Management Practices for Agricultural Nonpoint Sources

For many pollutants, a number of generally effective management practices (termed best management practices or BMPs) for addressing agricultural nonpoint sources have been developed. Many of these "BMPs" are now incorporated into the technological baseline of modern American agriculture and are so broadly implemented that they are taken for granted by the public as part of the agricultural landscape. These include basic measures for soil and water conservation, pesticide and nutrient application, handling of livestock wastes, and grazing management. Additional BMPs beyond this baseline are also used to varying degrees by growers, ranchers and forest landowners in the watersheds draining to the Sanctuary.

The term "BMP" is misleading, however. It cannot be said that any so-called BMP will be the most effective option in any particular circumstance. Experience, professional judgment, and experimentation are always required for the successful implementation of appropriate pollution controls on a site-specific basis. For this reason, the term "management practices" is generally used in this document rather than BMP.

Such generally effective "Best Management Practices" are described in detail in a variety of other documents resulting from a wide range of research, management studies and plans. These include the State Water Resources Control Board (SWRCB) and the California Coastal Commission's Management Measures to Address Sources of Nonpoint Pollution affecting California Waters, the NRCS Field Office Technical Guide, Department of Pesticide Regulation (DPR) and UCCE publications, and the watershed-specific plans cited in the bibliography.

Examples of these agricultural practices discussed in this document are not meant to imply that a prescriptive menu of "one size fits all" preferred practices be established for the watersheds draining to the Sanctuary. Identification of the most appropriate controls for site- and crop-specific conditions is best made by the landowner/operator relying on technical sources of expertise such as NRCS, UCCE, Agricultural Commissioners, private professional consultants, private agricultural industry associations, and local outreach agents such as the Resource Conservation Districts (RCDs) and Community Alliance with Family Farmers (CAFF). The WQPP recognizes the importance of supporting the continued evolution of improved agricultural management practices through public and private initiatives, utilizing economically sound adaptive management practices.

Overview of Management Practices

Erosion, sedimentation and runoff

 A wide variety of management practices are used to varying degrees in the watersheds that drain to the Sanctuary to reduce the impacts of runoff, erosion and sedimentation. Soil and water conservation practices to help retain sediment and reduce runoff include berms, water bars, sediment basins, drainage ditches, field drains and sumps, underground outlets, contour plowing, and drip irrigation. They also include grassing of waterways and field roads, vegetative buffers, windbreaks, cover cropping, mulching, retention of residual dry matter and minimum stubble heights, specialized treatment of logging slash, encouragement of perennial grasses on grazing lands, and fencing and offsite watering on grazing lands.

On some sites, sediment basins, water detention basins, and vegetative buffer strips at the edges of fields and waterways can help filter runoff and collect sediments and associated chemicals; grassed waterways and field roads can convey runoff and prevent erosion, trap sediments and use excess nutrients; underground outlets and furrow pickup lines can direct excess runoff from slopes to sediment basins for settling; diversions (earthen berms) can be used to direct runoff into natural channels, vegetated slopes or sediment basins. Cover cropping, critical area plantings, mulching, contour cultivation, furrow alignments, grade stabilization structures, and a variety of other management practices are also employed to reduce on-site erosion and runoff. A variety of practices are also available for rural road erosion control, and for biotechnical approaches to bank stabilization.

Most management practices can be successfully adopted by individual growers or ranchers, while others may function best as part of a collaborative project among a group of neighbors.

Water conservation

Water that moves away from crops may have unintended consequences of increasing erosion, and transporting nutrients and pesticides away from crops and into surface or ground water where they become pollutants. This water loss can also be an economic loss for the grower since it does not add to crop productivity although electrical costs were incurred for the pumping, and it contributes to ongoing overdrafting of the aquifers in the Central Coast region.

Water conservation practices underway in varying degrees throughout the watersheds include utilizing the California Irrigation Management Information System (CIMIS) or other irrigation scheduling guidelines, applying such technologies as drip or micro-irrigation and automated timers or controls with moisture sensors, regular inspections/repairs of the irrigation system, and increasing the uniformity in distribution of water. Water conservation practices also include capture of runoff and recycling of irrigation water to reduce water use (e.g., tailwater return systems, nursery recycling systems), the application of mulch, and reducing the impacts of runoff from impervious surfaces (e.g., greenhouses) by capturing water runoff from winter rains and using it for irrigation. Additional water supply developments include retention and detention ponds to capture winter rains for groundwater recharge and for irrigation use to reduce use of creeks in the summertime.

Nutrients

Excess nutrients that move off-site into surface or ground waters may lead to environmental and public health concerns, and may represent an economic loss to the grower since they are no longer contributing to crop productivity. A range of fertilizer management practices are employed in the region based on attempted estimates of appropriate agronomic rates, but accurate determination of the agronomic rate is dependent on a number of crop- and site-specific variables.

