Serious concerns over phosphorus (P) runoff continues to be a worry that could hold back future growth of no-till. These fears aren’t likely to disappear as algae blooms get more interest among environmentalists.

With soluble P from fertilizer and manure being the major culprit, harmful algae blooms, dead zones and fish kills develop in lakes, rivers, streams and oceans. As the algae dies and decomposes, it consumes oxygen, killing fish and other aquatic animals. It also produces carbon dioxide, which lowers the water pH and slows fish, shellfish and plant growth.

Excessive P runoff causes harmful algae blooms like the ones we’ve seen in Lake Erie, Michigan’s Saginaw Bay, Chesapeake Bay and the Delaware Bay. In the Gulf of Mexico, the size of the algae “dead zone” averages around 5,200 square miles each year.

Soil Macropore Worries

While no-till reduces soil erosion, lessens surface runoff, increases organic matter and enhances a soil’s water holding capacity, there’s a risk of P movement through the macropores in fine-textured clay soils. These macropores allow P to quickly move away from the soil surface without passing through drain tile, says Ehsan Ghane, a Michigan State University water quality and drainage engineer.

No-tilling fine-textured soils with nutrient banding works well, as it removes P from the path of runoff flow paths. On the other hand, broadcasting fertilizer runs the risk of serious P losses through the soil macropores.

Clay soils have a much greater potential for macropore development because of their swelling and shrinking characteristics…