Graduate Students Receive Top Honours

by Tanya Brouwers

On November 16, 2008 the town of Saskatoon sponsored the Organic Connections conference, an annual three day forum where producers can access the latest information on organic business opportunities, production methods and marketing techniques. In addition to the tradeshow and numerous lectures, attendees were also privy to the Research Poster Expo, a visual display of student and professional research projects pertaining to organic management practices. Emily Clegg of the Nova Scotia Agricultural College (NSAC) and Justin Renkema of Dalhousie University, both supervised by Dr. Derek Lynch of NSAC, received top student honours for their contributions to the event.

In Justin Renkema’s poster he asked if the activity-density of different species of ground beetle would be affected by different mulches in an organic highbush blueberry field. Over five, one-week periods, Justin compared beetle densities from blueberry plots heavily mulched, to a depth of 15 cm, with pine needles, composted pulpmill biosolids, a farm compost of horse manure and wood shavings and an unmulched control plot. His preliminary results indicated that combined beetle activity in the pine needle and biosolids mulch was, on average, 37% and 8% less, respectively, than the activity measured in the control. On the other hand, measurements of combined beetle activity in the farm compost were, on average, 30% greater than that of the control.

Justin’s initial results are exciting for organic blueberry producers, especially for those that rely on an export market. Highbush blueberry plants in Eastern North America are notoriously susceptible to blueberry maggots that cause the fruit to become mushy. Out of province export laws dictate a zero-tolerance policy where the maggot is concerned. Unfortunately, for organic producers, finding an approved method of dealing with these pests has been, historically, problematic.

The good news is that the ground beetle may be one of the blueberry maggot’s voracious predators. Justin’s efforts to find mulches that will support the largest numbers of these beneficials is a promising first step to bringing organic blueberry producers a preventative solution to a financially troublesome problem.

Emily Clegg’s poster, in line with current global concerns over global warming, noted that agricultural fields account for a major portion of the green house gasses released into the atmosphere annually. Fields planted conventionally to potatoes, in particular, will release large amounts of nitrous oxide (N2O) due, in part, to the high levels of post harvest nitrogen remaining in the soil. Emily pointed out that, as yet, not a lot of research has been conducted regarding the release of gasses from organically managed potato plots. Her objective in this study, then, was to determine the levels of N2O emissions from an organically managed potato/forage rotation based on factors of crop, timing of tillage and the effect of fertilization.

Emily’s preliminary results are encouraging, especially for proponents of organic agriculture. The initial data, accumulated over a two year period and at two different sites, suggests that the timing of tillage does not overtly affect the levels of N2O emissions. The type of crop and fertilization regime, on the other hand, does. She discovered that the plots treated with synthetic fertilizer had the highest dry matter tuber yields of up to 5.27 Mg ha-1 but released upwards of 11.6 kg N2O-N ha-1. The plots that were heavily composted, however, released only 3.57 kg N2O-N ha-1. The following year, the emissions from the composted plot, without reapplication, dropped further to 1.37 kg N2O-N ha-1 while the yields remained similar (4.44 and 4.87 Mg ha-1 in the first and second year respectively). The plot utilizing a nitrogen-fixing clover in a potato rotation also demonstrated low emission levels. Compared to the plot that was synthetically fertilized the emissions from this plot were nearly a third less at 4.4 kg N2O-N ha-1 while the yields remained comparable to the synthetically treated crop. Emily is hoping that further data analysis from 2006 and 2007 will continue to substantiate these initial findings.

Justin Renkema and Emily Clegg are each pursuing research topics that organic farmers and the public at large should find extremely interesting. Justin’s search for a method to control the blueberry maggot will help to ensure that Eastern Canadian organic blueberry farmers can profitably provide enough fruit to meet rising consumer demands. Emily’s initial findings will inform the agricultural community about ways to reduce greenhouse gas emissions. Together, these two bright individuals are bringing the Canadian organic community the resources and information it needs to move ahead, successfully.

 

Tanya Brouwers is a Consultant for the Organic Agriculture Centre of Canada. Please send comments or questions by phone to 902-893-7256 or by email to oacc@nsac.ca

 

Posted April 2009