Best Management Practices (BMPs) Descriptions

Below are the descriptions of the different BMPs that are available under NTT.

Auto Irrigation and Fertigation

Auto Irrigation:

Automatic irrigation systems are irrigation systems that are controlled by a computerized controller. These types of systems are convenient. Auto irrigation overall can greatly increase crop yield. However, if auto irrigation is applied to a region where there is no need (such as an area with ample rainfall) adding auto irrigation will cause little to no change from the baseline. The user needs to input in the information of the auto irrigation system, including:

Irrigation Type: Irrigation type is the kind of auto irrigation that the user will be using. They include: sprinkle, furrow/flood, drip, furrow diking, and pads and pipes – tailwater irrigation. If you select furrow diking, you also have to input the safety factor (#6 on this list).
Irrigation Efficiency: This value is the fraction of irrigation application that is not lost to runoff. This must be a value that is greater than or equal to 10 and less than or equal to 95%. The closer the value is to 0, the greater the percentage of water lost to runoff. A value of 100 means that no water is lost to runoff.
Irrigate a Maximum of every (0-365) days: This field is asking for the maximum frequency (in days) that irrigation can take place. Frequency is the days in between which auto irrigation takes place (if the value is 1, this means that there is auto irrigation every day; two means every other day; three means every three days; etc.) The value can be any whole number greater than zero and less than or equal to 365.
Plant Water Stress Level/Factor: This is the value that is used to trigger the start of auto irrigation. It is set to a default value of 0.8. The plant water stress factor can be any value greater than 0 and less than or equal to 1. While a value of 0 is not permitted, it would signify manual irrigation (no automatic irrigation). The closer the value is to 100, the less water stress is allowed before the automatic irrigation is turned on. If the value is equal to 1, water stress is not allowed.
Maximum Single Application: This value signifies the amount of water than can be applied in a single day. It is in inches, and it can be any number greater than 0. However, it is set to a default value of 3.
Add irrigation schedule for crop rotations: You also can select the start and the end date of auto-irrigation/fertigation within a rotation year.

Auto Fertigation:

Fertigation is the application of fertilizers, soil amendments, or other water-soluble products through an irrigation system. Auto Fertigation is an automatic fertilization process in which fertilizer is dissolved and distributed along with water in your drip or spray irrigation system*. This makes Auto Fertigation very similar to Auto Irrigation. In fact, all of the inputs into Auto Irrigation are in Auto Fertigation. To see these inputs, see Auto Irrigation. However, there is one additional input in Auto Fertigation:

Concentration of Nitrogen in irrigation Water (ppm): The amount of nitrogen in the Automatic Fertigation in parts per million.

Tile Drain:

Tile drainage is a practice for removing excess water from the subsurface of soil intended for agriculture. Drainage brings excessive soil moisture levels down for optimal crop growth. Tile drainage is often the best recourse for reducing high subsurface water levels to improve crop yields. Too much subsurface water can be counterproductive to agriculture by preventing root development, and inhibiting the growth of crops. Excessive water also can limit access to the land, particularly by farm machinery.

For NTT applications, underground drainage systems are simulated in APEX. The depth of the drainage system to reduce plant stress is a key parameter used in simulating tile drainage systems in NTT. Tile drainage simulation in NTT increases subsurface flow, which may provide an avenue for increased nutrient losses in subsurface flow. The input for Tile Drain is:

Depth: This is the depth in feet at which the drainage system is installed. It is any number greater than 0.
Tile Bioreactors: The primary purpose of a bioreactor is to remove nitrates from subsurface tile drainage water at the edge of a field.
Drainage Water Management: The process of managing the drainage volume and water table elevation by regulating the flow from a surface or subsurface agricultural drainage system.

Tile Drain Open Period: The period of time in a year when the tile drain is open. Otherwise it is open all year.

Saturated Buffer: A saturated buffer is a relatively new edge-of-field conservation practice to reduce nitrate loads from tile-drained areas, where, rather than drainage water flowing directly to the stream or ditch through the outlet pipe, the drainage water is diverted to flow as shallow groundwater through a vegetated buffer’s soil. This practice needs to be paired with a buffer.

Distribution pipe length: The length of vegetation buffer where water is diverted into the perforated distribution pipe.
Estimated fraction of annual tile flow: Estimated fraction of drainage water passing through saturated buffer(0-1). Only needed if there is no input for distribution pipe.

