Feature: Side-dressed urea helps reduce nitrogen leaching

Wednesday, June 1, 2011

by DON STONEMAN

A two year study in a well field near Woodstock shows that a side-dressed application of urea six weeks after corn planting is a better way to reduce leaching of nitrogen fertilizer than a coated, delay-release fertilizer.

Don King, an agronomist with the Source Resource Group, Guelph, says testing in a wet year, 2009, and a normal year, 2010, showed no yield advantage using an innovative delay-release urea nitrogen fertilizer. The delay-release fertilizer carried a 15-30 per cent premium on cost compared to regular urea fertilizer and therefore returns were reduced.

The coated urea fertilizer is supposed to be dependent upon moisture and temperature.

"It does seem to help in the very early stages (of growth after planting), but in the two years we used it there was not a significant delay," King says. A six-week delay with side-dressing a reduced amount of nitrogen, as recommended using the Ontario Corn Nitrogen Calculator, was more effective environmentally, he says. Nitrogen is available to plants when they are further into their growth cycle and able to use it.

Using reduced nitrogen and a red clover cover crop as a nitrogen source was also an economical and environmentally friendly way to fertilize the crop.

"We tried to be objective. I wish we had another year or two to test it," King says. There was no opportunity to test the technology in a dry year, he says. 

The project was conducted on a well field near the village of Sweaburg, south of urban Woodstock. The site was selected for the project because it is owned by the County of Oxford and contains more than 130 groundwater monitoring wells. Local residents drink water from four wells at the site.

The study was led by the County of Oxford in partnership with the Universities of Guelph and Waterloo, the Upper Thames River  Conservation Authority and the Ontario Ministry of Agriculture, Food and Rural Affairs. The Ontario Drinking Water Stewardship Program of the Ontario Ministry of the Environment funded the project.

Engineer Deborah Goudreau, manager of water services for the County of Oxford, says the property around the wells has been tendered back to farmers. One of the provisos of the tender states that no manure is to be spread. She says she looks after about 160 wells in the county.

The depth of the four wells at the test field, which provide water for Woodstock, are 25 metres (82 feet), 16.6 metres (54 feet), 27 metres (88 feet), 14.6 metres (47 feet),  and 32 metres (105 feet) deep respectively. BF