Jump to main content.


Calculating Buffer Zones; A Guide for Applicators

Current as of March 2013

This page will help fumigant applicators understand how to calculate buffer zones and learn ways to reduce buffer zones.

On this page:

What are Buffer Zones

Buffer zones provide distance between the application block (i.e., edge of the treated field) and bystanders. Buffer zones:
Buffer  Zone  →   A treated field diagram

For more information on buffer zones, see the EPA’s fact sheets on Buffer Zones and Posting Requirements for Buffer Zones.

Top of page

How to Use Look-Up Tables to Determine a Buffer Zone

The product labels provide look-up tables that a certified applicator will use to determine the buffer zone. The buffer zone distance will be determined by the broadcast equivalent application rate and the size of the application block. The broadcast equivalent rate is the application rate for the fumigant applied to the entire application block based on the amount of fumigant applied in beds/strips and the size of untreated areas. See the product label for instructions on calculating the broadcast equivalent rate.

When using the tables, round up to the nearest rate and block size, if applicable. Applications are prohibited for rates and block sizes that exceed what is presented in the buffer zone tables.

Top of page

Buffer Zone Distance Requirements

  • 25 feet is the minimum buffer zone distance, regardless of credits or site-specific application parameters
  • The application is prohibited if the buffer zone is greater than ½ mile (2,640 feet)


Example 1 – Basic Use of Look-Up Table

Metam Sodium – Shank Injection – Broadcast
Buffer Zone Distances in Feet
Example Only

  Application Block Size (acres)
60
80
100
120
160
Application
Rate
30 gal/acre
25
27
30
39
51
50 gal/acre
35
45
50
65
87
60 gal/acre
49
59
68
89
119
75 gal/acre
72
82
98
129
172
85 gal/acre
86
96
116
153
204

The table above is an example of a look-up table. Use the table from the label that is specific to the application method. Using the example table above, if an applicator applies metam sodium by shank injection to beds at the broadcast equivalent rate of 75 gallons per acre (gal/acre) to an application block that is 120 acres, the buffer zone is 129 feet.

Example 2 – Rounding Up When Using Look-Up Table

Using the same table, if the applicator is making the same application but at a broadcast equivalent rate of 80 gal/acre, you must round up to the next application rate – in this case, 85 gal/acre. The buffer zone for this scenario is 153 feet. 

Top of page

How to Use Credits to Calculate a Buffer Zone

Depending on the fumigant, credits which are listed on product labels can be used to reduce the buffer zone by up to 80 percent.  Reminder:  The minimum buffer zone distance is 25 feet regardless of buffer zone credits.

The credits that are listed on product labels are fumigant-specific but can be based on factors that reduce fumigant off-gassing such as:

Keep in mind that the types of credits allowed are product-specific. Always check the label to see which credits may be applicable.

To use a buffer zone credit, use the formula below to calculate the size of the reduced buffer zone:
 
Size of buffer zone – (size of buffer zone x % credit) = Size of reduced buffer zone

Example 1 – Basic Credit Reduction

Metam Sodium – Shank Injection – Broadcast
Buffer Zone Distances in Feet
Example Only

  Application Block Size (acres)
60
80
100
120
160
Application
Rate
30 gal/acre
25
27
30
39
51
50 gal/acre
35
45
50
65
87
60 gal/acre
49
59
68
89
119
75 gal/acre
72
82
98
129
172
85 gal/acre
86
96
116
153
204

An applicator wants to apply 75 gal/acre to 100 acres. Using the table above, we see that the buffer zone distance is 98 feet.

The applicator is applying to soil that has 2.5% organic matter, for which the product label allows a 20% credit to reduce the buffer zone. To calculate the reduced buffer zone, use the formula above:

98 – (98 x 20%) = Size of reduced buffer zone
98 – (19.6) = 78.4 feet

EPA expects that applicators will round to the nearest whole number. In cases where the decimal is .5 or above, the applicator should round up. In this case, the applicator would round down to 78 feet.

Example 2 – Multiple Credit Reductions

In some cases, there may be multiple credits that can be used. For example, an applicator may be able to use the following credits listed on a product label:

Note that the credits, in this case, cannot exceed 80%.

Using the same scenario above, we can calculate what the buffer zone will be with the multiple credits. First, you need to add the credits together.

20% organic matter credit + 10% soil temperature credit + 10% clay content credit = 40% credit

Then, using the same formula as above:
98 – (98 x 40%) = Size of reduced buffer zone
98 –39.2 = 58.8 feet
In this case, the applicator should round up to 59 feet.

Top of page

Other Ways to Reduce Buffer Zones


There are other ways, besides using buffer zone credits, to reduce the size of buffer zone. Some examples:

Example 1 – Use a Lower Application Rate

Metam Sodium – Shank Injection – Broadcast
Buffer Zone Distances in Feet
Example Only

  Application Block Size (acres)
60
80
100
120
160
Application
Rate
30 gal/acre
25
27
30
39
51
50 gal/acre
35
45
50
65
87
60 gal/acre
49
59
68
89
119
75 gal/acre
72
82
98
129
172
85 gal/acre
86
96
116
153
204

An applicator is making an application to a 120 acre application block. The applicator has determined that an application rate of 75 - 85 gal/acre will be effective. Using the table above, the applicator sees that the buffer zone is 153 feet with the 85 gal/acre application rate and 129 feet with the 75 gal/acre application rate. Using 75 gal/acre will result in a buffer zone that is 24 feet smaller than if the higher rate is used.

Example 2 – Divide the Application Block

The applicator chooses to use the 75 gal/acre application rate and still needs to apply the product to 120 acres but would like to further reduce the buffer zone. The applicator decides to divide the application block in half. Using the table above, the buffer zone for each 60 acre application block is 72 feet, significantly reducing the buffer zone for each application block.

Follow the label directions for applications regarding buffer zone proximity. For overlapping buffer zones, a minimum amount of time must elapse for most application methods before the second application can occur.

Example 3 – Using Application Parameters and Credits in Combination to Reduce Buffer Zones

The applicator is pleased to have reduced the buffer zone to 72 feet but checks to see if it is possible to use any buffer zone credits.

The applicator notes that the soil has 2.5% organic matter, for which the label allows a 20% credit to reduce the buffer zone. The applicator calculates the reduced buffer zone:

72 – (72 x 20%) = Size of reduced buffer zone
72 – (14.4) = 57.6 feet
The size of the buffer zone should be rounded up to 58 feet.

Using a combination of modifying the application parameters and applying credits, the applicator ends up with a buffer zone of 58 feet.

Top of page

Publications | Glossary | A-Z Index | Jobs


Local Navigation


Jump to main content.