Drought Measures for Dust Mitigation and Air Quality in California

Growers in California and other western U.S. locations can encounter extended droughts, high winds, soil erosion, and other circumstances that result in blowing dust. Agricultural soils may be exposed briefly between crops, or as fields are fallowed for 1 to 3 years, grazed by livestock, or taken completely out of production.

Wind erosion begins with particle creep (rolling) of large particles. Soon, saltation (bouncing) of sand particles begins. These energetic particles erode even stable soil, causing suspension of dust particles into the air.

Any process that reduces vegetation cover also invites dust problems. Wind speeds in this area can exceed 50 mph. When the wind blows, dust from unprotected areas will follow. Many public and private agencies are available to help growers manage their dust problems. In some cases, financial assistance is available. The techniques in the Agricultural Guide may serve as a starting point. However, a comprehensive erosion management program may require consultation with experts. Information in this guide will assist growers with control of blowing sand and dust. It is based on almost 20 years of research conducted in Antelope Valley by the Dustbusters.

It also provides information on cost sharing with federal agencies. Two other guides have been prepared, one for homeowners and another for large area land managers. The Homeowners Guide, Large Area Land Managers Guide, and Agricultural Guide may be accessed at the Antelope Valley Air Quality Management District (AVAQMD) website.

As a grower, you may choose to implement procedures that control dust, in order to improve visibility, reduce wind erosion and loss of topsoil, minimize damage to roads and structures, and limit health impacts due to poor air quality. Effective dust control methods conserve your topsoil, protect your downwind cropped acreage, and support compliance with air quality regulations. Soils remain viable for production only when soil loss is held below about 5 tons per acre per year.

To establish an effective dust control program, determine:

How long protection needs to last
Which crop will follow the protected period
How much irrigation water will be available

Drought Measures for Dust Mitigation and Air Quality in California

There are several strategies for mitigating dust associated with fallowed working lands. They are listed below and dependent on soil type and location. This list is not organized in any order of priority.

