor. As the extract was diluted, effect
of non-scented cultivars considerably reduced in comparison to scented group. Out of 11 wheat varieties, WH533 provided the
highest inhibition of germination (30 per cent) followed by WH542 (21 per cent). r 2002 Published by Elsevier Science Ltd.
Keywords: Allelopathy; Phalaris minor; Sunflower; Broad-leaved weeds; Rice–wheatsystem; Cultivars

1. Introduction
Wheat is grown on nearly 12 million ha in rotation
with rice in Indo-Gangetic plains of South Asia (Malik
et al., 1998). Rice–wheat rotation has become most
popular in assured irrigated areas of north western India
particularly the states of Punjab, Haryana and western
UP considered as grain bowl of the country. P. minor is
the most dominant weed of wheatcrop in this system
(Bir and Sidhu, 1979; Malik et al., 1981, 1985; Singh
et al., 1995; Bhan and Kumar, 1997). The continuous
use of isoproturon for more than a decade has resulted
into the evolution of resistance biotypes of this weed
(Malik and Singh, 1993, 1995; Walia et al., 1997; Singh
et al., 1999). Besides this, the rotation uses large
quantities of herbicides which has resulted inseveral
problems (environmental pollution, human and animal
health hazards). One of the alternatives to overcome
these problems is with the use of allelopathic strategies
for sustainable agriculture.
*Corresponding author. Tel.: +91-1746-84614; fax: +91-174684550.
E-mail address: hemant2k4v@yahoo.com (S.D. Dhiman).
0261-2194/02/$ - see front matter r 2002 Published by Elsevier Science Ltd.PII: S 0 2 6 1 - 2 1 9 4 ( 0 2 ) 0 0 0 2 5 - X

A number of weed and crop plants have been reported
to acquire allelopathic potential that affects the growth
of other plant species (Rice, 1984). Many plants have
allelopathic activity and release exudates from living
tissues or by decomposition of plant residues which
influence other plants in their surrounding vicinity
(Putnam, 1986; Mahalland Callaway, 1991; Inderjit,
1996; Einhellig, 1996; Noguchi, 2000).
Information is available on the allelopathic effect of
weeds on crop plants (Singh et al., 1988; Angiras et al.,
1988, 1988a; Das and Choudhury, 1996), crop plants on
weeds (Narwal and Sarmah, 1996; Das and Das, 1998;
Steinseik et al., 1982), weeds on weeds (Tripathy and
Vaishya, 1997, 1999) or crops on crops (Putnam andDuke, 1978; Barnes and Putnam, 1986). But the
information is lacking on the allelopathic influence of
companion weeds in a crop, alternate crops in the
cropping system as the seed remains exposed to the
allelo-chemicals released by the stubble or root stocks of
these crops in the cropping sequence.
Besides this, depleting fertility and degradation of the
soil physical condition in...