Abstract:
A study was conducted to find out the suppressing ability of floating weeds in T. aman
rice (Oryza sativa L.) at the Agronomy field of Sher-e-Bangla Agricultural University,
Dhaka, Bangladesh from July 2019 to December 2019. The experiment consisted of
two factors viz. rice varieties (3) i.e. Tulshimala, BR11(Mukta) and BRRI hybrid
dhan6, and weed management (4) i.e. weedy check (control), Integrated Weed
Management (one pre-emergence herbicide Pretilachlor 6% + pyrazosulfuron 0.15%
and one hand weeding), spreading of Water Lettuce (Pistia stratiotes), Duckweed
(Lemna minor) and Kariba weed (Salvinia molesta) in 0.5 m
ii
2
area. The experiment was
laid out in a split-plot design with three replications. The ranking of the relative rate of
spreading (RRS) over the experiment L. minor > S. molesta > P. stratiotes. A total of 6
weed species representing 5 families were found from the transplanting to the later stage
of rice growth where the occurrence of weed infestation related to rice variety and crop
growth. BRRI hybrid dhan6 significantly suppressed weeds in related plots. Integrated
weed management successfully control all weeds and gave the highest weed control
efficiency and weed control index. Although weed biomass significantly reduced, the
morphological and biomass characteristics of T. aman rice varieties got disadvantages
when grown with P. stratiotes and S. molesta. Cultivation of BRRI hybrid dhan6 along
with weed control through integrated weed management gave the highest grain yield
(5.92 t ha
-1
) and the highest economic return comparable to other treatment
combinations. However, the spreading of L. minor facilitated optimal weed control and
good yields were harvested without significant differences and as well as net return
irrespective of varieties. Therefore, weed competitive variety should be considered
along with the spreading of L. minor to reduce herbicide loads in the environment and
to the evolution of cross-resistant weed populations.
Description:
A Thesis
Submitted to the Department of Agronomy, Faculty of Agriculture,
Sher-e-Bangla Agricultural University, Dhaka in partial
fulfillment of the requirement for the degree of
MASTER OF SCIENCE (MS)
IN
AGRONOMY
