Campus News

Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338

News Release

September 07, 2001

Fertilize in the fall? Go ahead, U of G study says

Autumn fertilizer applications — once thought to be environmentally unfriendly — are no more risky than those applied in the spring, according to a new University of Guelph study.

Land Resource Science professors Gary Parkin and Claudia Wagner-Riddle and graduate student Jim Roy initially set out to study the fate of nitrate, the primary nutrient in fertilizer, after being applied to turfgrass. Fertilizers are commonly used on row crops, golf courses, private lawns and parklands, as well as by turfgrass farmers. Nitrate, which can leach into the environment, has been linked to cancer and diabetes and is known to cause oxygen deprivation in the tissues of infants if ingested at high levels. Nitrate levels higher than those recommended by the provincial government have been detected in rural wells and even in municipal drinking water throughout Ontario, Parkin said.

The researchers hoped to measure the contribution of spring, summer and autumn fertilizer applications to determine the best time of year to fertilize and minimize nitrate groundwater contamination. Previously, it was believed that fall was the worst time to fertilize because weather is cooler, plants are less active and there is more surplus water available to cause nitrate leaching. But it looks like that’s not true.

The study, conducted at the Guelph Turfgrass Institute, showed that virtually no leaching occurred in the spring, summer or early autumn, but began in mid-November. In addition, the researchers found that spring and fall applications can combine to contribute nutrients to underground water supplies.“Groundwater contamination can occur in any season,” Parkin said. “That means we must be extremely careful because protecting our groundwater from nitrate is very important.”

The experiments at the turfgrass institute were conducted in May, July and September, at three times the provincially recommended rate of fertilizer application. A higher-than-recommended rate was used to help detect nitrate in soil water. Nitrate levels were then measured at various depths and in drain water.

The researchers suggest that a significant amount of nitrate from the fertilizer could have reached groundwater supplies under application rates and climactic conditions similar to those in this study if applied to regular grass. Parkin and his team are also studying the leaching abilities of different types of fertilizers after application to turfgrass, so the one with minimal leaching ability can be recommended for use.

Prof. Gary Parkin
Department of Land Resource Science
(519) 824-4120, Ext. 2452

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