Long-Term Research Yields Results

By Brenda Frick, Ph.D.

The sustainability of agricultural systems has to be examined over the long-term. On the Canadian prairies, a decade of vision, hard work and reliable funding is paying off, as long-term studies in each province reveal important lessons for the future of organic systems.

The organic rotation studies on the prairies each includes three organic rotations that differ in the diversity of crops they include, from simple to more complex annual rotations and those including perennial forages. Each study compares these organic rotations to similar rotations with high input, and/or reduced tillage. The Glenlea study, near Winnipeg MB, compares a wheat-pea-wheat flax rotation, a wheat-clover-wheat-flax rotation and a wheat-alfalfa-alfalfa-flax rotation. The Alternative Cropping Study (ACS) at Scott, SK, compares a (lentil green manure)-wheat-wheat-(lentil green manure)-canola-wheat rotation with a (lentil green manure)-wheat-pea-barley-sweetclover-canola rotation and a canola-wheat-barley-alfalfa-alfalfa-alfalfa rotation. The Flexible Dryland Cropping Study (FDCS) at Lethbridge, AB, compares a sweetclover-wheat-sweetclover-wheat rotation with a sweetclover-wheat-pea-flax rotation and a (winter triticale and red clover)-flax-wheat-(barley and pea) rotation.

Each study compared yields under different management. The Glenlea and ACS studies show somewhat lower yields on organic rotations than on high input rotations. Good flax yield was possible in forage rotations when weeds were well controlled by the rotation. When weed populations were higher, delayed seeding was needed in addition to the rotational effects to maintain flax yields. This delayed seeded organic flax was not as high yielding as early seeded high input flax, but its economic returns were roughly three times as great. In the ACS, economic returns for organic rotations were favourable relative to high input systems, if premiums could be achieved on even half of the organic crops. In the FDCS, returns were higher under organic than under low input management in favourable years. In drought years, yields were less.

Soil fertility was also a concern. Analysis at the Glenlea study indicates that organic alfalfa rotations are depleting soil phosphorous. Nitrogen levels are lower on the annual organic rotations. The ACS showed that phosphorous depletion was an issue in all organic rotations, and nitrogen balance was problematic if green manures were used less frequently and one year in two. In the FDSC, with greater frequency of green manure, and with composted animal manure in the forage rotation, neither nitrogen nor phosphorous levels are depleting relative to low input rotations.

Greater weed pressures were evident in organic rotations at Glenlea. These are being addressed in the research by greater crop diversity to give greater competition to the weeds. In the ACS, weed competition was highest for the organic systems, but generally had a smaller impact on yields than the supply of soil nutrients. In the FDCS, weeds were well controlled in sweetclover rotation, but less well controlled when pea was used to replace sweetclover eaten by weevils.

Both the Glenlea and FDCS examined crop quality. Organic flax had higher levels of the micronutrients at Glenlea, and at FDCS organic forage was of higher quality than low input forage. Organic flax also had more mycorrhizae and soil organisms helpful in nutrient uptake than flax from other systems.

Environmental concerns were also addressed. The ACS showed that because chemical fertilizers take a great deal of energy to produce, organic rotations use roughly 40% as much energy.

A concern for organic producers is the potential for erosion in systems that rely on tillage. In the ACS, organic rotations had less protective residue cover than either high input or reduced input systems. This was especially severe in 2003, when grasshoppers removed most crop residues. The FDCS offers hope in this regard. In this study, cover crops were mulched rather than incorporated, and provided effective weed control, retention of moisture and increased soil nitrogen. Reduced tillage in organic systems should reduce erosion potential.

Each of these studies suggests that organic systems have potential. Economic yields are possible with good management. Organic systems offer benefits but also harbour challenges. Organic production requires attentive observation and proactive management if it is to be truly sustainable. Research projects across the prairies are helping to guide these efforts.

Brenda Frick, Ph.D., P.Ag., is the Prairie Coordinator for the Organic Agriculture Centre of Canada at the College of Agriculture, University of Saskatchewan. She welcomes your comments at 306-966-4975 or via email at brenda.frick@usask.ca.

For specific information about the Glenlea project, contact Martin Entz at 204-474-6077 or by email at m_enzt@umanitoba.ca or click here for the full report.

For specific information about the Alternative Cropping Study, contact Stewart Brandt at 306-247-2011 or by email at brandts@agr.gc.ca

For specific information about the Flexible Dryland Cropping Study, contact Jill Clapperton at 403-327-4561 or by email at clapperton@agr.gc.ca

This article first appeared in The Western Producer, and is published here on the OACC website with permission.