Wetlands:

Wetlands are those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas.

The wetland area is simulated as a shallow reservoir (1 ft. depth) with growing wetland vegetation – it is essentially simulated as an artificial wetland and not a natural wetland. The slope of wetland area is set as one percent. Simulated wetlands trap sediment, reduce runoff, increase infiltration, and also increase uptake of water and nutrients by the vegetation in the area covered by the wetland. The only input(s) required for wetlands is:

Area: The area of the wetland is input in acres. Since this area is no longer able to be used for crop production, there may be a lower total crop yield (although there may be a greater crop yield/acre).
Is the wetland area included in your AOI?: Here user indicates if the wetland being described is currently included in the area of interest/field as outlined in the map. If it is included in the outline, then NTT will subtract the wetland acres from the field. If it is not included in the outline, then NTT will assume it is adjacent to the field.

Ponds/Water and Sediment Control Basins:

Ponds are used to provide water for livestock, fish and wildlife, recreation, fire control, develop renewable energy systems, and other related uses, and to maintain or improve water quality by retaining the runoff from upland field. Only one input is required for ponds:

Fraction of Area Controlled by Ponds/WASCB: This is the fraction (a value between 0 and 1) and is simply the fraction of the subareas which flows through (is controlled by) ponds. This only affects only the hydrology that originates in this subarea. Inflow from other subareas is not routed through the ponds in this subarea. The exact location of the ponds, however, is unknown. A greater value could help improve water quality by retaining the runoff from the upland fields.

Stream Fencing (Livestock Access Control):

Access control means the temporary or permanent exclusion of animals from an area to achieve and maintain the desired resource conditions. * If it is only a temporary exclusion, the user can enter the information regarding how much time the animals actually spend within the fenced area. Because excluding the animals from the stream allows a grassed area to grow, the user must also add the information for a filter strip.

The following are the inputs for Stream Fencing:

Distance from the stream to the fence(ft): The value zero (0) means no buffer is created.

Streambank Stabilization:

Stabilization of streambanks is done to prevent the loss of land or damage to land uses or facilities adjacent to the banks of streams or constructed channels properties. Streambank stabilization results in: 1) Maintaining the flow capacity of streams or channels; 2) Reducing the offsite or downstream effects of sediment resulting from bank erosion; and 3) improving or enhance the stream corridor for fish and wildlife habitat, aesthetics, recreation.

If you would like to use the Streambank Stabilization, click on the Select button.

The input(s) for Streambank Stabilization inlude:

Crop: This is the type of grass or vegetation that will be present in the buffer section. Select one from the drop down list of options.
Width (ft): This is the width, in feet, including both sides of the vegetated channel. This can be any number greater than 0.
Length (ft)
Stream Side Slope (Percentage)

Grass Buffer/Forest Buffer

Grass Buffer:

Grass buffers, also known as a filter strips, are an area of vegetation, generally narrow in width and long across the downslope edge of a field, that slows the rate of runoff, allowing sediments, organic matter, and other pollutants that are being conveyed by the water to be removed by settling out. Filter strips reduce erosion and the accompanying sediment-bound pollution.

In NTT, filter strips function by providing for better infiltration of soluble nutrients, trapping of sediment, and increased uptake of water and nutrients by the filter strip vegetation. The saturated conductivity value is also modified for filter strip simulation in NTT.

The inputs for grass buffers are the same as for forest buffers (see Forest Buffer), with the additional requirement that the user specify type of vegetation.

Crop: This is the type of grass or vegetation that will be present in the buffer section. Select one from the drop down list of options.
Area (acres): This is the area of the buffer in acres and is simulated as a separate field. It must be a number greater than 0.
Grass Strip Width (ft): This is the width in feet of the filter strip. Filter Strips are typically narrow in width. This can be any value greater than 0.
Fraction of field treated by buffer: This is the estimated fraction (0.00-1.00) of the runoff from the field that is routed through the buffer.
Is the buffer area included in your AOI?: Here the user indicates if the wetland being described is currently included in the area of interest/field as outlined in the map. If it is included in the outline, then NTT will subtract the wetland acres from the field. If it is not included in the outline, then NTT will assume it is adjacent to the field.

