AGRICULTURAL AND ENVIRONMENTAL ENGINEERING
Agricultural and environmental engineering contributes to GWCAES research in several ways: in major phases of the Tuskegee/NASA Center for Food and Environmental Systems for Human Exploration of Space; for quantifying newly created mitigation wetlands; and for monitoring pond aeration in inland shrimp farming
Wetlands are land areas that are inundated with water at least half of the year. Though historically they have been seen as an impediment to agriculture and development, these unique areas have been found to have many beneficial characteristics. Wetlands provide habitat for a diverse collection of unique flora and fauna—mammals, birds, wetland plants and trees, insects, amphibians, reptiles, etc. Many of these species can survive only in wetland areas or have these areas as an integral part of their habitat and life cycle, i.e., for breeding. Wetlands also provide storage for runoff waters caused by intense rains or snowmelt. This ability can potentially reduce or eliminate the flooding of adjacent or downstream areas that are developed with houses or commercial buildings. Most recently, it has been found that wetlands actually treat water by removing pollutants as they pass through the wetland. Studies have shown that potentially harmful components such as sediments, nitrogen, phosphorus, organic compounds, metals, and pesticides can be removed from the water through the wetlands’ natural physical, chemical, and biological actions.
Natural wetland areas are lost though the normal activities of public agencies or private companies such as construction operations. A “mitigation” wetland is a wetland area that is set aside or created, from farmland mainly, to compensate this loss. This mitigation is required by federal government regulations to preserve the amount of wetland areas. Our research deals with the quantification of three wetland attributes—vegetation, hydrology, and soils—in several mitigation wetlands in Alabama.
The vegetation study involved an inventory of natural and planted species on the wetland site and an analysis of the usefulness of tree shelters, or tubes, in the growth of saplings. Our results showed that the survival of planted trees was higher with tree shelters because they prevented browsing by small animals and they limited competition. There was also an abundance of natural or volunteer seedlings depending on the proximity to the surrounding forest.
The hydrology study involved the measurement of water levels below the ground surface with shallow wells (1.2 meters long). Our results during the winter months, December to April, showed that the water table was at least two feet below the surface across the site and consistently at the surface in some of the wetter areas.
The soils study involved the analysis of the soil condition at sites near the shallow wells. As expected, the analysis showed the presence of waterlogged soils at the sites where the shallow wells were installed. These results support the findings of the hydrology study.(Project funded by U.S. Department of Transportation)
Energy Efficiency of Aeration in Inland Shrimp Farming
Inland saltwater shrimp farming in ponds is an emerging area of agriculture. The cost of electric aeration is one of the two major expenditures for this business. The demands for aeration can be considerable because shrimp are fairly sensitive to decreases in the dissolved oxygen that aerators provide. Additionally, unlike some fish, shrimp are not fast eaters, and much of the feed decomposes and uses up oxygen which aerators must supply. Fortunately, the scheduling of aeration can be automated using a pond monitoring system which turns the aerators on when needed and off when not.
Our research is a demonstration project where additional aerators and a pond monitoring system were installed at a small-scale inland shrimp operation. The pond monitoring system showed that the additional aeration was necessary to maintain the proper dissolved oxygen level for the shrimp, as suspected by the farmer. The monitoring system was used primarily for risk management through controlling the timing of supplemental aeration and monitoring the operation of all aerators.
The first year’s results showed the true requirements for aeration for this scale of operation and the need for automated monitoring for control and risk management. During this year, the monitoring system helped to maintain the dissolved oxygen levels at near-optimum levels for shrimp growth. The system even detected a fault in one of the primary aerators and prevented a costly repair or replacement. (Funded by the Alabama Department of Economic and Community Affairs)