PROFESSOR HIGHLIGHTS PHOSPHOROUS MANAGEMENT STRATEGIES

FAYETTEVILLE, Ark. - At a regional conference here today, a University of Arkansas professor will speak on the growing national problem caused by excess phosphorous in soil draining into water sources.

Tommy Daniel, professor of agronomy, will address phosphorous management as part of the Animal Waste Management session at the Nonpoint Source Watershed Conference on Tuesday afternoon at the University of Arkansas’ Center for Continuing Education.

Phosphorous, commonly found in animal manure used as fertilizer, helps plants grow. Excessive amounts can drain into water supplies and cause rapid growth of algae and other aquatic plants, depleting the water of oxygen and effectively aging lakes and streams.

Phosphorous-rich animal wastes have traditionally been spread over fields as fertilizer. But as animal operations have grown and large amounts of animal waste accumulate, it becomes increasingly difficult to spread it over a sufficient area to ensure minimal phosphorous runoff.

The problem has increased in the past two decades as farming practices have shifted away from mom and pop spreads to large operations.

"The whole way we produce protein has changed over the past 20 years," Daniel said. Most dairy farms now are moving in the direction to support 1,000-10,000 cattle. These animals consume tons of feed, so they produce a whole lot of phosphorous-containing manure.

Initially crops will use the phosphorous to grow, but excess amounts in the soil will be swept away in runoff - sometimes straight into lakes.

Heightened phosphorous levels can lead to fish kills, destroy drinking water sources, and lead to disease outbreaks, Daniel said.

"There’s lots of concern over this," Daniel said. "It will lead to high-profile regulatory decisions being made."

Managing practices for phosphorous differ from farm to farm. High concentrations of soil phosphorous vary in runoff depending upon the composition of the soil, the geology, the farming history and current farming practices, Daniel said. For example, in sandy soils phosphorous doesn’t end up in runoff, but it often appears in the water table below the fields. Soils with low iron and aluminum content quickly reach phosphorous capacity and immediately start to lose phosphorous in runoff after heavy rains.

"The science is there but we need more information," Daniel said. "The saturation level is going to vary with every soil. We need to determine what this means, and how it translates into policy."

Texas is the only state that currently limits the amount of phosphorous-containing manure applied to cropland. Many states are considering a guidance number, Daniel said.

While Daniel focuses on how phosphorous moves from cropland into water sources, other University of Arkansas scientists are looking at ways to reduce phosphorous in animal wastes. Enzymes are being used to help animals digest the phosphorous in their feed, and manure can be treated with alum, an additive that absorbs the phosphorous, to reduce phosphorous loss in runoff.

# # #