Nutrients with staying power
By Lisa McLean Farm & Food Care
By Lisa McLean Farm & Food Care
Dr. Steven Frey, senior scientist, Aquanty Inc.
January 6, 2015, Guelph, Ont – The fields may be frozen at this time of year, but researchers remain hard at work studying how to minimize nutrient losses off fields in the non-growing season.
They’re looking at how manure application methods and tile drainage management systems influence the likelihood of nutrient loss in different soil types and different weather conditions – all through the convenience of a new computer modeling system.
The system’s development is part of a project led by Dr. Steven Frey, senior scientist, Aquanty Inc. Funded by the Water Adaptation Management and Quality Initiative (WAMQI), Frey used field experiment data from three sites in Ontario –Winchester, Delhi and Sebringville – to benchmark model simulations. Specifically, the simulations are designed to assess the best scenarios to promote non-growing season nutrient retention after fall liquid manure applications.
“Ontario has approximately 1.6 million hectares of agricultural land that has had drainage improvements – much of that involves tile drainage,” Frey says. “For this particular project, we wanted to develop technology to help predict where the manure goes when it is applied.”
Frey’s model incorporates field data from a 2012 study, in which researchers applied liquid manure to a field in late fall, prior to an over-winter monitoring period. Over the course of the winter and early spring, the researchers measured water quality to see how far the nutrients traveled.
“We monitored groundwater, tile drainage, and soil water,” says Dr. David Lapen, a research scientist at Agriculture and Agri-Food Canada’s Eastern Cereal and Oilseed Research Centre. “We looked at water quality and water quantity to facilitate modeling activities at this site.”
“There are advantages and drawbacks to various manure application methods, for how they influence the likelihood of nutrient loss,” says Frey. For example, manure injection reduces the risk of surface runoff losses, but those nutrients may end up collected by the tile drains instead of remaining in the soil. Conversely, surface application reduces losses through tiles but can increase losses through surface runoff.
“The results from this experiment will allow us to see how computers can be used to simulate the movement of liquid manure under different applications and climate scenarios,” says Frey. “We can compare data from the field experiments and our computer modeling results to get a really good visual sense of what goes on below the soil surface when manure is applied using different application methods.”
At the Winchester site, researchers worked with control tile drainage, an emerging beneficial management practice that’s still a new concept to many Canadian farmers. The system is designed with edge of field tile control structures that have adjustable gates that allow operators to change the water table in a field while blocking or regulating tile drain discharge.
“With the controlled tile drainage system in this experiment, we were able to restrict and control flow, and examine water quality and water quantity associated with managing tile drainage,” says Lapen.
And, by managing the water table, controlled tile drainage allows researchers to test nutrient management application techniques under different soil moisture conditions.
“With the controlled tile drainage system, we can simply hold water back in the soil profile to evaluate manure applications on wetter soil,” says Frey.
“By simulating an experiment that was conducted at an individual field site, we can develop a model that allows us to take the results from a field experiment and extrapolate them to different crop and soil types, tillage practices and times of year,” says Frey.
Frey says the model will go a long way in helping researchers test different nutrient management procedures – including spread patterns and rates – without having to wait for real-time field trials.
“We use field experiments to validate and calibrate the model,” he says. “At this stage we’re able to run virtual field experiments that don’t need a field – or a full growing season – to run.”
The modeling work is based on ongoing field research being conducted at the University of Guelph’s, Kemptville Campus Winchester Field Research Station.