Critical Concerns

Water quality impacts from agricultural land use often involve the movement of sediment, nutrients, and pesticides from a field site. Erosion leads to downstream sedimentation concerns. Nutrients, regardless of whether they are point or no point sources, support plant growth in water, resulting in hypoxia (low oxygen) and the formation of toxin accumulation. Pesticides can add to health concerns for potable water supplies. How water is used within a watershed for recreational activities, potable water sources, or the existence of unique ecosystems will determine what impairments to water quality from sediment, nutrients, and pesticides exist.

Many of Ohio's current water quality issues focus on erosion and nutrient concerns that lead to excessive plant and cyanobacteria growth. Current critical concerns fall into three areas of agricultural management: erosion, nitrogen, and phosphorus.

 Erosion 

  • Sediment is deposited as the water slows in the water course (ditch, stream, or river). Removal is required to maintain navigation courses.
  • Sediment adds to the suspended solids component of water and requires filtering for water systems using surface water as a water source.
  • Sediment can also affect aquatic animals by smothering nests and eggs, clogging gills, and affecting water temperature.
  • Nutrients are associated with the sediment that enhances nutrient enrichment.
Critical Concern in the field. Description of Critical Concern and Potential BMP's

Inter-rill and rill erosion moves soil within the field boundary

Gully erosion via concentrated surface flow resulting in off-site deposition

Ditch/Streambank Collapse adds sediment downstream

Surface Inlet

Surface water leaving via field edge or tile risers results in higher nutrient concentrations entering a stream.

 

Nitrogen 

  • High concentrations in water will result in excessive plant growth that affects recreational activities and use as a water source to drinking water systems. High nitrates (above 10 PPM) trigger water system warnings for users.
  • Decomposing plant materials from aquatic plant blooms can cause hypoxia (low oxygen) concerns in deeper areas of a body of water.
  • High nitrate concentrations in source water for drinking water systems might result in warnings to consumers. Nitrates above 10 parts per million (PPM) trigger water system warnings for susceptible users.
  • High ammonia levels are toxic to fish.
Critical Concern in the field. Description of Critical Concern and Potential BMP's

Evaluate rate to account for organic and inorganic nitrogen sources applied

Tiled fields lead to nitrate losses during the non-growing season

 

Phosphorus 

  • Higher concentrations in water result in plant growth that affects recreational activities and potable water system use.
  • Decomposing plant materials from aquatic plant blooms can cause hypoxia (low oxygen) concerns in deeper areas of a body of water.
  • The trigger nutrient for cyanobacteria growth has been an issue in Lake Erie, Grand Lake St Marys, Ohio River, and other water bodies in the state. Cyanobacteria can often produce toxins that affect animals and humans. For example, the toxin triggered a "do not drink" warning for Toledo, Ohio, in August 2014.
Critical Concern in the field. Description of Critical Concern and Potential BMP's

Soil test P value less than 50 PPM (or 100 lbs/A) Mehlich III

or "Lower" P Risk Assessment

Soil Test P-value between 50 PPM (or 100 lbs/A) and 120 PPM (or 240 lbs/A) Mehlich III

or "Moderate" P Risk Assessment

Soil Test P-value greater than 120 PPM (or 240 lbs/A) Mehlich III

or "High" to "Very High" P Risk Assessment

Potential loss paths of surface applied P

Surface applied nutrients are exposed to loss from rainfall after application

 

Fields with a higher risk loss potential for sediment or nutrient loss can be identified when working in agricultural fields or reviewing crop production plans, such as nutrient management plans. The visual cues for critical concerns are shown in the first section of this publication. Higher risk situations are often a combination of inherent soil characteristics, past agronomic management, and current environmental concerns. Identifying critical concerns is the first step in seeking remedial solutions.

Often, several BMP options exist for a particular field that can lessen sediment and nutrient impacts downstream. Selecting the BMP with the best fit in the field landscape or that compliments a farm's practices have the best potential to reduce sediment and nutrient losses. These practices can be self-designed in some cases, but other practices require assistance to be designed effectively. The second section of this publication provides information on an individual BMP, where it is best used, and expected outcomes, including effectiveness and economic cost, when known. Also offered are design information for engineering practices and information about where a farmer/landowner can find additional financial and technical assistance.

As you identify critical concerns on your farm, a set of basic information can be noted on the included form and taken to NRCS, SWCD, or other conservation professionals for advice.