Agricultural Air Quality

Conservation Measures

Reference Guide for Cropping Systems 

And General Land Management

 

October 2012
Introduction

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Purpose

The United States Environmental Protection Agency (EPA) and the United States Department of 

Agriculture - Natural Resources Conservation Service (USDA-NRCS) have collaborated to

develop this reference guide to provide a compilation of conservation measures for air pollutant 

emission reductions and/or reduction of air quality impacts from agricultural land management 

and cropping operations. Livestock operations will be covered in a separate reference guide in 

the future. This reference guide can be used to address agriculturally-related air resource 

concerns in areas where agricultural emissions from cropping systems and general land 

management are determined to be significant contributors to air quality impairment. The 

methods presented in this guide are consistent with USDA objectives that promote the use of 

cost-effective practices and innovative technologies to address air resource concerns from 

agricultural operations and to meet federal, state and local regulatory requirements. Many of the 

measures provided in this guide also have additional resource benefits such as soil, water or 

energy conservation. Some co-benefits are identified, but this document is primarily focused on 

air quality. 

Over the past several years, EPA has received multiple requests to identify USDA-approved 

measures that may be considered to manage air emissions from cropping systems and general 

land management sources and potentially satisfy State Implementation Plan (SIP) requirements. 

These requests have come from a variety of stakeholders, including USDA’s Agricultural Air 

Quality Task Force, agricultural producers, industry representatives and state and local agencies. 

In the 2006 Particulate Matter (PM) National Ambient Air Quality Standards (NAAQS) and 

2008 Ozone NAAQS preambles, EPA recommended that in areas where agricultural activities 

have been identified as a contributor to a violation of the NAAQS, when properly implemented 

to control airborne emissions of the desired NAAQS pollutant, USDA-approved conservation 

systems and activities may be implemented to achieve reasonably available control measure 

(RACM) and best available control measure (BACM) levels of control. 

This reference guide is chiefly designed as a technical tool to provide a compilation of USDANRCS approved practices to address air emissions from agricultural sources in areas where 

agricultural activities have been demonstrated to contribute to air quality issues. To learn more 

about NRCS practice standards please contact your local NRCS state office. Contact information 

for NRCS state offices can be found under the “browse by location” link at www.nrcs.usda.gov. 

USDA-NRCS may be able to offer technical and financial assistance to agricultural producers 

for implementing these and other conservation practices. Additionally, national funding 

assistance may be available from the EPA.

Furthermore, the USDA-NRCS was involved in the development of additional conservation 

measures for air quality purposes in California and Arizona and, where appropriate, references to 

these USDA-NRCS approved measures are included in this guide. Some of these conservation 

activities were patterned after NRCS conservation practice standards, but despite similarities in 

some of the names, application of these conservation activities may differ slightly from 

application of the NRCS practice standards.
Introduction

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For more information on the California measures, please see the Agricultural Air Quality 

Conservation Management Practices for San Joaquin Valley Farms handbook and table, which 

are available at: 

Handbook: http://www.valleyair.org/farmpermits/updates/cmp_handbook.pdf

Table: http://www.valleyair.org/farmpermits/applications/cmp/cmp_list.pdf

For more information on the Arizona measures, please see the handbook for Agricultural PM10

Best Management Practices, which is available at:

Handbook:http://www.azda.gov/ACT/Best%20Management%20Practices%20Guide%20

for%20web%20view%20reducec.pdf

This Reference Guide is Intended to:

Provide a broad, though not comprehensive, set of USDA-NRCS approved practices that may 

be relied upon to address air resource concerns.

Provide regional, state and local regulatory agencies with technical tools and information on 

how to manage agricultural air emissions with USDA-NRCS approved measures and USDA 

and EPA expertise.

Allow stakeholders the flexibility in choosing which measures are best suited for their specific 

situations/conditions and desired purposes.

This Reference Guide is NOT Intended to:

Identify agricultural sources as a significant contributor to air quality issues in all areas.

o There are currently only a handful of areas in the United States where agricultural sources 

have been identified as a significant contributor to nonattainment of the PM and Ozone 

NAAQS. However, for those areas where it is demonstrated that agricultural sources are 

a significant contributor, this document can be useful to the state or local regulatory 

agency as it reviews options for managing air emissions from agricultural sources.

Provide a comprehensive listing of all potential emissions reduction measures for mitigating 

agriculturally-related air quality impacts. 

Provide conservation measures that will be suitable for every specific case. 

o Geographic location, environmental conditions and intended purposes will differ for each 

particular agricultural situation. Thus, USDA and EPA strongly encourage state and local 

agencies to work with individual producers and NRCS conservationists to develop plans 

that include feasible and effective measures for each site.

Provide any regulatory measures from the EPA. 

o This document is solely for informational purposes. It may be useful for states and local 

air agencies needing additional information on how to reduce emissions in areas where 

agricultural sources are demonstrated to contribute to a non-attainment designation.

Provide details about the numerous co-benefits of these measures with respect to water quality, 

soil health, energy savings, greenhouse gases and many others.

o Many of the practices listed in this guide may already be implemented to achieve other 

resource benefits (e.g. soil conservation, water conservation, etc.). This document was 
Introduction

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designed to solely focus on the air quality benefits achieved from implementation of the 

conservation measures. It should be noted that in some cases, measures taken to achieve 

air quality benefits may cause other environmental impacts, and each situation needs to 

be carefully analyzed to achieve mutually beneficial outcomes.

When Implementing Conservation Measures:

Regional, state, and local regulatory agencies should coordinate (as appropriate) with the 

producers, landowners, operators, state and local agencies, NRCS, and EPA to determine 

which measures may be best suited for a particular situation to attain the desired goals.

Consider the geographic location and environmental conditions (soil type, precipitation, 

humidity, temperature, water availability, wind conditions, terrain, etc.) in which the practices 

will be implemented, as they will also play a role in deciding which conservation measures are 

most suitable. 

Assess implementation costs and benefits to determine the most cost-effective control 

measures that provide the greatest emissions reductions.

Refer to the most up-to-date NRCS conservation practice standards or guidance to ensure that

implemented measures follow current guidelines.
Introduction

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Using the Reference Guide

This technical tool identifies the current USDA-NRCS approved conservation measures 

available to the agricultural industry for the emission reductions of PM, PM precursor and ozone 

precursor emissions from agriculture operations. The measures are listed in eight sections, each 

categorized by type of activity or result to be achieved. For example, measures intended to 

maintain soil surface cover, and thus reduce PM emissions from erosive agents (wind, vehicle 

tires, implements, etc.) are included in Section 1.

It should be noted that all practices will not be well-suited for every region or specific farm/ranch

or land management operation. Thus, the conservation measures are designed so that producers 

will have options and flexibility in selecting the most effective practices for their operation.

This guide is intended to provide information on USDA-NRCS approved measures that reduce 

air emissions. However, many of these measures also provide co-benefits for other resource 

concerns that are not identified in the document. To learn more about co-benefits from practices 

outlined in this guide, please contact your local NRCS State Office. Note that USDA-NRCS may 

also be able to offer technical and financial assistance to agricultural producers for implementing 

these and other conservation practices.

