Good Fruit Grower / August 2012 / Canadian research looks at CO2 ­emissions

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Canadian research looks at CO2 ­emissions

Scientists hope to identify orchard practices that increase yields while reducing greenhouse gas emissions.

Researchers at the University of British Columbia’s Okanagan campus in Canada have embarked on a federally funded three-year study aimed at reducing greenhouse gas emissions while improving irrigation and fertilizer practices on Okanagan area orchards and Fraser Valley berry farms.

“The investigations undertaken by UBC scientists Drs. Melanie Jones, Louise Nelson, and Craig Nichol will improve our understanding and help increase yields, while still reducing agriculture’s environmental footprint in the Okanagan,” said Miriam Grant, UBC-O vice-provost and dean of research, at a news conference.
The project’s funding, a $1.2-million grant, comes from Agriculture Canada’s $27-million greenhouse gas program, which represents Canada’s initial contribution to the Global Research Alliance of Agriculture Greenhouse Gases, an initiative with 38 signatory countries.

Soil microbiologists Jones and Nelson and hydrogeologist Nichol will examine the long-term fluxes of greenhouse gases (carbon dioxide, methane, and nitrous oxide) from three ongoing research trials of grape, raspberry, and apple in response to varying irrigation and ­fertilization practices.

“My part of the project is looking at the soil microorganisms [bacteria] that are involved in the nitrogen cycle,” said Nelson. “In particular, we’re going to be looking at the nitrifying and denitrifying populations, both of which can contribute to nitrous oxide emissions.

“I will be taking soil samples and looking at the activity of these two different soil populations that can contribute to nitrous oxide, and we’ll be looking at the effects of different types of irrigation and different nitrogen fertilizer applications.”

She noted that agriculture is a major source of nitrous oxide, contributing 70 percent of the nitrous oxide in greenhouse gas emissions.

“Nitrous oxide is 300 times more potent than carbon dioxide in its ability to retain heat, so it’s a very potent greenhouse gas. What we want to do is figure out which practices will minimize the amount of nitrous oxide ­emitted.

“At the end, hopefully we’ll be able to say to the farmer, ‘Your best bet, if you’re interested in growing a good crop but keeping greenhouse gas emissions to a minimum, would be to use this type of irrigation system and you should apply your nitrogen this way.’”

Soil samples will be analyzed and greenhouse gases measured at apple and grape plots in Summerland and raspberry plots in Agassiz.

New carbon

Jones will be studying isotopes of carbon from soil samples to determine what portion of the carbon dioxide coming out of the soil is being emitted from old soil carbon and what portion from new carbon.

New carbon is carbon that the plant has recently photosynthesized, converted to sugars, and sent to the roots. The roots have then burned up and emitted it as carbon dioxide. But some of the other carbon in the soil, known as old carbon, is sequestered, unless microbes start to break it down or it is released by agricultural practices.

“Basically, we would like to find production practices that encourage more carbon to stay in the soil: more carbon being taken in through photosynthesis, being sent down to the roots and staying in the soil, either in dead roots or as organic matter, rather than it being respired back out again,” Jones said.

Carbon occurs in slightly different weights (isotopes) and, by measuring those differences, researchers can trace if the carbon dioxide that’s being respired by the soil is coming from carbon dioxide that the plant has just photosynthesized or from carbon sequestered in the soil.

Nichol’s group, meanwhile, will measure greenhouse gas emissions with two types of devices that will be installed at the research locations.

One is a set of automated plexiglass chambers that will run continuously and monitor carbon dioxide fluxes across the ground surface using sensors and sophisticated computer software. For nitrous oxide, methane and carbon dioxide readings, samples are collected manually from smaller chambers.

“Each experiment is designed to be testing different types of irrigation, different types of fertilization, and different types of surface cover of mulch or compost,” Nichol said. “We’ll have anywhere between one and four chambers in each plot to cover parts of a row or next to a dripper or in the alleyway between rows, so we may have somewhere between 100 or 150 with each site.”

Global concern

Jones said the project is in response to a global concern about greenhouse gas emissions. Although agriculture may not be as intensive a contributor as other major industrial complexes, because agriculture occurs over such a large part of the landscape, it has the potential to have an influence.

“The water-use part is key as well,” she said. “The end product that we have promised to the government, that the government demands as part of this program, is that we will recommend best practices for orchardists and berry producers that will maximize both efficient practices and reduction of greenhouse gases, the carbon sequestration and the reduction of the nitrous oxide together with the efficient use of water.”

Three researchers from New Zealand are also involved in the project, Nelson said.

“The people from New Zealand are looking at the carbon sequestrations—how can we sequester more carbon in the soil and release less carbon dioxide into the atmosphere. They have this very sophisticated technique that they are going to be bringing here for us and working with us for measuring where the carbon comes from that is released as carbon dioxide and how best to keep it sequestered in the soil.”

Jones, the lead researcher on the Canadian team, pointed out that this project presents a unique opportunity for her team of scientists.

“There’s so much opportunity for advancement if we work with scientists in other disciplines. As a soil microbiologist, I had never worked on a project together with an expert in gas emissions, and so that’s what really excites me. It’s going to be quite an interesting learning ­experience.

“I really like to work on projects where there is going to be a real benefit to society one way or another. It’s ideal if there are going to be management implications. That’s what really prompted me to become involved in this research.”