INTEGRATED WEED MANAGEMENT IN FORAGE LUCERNE (Medicago sativa L.)
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Date
2009
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
A field experiment was conducted on “Integrated weed management
practices in forage Lucerne (Medicago sativa L.)” during rabi 2008-09 at
Students Farm, College of Agriculture, Rajendranagar, Hyderabad. The
treatments consisted of salt (10 %) treatment to seeds of lucerne + farmers
practice, salt (10 %) treatment to seeds + imazethapyr @ 75 g a.i. ha-1 at 12
DAS, salt (10 %) treatment to seeds + pendimethalin @ 0.5 kg a.i. ha-1 at 12
DAS, stale seed bed + hand weeding at 30 DAS, pendimethalin @ 0.5 kg and
0.75 kg a.i. ha-1 as PE, imazethapyr @ 75 g and 100 g a.i. ha-1 at 12 DAS, pure
seed of lucerne + farmers practice, farmers practice (Hand weeding at 30 DAS
and after each cut), weedy check and weed free check. The experiment was
laid in RBD replicated thrice.
Weed flora found in different treatmental plots include Cyperus
rotundus, Cynodon dactylon, Dactylactenium aegyptium, Parthenium
hysterophorus, Chicorium intybus, Digera arvensis, Euphorbia hirta and
Trichodesma indicum and one parasitic weed Cuscuta chinensis. The
experimental results indicated that application of imazethapyr @ 100 g a.i.
ha-1 at 12 DAS reduced the density of Parthenium hysterophorus but weed
shift was observed towards grasses and sedges. Application of pendimethalin
at higher dose (0.75 kg a.i. ha-1) was found effective than lower dose (0.5 kg
a.i. ha-1) in controlling broad leaved weeds and it was not effective against
grasses and sedges.
Weed density and weed dry weight of weeds (excluding cuscuta) was
significantly lower with weed free check and higher with weedy check
treatment throughout the study period. Next to weed free check treatment,
mean weed density was found significantly lower with the application of
imazethapyr @ 100 g a.i. ha-1 at 12 DAS and was found on par with sowing
pure seed of lucerne fb farmers practice of weed control, farmers practice
alone (hand weeding at 30 DAS and after each cut), and application of
pendimethalin @ 0.5 and 0.75 kg a.i. ha-1 as PE showed higher weed control
efficiency over the remaining treatments. Dry weight of weeds recorded by
sowing pure seed of lucerne fb farmers practice of hand weeding at 30 DAS
and after each cut and application of imazethapyr @ 75 and 100 g a.i. ha-1
applied at 12 DAS was found on par with that of weed free check treatment at
30 DAS and recorded higher weed control efficiency. Application of
pendimethalin @ 0.5 and 0.75 kg a.i. ha-1 as PE or in combination with salt
(10 %) treatment to seeds was found less effective in reducing the dry weight
of weeds over imazethapyr and registered lower weed control efficiency.
Cuscuta chinensis was completely prevented by application of
pendimethalin @ 0.5 and 0.75 kg a.i. ha-1 as PE or imazethapyr @ 75 and 100
g a.i. ha-1 at 12 DAS, salt (10 %) treatment to lucerne seeds + pendimethalin
@ 0.5 kg a.i. ha-1 or imazethapyr @ 75 g a.i. ha-1 at 12 DAS and sowing pure
seed of lucerne fb farmers practice of hand weeding at 30 DAS and after each
cut. Salt (10 %) treatment to seeds + farmers practice and stale seed bed +
hand weeding at 30 DAS registered lower dry weight of cuscuta and high
cuscuta control efficiency than farmers practice, weedy and weed free check
treatments at all the three cuts.
Plant stand of lucerne recorded at 25 DAS was higher with sowing of
pure seed of lucerne fb farmers practice of hand weeding at 30 DAS and afer
each cut and was found on par with all other treatments, except pendimethalin
@ 0.5 and 0.75 kg a.i. ha-1 applied as PE and @ 0.5 kg a.i. ha-1 applied at 12
DAS in combination with salt (10 %) treatment to lucerne seeds due to
phytotoxicity effect on germination and plant stand of lucerne. Average plant
height of lucerne over the three cuts was significantly higher with sowing pure
seed of lucerne + farmers practice of hand weeding at 30 DAS and after each
cut and was found at par with all herbicide applied treatments (T2, T3, T5, T6,
T7 and T8) and salt (10 %) treatment to lucerne seeds fb farmers practice. Leaf
stem ratio of lucerne was not influenced by integrated weed management
practices at all the three cuts.
Total green, dry and crude protein yield of lucerne (Total of 3 cuts) was
significantly higher with application of imazethapyr @ 75 g a.i. ha-1 at 12
DAS and was found on par with pure seed of lucerne fb farmers practice of
hand weeding at 30 DAS and after each cut, salt (10 %) treatment to seeds +
imazethapyr @ 75 g a.i. ha-1 at 12 DAS. Application of pendimethalin @ 0.5
and 0.75 kg a.i. ha-1 as PE and in combination with salt (10 %) treatment to
seeds applied at 12 DAS observed significantly less green, dry and crude
protein yield of lucerne. Salt (10 %) treatment to lucerne seeds fb hand
weeding at 30 DAS and after each cut alone recorded less total green and dry
fodder yield but its combination with pendimethalin @ 0.5 kg a.i. ha-1 and
imazethapyr @ 75 g a.i. ha-1 at 12 DAS increased green and dry fodder yield
to an extent of 40.0 and 64.0 per cent over above treatment. Lowest green, dry
and crude protein yield of lucerne was recorded with weedy check treatment
and was found on par with farmers practice, stale seed bed + hand weeding at
30 DAS.
Lower mean weed index was observed with imazethapyr @ 75 g a.i.
ha-1 applied at 12 DAS and was closely followed by pure seed of lucerne fb
hand weeding at 30 DAS after each cut, salt (10 %) treatment to seeds +
imazethapyr @ 75 g a.i. ha-1 at 12 DAS and application of imazethapyr @ 100
g a.i. ha-1 at 12 DAS respectively.
Residues of pendimethalin or imazethapyr were not detected in green
fodder of lucerne as both the herbicides were degraded completely by the time
lucerne was harvested (68 DAS). Gross, net returns and benefit cost ratio were
higher with application of imazethapyr @ 75 g a.i. ha-1 at 12 DAS and was
closely followed by salt (10 %) treatment to seeds + imazethapyr @ 75 g a.i.
ha-1 at 12 DAS. Sowing pure seed of lucerne fb farmers practice of hand
weeding at 30 DAS and after each cut gave higher gross and net returns but
benefit cost ratio was less due to increased cost on hand weeding.
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Keywords
INTEGRATED, WEED, MANAGEMENT, FORAGE, LUCERNE