Runoff from crops | Project takes a closer look at crops, production and water quality
SIOUX VALLEY, Man. — Henry Wilson bends over to inspect a device that looks an awful lot like R2D2 from Star Wars.
The Agriculture Canada research scientist from nearby Brandon is standing on a flat area of a hilly field, still covered with canola stubble and patches of snow in late April.
He releases the top hatch of the unit to expose a small computer. After pressing a few buttons, he pulls the computer off the unit and reveals the purpose of the 90 centimetre tall, cylindrical machine.
The machine is an automatic sampler, which houses two dozen plastic containers inside its base. Every four hours, the machine samples water from a runoff channel two metres away.
Wilson will use the unit this spring to collect runoff water during the snow melt. He will also take samples from nine other annual crop fields in southwestern Manitoba.
As well, Wilson and his Agriculture Canada colleagues will take water samples from creeks and streams to evaluate how much nitrogen, phosphorus and carbon are running off fields in the region.
Wilson, a hydrologist and biogeochemist, is interested in how runoff affects water quality downstream of a field.
He and his colleagues are also seeking answers to a number of related questions.
“What’s leaving the field? What’s staying in the field? What’s the relative importance of management at the field scale? How is that affected by landforms? How is that affected by soil properties on the landscape?” said Alan Moulin, an Agriculture Canada soil management expert.
“These are some the questions that are priorities, which will be addressed by this research.”
Moulin has been studying the yield impact of varying fertilizer rates for the last few years at the Manitoba Zero Tillage Research Association Farm north of Brandon.
He defined areas on the farm that were high, average and low production zones, based on historical yield data, and then applied fertilizer at varying rates to those zones, ranging from zero to 150 percent of the recommended rate.
“Our hypothesis was that areas with high production would benefit from higher rates of nitrogen,” Moulin said in 2010.
Results from 2012 suggest that applying higher concentrations of fertilizer to areas with average and high yield potential does produce larger yields. Therefore, it could be an effective way to generate higher yields and potentially save on input costs by reducing fertilizer rates on low production zones.
Wilson and Aaron Glenn, an agro-micrometeorology specialist with Agriculture Canada, are working with Moulin and his variable rate research to understand the interaction between production choices, land form, soil conditions, yield and environmental consequences.
As an example of the link between Moulin’s research and Wilson’s water sampling, a producer might have a hilly field that slopes down to a nearby creek.
If the sloping area is a low production zone, a farmer might want to reduce fertilizer rates, which would cut input costs and minimize the nutrient running off into the stream.
Before making such a recommendation, Wilson, Moulin and Glenn would need to collect runoff, soil and yield data to understand the complex interactions at the field scale.
Wilson said the collaborative project represents an opportunity to move beyond his expertise in hydrology and biochemistry and learn about soil fertility and soil management from a colleague such as Moulin.
Some of the farmers Wilson is working with in southwestern Manitoba practice no-till, others are organic and some till their fields conventionally. That variability will help Wilson understand how production practices influence water and nutrient retention.
“Once we have the (data), we can start to ask questions and make predictions about nutrient concentrations in the soil and how much of those nutrients to expect in runoff,” he said.
“My ongoing research has focused on identifying how the mosaic of land cover … land management, soil properties … influences the ratio of carbon, nitrogen and phosphorus (leaving the field).”
Wilson is particularly interested in the ratio of nutrients leaving the field because it has implications for water quality in creeks and rivers.
For example, more phosphorus running into a creek can trigger the growth of more toxic algal species, such as cyanobacteria.
“A lower nitrogen to phosphorus ratio tends to favour … the dominance of certain type of algae, which we tend to think of a nuisance algae or something that can release toxins,” he said.
“If there is more nitrogen, it can still be quite productive (for algae), but it might be a different algae.”
The scientists are also interested in how soil nutrients, land forms, climate and land management choices effect greenhouse gas emissions.
“We’re trying to bring together the different aspects of the air, water and soil … and understand interactions among them,” Glenn said.
“This sort of thing has been identified as being fairly crucial to agricultural research and broader ecological research.”
It will take several years of water sampling and data collection to accumulate sufficient information to understand the interactions between land management, land forms, soil nutrients and climate and how those factors influence soil productivity, water and air quality.