USDA-NRCS has developed conservation practice standards using scientifically-proven research 

and demonstration of technologies. For measures that have related practice standards, the NRCS 

Practice Codes are listed. The conservation practice standards contain information on why and 

where the conservation practice is applied and set forth minimum quality criteria that must be 

met during application to achieve the intended purpose(s).

State-specific versions of the conservation practice standards are available through the NRCS 

Field Office Technical Guide (FOTG) for each state. If no state conservation practice standard is 

available in the FOTG, please contact the appropriate NRCS State Office or local USDA Service 

Center. These offices are available to answer state and local questions and provide many forms 

of assistance. The locations of these offices can be found at the following websites:

NRCS State (and Local) Offices: www.nrcs.usda.gov

USDA Service Center Locator: http://offices.sc.egov.usda.gov

Additional Resources

NRCS has developed educational tools that are designed to provide information about air quality 

and are accessible to the public. To view these online courses please visit: 

www.airquality.nrcs.usda.gov.

EPA has developed a website that provides links to various agriculture and air quality related 

topics. For more information, please visit: http://www.epa.gov/airquality/agriculture.

Contributors

USDA – Natural Resources Conservation Service (NRCS) – Air Quality and Atmospheric Change Team

U.S. EPA – Office of Air Quality Planning and Standards (OAQPS)
Table of Contents

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Table of Contents

Page

Section 1: Maintaining Soil Surface Cover ..............................................................................6

Section 2: In-Field Pass Reductions........................................................................................10

Section 3: Soil Conditioning and Timing of Operations Modifications ................................13

Section 4: Unpaved Roadways and Other Areas ...................................................................17

Section 5: Wind Barriers ........................................................................................................21

Section 6: Equipment Modifications ......................................................................................25

Section 7: Fire and Smoke ......................................................................................................27

Section 8: Other.......................................................................................................................31
Section 1: Maintaining Soil Surface Cover

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Section 1:

Maintaining Soil Surface Cover

Soil surfaces can be sources of PM

emissions when winds of sufficient 

speeds act upon the surface to cause 

erosion, suspension and entrainment 

of soil particles or when the action 

of machinery on soils leads to 

particulate generation. Both wind 

erosion and machinery action can 

lead to significant soil quality issues 

with the loss of valuable topsoil and 

deposition of soil on areas where it 

is not desired, including water 

bodies and streams (becoming a 

water quality issue). The degree to 

which soils erode and particles 

become airborne by wind or mechanical action is dependent on several factors, including the 

amount, type and spatial distribution of surface cover (residue, vegetation or other cover), soil 

type, soil moisture, the amount of compaction versus looseness of the top soil layer and the 

roughness (micro-topography) of the soil. Conservation practices that maintain soil cover and 

reduce these wind- and machinery-driven erosion factors will greatly reduce the risk of wind 

erosion and mechanically-generated PM by separating contact of the erosive agent (i.e., wind, 

vehicle tires, or implements) from the soil surface. This section is focused on soil cover 

measures, and Section 3 addresses soil condition measures.

Measures:

Residue and Tillage Management and Mulching

Cover Crops and Other Vegetative Surface Covers

Perennial Crops and Other Vegetation

 Conservation Measure Description: Residue and Tillage Management and Mulching

Utilizing tillage systems that retain residue on the soil surface and reduce tillage intensity (less 

soil disturbance), as well as the reduction in vehicular traffic on fields will reduce the potential 

for PM generation. Where tillage and/or vehicular movement are needed, adopting conservation 

tillage and residue management, to the extent possible, will help retain topsoil structure and the 

ability of the soil surface to stay intact and not generate PM. Soil surface cover can also be 

achieved by mulching, which utilizes materials not present on the field. In cases where soils are 

bare (especially during times of severe drought when maintaining some type of surface cover 

becomes impossible) mulching can be very effective. If mulching is not feasible it may become 

necessary to invoke other conservation actions to prevent significant PM emissions (such as 

surface roughening, wind barriers, etc.—see Sections 3 and 5). 
Section 1: Maintaining Soil Surface Cover

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Several NRCS conservation practices are specifically designed for managing tillage and residue 

on soil surfaces and for application of mulches. Residue and Tillage Management No Till/Strip 

Till/Direct Seed is used for managing the amount, orientation, and distribution of crop and other 

plant residue on the soil surface year-round, while limiting soil-disturbing activities to those 

necessary to place nutrients, condition residue, and plant crops. This is the most stringent NRCS 

residue and tillage management practice, and its application retains the most residue of any 

practice. It also can greatly reduce tillage-induced PM generation, since tillage is eliminated or 

greatly reduced. One of the specified purposes of this practice is to reduce soil particulate 

emissions.

Other conservation tillage practices, such as Residue and Tillage Management Mulch Till,

Residue and Tillage Management Ridge Till, and Residue and Tillage Management Seasonal

manage both tillage and surface residue retention, and thus reduce the potential for PM 

generation compared to conventional tillage systems (though not to the extent of the no-till 

practice). Mulching is the application of plant residues (or other suitable materials produced offsite) to the land surface. Other suitable materials include natural products like wood chips and 

rice hulls, as well as artificial materials like plastic or fabric. Among other purposes, mulching 

can be used to reduce airborne particulates, conserve soil moisture, moderate soil temperatures, 

and improve soil condition. 

NRCS Conservation Practice Standards

Residue and Tillage Management No Till/Strip Till/Direct Seed (329)

Residue and Tillage Management Mulch Till (345)

Residue and Tillage Management Ridge Till (346)

Residue and Tillage Management Seasonal (344)

Mulching (484)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Alternate Till

o Conservation Tillage

o Mulching

o Non Tillage / Chemical Tillage

o Soil Amendments

o Transplanting

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Reduced Tillage System

o Residue Management

o Mulching
Section 1: Maintaining Soil Surface Cover

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 Conservation Measure Description: Cover Crops and Other Vegetative Surface Covers

Cover crops and other vegetative surface covers are typically annual plantings that are part of a 

cropping sequence. They often are used during the non-cropping part of a rotation to maintain 

soil surface cover, as well as to increase soil organic matter content, manage soil moisture, 

minimize and reduce soil compaction, and capture and recycle or redistribute nutrients in the soil 

profile. Cover Crop is typically used in conjunction with Conservation Crop Rotation.

Stripcropping, the practice of growing planned rotations of row crops, forages, small grains, or 

fallow in a systematic arrangement of equal width strips across a field, can also be used 

effectively for seasonal soil cover maintenance.

NRCS Conservation Practice Standards

Conservation Crop Rotation (328)

Cover Crop (340)

Stripcropping (585)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Cover Crops

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Cover Crop

o Sequential Cropping

 Conservation Measure Description: Perennial Crops and other Vegetation

Greater soil cover (both spatially and temporally) can be achieved by utilizing perennial crops or 

perennial vegetation, when appropriate. With these practices, soil cover is almost always 

maintained, and PM generation from wind erosion or mechanical/vehicular action is greatly 

reduced or eliminated. These practices can be very effective for long-term soil stabilization and 

improvement in soil quality. They can be grouped into: 

Perennial cropping and cropping-related practices which allow for the permanent and 

semi-permanent establishment of forage and/or biomass crops, and buffer areas that 

maintain soil cover. These include Field Border and Forage and Biomass Planting.

