Vegetative treatment systems (VTS) have been explored as a manure treatment option for small farms as well as large Confined Animal Feeding Operations (CAFOs).
Vegetative Treatment System (VTS) Types
There are many different types or flavors of vegetative treatment systems (VTS). Soil available water holding capacity, soil infiltration rate, topography, depth to groundwater, distance to surface water, and slope are the primary factors that determine whether a particular type of VTS is appropriate for a site. Below are but some of the system types.
Sloped VTS
A sloped VTA is defined a vegetative area with slopes between 1-5 % in grade. This is the most popular type of VTS and is one of the most simple. The advantage of the sloped VTA is that the gradual slope works well for achieving uniform distribution across the VTA. The disadvantage of the sloped VTA is that is can allow runoff to leave the system during large storm events. Design of sloped VTA’s is similar to border irrigation design, that is the area is divided into increment borders to match haying equipment width and to minimize land leveling.
Virtual tours of some sloped VTS
- Virtual tour of a vegetative treatment system at the Meat Animal Research Center (MARC), Clay Center, Nebraska Heartland Project Alternative Technology Resources
- See Virtual tour of some Kansas VTS sites
- Livestock Producer Environmental Assistance (LPEAP) website under "Projects" include many types, some of which are sloped VTS
Level VTA and Vegetative Infiltration Basins
A level VTA is defined as having a level area (0-1%) or is a designed as a vegetated shallow basin. Berms for level VTA’s are usually in the 1 to 2 foot range and have the advantage of containing and treating large runoff events. For small runoff events even distribution across the VTA is more difficult. Level VTA are level vegetated basins and Vegetative Infiltration Basins are level vegetated basins with a sub surface drainage system beneath the root zone of the VTA to collect excess percolation for further treatment.
An example of a VIB-VTA system can be seen at the Virtual tour of a vegetative infiltration basin and wetland system to treat open beef feedlot runoff at an Iowa State University farm. [1]
Terrace Systems
A VTA terrace systems are typically designed as serpentine broad base terraces or as storage terraces. They have the advantage of having a long contact time, but are difficult to construct with an adequate vegetated area. That is a terrace system may need to be twice as large as a sloped area for the same treatment area, as so much area is lost to slopes. The other disadvantage of a terrace system is the difficulty in achieving uniform distribution across the entire VTA.
Constructed Wetlands
Constructed wetlands are shallow impoundments (3-4 feet maximum depth) that use the liquid surface to treat the nitrogen (denitrify) in the runoff water. Cattails and bulrush have been used successfully in constructed wetlands. Usually the bottom is flat and liquid levels are maintained at six to twelve inches. The advantage of a constructed wetland is that they need less space than a conventional VTA, because they are able to treat more nitrogen per unit area than, say a sloped VTA.
Their disadvantage is that they cannot completely clean the water, so they need to be coupled with another type of VTA to be effective. The other main disadvantage is that they are very costly, and depending upon the geology of the site, need a liner to be acceptable (with the addition of fill on top of the liner for plant media).
Sprinkler and Pump VTA’s
A pump or sprinkler VTA concept uses a pump or mechanical device to convey runoff water to a distribution system, up gradient of the sediment settling structure. A sprinkler VTS uses sprinkers to distribute runoff. A pump VTS uses low pressure mechanisms, such as gated pipe or concrete spreaders to distribute runoff to a VTA. The advantage of sprinker and pump VTS is that they can be constructed in situation where suitable land below the sediment settling structure is not available, but is available up gradient. The disadvantage of pump and sprinkler systems is that they are more costly and require more maintenance to maintain the pump and distribution system. An example or tour of a sprinkler and pump VTS can be found at the Livestock Producer Environmental Assistance Project (LPEAP).
Dual and Multiple VTA Systems
Dual and Multiple systems combine more than one VTA type, and have the advantage of increasing the performance and efficiency of a VTS. An examples and tours of a multiple VTS can be found at the Livestock Producer Environmental Assistance Project (LPEAP). Whenever possible dual or multiple system are preferable to single type systems.
Page developed and maintained by: Chris Henry, University of Nebraska Extension
Content reviewed by: Mark Rice, North Carolina State University
