Horse Gestation

Archive for January, 2008

Traditional irrigation systems that apply wastewater and freshwater are designed to provide supplemental water to a growing crop when it is most opportune for the crop. This is not the purpose of the sprinkler Vegetative Treatment System (VTS). Design principles between a sprinkler vegetative treatment area (VTA) and a conventional irrigation system are the same (pressures, friction loss, etc.). However, there are a few additional criteria to consider in the design of a sprinkler VTA that would not be applicable to a conventional system. First, the system must have the ability to operate at near-freezing temperatures (in cold climates) and be easy to drain between uses. Second, the distribution system must be able to operate when the soil is at or near field capacity. Solid set and K-line irrigation systems have this capability. While operation under such circumstances is not desirable, extended wet periods can make this necessary. Next, the system must have the ability to distribute the runoff from the production area in a short period of time yet not at a rate that will generate runoff. We try to design our systems so that they can be empty from a 25-year, 24-hour storm in less than 48 hours (this is our self-imposed criteria). In addition, the VTA is sized to uptake the nitrogen generated and to store the liquid in the root zone. The system must also be able to withstand the corrosive effects of being in contact with manure. Equipment made of galvanized steel, for example, will deteriorate over time from use only with feedlot runoff. A conventional system applying wastewater and freshwater will not deteriorate since components are flushed out with clean water. We make sure the pumps, pipes, and sprinklers can withstand exposure. Our risers are galvanized and will need to be replaced periodically. However, the cost of replacement for those items is far less than a small pivot (one reason a pivot is not used in our systems). Author: Chris Henry, Biological Systems Engineering, University of Nebraska

From our experience, producers prefer plants that have forage value, which is also an incentive for the producer to harvest the vegetative treatment area (VTA) annually. Wetland plants such as cattails and bulrush could work well and are the recommended vegetation in the literature for constructed wetlands. We have used cattails in two constructed wetland projects with marginal success. For level VTAs (or vegetative infiltration basins [VIBs]), grass species that are successful at surviving wet soils conditions are preferred. Iowa State University has used reeds canary grass in their VIB, and we have used creeping foxtail; both species are tolerant of wet soil conditions. Eastern gammagrass has been used successfully at a vegetative treatment system (VTS) in Kansas but is more difficult to establish. Every region is different, so what works here may not be as successful in another part of the country. In Nebraska, we are evaluating the use of some other lesser-known species, such as orchard grass, switchgrass (warm season), and timothy in one of our projects. For additional information, see: • Chapter 6 of the collaborative report on Vegetative Treatment Systems for Open Lot Runoff • USDA Conservation Plants Pocket Guide • USDA VegSpec Web site VTA refers to permanently vegetated area used to infiltrate runoff from an open lot. VTS refers to the overall system, including the VTA and other treatment components such as a settling basin. Author: Chris Henry, University of Nebraska

First, the SPAW model was never designed to be used to assess the hydrology of a vegetative treatment system (VTS). Components of SPAW are useful for assessing components of a vegetative treatment area (VTA), but it is not a design tool. At Iowa State University, we have a graduate student analyzing results from SPAW versus results of the ISU-developed Effluent Limitation Guideline and VTA models for use with vegetative treatment systems. Two papers covering this topic will be available through ASABE following the international meeting in June 2008. SPAW is a daily hydrologic budget model for agricultural fields and ponds. Additional Information on SPAW Author: Lara Moody, Iowa State University

Federal ELG requires that there be no discharge from a CAFO except for the overflow from a system designed and operated to retain the 25-year, 24-hour storm event except if the precipitation event exceeds the 25-year, 24-hour storm? To demonstrate the ability of VTS to achieve the runoff control equivalent to the ELG, the results are compared using a computer model for predicting performance for a traditional system based on the ELG of the CAFO regulations and using the weather files generated at the site in question. It is incorrect to assume that traditional systems designed and managed according to the ELG of the CAFO regulations overflow only during storm events in excess of the 25-year, 24-hour event. Chronic wet periods are the primary reason for discharges in many wetter regions. Several published modeling studies for traditional system design suggest discharge is common for storm events less than the ELG. No discharge except for storm events greater than the ELG is achieved only in the western regions of the High Plains (e.g., western Kansas and Nebraska). Chronic rainfall events over a several day period (none exceeding the design storm event) are a common cause for discharges from traditional well-designed and managed systems in many Corn Belt states. Author: Lara Moody, Iowa State University

The answer is generally yes for many areas. If, however, diets, manure handling measures, and manure treatment are consistent throughout the year in areas where extremely cold temperatures do not occur (for example, an anaerobic lagoon in the southeast United States with consistent inputs and outputs), then only minor changes in manure nutrient concentrations may occur. On the other hand, variations in manure handling and storage, including changes in moisture content, or drastic changes in environmental conditions (temperature) can have a significant effect on manure nutrient concentrations. Nitrogen is the nutrient that is the most dynamic. Changes in feed sources can also result in significant changes in manure nutrient concentration. It is critical that all manure be sampled close to the time of land application to determine the nutrient content at the time of application. A new manure sample should be evaluated every time there is a change in these conditions: - handling of manure, - moisture contents, or - feed sources for the animals. Author: Karl Shaffer, Extension Associate for Soil Science, North Carolina State University