Perennial vegetation practices that establish vegetation for a long period of time. These 

include Conservation Cover, Range Planting and Tree/Shrub Establishment. Critical 

Area Planting is intended to establish permanent vegetation on sites that have, or are 

expected to have, high erosion rates, and on sites that have physical, chemical or 

biological conditions that prevent the establishment of vegetation with normal practices.

Agroforestry practices such as Alley Cropping, Multi-Story Cropping, Silvopasture 

Establishment and Windbreaks also can be used to maintain soil cover, and thus reduce 

potential PM generation, as well as provide additional natural resource benefits. These 

are also very effective wind barriers and are described more fully in Section 5.
Section 1: Maintaining Soil Surface Cover

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NRCS Conservation Practice Standards

Alley Cropping (311)

Conservation Cover (327)

Critical Area Planting (342)

Field Border (386)

Forage and Biomass Planting (512)

Multi-Story Cropping (379)

Range Planting (550)

Silvopasture Establishment (381)

Tree/Shrub Establishment (612)

Windbreak/Shelterbelt Establishment (380)

Windbreak/Shelterbelt Renovation (650)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Permanent Crop

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Multi-Year Crop

o Permanent Cover

Geographic and Physiographic Factors:

In general, areas of the United States with lower precipitation and higher winds will be most 

likely to benefit from implementing measures found in this section. The High Plains from eastern 

Montana and the Dakotas southward to western Texas and eastern New Mexico can frequently 

be vulnerable to wind erosion and PM generation and transport, especially during drought 

periods. Other areas like the winter wheat / summer fallow region of eastern Washington and 

Oregon also occasionally experience these issues, with the juxtaposition of bare soils, dryland 

farming and infrequent high wind events. In general, erosive wind events are quite rare in the 

United States, and years may pass in some areas before atmospheric and soil conditions align for 

PM generation and transport. Since soil moisture and topsoil conditions are critical for PM 

generation, it is necessary that these factors, in addition to wind statistics, be strongly considered 

in determining a location’s vulnerability for erosive events and consequently air quality 

degradation. Thus, during severe drought episodes, there may be very little that can be done to 

avoid significant wind erosion and PM generation. In fact, this is the very source of the world’s 

loess soils.

Tool: The NRCS/Agricultural Research Service (ARS) Wind Erosion Prediction 

System (WEPS) is the primary model used by USDA to estimate wind erosion 

potential. Users can specify soil surface characteristics and management options, 

such as those described in this section. WEPS also has the capability to model crop growth and 

include cover crops or perennial vegetation (and barriers). The model delivers estimates of total 

soil loss as well as PM10 emissions from a specified land area. WEPS is not an online tool, but 

those interested in applying the model should work through their appropriate state and/or local 

NRCS agronomist.
Section 2: In-Field Pass Reductions

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Section 2:

In-Field Pass Reductions

Agricultural field operations, such as tilling, 

planting, weeding, fertilizing, harvesting, 

mowing, cutting, baling, and spreading of 

manure or compost can produce air 

pollution emissions. These emissions can be 

directly emitted from the action of wheels 

and machinery on soil or from engine 

combustion. Vehicular and machinery 

action can break up soil aggregates, making 

the finer particles more likely to be 

suspended by additional field actions and/or 

wind. The amount of dust produced and 

transported off the field is largely a function 

of the number of individual operations on a given field and associated atmospheric conditions.

Reducing the number of operations reduces the amount of dust produced in the field, as well as 

engine emissions. Therefore, a reduction in the number of passes over a field can: 1) reduce soil 

abrasion and the breakup of soil aggregates, 2) reduce direct suspension of PM from vehicle 

wheels/etc., and 3) reduce engine emissions (ozone precursors [especially oxides of nitrogen

(NOx)], and PM).

Measures:

Modify Operations

Precision Delivery

 Conservation Measure Description: Modify Operations

Reducing in-field passes can be accomplished by modifying operations and improving 

operational efficiency. This can be achieved by applying conservation tillage, increasing

equipment efficiencies, optimizing field space, or combining operations. Overall, these

conservation measures can be quite effective at reducing PM emissions. Reduced engine 

emissions are approximately proportional to the number of reduced passes, taking into account 

implements used and additional power needs with the combined operation. Conservation tillage 

limits soil-disturbing activities to only those necessary to place nutrients, condition residue and 

plant crops. Optimizing field space through adjustments in bed/row spacing (which can increase 

plant density/canopy through reduction of row width) reduces the number of passes and the 

resultant soil disturbance. Certain crop cultural practices (including organic practices for 

reducing pesticide application passes, hand harvesting, and those practices associated with fruit 

crops, including the use of a continuous tray/dried-on-the-vine system such as that applied in 

California) can also result in reduced passes. However, in some cases organic production can 

actually increase field passes, such as increasing cultivation for weed control. In these cases, this 

measure should not be used as a control measure for reducing PM emissions. Many in-field pass 

reductions can be applied relatively independently of geographic location. Residue and Tillage 
Section 2: In-Field Pass Reductions

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Management Mulch Till and Residue and Tillage Management No Till/Strip Till/ Direct Seed are

conservation practice standards that may be used for managing the residue on soil surfaces, thus 

reducing required in-field passes. 

NRCS Conservation Practice Standards

Residue and Tillage Management Mulch Till (345)

Residue and Tillage Management No Till/Strip Till/Direct Seed (329)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Alternate Till

o Bed/Row Size or Spacing

o Combined Operations

o Continuous Tray/Dried on the Vine, New Drying Techniques for Dried Fruit

o Conservation Tillage

o Floor Management

o Equipment Changes/Technology Improvements

o Green Chop

o Hand Harvesting

o Fallowing Land

o Mulching

o Non-Tillage/Chemical Tillage

o Organic Practices (for biological control of pests)

o Shed Packing

o Shuttle System/Large Carrier

o Transplanting

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Combining Tractor Operations

o Green Chop

o Reduced Harvest Activity

o Reduced Tillage System

 Conservation Measure Description: Precision Delivery

Application of advanced technologies and methodologies, such as Integrated Pest Management, 

Nutrient Management, Irrigation System Microirrigation, Irrigation System Surface and 

Subsurface, application efficiencies, precision farming and chemigation/fertigation, can precisely 

deliver herbicides/pesticides and water to crops. These technologies and methodologies can also

reduce: operation overlap, number of field passes, soil compaction (which requires additional 

tillage) and excess water that can enhance weed growth (where weed treatment could require 

additional tillage and field passes). Integrated pest management and nutrient management are 

comprehensive practices designed to precisely deliver pesticides and nutrients to the agricultural 

system. Nutrient and pest management conservation practices strive to apply fertilizer and 

pesticides from the right source, at the right rate, at the right time, and in the right place (known 

as the 4R’s of nutrient stewardship). Getting the nutrient or pesticide applied in the right place 
Section 2: In-Field Pass Reductions

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(precision delivery) can take the form of smart sprayer technology, which places the pesticide 

precisely on the desired plant location or precision delivery systems, which lead to the

elimination of operation overlap. These practices not only reduce direct PM emissions from 

vehicles and mechanical disturbance of the soil, but also can prevent or mitigate pesticide and 

nutrient volatilization losses and drift (including volatile organic compounds (VOC) and NOx).

