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Studies on pre- and post-emergence use of metribuzin in soybean and its after effects on succeeding wheat

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Title Studies on pre- and post-emergence use of metribuzin in soybean and its after effects on succeeding wheat
M Sc
 
Creator MANGAL DEEP TUTI
 
Contributor T.K. Das
 
Subject weeds, heterocyclic compounds, soybeans, wood, yields, control methods, herbicides, wheats, tillage, sowing
 
Description T-8346
Heavy weed infestation poses enormous challenge for soybean production. Herbicide,
among weed control options, is often cost-effective, easier to apply and an efficient tool. Metribuzin
is an effective herbicide for soybean, but used exclusively as pre-emergence, which usually fail to
control late-emerging weeds. This necessitates the use of metribuzin as post-emergence, but has
hardly been studied in India or elsewhere. Therefore, a field experiment with 13 weed control
treatments was laid out in a randomized block design with three replications during the rainy (kharif)
and winter (rabi) seasons of 2006-07 and 2007-08 at the Indian Agricultural Research Institute, New
Delhi to develop an efficient and economical way of controlling weeds through sequential
application of metribuzin (pre-emergence followed by post-emergence), and to evaluate postemergence
metribuzin for toxicity to non-target microorganisms, defence mechanism in soybean and
residual effect in wheat. In wheat, previous rainy season weed control treatments were supplemented
with two sub-plot treatments viz. conventional and zero-tillage. The soil was sandy loam, pH 7.6,
organic C (0.52%), medium in available N (272.6 kg/ha), medium in P (18.4 kg/ha) and K (191.6
kg/ha).
Result revealed that pre-emergence metribuzin at 0.5 kg/ha was most effective in controlling
wide-spectrum of weeds including Cyperus rotundus L in soybean, and caused an increase in weed
control efficiency and soybean seed yield. It also resulted in a significant reduction in the removal of
N, P and K by weeds. Metribuzin as post-emergence irrespective of dose (0.1 and 0.2 kg/ha), volume
rate (200 and 400 l/ha) or time of application (20 and 30 days after sowing/DAS) did not affect
number and dry weight of nodules in soybean. These treatments, however, inhibited acetylene
reduction, dehydrogenase activity and total microbial population up to 20 days of their application.
All metribuzin treatments except the pre-emergence treatment with 0.5 kg/ha had negligible amount
of residue in soil at harvest of soybean, indicating safe use of metribuzin as post-emergence in
soybean without carry-over effect to wheat. Decreased photosynthesis rate, and increased activities
of superoxide dismutase and ascorbate peroxidase in the sequential applications of metribuzin
irrespective of dose, volume rate and time of application indicated possible defence mechanism in
soybean, which resulted in negligible phytotoxicity to soybean plants. Weed density in wheat during
winter was not significantly affected due to weed control measures adopted in the previous season,
especially between the sequential applications of metribuzin. However, conventional tillage resulted
95
in significant weed suppression compared to zero tillage. Higher weed growth under zero tillage
reduced nutrient uptake and yield of wheat.
Pre-emergence metribuzin at 0.5 kg/ha, and sequential application of metribuzin with 0.25
kg/ha pre-emergence followed by 0.1 kg/ha post-emergence with a 200 l/ha volume rate applied at
20 DAS gave higher weed control efficiency and soybean yield. Therefore, either of these two
treatments is worth recommending. However, considering the possibility of greater phytotoxicity to
soybean plants, higher residue in soil, and greater reduction in microbial populations at a higher dose
aside from the higher cost, the pre-emergence application of metribuzin with 0.25 kg/ha followed by
0.1 kg/ha post-emergence with a 200 l/ha volume rate applied at 20 DAS, which is comparable with
pre-emergence metribuzin at 0.5 kg/ha on almost all the variables of weeds, soybean and wheat
studied, may be recommended. Certain weed control measures, however, must be adopted with
conventional or zero tillage for economic and sustainable wheat cultivation.
 
Date 2016-10-24T10:19:05Z
2016-10-24T10:19:05Z
2010
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/81441
 
Format application/pdf
 
Publisher IARI, DIVISION OF AGRONOMY