Management measures, underway to varying degrees throughout the region, include minimization of water and nitrogen loss by leaching and runoff through effective application and timing of irrigation water, utilizing CIMIS or other irrigation scheduling guidelines; using multiple small doses of nutrients rather than one or two large applications; preapplication testing of nutrient levels in soil or plant tissue; consideration of the nitrogen content of irrigation water in making fertilizer decisions; the use of slow-release nitrogen; avoiding fertilizer material spills during transport, storage and application; and various techniques to position and concentrate the fertilizer near the crop roots, instead of leaving it spread out over 100% of the field. Where appropriate and economically practical, leaching and runoff of remaining nitrogen from fallowed lands may be minimized through the use of cover crops, and numerous types of organic materials may be incorporated into the soil such as crop residues, cover crops and manures. Vegetative buffers around fields may also be used in some locations to reduce off-site transport of nutrients.

Considerable research is underway via UCCE and the industry-financed Fertilizer Research and Education Program to refine management techniques for the specialized vegetable production on the Central Coast to reduce potential nitrate contamination while increasing the efficiency of fertilizer and water use. Growers should be able to use this research to continually modify and improve their management practices.

Pesticides

Flood events, storm water runoff, and irrigation can all cause offsite transport of persistent pesticides which are no longer in use, such as DDT and toxaphene. Although flood events can be reduced in frequency and severity, they cannot be eliminated; and severe flooding can overwhelm the most prudent land management practices. Reduction of offsite transport of old persistent pesticides from ordinary stormwater runoff and irrigation return flows, and to some extent from flood events, will depend on erosion control practices, since these compounds often remain adsorbed on soil particles for long periods of time. A range of potential management practices for erosion control were identified above.

Growers do not intentionally apply pesticides excessively, since application and purchase are significant business costs. County Agricultural Commissioners regulate usage of restricted materials, issuing permits which are specific as to the pesticides used, crops treated, application method and field locations. Pest and disease outbreaks, consumer demand for unblemished products, regulatory fruit and vegetable quality standards, and food processor "zero tolerance" for insect damage will continue to be important factors necessitating the use of pesticides in production agriculture. However, ongoing efforts to research and develop genetically disease-resistant plant varieties, biological control agents, Integrated Pest Management Systems (IPM) and environmentally benign chemical control agents are creating a greater variety of effective pest control options for growers to utilize.

Many growers in the watershed use some form of IPM techniques, to varying degrees. These techniques include closer monitoring of pest populations in the field to detect and target pest buildups; use of cultural, physical and biological controls before consideration of pesticide application; establishment of an economic threshold for each pest buildup problem on the crop beyond which it becomes cost-effective to apply pesticides; and use of non-chemical techniques where appropriate. IPM relies on the targeted use of pesticides when necessary and recognizes that existing biological controls are not always appropriate or effective. This suggests a need for continuing investment in the development of commercially feasible IPM tools.

Additional management practices which are underway in some areas include alternatives to the "clean farming" approach of complete weed control, such as use of hedgerows and grass plantings. Where appropriate, they may also include encouragement of native habitat that can harbor beneficial insects/wildlife (i.e., those that prey on pests in areas close to fields) as a method of reducing the need for pesticides.

In discussing pesticide management practices, it is important to also recognize that homeowners often use high-risk products with little or no knowledge about effects, proper use, or disposal. Education for urban residents about potential impacts and ways to reduce runoff of pesticides and fertilizers is being conducted as part of the WQPP's Urban Runoff Plan.

Livestock wastes

The number of confined animal facilities, dairies and poultry ranches has decreased greatly on the Central Coast over the past 30 years. However, these facilities still exist, as well as small rural ranchettes with recreational livestock, and may present a localized threat to water quality through runoff of sediments, nutrients and pathogens. The larger facilities are regulated by the RWQCB. Smaller unregulated facilities have a range of management practices in use to varying degrees, including dikes and diversions to reduce contamination from manure areas; water and sediment control basins; establishment of vegetative cover or surfacing with suitable materials in heavy use areas; liquid containment structures for waste storage and treatment; reducing or rotating access of livestock to riparian areas; use of vegetative filter strips to remove sediment, organic matter and other contaminants from runoff and wastewater; and composting facilities.

Grazing practices

Although the management practices described above address irrigated agriculture and confined animal facilities, the region's watersheds also contain extensive expanses of grazing lands. Effectively managed grazing lands are an important part of a healthy watershed, providing sites for recharge, wildlife habitat, slowing runoff and filtering potential pollutants. The following discussion adapted from the California Rangeland Water Quality Management Plan describes water quality issues and management practices for grazing lands.13

Livestock and wildlife's use of rangelands may impair beneficial uses of water by adding inorganic and organic sediments and bacterial contaminants to water, and by physically altering riparian and instream habitats. Animals may affect soil compaction and removal of vegetation which can, on some sites, decrease infiltration rates and increase erosion.