NRCS Conservation Practice Standards

Integrated Pest Management (595)

Nutrient Management (590)

 Irrigation System Microirrigation (441)

 Irrigation System Surface and Subsurface (443)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Application Efficiencies

o Conservation Irrigation

o Chemigation/Fertigation

o Integrated Pest Management

o Precision Farming (Global Positioning System)

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Chemical Irrigation

o Integrated Pest Management

o Precision Farming
Section 3: Soil Conditioning and Timing of Operations Modifications

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Section 3:

Soil Conditioning and 

Timing of Operations Modifications

Soil conditioning and timing are critical 

when it comes to cropping systems.

Modifying agricultural activities that help 

condition the soil (such as cultivating, 

ridging, etc.), as well as modifying the 

timing of operations, is not always

practical but may sometimes be 

necessitated by local or regional air 

quality conditions. In regions of the 

country where agriculture has been 

identified as a source that contributes to 

compromised air quality, atmospheric 

concentrations can be minimized by 

adopting soil conditioning practices and 

modifying the timing of operations. Conservation measures and activities that can be adopted to 

reduce agricultural air emissions include: no-till farming, precision agriculture, monitoring soil 

moisture, soil amendments, residue and tillage management, closely monitoring weather and 

atmospheric conditions, and adjusting the timing of operations to minimize air quality impacts.

Farming and ranching operations almost always involve critical timing components that are, at 

very best, marginally flexible. Producer operations almost always hinge on a suite of dynamic 

factors, and when the majority of these factors are favorable, the intended farming operations 

(i.e., tillage, harvest, soil amendments) occur. Implementing one or more proactive conservation 

measures and timing operations to coincide with favorable atmospheric conditions (wind speed 

and direction, relative humidity, atmospheric stability, background ambient air quality 

concentrations, etc.) can prevent adverse agricultural air quality impacts. Producers often need to 

modify operations due to weather conditions. Air quality can sometimes benefit from modifying 

the timing of operations, where practicable. In some areas of the country, the calculations behind 

agricultural decision making have become more complex due to air quality. In these regions,

weather conditions and economics are the primary variables; however, ambient air quality must 

also be considered as a variable in the agricultural decision-making process. 

This section focuses on utilizing conservation techniques related to soil conditioning and timing 

of operations to minimize air emissions while accomplishing the necessary farm/ranch business 

requirements. Minimizing agricultural emissions can be accomplished through a variety of 

innovative solutions and good decision-making.

In some regions of the country, the adoption of conservation measures is required of producers.

Producers, particularly in these regions, should be cognizant of air emissions from agricultural 

activities. Careful evaluation of soil conditions and timing of operations to minimize the 

possibility of agriculturally-produced emissions (which can contribute to compromised ambient 

Photo: Dusty Eddy, NRCS
Section 3: Soil Conditioning and Timing of Operations Modifications

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air quality) should be pursued, when feasible. Clearly, producers have many decision-making 

factors, and there are times when it is critical to proceed with operations (such as completing 

planting or harvest before a significant weather event). When economic and other considerations 

allow, modifying timing of operations to ensure adequate air quality should be strongly 

considered. For example, when meteorological and soil conditions align to indicate a high-wind 

dust event could occur, limiting in-field activity can be an effective measure for reducing PM

emissions. 

Emission prevention techniques are generally applicable throughout the country in a variety of 

agricultural contexts. Conservation measures are most effective when they are prescribed and 

customized for a particular locality, even a specific agricultural operation under a specified set of 

parameters. Conservation measures can be most effective in areas where topsoil can easily 

become airborne due to moisture and physical soil properties and may be most necessary in 

regions where agriculture occurs in close proximity to population centers. Local regulations and 

ordinances should be followed and harmonized with conservation measures to meet air quality 

objectives.

Many of the practices and activities that can be implemented to reduce agricultural emissions 

also have ancillary benefits and can preserve valuable topsoil, conserve water, and increase 

productivity. 

Measures:

Soil Conditioning

Modifying the Timing of Operations

 Conservation Measure Description: Soil Conditioning

Increasing the soil moisture content through residue and cover crops can be an effective 

approach to increasing soil health and minimizing airborne PM. Cover Crops can be used 

through fallow periods in some cropping systems and in areas with sufficient precipitation to 

reduce soil erosion, increase soil nutrients, and address wind erosion. Several NRCS 

conservation practices, such as Nutrient Management, have been identified as beneficial soil 

conditioning practices. PM emission reductions from Residue and Tillage Management, and 

Stripcropping are practices that can help address ambient air quality concerns while 

simultaneously improving soil tilth. Conservation Cover and Mulching also add organic matter 

and stabilize the soils to effectively reduce air emissions, even when soils are bare. Pre-harvest 

soil preparation, such as Irrigation Water Management and Sprinkler Irrigation Systems can be 

used to improve air quality. Water or stabilizing material can be applied to the soil prior to 

agricultural operations to control dust. However, this should only be an option when ample water 

supplies exist. Surface Roughening is also a proven method of reducing wind-blown PM in cases 

of extreme dryness, lack of vegetation, and impending strong winds. However, this is an

emergency practice only utilized when no other options for controlling dust exist.

NRCS Conservation Practice Standards

Conservation Cover (327)

Cover Crop (340)
Section 3: Soil Conditioning and Timing of Operations Modifications

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Irrigation Water Management (449)

Irrigation System Sprinkler (442)

Mulching (484)

Nutrient Management (590)

Residue and Tillage Management Mulch Till (345)

Residue and Tillage Management No-Till / Strip Till / Direct Seed (329)

Residue and Tillage Management Ridge Till (346)

Stripcropping (585)

Surface Roughening (609)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Alternate Till

o Conservation Tillage

o Cover Crops

o Floor Management

o Mulching

o Non Tillage / Chemical Tillage

o Organic Practices

o Pre-Harvest Soil Preparation

o Permanent Crops

o Soil Amendments

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Reduced Tillage Systems

o Aggregate Cover

o Synthetic Particulate Suppressant

o Cover Crop

o Cross-Wind Ridges

o Mulching

o Residue Management

o Surface Roughening

 Conservation Measure Description: Modifying the Timing of Operations

Timing is critical in farming. Adjustments in the timing of operations and/or proper soil 

conditioning can minimize many agricultural air quality issues. Agricultural operators located in, 

or in close proximity to, air quality nonattainment areas should integrate air quality 

considerations into their decision-making criteria.

