07/01/1991

Wetlands Tour Highlights Waste Utilization Field Day

CROSSVILLE, Ala.—A two-tiered wetlands system at the Sand Mountain Substation located here has proven to be an effective and economical method of removing harmful chemicals from waste collected in swine lagoons, according to Alabama Agricultural Experiment Station researchers.

Speaking at a recent Waste Utilization-Crop/Livestock Production Field Day at the Substation, Tom McCaskey, a professor of animal and dairy sciences at Auburn University, noted that water that goes from the lagoon, into a mixing tank, then through both tiers of plants in the wetlands system is actually clean enough to be returned to streams. He stressed, however, that a discharge permit must be obtained before treated waste water can be reused.

The Sand Mountain wetlands system mixes water from swine house lagoons in a 50:50 ratio with clean water from a nearby pond. After mixing, the water passes through one tier of plants that filter nitrogen, ammonia and other potentially harmful chemicals, called nutrients, from the waste water. This water then passes through a second tier of plants that further filters out these nutrients by taking them up via their root systems.

"In warm months, when plants are rapidly growing, there is no water coming out the bottom end of the second tier of plants," McCaskey noted. He explained that, although 2,500 gallons of effluent per day goes into the system, the bull rushes, reeds, cattails and other deep rooted plants use up virtually all the nutrients in the water. More than 95 percent of such nutrients as ammonia and nitrogen are removed from the waste water, which is well within the guidelines set up by regulatory agencies for reuse, according to McCaskey.

In addition to the wetlands project, the crowd of about 60 farmers, cattlemen and agribusiness people saw and heard results of projects on the use of chicken litter for fertilizer and for re-feeding to livestock.

McCaskey and Darrell Rankins, an assistant professor of animal and dairy sciences at Auburn, pointed out the importance of stacking and covering poultry litter used as a supplement feed for beef cattle. McCaskey said that litter should be less than 25 percent moisture when it is stacked to minimize excess heat, which can reduce its nutrient value. Rankins noted that litter covered with a thin sheet of plastic had 20 percent more nitrogen available to cattle than litter from the same poultry house, but left uncovered.

Visitors also saw results of the use of 2.5 and five tons per acre of chicken litter as a fertilizer for cantaloupes and watermelons. James Brown, an associate professor of horticulture at Auburn, noted that optimum production appears to come from the 5 tons per acre rate, applied broadcast. He pointed out that both the 2.5 and five tons per acre rates caused some burning and stunting of vines when the litter was placed directly under the plant. When applied broadcast, however, litter, compared to 13:13:13 commercial fertilizer, appears to produce thicker, greener vines. "We will have to wait until we harvest the crop to see how much yield difference we have, but visual ratings of the plants show an advantage for broadcast-applied litter versus commercial fertilizer," according to Brown.

Dan Porch, an area extension vegetable specialist, told the group that litter at higher rates, of up to 20 tons per acre, speeded maturity of tomatoes and corn. Harvesting these crops 10-14 days early can be a big economic advantage, according to Porch. He also pointed out that despite the high rates of litter, no detrimental effects were evident on the crops.

The meeting was co-sponsored by the Alabama Agricultural Experiment Station and the Alabama Cooperative Extension Service. The 536-acre Sand Mountain Substation is site of Alabama Agricultural Experiment Station research on a broad range of agronomic, vegetable and fruit crops, in addition to livestock studies on cattle, sheep and swine. Substation Superintendent John Eason, Associate Superintendent Marvin Ruf, Herdsman Eddie Peacock and Research Technician Wayne Boldin also participated in the field day.

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By:
Roy Roberson