Management practices underway to varying degrees throughout the region's grazing lands include livestock management practices which assist with the control, time, frequency or intensity of grazing, in order to maintain sufficient vegetative cover to protect soil and enhance desired vegetation such as perennial grasses. Such practices include prescribed grazing, feeding and salting locations, and alternative sources of water and shade. Structural improvements (e.g., water development, fencing, erosion control, etc.) and structures associated with normal livestock production operations such as barns and corrals may be used to facilitate grazing management. Land treatments (e.g., burning, mechanical manipulation, seeding, weed control) may be used to manage vegetation, reduce erosion, and improve range or wildlife habitat.

Improving the quality of grazing lands has important benefits to both the rancher and the environment, if done in an economically viable and sustainable fashion. Healthier soil and grass, and greater control over livestock use patterns increase agricultural production. Appropriate grazing practices may promote a diversity of plants, protect waterways, reduce erosion, reduce fuel loads and are key to the long-term health of the region's watersheds and for meeting water quality goals.

The State Water Resources Control Board has endorsed the California Rangeland Water Quality Management Plan (RWQMP) which was developed with the assistance of the California Board of Forestry's Range Management Advisory Committee to be the rangeland component of the state's Coastal Nonpoint Source Plan required by the Coastal Zone Act Reauthorization Amendments of 1990. The RWQMP is currently being implemented within the Central Coast region through a series of formal "short courses" conducted by the University of California Cooperative Extension and NRCS, with the assistance of individual county Cattlemen's Associations and county Farm Bureaus, and under the oversight of the RWQCBs. Continuing and building on these short courses is addressed in Section 2 of this document.

Facilitating Implementation of Management Practices

As indicated above, the management practices discussed here are not meant to be a prescriptive list of practices, but simply to illustrate the range of practices frequently cited as being useful for protecting water quality. Effective management practices for specific sites and crops are best determined by the individual landowner relying on available technical expertise, and will continue to evolve as additional research and technology becomes available. Self-monitoring, as discussed later in Section 1 and Strategy 2-7, will play an important role in helping growers determine the effectiveness of management practices for their specific conditions.

Although the available data support general conclusions about the mechanisms of pollutant transport from nonpoint sources through the watershed, the limited level of understanding of hydrological systems and the location, significance and mechanics of nonpoint sources limits our ability to control pollution through the prescriptive application of effective management practices. Although much can be accomplished with existing information on management practices, effective control of pollutant sources will require an ongoing planning and adaptive management process. This should include development of a baseline for sediment transport and other pollutants in the watershed, further research into the identification of both natural and human-induced sources, and assessment of their significance. It should also include refining general classes of management practices to address site-specific conditions, monitoring near- and long-term results, and encouraging continual evolution of practices to improve source control.

Moving Toward Solutions

In considering ways to address water quality issues in the watersheds that drain into the Monterey Bay National Marine Sanctuary, several related problems were cited by growers and ranchers, agricultural representatives, resource management agencies and the public during the initial WQPP workshops held in Salinas, Watsonville, and Half Moon Bay. Various institutional and economic barriers were identified that impede the development and adoption of agricultural practices that improve water quality. These barriers ranged from inaccessible technical information and economic analyses for choosing appropriate practices, to insufficient funding or incentives for trials or installation, to regulatory hurdles that may be disincentives to making improvements.

Although many management practices produce water quality improvements, site-specific knowledge and voluntary implementation of these practices is not as widespread as it could be. Existing agricultural organizations with extensive membership networks such as Farm Bureaus could play a greater role in expanding development and implementation of effective management practices. Developing greater public understanding of the complexity of the issues and the importance of agricultural lands will also be important for the WQPP's nonpoint source components to succeed.

The Strategies

In developing this document, participants generally looked for a range of solutions that would enhance and protect water quality, while sustaining the economic viability of agriculture. Approximately 40 initial recommendations by participants fell into six strategy categories: identification and adoption of more effective management practices through development of industry networks; expansion and coordination of technical assistance/outreach; public education and public relations; regulatory coordination/permit streamlining for conservation measures; improved funding mechanisms and tax incentives; and strategies for public lands and rural roads.

Strategies in Section 1 of this document outline a framework for utilizing existing industry networks such as Farm Bureaus and other agricultural groups in establishing an agricultural water quality program, under the umbrella structure of the WQPP, and in cooperation with the Regional Water Quality Control Boards. These strategies, added by the Central Coast Farm Bureau Coalition, are key to ensuring on-the-ground implementation of management measures by local growers. Strategies in Sections 2 through 5 deal with technical outreach and education, funding and incentives, and coordination/streamlining of the existing regulatory system to reduce barriers to the development and implementation of erosion control practices that may require the approval of more than one regulatory agency. Section 6 addresses nonpoint issues on public lands and rural roads.

Table 1 summarizes each of the strategies, the key activities involved, and a general priority for implementation. For strategies indicated as high priority, we expect substantial implementation to be underway in the next three to five years.

Table 1
Summary of Strategies and Implementation Priorities