Minimizing soil-disturbing activities and timing these activities to coincide with favorable 

atmospheric conditions can reduce agricultural air emissions. Timing tillage, planting, and 

harvesting to occur when the soil has the appropriate moisture content has multiple benefits. In 

addition to the air quality benefits that also prevent wind erosion, performing field operations 

during times of favorable soil moisture can improve yield and soil health. Innovative 
Section 3: Soil Conditioning and Timing of Operations Modifications

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conservation measures like Integrated Pest Management, Nutrient Management, and Residue 

Management attempt to maximize the efficiency of field operations while minimizing adverse 

impacts.

Timing, one of the 4R’s of nutrient stewardship, is also critical for integrated pest management.

Producers can monitor crops for pests to ensure effective spray timing and incorporate biological 

practices into the farming operation to reduce the need for spraying.

Other practices, such as limiting agricultural activities during high-wind events, and farming at 

night when relative humidity and surface soil moisture is higher and temperatures and wind 

speeds are typically lower, can effectively reduce PM emissions. Maintaining cover crops and 

managing residue can minimize wind erosion while adding valuable organic matter to the soil 

(see Section 1 for more details). In regions where residue burning is common, smoke 

management should be considered as part of planning and executing the burn. See Section 7 of 

this guide for additional information on Prescribed Burning and smoke management.

NRCS Conservation Practice Standards

Integrated Pest Management (595)

Nutrient Management (590)

Residue Management Seasonal (344)

Prescribed Burning (338)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Combined Operations

o Equipment Changes / Technology Improvements

o Fallowing Land

o Night Farming

o Night Harvesting

o Precision Farming (GPS)

o Time of Planting

o Transplanting

o Green Chop

o No Burning

o Reduced Pruning

o Integrated Pest Management

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Green Chop

o Limited Activity during a High-Wind Event

o Planting Based on Soil Moisture

o Tillage Based on Soil Moisture

o Timing of a Tillage Operation

o Integrated Pest Management

o Sequential Cropping
Section 4: Unpaved Roadways and Other Areas

17 | P a g e

Section 4:

Unpaved Roadways and Other Areas 

Roadways and farmstead areas 

that are unpaved or not covered 

with some type of vegetation or 

other surface bonding (grass, 

wood chips, etc.) can generate 

airborne soil particles. This 

includes roads, traffic areas, 

parking lots, staging or assembly 

areas, equipment storage lots, 

runways and loading/unloading

areas of farms and ranches. 

Vehicular action on parental 

material (soil, rock, etc.) causes 

mechanical fracture (i.e.,

crushing) into smaller particles 

that can become airborne. These 

unpaved areas can also produce dust by natural disaggregation of the parent material when wind 

acts upon them—though typically wind-eroded particles are larger than those produced by 

vehicular action.

The principal means of preventing dust generation is via the use of dust suppressants. These are 

substances applied to unpaved roads and other areas that bind together soil, gravel, dust particles 

and other materials. Suppressants, sometimes called palliatives, can be very effective in reducing 

or eliminating the generation and suspension of PM. Another effective method of reducing PM is 

by controlling the frequency, duration and intensity of mechanical action on unpaved roads and 

other areas via controls on vehicular actions. Finally, if PM is generated from unpaved roads and 

surfaces on farms and ranches, vegetation can be used to intercept it and retard its transport into 

adjoining lands.

Measures:

Dust Suppressants

Vehicular Controls

Vegetation Controls on Wind and Dust Interception

 Conservation Measure Description: Dust Suppressants

Dust suppressants, or palliatives, come in many forms, and can vary greatly in PM control 

effectiveness and longevity. Suppressants such as water are typically effective for only a short 

period of time (hours to a day or two), while biologically-based products like lignosulfonate have 

longer lifetimes, and petroleum-based products (like heavy road oil) can have lifetimes of a year 

or more.
Section 4: Unpaved Roadways and Other Areas

18 | P a g e

A primary NRCS conservation practice that can be used for this purpose is Dust Control on 

Unpaved Roads and Surfaces. This practice describes various means of controlling unpaved road 

and surface dust, most typically using some type of suppressant. Results from the utilization of 

this practice vary according to the suppressant used, but may result in a 50% or greater reduction 

in PM emissions over the untreated case. Cost and environmental impacts are considerations in 

suppressant choice. Long-term cost-benefit analyses typically inform landowner decisionmaking. For instance, water may be the cheapest single-application alternative, but due to the 

need for repeated applications, it may be cost-prohibitive for long durations and frequent 

applications. In addition, water may simply be unavailable in arid regions and/or during 

droughts. There may be environmental impacts of all other suppressants, including salts and 

petroleum products, and these impacts should be considered when making dust control decisions.

Additional NRCS practices that may also be used for PM emissions control on unpaved areas 

include Irrigation System, Sprinkler; Heavy Use Area Protection and Mulching. These practices 

can be used to provide surface protection and cover to unpaved areas, thus making them less 

susceptible to erosion.

NRCS Conservation Practice Standards

Dust Control on Unpaved Roads and Surfaces (373)

Irrigation System, Sprinkler (442)

Heavy Use Area Protection (561)

Mulching (484)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Chips / Mulches, Organic Materials, Polymers, Road Oil and Sand

o Gravel

o Paving

o Water

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Aggregate Cover

o Synthetic Particulate Suppressant

 Conservation Measure Description: Vehicular Controls

Control of both the speed and frequency of vehicular movement on roadways and other areas is 

also an effective strategy for PM control. Access Control and Dust Control on Unpaved Roads 

and Surfaces promotes PM control via posted speed limits, speed controls directly applied on 

engine components of vehicles/farm machinery, reduction of vehicular movement via combining 

operations, and other methods such as those suggested in Section 2 for farm/ranch fields that 

could be applicable to unpaved roads and surfaces. In addition, PM can be generated from soil 

transported from unpaved areas onto hard-paved surfaces that is then disaggregated, and can 

become airborne by vehicular action on the paved road. Reducing this “track-out” of soil (via 

mud on tires and other vehicle surfaces) onto hard-surfaces can thus be an effective PM control 

strategy.
Section 4: Unpaved Roadways and Other Areas

19 | P a g e

NRCS Conservation Practice Standards

Access Control (472)

Dust Control on Unpaved Roads and Surfaces (373)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Combined Operations

o Mechanical Pruning

o Restricted Access

o Speed Limits

o Track-out Control

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Access Restriction

o Reduce Vehicle Speed

o Track-out Control System

 Conservation Measure Description: Vegetation Controls on Wind and Dust 

Interception

Dust Control on Unpaved Surfaces may also be achieved by intercepting airborne particulates 

via vegetative barriers such as Windbreaks or Critical Area Plantings. However, dust control is 

best accomplished by preventing its initial generation. Vegetation placed along an unpaved 

roadway or other area can help contain and capture dust and prevent its transport away from the 

roadway area. This may be accomplished by following the practice standards: Field Border, 

Hedgerow Planting, Herbaceous Wind Barriers, or Tree/Shrub Establishment. Care must be 

taken to apply the proper vegetation to withhold the expected dust load (especially on younger 

plantings) and will do an effective job of intercepting the dust. A complete description of wind 

barriers can be found in Section 5.

