GOLANDAS BAGHEL

(160111006)

WEED INDICES FOR JUDGING THE EFFICACY OF WEED CONTROL TREATMENTS

WEED INDICES

“weed indices are use to study the effect or weed density growth and suppression effect of weed on crop plant. The common indices uses for weed flora study are Weed Infestation, weed index, Weed control efficiency and smothering efficiency”

The under listed terms provide a logistic support in impact assessment, interpretations and drawing appropriate conclusions in weed management research.

To study the weed and crop response to weed control treatment To study the efficiency of herbicide To determine the efficiency of intercropping system in suppression of weed

OBJECTIVE OF WEED INDICES

• Weed infestation

• Weed index

• Weed control efficiency (WCE)

• Weed smothering efficiency (WSE)

• Weed persistence index (WPI)

• Crop resistance index (CRI)

• Pest (weed) management index (PMI or WMI)

• Agronomic management index (AMI)

• Treatment (Herbicide) efficiency index (TEI)

• Weed intensity

Different weed indices

WEED INFESTATION

It refers to the percentage of weeds in the composite population of weed and crop plants.

Total number of weeds in an unit area Total number of weed and crop plants in the same area

×100WI (%) =

WEED INDEX

Weed Index =

It refer to the reduction in crop yield due to the presence of weed in comparison to weed-free plots.

Yield from weed free (hand weeded) plot-yield from treated plot

Yield from weed (hand weeded) plot

This is used to assess the efficacy of a herbicide. Lesser the weed index, better is the efficiency of a herbicide.

WEED INDEX COUNTI..

Example: Calculate the weed index for atrazine and simazine applied in the maize from the following data:

1. Yield of maize from weed free plot = 20 q/ha 2. Yield of maize from atrazine treated plot = 1 8 q/ha 3. Yield of maize from simazine treated plot = 19 q/ha

Calculation

20 - 18 20

1.) Weed index for atrazine = X 100 =10%

2.) Weed index for simazine =

20 - 18 20

x 100 =10%

Result:The weed index is less (5%) for

simazine, compared to atrazine (10%). Therefore, simazine to be applied in maize for effective control of weeds.

Weed Control Efficiency (WCE): It indicates the percentage reduction in weed

population or dry weight of weeds under treated plot (herbicide) in comparison to untreated plot (weedy). This index is used to compare the different weed control treatments. It is also known as Weed Control Index (WCI). Higher the WCE, better is herbicidal / weed control treatment.

WCE (%) = Weed count in unweeded plots - Weed count in treated

plots Weed count in unweeded plots

X 100

Dry matter of weeds in unweeded plots-Dry matter of weeds treated plots

Dry maUer of weeds in unweeded plots X 100

Example : In a weed control experiment in wheat

crop, dry-weight d weeds in un weeded plots was 500 kg/ha, whereas in isoproturon and metsulfuron treated plots, it was 250 and 150 kg/ha, respectively. Find out the WCE and report which one herbicide in better

Solution

1.) WCE for isoproturon = 500 – 250 500

X 500 = 50%

2.) WCE for metsulfuron =

500 – 150 500

X 500 = 70%

Result Since the WCE of metsulfuron is

higher (70%) than that of isoproturon (50%), so metsulfuron is better than isoporoturon in controlling weeds in wheat crop.

Weed Smothering Efficiency (WSE):

This index is used to determine the effect intercropping on suppres­sion of weeds in comparison to sole crop stand .

WSE (%) =

Weed dry weight in sole crop stand plots - Weed dry weight in intercropped plots

Dry matter of weeds in sole crop stand

X 100

Pest (weed) management index :(PMI or WMI)

Agronomic management index (AMI)

Weed persistence index (WPI)

Crop resistance index (CRI)

Treatment (Herbicide) efficiency index: (TEI)

Weed intensity:

References:

Practical manual of weed science by Kewat M.L. and Sharma R.S.

Principles of agronomy by Reddy And Reddy. Modern concepts and advance principles in crop

production by Panda S.C. Fundamentals of Agriculture by Arun Katayan. Hand Book of Agriculture by ICAR New Delhi.

Thanking you for ………………….patience hearing