Measure	Application and Limitation	Reference
Organic matter inclusion (urban recycling)/organic matter to surface of soil	Not enough on-farm course matter for entire state. Would be beneficial to include Cal Recycle so organics can be used on farms.	Antelope Valley Dustbusters Research Group, 2011
Cover crop (between plantings of annual crops) - initiate with irrigation	Cover crops require irrigation to establish. Stopping irrigation activities will lead to loss of cover crop above ground but roots will hold soil together. Cost of seed and requires some irrigation water. Appropriate choice of cover crop can improve soil and improve yield of following crop.	Antelope Valley Dustbusters Research Group, 2011 USDA NRCS CA
Cover crop (between rows of perennial crops)	Planted in fall so that irrigation is not required if adequate rainfall; can harbor pests as well as beneficials.	Antelope Valley Dustbusters Research Group, 2011
Strip-cropping Use of wind erosion equation or USDA NRCS Wind Erosion Prediction System (WEPS)	Determine when dust would be greatest in specific regions of valley.	NRCS software
Conservation tillage (undercutter tillage)	Not a unique dust mitigation strategy but rather more of a soil health conservation strategy.	Sharratt and Feng 2009
Strip-cropping	Many of the benefits of cover cropping but at a reduced expense because only strips of cover crop are planted and maintained.	Antelope Valley Dustbusters Research Group, 2011
Surface Roughening (or furrows perpendicular to the wind)	This brings larger soil particles and rocks to the surface, creating a barrier to capture the smaller particulates (sand) that are blown. Blown particulates are captured within the furrows. The soil type is very important and will dictate the spacing and depth of the tillage. This technique can prove most effective in areas with heavy (clay) soil, but is usually not appropriate in sandy or light soils.	Presley, et al. 2013 USDA NRCS Conservation Practice Standard Code 609
Wind barrier - solid fence	Can be used along highways. Slow or block the wind and collect particulates (sand) on the upwind side. Must remove sand on upwind side of the barrier to maintain effectiveness. Very effective in reducing dust. Expensive. Good for boarding highways to maintain driving visibility.	Grantz, et al. 1998d Antelope Valley Dustbusters Research Group, 2011
Windbreak - porous fence	Slow the wind and collect particulates (sand) on the downwind side. Must remove sand that builds up, but less often than a solid fence. Very effective in controlling dust.	Grantz, et al. 1998d Antelope Valley Dustbusters Research Group, 2011
Windbreak - straw bales	Straw bales can be used to create solid or porous windbreaks, but should be at least 6 ft high.	Grantz, et al. 1998d Antelope Valley Dustbusters Research Group, 2011
Wind barrier - berms (built with soil and/ or wood chips).	Semi-permanent large berms are built perpendicular to the blowing wind. Must remove sand on upwind side to maintain effectiveness.	Grantz, et al. 1998d Antelope Valley Dustbusters Research Group, 2011
Windbreak with trees/shrubs	New plantings needs irrigation and also need protection from sandblasting and accumulation of sand. Improves aesthetics.	Grantz, et al. 1998d Antelope Valley Dustbusters Research Group, 2011
Chemical coating	Only applies to roads and equipment yards	Antelope Valley Dustbusters Research Group, 2011
Gravel mulch	Only applies to roads and equipment yards	Antelope Valley Dustbusters Research Group, 2011
Paving	Only applies to roads and equipment yards	Antelope Valley Dustbusters Research Group, 2011
Wood chip mulch	May be appropriate in cropping system	Antelope Valley Dustbusters Research Group, 2011
Plastic mulch	May be appropriate in cropping system	Antelope Valley Dustbusters Research Group, 2011
Watering	Requires water use. Can cause crusting of the soil and thereby limit wind erosion temporarily.	Antelope Valley Dustbusters Research Group, 2011
Revegetation - direct seeding of native plants	Careful planning of the species planted and timing of planting is important. Preparations can include burning annual vegetation, soil preparation, seeding by ground or aerially. Results are best when soil conditions are optimal (low residual nitrate, high microbe activity). Low success rate; difficult to establish in years of drought. High cost, requires irrigation to initiate. Applies when land is to be fallowed for long period of time, will hold soil in place and reduce dust.	Grantz et al. 1998
Revegetation - transplanting of native plants	Transplants need irrigation and protection such as wire or plastic cages. Expensive and difficult to establish in years of drought. High cost, requires irrigation initially. Applies when land is to be fallowed for long period of time, will hold soil in place and reduce dust.	Grantz et al. 1998
Dust suppressant materials (MgCl₂)	All literature found was related to use on unpaved roads, not agricultural fields. Concerns for water quality.	Antelope Valley Dustbusters Research Group, 2011
Mulching (with manure, plant materials such as straw or other course organic matter).	Only practical on small parcels. Must use caution not to create disruption to the soil (wheel paths) parallel to the wind direction which can promote dust blowing. Only partially incorporate crop residues to maintain soil structure; type of conservation tillage.	Presley, et al. 2013 USDA NRCS Conservation Practice Standard Code 345
Restricted access	Expensive to fence property, but can reduce dust caused by disturbance of soil (vehicles)	Imperial County Air Pollution Control District, 2012

References

Hudson Minshew
District Conservationist
USDA Natural Resources Conservation Service
44811 N. Date Ave., Ste. G, Lancaster, CA 93534-3152
Phone: 661.945.2604 Ext. 110
Antelope Valley Dustbusters Research Group. Agricultural Guide to Controlling Windblown Sand and Dust. 2011.
Grantz, David et al 1998a. Though difficult to achieve, revegetation is best way to stabilize soil. California Agriculture 52:4 p8-13.
Grantz, David et al. 1998b. Seeding native plants to restore desert farmland and mitigate fugitive dust and PM10. J. Environ. Qual. 27:1209-1218.
Grantz, David et al. 1998c. Transplanting native plants to revegetate abandoned farmland in the Western Mojave Desert. J. Environ. Qual. 27:960-967.
Grantz, David et al. 1998d. Wind barriers suppress fugitive dust and soil-derived airborne particles in arid regions. J. Environ. Qual. 27:946-952.
DeAnn Presley, et al., Emergency Wind Erosion Control, Kansas State University, March 2013.
USDA, Natural Resources Conservation Service, National Agronomy Manual, 3rd. Ed., October 2002. Part 502 Wind Erosion.
Brenton Sharratt and Guanglong Feng. 2009. Friction velocity and aerodynamic roughness of conventional and undercutter tillage within the Columbia Plateau, USA. Soil and Tillage Research 105: 236-241.
Imperial County Air Pollution Control District. Agricultural Air Quality Conservation management Practices for Imperial County. 2012.