![]()
Genomics and Applied Biology 2015, Vol. 6, No. 3, 1-14
http://gab.biopublisher.ca
9
Weed seed bank in the soil are exposed to various
influences and changes and the result
of its studies
provide immediate, but not general insight into the
situation in the field
(Menalled, 2008). In a weed seed
bank study, application of pre-emergence oxyfluorfen
(23.5% EC) at 300 and 400 g ha
-1
resulted in lesser
density of grasses, broadleaved weeds and total weeds
(Sathya Priya, 2011).
Herbicide Residue Analysis
Sulfonylurea herbicides show a wide range of
persistence in both laboratory and field conditions,
depending upon soil pH, temperature, and soil
moisture. Several authors reported that persistence of
sulfonylurea herbicides increased with increasing rate
of application (Kotoula-Syka
et al
., 1993), increasing
soil pH and decreasing organic matter content (Goetz
et al
., 1989; Castro
et al
., 2002 and Bedmar
et al
.,
2006).
Even at low rates, chlorimuron and metsulfuron herbicides
can persist in the soil throughout more than one growing
season and may injure rotational crops (Junnila
et al
., 1994
and Vicari
et al
., 1994). Pendimethalin at 1.0 and 1.5
kg ha
-1
did not persist for more than 60 days in
soybean soil (red sandy loam soil) as reported by Devi
et al
., 2000
.
Harvest-time residues of the herbicide
decreased gradually over the years and at the end of
five years less than 3 per cent of applied
pendimethalin was recovered from soil as against 18
per cent in the first year (Kulshrestha
et al
., 2000). No
leaching of pendimethalin was observed below 10 cm
during 230 days of cotton growing condition
(Tsiropoulos and Lolas, 2004). Metribuzin is
considered to be of short to moderate persistence in
soils, the half-lives measured have been specified at
between 5 and 50 days (Perez
et al
., 2006).
Pendimethalin at 1.0 kg ha
-1
applied to different
rabi
crops persisted in soil upto 75 DAS and afterwards
degraded completely leaving no toxic residue in post
harvest soil (Arora and Tomar, 2008). Atrazine residue
studies carried out in sorghum based cropping system
showed at higher levels i.e. 0.5 and 1.0 kg ha
-1
of
atrazine application the residues (estimated with
colorimeter) were 0.0725, 0.1150 and 0.625, 0.110
ppm respectively in grain and straw. The atrazine
residue was not detectable in subsequent crop of
finger millet in both grain and straw (Chinnusamy
et
al
., 2008).
Straw samples contained 0.01 and 0.03 mg g
-1
and in the
soil 0.028 and 0.03 mg g
-1
of oxyfluorfen residues were
detected when applied at 240 and 500 g a.i. ha
-1
,
respectively. However in rice grains, 0.018 and 0.106
mg g
-1
of oxyfluorfen residues were found in 240 and
500 g a.i. ha
-1
treated plots (Shobha, 2009). Chenhui
Shi
et al.
(2010) reported that in rice 0.001 mg kg
-1
and 0.005 mg kg
-1
of oxadiargyl residue was found in
grain and soil, respectively. Residue of oxyfluorfen
was not found in post-harvest soil and plant sample as
reported by Jayakumar (2010) in tea and Sathya Priya
(2011) in onion. According to Janaki (2014), the
residue of metribuzin in soil was below the detection
level in all the treatments irrespective of doses in
post-harvest soil of sugarcane. Revathi (2014)
reported that 0.0333 ppm of metsulfuron methyl
residue found in post-harvest soil sample of rice.
Economics
According to Mannikeri (2006), the weed free
control (hand weeding) resulted in maximum B:C
ratio (2.74:1) followed by the application of
pendimethalin (2.39:1) and clomazone (2.19:1) in
turmeric.
Babu (2008) reported that among herbicide treatments,
the application of pendimethalin at 1.5 kg ha
-1
recorded the maximum B:C ratio (2.13) closely
followed by pendimethalin at 1.0 kg ha
-1
(2.10) in
turmeric. In turmeric, pre-emergence application of
pendimethalin + straw mulch 9 t ha
-1
recorded higher
net return ( 1,03,000) and B:C ratio (2.30) compared
to all other treatments (Kaur
et al
., 2008).
Ratnam
et al
. (2012) reported that among the weed
management treatments, the higher net return of
1,21,073 ha
-1
and B:C ratio of 0.61 was recorded with
pre-emergence application of oxyfluorfen 0.25 kg ha
-1
followed by quizalofop ethyl 0.05 kg ha
-1
at 30 DAS
supplemented with hand weeding at 60 and 90 DAS in
turmeric. According to Jadhav and Pawar (2014),
pre-emergence application of metribuzin 0.70 kg ha
-1
followed by straw mulch 10 t ha
-1
followed by one
