ARS Study: More Fertilizer Doesn’t Always Mean More Yield

A ten-year study conducted by researchers at the US Department of Agriculture's Agricultural Research Service (ARS) and Colorado State University revealed that more fertilizer doesn't always mean more yield. The researchers, led by Ardell Halvorson, evaluated and compared potential management strategies for reducing nitrogen and nitrate nitrogen levels in soil and groundwater.

Halvorson and his colleagues planted onion in a region in Colorado that has high levels of nitrate nitrogen in the fields and groundwater. They found that onions used only about 12 to 15 percent of the fertilizer nitrogen applied to the crop. The next year, the scientists planted corn on the same land. It turns out that corn is a very good nitrogen scavenger. They found that it recovered about 24 percent of the fertilizer nitrogen that had been applied to the onion crop the year before.

Unfertilized corn grown on the field yielded around 250 bushels per acre. By comparison, a plot supplied with 250 pounds of nitrogen per acre yielded about 260 bushels. That's a small increase that required a significantly higher investment of time and money.

The article is available at http://www.ars.usda.gov/is/AR/archive/feb09/nitrogen0209.htm