TY  - BOOK
AU  - Thumu Venkateswara Reddy
AU  - Meera V Menon (Guide)
TI  - Bio-efficacy of tank mixed herbicides and urea in wet  seeded rice 
U1  - 630 
PY  - 2021///
CY  - Vellanikkara 
PB  - Department of Agronomy, College of Agriculture
KW  - Agronomy
KW  - Bio-efficacy
N1  - PhD
N2  - The use of herbicides has become an indispensable part of agriculture, 
particularly in rice cultivation, where weeds are the most harmful of the biotic 
constraints to production. A usual practice among rice farmers in the Kole lands of 
Kerala is the tank mixing of herbicides, for a broader spectrum of weed control, 
enhanced weed control efficiency and reduction in the cost of application. However, 
mixing of herbicides is done without any knowledge of the probable synergistic or 
antagonistic interactions on weed flora. Herbicides are also mixed with fertilizers like 
urea under the common belief that herbicidal efficiency is enhanced by this practice. 
Application of herbicides may affect various plant pathogens and microbial 
bioagents which occur naturally in the rice ecosystem. Information of the effect on 
main disease causing as well as beneficial microorganisms would help in selecting 
appropriate herbicides. 
Hence the major objectives of the research programme entitled “Bio-efficacy 
of tank mixed herbicides and urea in wet seeded rice” were to study the synergistic or 
antagonistic effect of tank mixing of commonly used herbicides, and to evaluate the 
efficiency of these herbicides on mixing with urea, on major weeds of rice. The effect 
of these herbicides on beneficial and pathogenic microorganisms were also 
investigated. 
Two field experiments were conducted at Alappad padasekharam in the Kole
lands of Thrissur from October to January 2019-20 and 2020-21. The soil of 
experimental field was clayey in texture, high in organic carbon (1.1-1.3%), low 
available nitrogen (180-188 kg/ha), and medium phosphorus (20-21.5 kg/ha) and 
potash (152-159 kg/ha), with a soil pH of 4.5-4.7. The feasibility of mixing herbicides 
was evaluated in experiment I (Bio-efficacy of tank mixed herbicide combinations in 
wet seeded rice). There were fourteen treatments and they included tank mixtures and 
sequential applications of five herbicides viz., fenoxaprop-p-ethyl (0.06 kg/ha), 
(chlorimuron-ethyl + metsulfuron-ethyl) (0.004 kg/ha), carfentrazone ethyl (0.02 
ii 
kg/ha), bispyribac-sodium (0.025 kg/ha), and (cyhalofop-butyl + penoxsulam) (0.15 
kg/ha). These were compared with two broad spectrum herbicides, bispyribac-sodium 
(0.025 kg/ha) and (cyhalofop-butyl + penoxsulam) (0.15 kg/ha), as well hand weeded 
and unweeded controls. In experiment II (Bio-efficacy of tank mixed herbicides and 
urea in wet seeded rice), there were twelve treatments. Six herbicides, viz., cyhalofop 
butyl (0.08 kg/ha), (cyhalofop butyl + penoxsulam) (0.15 kg/ha), bispyribac-sodium 
(0.025 kg/ha), fenoxaprop-p-ethyl (0.06 kg/ha), carfentrazone ethyl (0.02 kg/ha) and 
(chlorimuron ethyl + metsulfuron methyl) (0.004 kg/ha) were applied with and 
without urea (1%) mixing. Hand weeded and unweeded controls were also included 
for comparison. Randomized Block Design with three replications was adopted for 
both experiments. Wet seeding of rice at the seed rate of 100 kg/ha was done. 
Nitrogen, phosphorus and potassium @ 90:35:45 kg/ha were supplied through urea, 
factomphos and muriate of potash (KAU, 2016). 
In experiment III (In vitro evaluation of herbicides on beneficial and 
pathogenic microorganisms) treatments included the effect of herbicides mentioned in 
experiment II which were evaluated under in vitro conditions with recommended, 
higher and lower doses on beneficial microbial bioagents (Trichoderma viride and 
Pseudomonas fluorescens) and pathogenic microorganisms (Rhizoctonia solani, 
Pyricularia oryzae and Xanthomonas oryzae pv. oryzae). Factorial Completely 
Randomized Block Design was adopted with 18 treatments and three replications 
each.
Tank mixing of herbicides was found to be more effective than their sequential 
application for most of the combinations. Tank mixed combination of (cyhalofopbutyl + penoxsulam) with (chlorimuron-ethyl + metsulfuron-methyl) showed 
synergistic effect and had lowest weed density (32, 16 and 20 nos./m2
), lowest weed 
dry matter production (14.68, 50.50 and 88.95 kg/ha), and highest weed control 
efficiency (91, 88, and 82%) at 15, 30 and 60 days after application respectively. The 
number of tillers per sq. m (411), number of panicles per sq. m (288), number of 
grains per panicle (103), percentage of filled grain (91.6) at harvest, nutrient uptake 
by rice at 60 DAS (105.06, 14.32 and 74.28 kg/ha of N, P and K respectively), grain 
iii 
yield (3.97 t/ha), net returns (Rs.71,406/ha) and benefit: cost ratio (2.25) were highest 
in the same treatment. The next best treatment was fenoxaprop-p-ethyl + bispyribac 
sodium. 
On tank mixing of herbicides with urea, bispyribac-sodium and urea interacted 
synergistically, resulting in highest weed control efficiency (82.5 and 78% at 15 and 
30 days after application respectively), highest grain yield (5.03 t/ha), and profitability 
(Rs. 93,509/ha) over the other treatments. Mixing of (cyhalofop-butyl + penoxsulam) 
with urea could also be recommended for good results (grain yield of 4.94 t/ha and net 
returns of Rs.87,463/ha). 
In vitro evaluation of herbicides revealed that bispyribac-sodium and 
(cyhalofop-butyl + penoxsulam) had greatest inhibitory effect on pathogenic 
microorganisms Rhizoctonia solani and Pyricularia oryzae, but showed no effect on 
Xanthomonas oryzae pv. oryzae, and were less harmful to biocontrol agents 
Trichoderma viride and Pseudomonas fluorescens at recommended doses. 
 Tank mix combination of (cyhalofop-butyl + penoxsulam) with (chlorimuronethyl + metsulfuron-methyl) was the best treatment with compatibility, efficient weed 
control, high grain yield and net returns. Tank mixing of bispyribac-sodium with urea 
1% had synergistic effect resulting in highest weed control efficiency, production and 
profitability over the other treatments. Mixing of (cyhalofop-butyl + penoxsulam) 
with urea 1% could also be recommended for good results. Bispyribac-sodium and 
(cyhalofop-butyl + penoxsulam) were the best herbicides on in vitro evaluation in 
their effect on pathogenic microorganisms Rhizoctonia solani and Pyricularia oryzae, 
and at recommended doses were compatible with biocontrol agents Trichoderma 
viride and Pseudomonas flourescens
UR  - https://krishikosh.egranth.ac.in/handle/1/5810195868
ER  -