NRCS Conservation Practice Standards

Critical Area Planting (342)

Dust Control on Unpaved Roads and Surfaces (373)

Field Border (386)

Hedgerow Planting (422)

Herbaceous Wind Barriers (603)

Tree/Shrub Establishment (612)

Windbreak/Shelterbelt Establishment (380)
Section 4: Unpaved Roadways and Other Areas

20 | P a g e

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Wind Barrier

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Artificial Wind Barrier

o Critical Area Planting

o Tree, Shrub or Windbreak Planting

Geographic and Physiographic Factors:

Regions of the U.S. where extended dry conditions occur and where there is an abundance of 

unpaved farm roads and surfaces are the most likely places where this issue will be most 

prevalent. This includes most of the western U.S., the high plains, and the eastern third of the 

country (where more erosive soil types are found).
Section 5: Wind Barriers

21 | P a g e

Section 5:

Wind Barriers

Vegetative and artificial barriers can: 1) disrupt 

the erosive flow of wind over unprotected 

surfaces by changing (slowing) the airflow 

pattern over the land surface and 2) provide 

filtration and/or interception of airborne 

particles and gases. Wind barriers can also 

reduce the area of exposed soils, and in the case 

of vegetative barriers, the root structure will 

further hold the soil in place. Artificial 

windbreaks can include structures such as 

fences and stacked hay bales and can be 

designed with various physical dimensions and 

porosities to alter wind flow. For all cases, 

whether reducing the suspension of particles or intercepting airborne particles and gases, wind 

barriers are most effective when oriented perpendicular to the erosive wind direction. A dry and 

disturbed soil in flat terrain without vegetation is the situation most likely to lead to the 

suspension of surface material, and many of the conservation practices in this section are 

designed to keep soil at the surface and reduce its migration offsite.

Measures:

Disrupt Erosive Wind Flow

Intercept Airborne PM and Gases

 Conservation Measure Description: Disrupt Erosive Wind Flow

When wind blows over a surface, a vertical wind speed profile exists where wind speed is nearly 

zero at the surface and then increases with height away from the surface. On a bare surface, wind 

speed quickly increases with height because the surface elements have little drag effect and thus 

wind speeds can be high quite close to the surface. Roughness elements such as soil aggregates 

and vegetation create additional drag on the wind, modifying the vertical wind speed profile such 

that wind speed does not increase with height as rapidly. Thus, the wind in contact with the 

surface is decreased, reducing wind erosion. Air trapped by clods and other cover elements also 

reduces the wind energy intensity at the surface. Barriers such as vegetative or artificial 

windbreaks, vegetative strips, or shallow barriers like surface residue and other types of soil 

cover (see Section 1) or surface roughening (typically mechanical plowing or cultivation on bare 

soil) all to some degree alter the vertical wind speed profile, reducing wind speeds near the 

surface.

NRCS has a selection of conservation practice standards that can be applied to disrupt and 

reduce the erosive flow of wind over the landscape. Windbreak/Shelterbelt Establishment is one 

of the most effective measures where single or multiple rows of trees or shrubs are planted in a 

linear fashion, typically perpendicular to the predominant wind direction. Barrier length and 
Section 5: Wind Barriers

22 | P a g e

height have the greatest effect on the downwind shelter area. Shelter areas are described in terms 

of the windbreak height (H) and can range from 14.5H to 25H in length. Taller windbreaks 

reduce wind speed over a greater distance, with longer and wider windbreaks typically more

effective than short and narrow ones. Local NRCS offices have information about recommended 

tree species for their specific areas.

Other herbaceous and woody vegetation practices, such as Field Border, Hedgerow Planting, 

Cross Wind Trap Strips, Herbaceous Wind Barriers, and Tree/Shrub Establishment, have the 

corollary benefit of reducing wind speeds, but are often implemented for other reasons (i.e., 

protecting crops from abrasion by windblown particles). Cropping practices such as 

Stripcropping and Alley Cropping can also have corollary benefits of reducing wind speeds near 

the surface and providing shelter to crops downwind.

As a non-primary means of controlling wind erosion, Surface Roughening can be implemented to 

create random roughness at the soil surface. This is only applicable for bare soils with a surface 

layer suitable for clod formation and is generally an emergency procedure used in dryland 

drought situations. Cross Wind Ridges can also be formed, which are ridges formed by tillage, 

planting or other operations. In both cases, wind energy at the surface is somewhat reduced.

NRCS Conservation Practice Standards

Alley Cropping (311)

Cross Wind Ridges (588)

Cross Wind Trap Strips (589C)

Field Border (386)

Hedgerow Planting (422)

Herbaceous Wind Barriers (603)

Stripcropping (585)

Surface Roughening (609)

Tree/Shrub Establishment (612)

Windbreak/Shelterbelt Establishment (380)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Cover Crop

o Permanent Crops 

o Surface Roughening

o Wind Barrier

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Artificial Wind Barrier

o Cross-Wind Ridges

o Cross-Wind Strip-Cropping

o Cross-Wind Vegetative Strips

o Surface Roughening

o Tree, Shrub or Wind Break Planting 
Section 5: Wind Barriers

23 | P a g e

 Conservation Measure Description: Intercept Airborne PM and Gases

Wind barriers such as vegetative or artificial windbreaks and other vegetative strips can also 

intercept airborne PM and gases. Their design effectiveness is dependent upon the barrier height 

and porosity, the particle size being intercepted, vegetative or structural elements, and location of 

the particle or gas source in relation to the wind barrier. Higher barriers can intercept particles 

and gases that were released at greater upwind distances. Porosity of the barrier plays a role in 

particle/gas interception. Porosity in vegetative barriers can increase with vegetation height 

(depending on the vegetation), and increasing wind speeds can increase porosity by streamlining 

the vegetation. Vegetative elements also help determine particle/gas capture where tighter

vegetation elements (e.g. conifers) can capture more PM than broadleaf species. The type of 

pollutant being intercepted can also impact the health of the vegetative barrier. For example, if 

intercepting a nitrogen containing compound such as ammonia or oxides of nitrogen, a wide 

range of impacts have been observed from necrosis to enhanced growth (depending on the plant 

species). Other factors such as length of exposure, degree of exposure, and other environmental 

considerations (ex. atmospheric temperature, moisture, etc.) are important as well.

NRCS has a selection of conservation practice standards that can be applied to intercept airborne 

PM and gases. Windbreak/Shelterbelt Establishment is one of the most effective measures where 

single or multiple rows of trees or shrubs are planted in a linear fashion. Barrier length, height, 

porosity, and vegetation type have the greatest effect on the interception of airborne PM and 

gases. Local NRCS offices have information about recommended tree species for their specific

areas.

As another means of intercepting particles and gases, practices planting herbaceous and woody 

vegetation such as Field Border, Hedgerow Planting, Cross Wind Trap Strips, Herbaceous Wind 

Barriers, Tree/Shrub Establishment, Alley Cropping, and Stripcropping can be implemented.