Forest Buffer:

Forest buffers are linear wooded areas with well-developed root systems, an organic surface layer, and understory vegetation. When they are adjacent to open water they are referred to as riparian forest buffers. Non-riparian buffers are linear wooded areas along down-slope field edges. Forest buffers trap sediment and increase infiltration, thereby reducing sediment and nutrient losses. Forest buffers often include a grass buffer between the field and the forested buffer. If present, please also include the width of the grass buffer.

The input(s) for Forest Buffer are the following:

Forest Strip Width (ft.): This is the width of the mix of grass and trees in the portion of the forest buffer (not including the grass strip).

Grass Waterway:

Waterways are vegetated channels that conduct and dispose of overland flow from upstream areas. Waterways typically work by increasing the surface roughness (with the vegetation) which reduces the velocity of flow.

The inputs for Waterways are the following:

Crop: This is the type of grass or vegetation that is used in the channel.
Width: This is the width, in feet, including both sides of the vegetated channel. This can be any number greater than 0.
Length (ft)
Fraction of field treated by Grass Waterway: The fraction of the field that drains to the grass waterway. A number between 0.00 and 1.00. In NTT, this fraction is set as 1, assuming that all the runoff from field passes through grass waterway.

Contour Buffer (Strip Farming):

A contour buffer strip is an area of land maintained in permanent vegetation that helps to control air, soil, and water quality and other environmental problems primarily on land that is used for agriculture. Buffer strips trap sediment and enhance filtration of nutrients and pesticides by slowing down runoff that could enter the local surface waters.

The buffer strip is simulated based on the width of the buffer and main crop, and the vegetation planted in the buffer. The number of strips and area are calculated according to the total field area and the widths of buffer and main field, which are inputs to the model.

The inputs for Contour Buffer are:

Crop: This is the type of grass or vegetation that will be present in the buffer section. Select one from the drop down list of options.
Grass Buffer Width (ft): This is the width, in feet, of the buffer strips. It can be any number greater than 0. Buffer width, along with crop width, determine the number of buffer and crop strips in the field.
Crop strip width (ft): This is the width of the commercial (main) crop strips.

Land Leveling:

Land leveling is used to reduce the slope on very high soil slopes. By reducing the slope, the surface land is better able to retain irrigation and soil water. The input for land leveling is:

Slope reduction: To simulate this management practice in NTT, users need to provide the percent reduction of original field slope after the land treatment.

Terrace System:

A terrace system is a leveled section of a hill cultivated area, designed as a method of soil conservation to slow or prevent the rapid surface runoff of water. Terraces decrease hill slope-length, reduce formation of gullies, and intercept and conduct runoff to a safe outlet thereby reducing sediment content in runoff water. Often, in application the landscape is formed into multiple terraces, giving a stepped appearance. Terraces are simulated by reducing the practice factor (PEC). If you would like to apply a terrace system, click on the Select button.

Reservoir:

Elevation at Emergency Spillway (ft): This is the height to the top of the reservoir.
Surface Area at Emergency Spillway (ac): Total reservoir surface area at emergency spillway elevation.
Volume at Emergency Spillway (in): Runoff volume from reservoir catchment area at emergency spillway elevation.
Elevation at Principal Spillway (ft): This is the height to the base of the reservoir.
Surface Area at Principal Spillway (ac): Total reservoir surface area at principal spillway elevation.
Volume at Principal Spillway (in): Volume at principal spillway elevation.
Initial Volume (in): This should be 0 in most cases.
Average Principal Spillway Release (days): This will be the rate at which the water seeps through the straw bale, sand bags, etc.
Initial Sediment Concentration (ppm): Initial sediment concentration in reservoir.
Normal Sediment Concentration (ppm): Normal sediment concentration in reservoir.
Hydraulic conductivity of reservoir bottoms (mm/h): Hydraulic conductivity of reservoir bottom.
Time Sediment to Return to Normal (days): Time for sediment concentrations to return to normal (days) following a runoff event.
Bulk Density of Sediment (t/m3): Bulk density of sediment in reservoir.

Auto Lime Application:

Auto Lime Application: Auto lime application enables the user to simulate application of agricultural limestone to increase soil pH and/or reduce soil aluminum saturation. As the default, NTT automatically applies Lime. (Check the box to automatically apply lime as needed).

Reference

* See USDA website: http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/technical/?&cid=nrcs143_026849 for more detailed term descriptions.