MSc

The study entitled “Directed application of pre and post emergence herbicides for
weed management in sesame (Sesamum indicum L.)” was undertaken during 2020-2022
at College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, with the objective to
evaluate the efficiency of pre and post-emergence directed application herbicides for
weed management, and their effect on growth, yield and phytotoxic effect on sesame
crop.
Field experiment was laid out at Onattukara Regional Agricultural Research
Station, Kayamkulam in Randomized Block Design with twelve treatments and three
replications during summer 2022 (02/02/2022 to 30/04/2022). Per emergence (PE)
oxyflourfen 80 g ha-1 at 2 DAS fb carfentrazone ethyl 20 g ha-1 at 25 DAS (T1), PE
oxyflourfen 80 g ha-1 at 2 DAS fb imazethapyr 50 g ha-1
at 25 DAS (T2), PE oxyflourfen
80 g ha-1
at 2 DAS fb mechanical weeding with wheel hoe weeder at 25 DAS (T3), PE
pendimethalin 500 g ha-1 at 2 DAS fb carfentrazone ethyl 20 g ha-1
at 25 DAS (T4), PE
pendimethalin 500 g ha-1 at 2 DAS fb imazethapyr 50 g ha-1
at 25 DAS (T5), PE
pendimethalin 500 g ha-1
at 2 DAS fb mechanical weeding with wheel hoe weeder at 25
DAS (T6), PE diclosulam 12.5 g ha-1
at 2 DAS fb carfentrazone ethyl 20 g ha-1
at 25
DAS (T7), PE diclosulam 12.5 g ha-1 at 2 DAS fb imazethapyr 50 g ha-1
at 25 DAS (T8),
PE diclosulam 12.5 g ha-1
at 2 DAS fb mechanical weeding with wheel hoe weeder at 25
DAS (T9), Mechanical weeding with wheel hoe weeder at 15 and 30 DAS (T10), Hand
hoe weeding at 15 and 30 DAS (T11) and weedy check (T12) constituted the treatments.
Herbicides were applied using crop protective herbicide applicator, and sowing was done
with seed cum fertilizer drill. The sesame variety used for the study was “Thilak”.
Weed management practices had significant effect on growth parameters viz.,plant
height at 40, 60 DAS and at harvest, number of branches at 60 DAS, and leaves and leaf
area per plant at 40 and 60 DAS, and DMP at 40, 60 DAS and at harvest. At 40, 60 DAS
and at harvest, the treatment T10 recorded the highest plant height. However, at 40 DAS,
T6 and at 60 DAS T10 recorded the highest number of leaves per plant. The treatment T10
recorded the highest leaf area per plant at 40 DAS, and at 60 DAS T4 recorded the
highest. At 60 DAS, T10 recorded the highest number of branches. However, DMP was
found to be the highest in T10 at all stages of observation (40, 60DAS and at harvest).
Among physiological parameters viz., RGR at 20-40 DAS and 40-60 DAS, CGR
at all time intervals, and LAI at 40 and 60 DAS were significantly influenced by weed
management practices. At 20-40 DAS and 40-60 DAS time interval T6 and T4 recorded
the highest RGR. However, T10 recorded the highest CGR at all time intervals. The
highest LAI was observed in T10 at 40 DAS and T4 at 60 DAS.
Days to 50 per cent flowering did not vary significant effect. The treatment T10
recorded the highest number of capsule per plant (43.8) and T6 recorded the highest
number of seeds per capsule (64.95).
Seed yield and haulm yield were significantly influenced by weed management.
The treatment T10 resulted in the highest seed yield (478 kg ha-1
) and haulm yield (1177
kg ha-1
) which was comparable with T6 and T4. Weed index was the lowest in T10 which
was followed by T6 and T4.
Organic carbon content, soil available N, P and K status of post harvest soils and
nutrient uptake by crop at harvest were significantly influenced by weed management.
The treatment T10 recorded the highest organic carbon content, soil available N, P and K
and also the highest total N (53.64 kg ha-1
), P (11.04 kg ha-1
) and K (31.67 kg ha-1
)
uptake by the crop at harvest.
Weed dry management profoundly influenced the nutrient uptake by weeds at 20,
40 and 60 DAS. The treatment, T11 recorded the lowest N removal by weeds (1.14 kg ha1
) at 20 DAS, T10 (4.16 kg ha-1
) at 40 DAS and T4 (6.46 kg ha-1
) at 60 DAS. The treatment
T10 recorded the lowest P removal by weeds at 20, 40 and 60 DAS (0.03, 0.17 and 0.48
kg ha-1
). The treatment T10 recorded the lowest K removal by weeds at 20, 40 and 60
DAS (0.25, 2.05 and 2.91 kg ha-1
).
The predominant weeds associated with sesame in the experimental field were
Echinochloa colona, Eleusine indica, Melochia corchorifolia and Cleome viscosa.
Weed dry weight was also significantly influenced by weed management. The
treatment T10 recorded the lowest weed dry weight at 20 and 40 DAS (13.64 g m-2
and
21.48 g m-2 , respectively). However at 20 DAS, T10 was statistically on par with T11 and
T6 and at 40 DAS T10 was statistically on par with T6 and T4. At 60 DAS, T6 recorded the
lowest weed dry weight (32.65 g m-2
) which was on par with T10 and T4.
Among the treatments, T10 recorded the highest weed control efficiency at 20 and
40 DAS which was followed by T11 and T6 at 20 DAS, T6 and T4 at 40 DAS. At 60 DAS,
T6 (77.19 %) recorded the highest WCE which was followed by T10.
The highest gross income was observed in the treatment T10 (Rs. 71,726 ha-1
)
which was comparable with T6, T4 and T11. However, the net return and B: C was recorded
highest in T6 (Rs. 37,070 ha-1
and 2.09) and remained at par with T4 and T10.
The yield and economics of treatments T10 , T6 and T4 were comparable. Hence the
study revealed the possibility of three weed management options for sesame. Mechanical
weeding with wheel hoe weeder at 15 and 30 DAS (T10) could be recommended as a non
chemical weed management practice. Pre emergence pendimethalin 500 g ha-1
at 2 DAS fb
wheel hoe weeding at 25 DAS (T6) could be recommended as an integrated weed
management practice and pendimethalin 500 g ha-1
at 2 DAS fb post directed application of
carfentrazone ethyl 20 g ha-1
at 25 DAS (T4) could be recommended as a chemical weed
management practices for higher yield and return in sesame.