Some of these practices are specifically intended to protect crops from abrasion by particles (e.g. 

Cross Wind Trap Strips) or can be designed to intercept particles and gases from pesticide 

applications (e.g. Hedgerow Planting).

NRCS Conservation Practice Standards

Alley Cropping (311)

Cross Wind Trap Strips (589C)

Field Border (386)

Hedgerow Planting (422)

Herbaceous Wind Barriers (603)

Stripcropping (585)

Tree/Shrub Establishment (612)

Windbreak/Shelterbelt Establishment (380)
Section 5: Wind Barriers

24 | P a g e

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Cover Crop

o Permanent Crops 

o Wind Barrier

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Artificial Wind Barrier

o Cross-Wind Strip-Cropping

o Cross-Wind Vegetative Strips

o Tree, Shrub or Wind Break Planting 

Tool: The NRCS/ARS Wind Erosion Prediction System (WEPS) is the primary 

model used by USDA to estimate wind erosion potential. The model allows users to

specify soil surface characteristics and management options. WEPS also has the 

capability to model crop growth and include cover crops or perennial vegetation. The model has 

a wind barrier submodel that takes into account important vegetative windbreak characteristics.

The user defines the wind barrier’s length, width, height, porosity, number of rows, and tree 

type. Users can choose from the following vegetation types for a wind barrier: shrub, conifer, 

deciduous, pruned trees, nut trees, dwarf/semi-dwarf orchard, standard orchard, and vineyard.

WEPS delivers estimates of total soil loss as well as PM10 emissions from a specified land area.

WEPS is not an online tool, but those interested in applying the model should work through their

appropriate state and/or local NRCS agronomist.
Section 6: Equipment Modifications

25 | P a g e

Section 6:

Equipment Modifications

Various types of modifications to agricultural 

equipment can help to prevent or mitigate 

emissions of PM, VOC, and/or NOx. Since the 

emissions addressed by equipment modifications 

are typically episodic (related to equipment 

operation more so than geography or 

meteorological conditions), the use of equipment 

modifications may be appropriate in any area 

where agricultural emissions are contributing to an 

air quality issue. Equipment modifications can be 

a broad array of simple or sophisticated changes and can include new equipment, manufacturer 

options, and independently-customized alterations.

Measures:

Combustion Equipment Replacement/Retrofit and Operation

Non-combustion Equipment Changes/Technology Improvements

 Conservation Measure Description: Combustion Equipment Replacement/Retrofit and 

Operation

Uncontrolled, older and/or less efficient combustion equipment typically have higher air 

emissions (especially for PM and NOx) than controlled, newer and/or more efficient combustion 

equipment. Combustion equipment includes stationary and mobile sources, such as irrigation 

engines, tractor engines, heaters, boilers, etc.

Replacing higher-emitting combustion units with lower emitting or non-combustion alternatives 

can result in significant air quality improvement, as well as possible energy savings. Also, 

retrofitting existing combustion units with air emission controls or new technologies to improve 

combustion efficiency can reduce the amount of air emissions from the units.

Proper maintenance and operation is extremely beneficial to minimizing emissions from existing 

combustion equipment, as well as ensuring the equipment performs as it was originally intended.

The load on the engine is reduced when equipment is operating at maximum efficiency, which 

can result in decreased engine operation time and thus less PM emissions. In some cases, making 

energy efficiency improvements can also result in decreased fuel use in combustion equipment 

and/or decreased combustion emissions.

Combustion System Improvement and Pumping Plant may be used if agricultural combustion 

systems and/or related components or devices are replaced or retrofitted for air quality and 

energy efficiency improvement.
Section 6: Equipment Modifications

26 | P a g e

NRCS Conservation Practice Standards

Combustion System Improvement (372)

Pumping Plant (533)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Irrigation Power Units

o Conservation Irrigation

 Conservation Measure Description: Non-combustion Equipment Changes/Technology 

Improvements

Agricultural equipment changes and technology improvements for reducing air emissions can 

take many shapes and forms. These can include relatively simple fixes, like using a shield or 

deflector to knock particulates out of an airstream before they are released, or using lowerpressure pesticide application nozzles to limit volatilization and chemical drift. These can also 

include more advanced techniques, like making internal design changes to harvesting equipment 

to separate and deposit residue and dust prior to entrainment. Other examples include utilizing 

water spray bars and variable rate or targeted pesticide applicators.

NRCS Conservation Practice Standards

Integrated Pest Management (595)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Equipment Changes/Technological Improvements

o Application Efficiencies

From the Arizona Guide to Agricultural PM10 Best Management Practices, (Handbook):

o Equipment Modification
Section 7: Fire and Smoke

27 | P a g e

Section 7:

Fire and Smoke

Federal, state, and private landowners utilize fire for a range of 

reasons, such as to:

Control undesirable vegetation

Prepare sites for harvesting, planting or seeding

Control plant disease

Reduce fuel hazards that lead to wildfire

Improve wildlife habitat

Improve plant productivity, health and vigor

Remove slash and debris

Enhance seed and seedling production

Facilitate distribution of grazing and browsing animals

Restore and maintain ecological processes and ecological 

site integrity

Protect air quality from wildfire smoke impacts

Fires impact air quality by releasing PM and ozone precursor 

trace gases into the atmosphere. The quantity of these trace gases 

and particulates released to the atmosphere is a function of combustion efficiency, where 

complete combustion produces carbon dioxide (CO2) and water, and incomplete combustion 

produces a complex mixture of trace gases and particulates. Combustion efficiency is a function 

of the physical and chemical properties of the fuel (i.e., fuel type, arrangement, moisture, and 

size) and environmental parameters (i.e., wind speed, temperature, and relative humidity).

Meteorological information, fuels information, and how such knowledge impacts fuel 

combustion are key facts used to manage a fire, help reduce emissions from a fire, and manage 

the smoke from a fire. A suite of conservation practices are available to: mitigate the occurrence 

of wildfires, inhibit wildfire spread, reduce the quantity of emissions from a fire, provide 

alternatives to burning, and manage smoke before, during and after prescribed burning 

operations. In all cases, practices should: be applied as part of a conservation management 

system, take into account landowner objectives, and balance other ecological needs of soil, 

water, plants and animals.

Measures:

Smoke Management 

Alternatives to Burning

Reduce Trace Gas and PM Emissions from Prescribed Burns

Reduce Wildfire Risk
Section 7: Fire and Smoke

28 | P a g e

 Conservation Measure Description: Smoke Management

Where Prescribed Burning is implemented, the fire manager should observe the rules and 

regulations governing burning activities in their area, and follow the appropriate smoke 

management program (SMP), if one is in place. If a SMP is not in place, there are basic smoke 

management practices (BSMPs) that can be implemented to manage the downwind smoke 

impacts. Sensitive receptors, such as roads and highways, schools, housing developments, etc.,

should be identified and meteorological conditions can then be used to try to schedule the burn to 

avoid impacting those locations. Wind direction and speed, atmospheric stability, and mixing 

height are some of the key atmospheric parameters influencing where and how the smoke 

disperses. Wind direction is a major determinant of where the smoke will go while wind speed 

controls how quickly the smoke will move and disperse. Both surface and upper level transport 

winds should be noted, as they can sometimes have very different wind directions. The mixing 

height is the height through the atmosphere where pollutants can mix and the more unstable the 

atmosphere the greater is the mixing height, and the more vertical mixing is achieved. Unstable 

atmospheres can also lead to erratic fire behavior. The National Weather Service (NWS) 

provides fire weather information that can often be used for managing smoke 

(http://radar.srh.noaa.gov/fire/).

