Maintaining yields and improving water quality

A SOURCE WATER PROTECTION PROJECT IN OXFORD COUNTY SEES SUCCESS

clean drinking water is easy to take for granted in a province which is surrounded by the Great Lakes. But, some communities experience alarming rates of nitrates in their drinking water wells. Fortunately, research undertaken in Oxford County shows that certain management practices put in place in a relatively small area around wellheads makes a significant difference.

“The Thornton well field in Oxford County has had chronic, progressive increases of nitrates,” says Dr. David Rudolph, environmental scientist from the University of Waterloo. “We concluded in the late 1990s that long term application of fertilizer has likely contributed to these increases in nitrates in the wells,” he says.

In 2003, Oxford County purchased the land directly surrounding the wells and hired an agronomist to recommend the best practices for the crops and the wells. “Oxford County took a very proactive approach. They made a commitment right off the bat that they would not take the land out of production,” says Rudolph. “We are following along the way many other parts of the world have already moved which is being very careful with agricultural land management and keeping it in production while protecting sensitive areas.”

success with management
Managing nitrogen in the wellhead lands has included changing the way nitrogen is supplied to the corn and wheat crops.  Nitrogen application for corn for example is determined using a combination of the Ontario Corn Nitrogen Calculator and Pre Sidedress Nitrate Tests.  Nitrogen is applied after the five leaf stage of corn as liquid 28 percent according to management zones within the field.  Zero nitrogen strips in various locations in the field give important nitrogen to corn yield response data.

To determine the effectiveness of the change in practices on the water supply since 2003, Rudolph and his associates studied the unsaturated zone in the soil which captures many years of land application practices. “We studied the amount of nitrogen in the unsaturated zone over a period of eight years which lined up with the application of the best management practices,” says Rudolph.

“We’ve documented significant improvement in upwards of 50 percent reduction in nitrogen stored below the root zone,” says Rudolph. “One issue that is hard for us to grasp is the time it takes for best management practices to impact an entire well field; it’s almost an entire decade.”

The other outcome Rudolph was interested to find was the size of area around the wellheads required to make an impact. “It’s a small area of farm land around this well field relative to the entire agricultural region that has seen these changes in nitrogen management. Such positive results from such a small area indicate that taking these types of steps can have a significant impact,” he says.

Don King from the Soil Resource Group was the hired agronomist who also led a recent research study in the well field. “We looked at many different nitrogen management practices including conventional and new technologies,” says King. Included in the research was the use of ESN, or Environmentally Safe Nitrogen which has a poly-coating to slow the release of the nutrient, the Ontario corn N calculator rates, side-dressing lower rates of nitrogen, red clover as a nitrogen source and new hybrids which are supposed to be more nitrogen-use efficient.  Nitrogen in the soil and soil water over the season were also measured at upper and lower areas of the fields where nitrogen levels differ naturally.  The results can be viewed on the Oxford County website.

on-farm impacts
With the agronomic changes to nitrogen management in this area, there has been some concern about productivity of the land. David Start, an Oxford County farmer has farmed the land surrounding the county-owned well heads and participated in the research and has been quite impressed with the impact of the red clover management treatment on the farms.

“We broadcast the clover on the winter wheat crop in early spring before the wheat breaks dormancy,” says Start. “Our goal on the Oxford County land is to make nitrogen the yield limiting factor for the growing corn crop,” says Start of his efforts with the county to reduce the buildup of nitrates in the wells.

Beyond the obvious benefits of improving the quality of his own drinking water, Start was pleasantly surprised with the agronomic qualities of underseeding his wheat with red clover. “We saw much less yield reduction than expected,” he says. “With the red clover, we’ve reduced nitrogen applications by up to 80 percent and we get full yield with most varieties.”

With these new red clover management practices – which Start recognizes are actually “very old” management practices – he has seen some other benefits. “Right now, fertilizer prices are increasing. If I can supply a lot of my nitrogen with red clover then I can spend the saved money on other yield enhancing inputs. It also reduces my carbon footprint in the production of corn, which will be important in the future,“ he says.  Our challenge with red clover is getting consistent stands of clover.  It would be highly beneficial to farmers if the questions of successful red clover establishment could be answered.  That is where my personal interest now lies.“

PHOTO 1: DAVID START CHECKS OUT HIS STAND OF RED CLOVER IN THE THORNTON WELL FIELD.

limited loss
It’s important to note that red clover is still capable of leaching nitrogen into the groundwater if it isn’t credited for the nitrogen it supplies. Typically, red clover releases its nitrogen slowly as the soil warms in the spring; this process often coincides with important corn growth stages when the plants need nutrients most.

In King’s studies, the amount of residual nitrogen in the soil aligned with the weather. “After a cool, wet season like 2009 we did not see any difference in residual levels of nitrogen in the red clover trials from the rest of the practices. In 2010 with the long warmer, wet season, we saw more breakdown of the organic matter which resulted in more release of nitrogen that was available for leaching,” he says.  The good news was the corn crop responded to the favourable growing conditions and used up more nitrogen and there was no more nitrogen loss from the red clover than the recommended fertilizer practices. 

Overall, this research project involving the county, agronomists, environmental scientists and farmers has been a great success. “We have a very advanced farming community that understands the technology that helps manage nitrogen levels,” says Rudolph of his experience working on the project. “The agricultural community sees the sustainability of the landscape as protecting their livelihoods.” •