Studies On Ecology And Biology Of Red Sprangletop [Leptochloa Chinensis (L.) Nees] And Its Management In Direct Seeded Rice
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Date
1997-03
Authors
Pane, Hamdan
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Abstract
Studies on the ecology and biology of red sprangletop [Leptcx;hloa chinensis
(l.) Nees] and its management in direct seeded rice were conducted at the laboratory
and the greenhouse of the School of Biological Sciences, Universiti Sains Malaysia'
(USM), Penang. Field surveys in the Muda ricefields and field trials at Alar Serdang,
the Training Farm of Muda Agriculture Development Authority (MADA), Kedah, were
also carried out.
Ecological studies from the survey conducted in 1994 showed that the whole
Muda ricefieldwas infested by 12 dominant weeds. The most dominant weed species
was L. chinensis which heavily covered 75% of the sampling sites. From soil seed
bank study, ten common weed species and seven other weed species which had
relatively low numbers of seed emergence were recorded. The total viability of seeds
germinated from the soil was about 29,551 seeds' m2 and it comprised 26.9% of L.
chinensis seeds. From life-table study, under treatment of. 135 kg N ha-1 the total
seed production from all survival adult individuals was 1,6 x 106 seeds. This value
was 2.4 times higher than the total production of seeds from all survival individuals
without nitrogen (0.67 x 106 seeds). Under substitutive competition with replacement
series experiment, based on Relative Yield Total (RYT) value, growth characters and
dry weight of straws were greater than 1.0. Ecologically, the values showed that both
species were trying to avoid competition, indicating that there was no significant
aggressiveness of red sprangletop competition against rice crop.
The populations of red sprangletop collected from Muda area and Balik Pulau
did not show much morphological differences. L. chinensis has three groYw1h stages;
first. slow growing stage [within the first 3 weeks after emergence (wae)]; second,
active growing stage (3 to 9 wae) and finally, maximum growing stage (9 to 15 wae).
M uda populations produced 0.95 x 105 to 1.09 x 105 seeds and Balik Pulau
populations produced 0.21 x 105 to 0.73 x 105 seeds, respectively. An additive
competition trial 'indicated that the rice yields declined significantly when the rice
plants competed with the weed at a density of 16 plants per-m2 and yield decreased
as the weed population increased. Evidently, the critical period for controlling red
sprangletop in direct seeded rice was initiated from 2 to 4 wae.
From a management aspect. the species could be suppressed with the flooding
from 2.5 to 5.0 cm water depth at 0 and 7 days after emergence·(dae). Different
rates of nitrogen were tested and the results showed that the competition of red
sprangletop in rice caused 39-48% yield reductions, irrespective of nitrogen level.
Nitrogen absorbtion by red sprangletop ranged from 0.03 to 0.13 g per-plant (4.0 to
21 kg N ha"1). Propanil and thiobencarb separately or mixed as an earty
postemergent herbicide controlled red sprangletop effectively. Foliar application of
fenoxaprop-P - ethyl proved to be the best among all tested herbicides.
Description
Keywords
Red Sprangletop [Leptochloa Chinensis (L.) Nees] , Seeded Rice