Other basic smoke management practices that can be employed include monitoring the effects 

smoke has on air quality, record keeping (smoke journal), communication/public notification, 

consideration of emission reduction techniques, and coordination of area burning. These various 

smoke management practices have applicability depending on the type of burn, fuels to be 

burned and level of effort needed to address air quality concerns. Not all are applicable to all 

situations, therefore fire managers are urged to investigate the information available and 

applicable to their area and needs. Furthermore, the BSMPs mentioned here constitute only a 

subset of possible BSMPs and others can be adopted as needed. 

NRCS Conservation Practice Standards

Prescribed Burning (338)

 Conservation Measure Description: Alternatives to Burning

Alternatives to burning include options that may be viable to reduce PM and trace gas emissions 

to the atmosphere. They do, however, need to be evaluated in terms of the other ecological 

benefits that may only be achieved with fire. In many forest and rangeland systems, fire is a 

natural and necessary component to the ecological health of the system: but in many areas, the 

exclusion of fire has resulted in conditions that could be dangerous if re-introduced directly.

Furthermore, it is often not desirable to employ fire close to homes or other structures. In such 

cases mechanical treatments such as mowing, thinning, selective timber harvest and removal of 

non-commercial trees and brush can be employed. Thinning stands of trees (covered under the 

NRCS Forest Stand Improvement conservation practice standard) to reduce competition for light, 

moisture, and nutrients can enhance forest health and provide desired forest structure. Other 

mechanical treatments that do not remove material from the forest are shredding, lopping, or 

scattering, which are all covered under the Woody Residue Treatment conservation practice 

standard. Other means of manipulating the landscape can potentially serve as an alternative to 
Section 7: Fire and Smoke

29 | P a g e

burning such as managing woody plants via Brush Management or herbaceous weeds via 

Herbaceous Weed Control. These practices involve managing the plant community with 

mechanical, chemical or biological methods. Biological controls can be grazing animals and in 

that case the Prescribed Grazing practice applies.

Alternatives to burning are also available for cropping systems. A cost-effective means of 

disposing of orchard tear-outs, vineyard removals, and encroaching juniper trees is pile burning. 

However, as an alternative, chipping/grinding/shredding (covered under the NRCS Woody 

Residue Treatment conservation practice standard) may be an option, and depending upon the 

region, the residue can be used for animal bedding, ground cover, or biomass energy production.

Soil incorporation of crop residue, chemical breakdown of the residue, or removal by baling are 

also options for cases such as grass seed and winter wheat systems. The best system is very 

locally-dependent on climate and other factors.

NRCS Conservation Practice Standards

Brush Management (314)

Forest Stand Improvement (666)

Herbaceous Weed Control (315)

Prescribed Grazing (528)

Woody Residue Treatment (384)

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Baling 

o Soil Incorporation

o Grinding/Chipping/Shredding

o No Burning

 Conservation Measure Description: Reduce Trace Gas and PM Emissions from 

Prescribed Burns

Emissions from prescribed burning can be reduced by controlling how the burn is implemented 

and applying other conservation measures to reduce fuel load to be consumed. Prescribed 

Burning can be conducted to improve combustion efficiency and thus reduce the quantity of 

trace gases and PM emitted to the atmosphere. Backing fires (fire spreading, or ignited to spread, 

into (against) the wind or downslope) ensures that more fuel is consumed in the flaming phase 

where combustion is cleaner (i.e. fewer trace gases and PM are released) than during the 

smoldering phase. Burning in clean and dry piles or windrows also results in a fire that generates 

greater heat and burns more efficiently.

As part of the conservation planning process, many practices can have a corollary benefit of 

reducing fuel loads and thus the emissions from prescribed burning operations. These practices 

can include: Prescribed Grazing, Forest Stand Improvement, Brush Management, Herbaceous 

Weed Control, and Woody Residue Treatment.
Section 7: Fire and Smoke

30 | P a g e

NRCS Conservation Practice Standards

Brush Management (314)

Forest Stand Improvement (666)

Herbaceous Weed Control (315)

Prescribed Burning (338)

Prescribed Grazing (528)

Woody Residue Treatment (384)

 Conservation Measure Description: Reduce Wildfire Risk

The risk of wildfires can be increased by a build-up of understory fuels, dense tree canopies, the 

presence of ladder fuels (which allow the fire to climb from the ground into the canopy), and 

dry/dead vegetation. Certain invasive species can also be highly flammable. Many conservation 

practices can address these issues on the landscape to help reduce the risk of a wildfire and the 

associated release of high concentrations of PM and ozone precursors to the atmosphere.

Conservation practices such as Prescribed Grazing, Prescribed Burning, Forest Stand 

Improvement, Brush Management, Herbaceous Weed Control, and Woody Residue Treatment 

reduce the risk of wildfire by reducing the build-up of understory fuels and ladder fuels, 

disrupting fuel continuity over the landscape (giving a “patchiness” to the fuels), and by 

controlling weeds and invasive species, which can alter the natural fire regime. Conservation 

practices such as Firebreak and Fuel Break can inhibit wildfire spread thereby protecting air 

quality from the elevated PM and ozone concentrations associated with wildfires.

NRCS Conservation Practice Standards

Brush Management (314)

Firebreak (394)

Forest Stand Improvement (666)

Fuel Break (383)

Herbaceous Weed Control (315)

Prescribed Burning (338)

Prescribed Grazing (528)

Woody Residue Treatment (384)
Section 8: Other

31 | P a g e

Section 8:

Other

Additional measures that do not necessarily fit 

into the other sections in this document may also 

be implemented to reduce air emissions. The need 

for these measures and their usefulness can be 

dependent on geographic and/or climatic factors, 

or they may be independent of these influences. 

In particular, the handling of bulk solid materials, 

such as compost, soil, gravel, etc., in a manner 

that reduces disturbance of the material, will also 

reduce emissions from material storage piles.

Measures:

Bulk Materials Handling

 Conservation Measure Description: Bulk Materials Handling

Handling and disturbance of bulk material piles can result in the entrainment of particles or the 

release of gases due to the exposure of a greater surface area of the material to the air and 

airflow/wind. Minimizing the disturbance of a pile, such as covering the pile, limiting the surface 

area from which material is removed, and limiting the number of times the material is handled 

and the duration of disturbance, will reduce the potential for air emissions from the pile.

Additional Conservation Activities

From the San Joaquin Valley Unified Air Pollution Control District Agricultural Air 

Quality Conservation Management Practices, (Table, Handbook):

o Bulk Materials Control