Effects of Grain Legumes in No-Till Crop Systems are Being Investigated

Source: Saskatchewan Agriculture and Food

Dr. Guy Lafond’s passion for no-till agriculture has been part of the Saskatchewan agricultural knowledge landscape for some time. Now, the Agriculture and Agri-Food Canada scientist working at the Indian Head Agricultural Research Foundation can count on a Saskatchewan Agriculture and Food Agriculture Development Fund (ADF #20050704) grant to further our knowledge on the contribution of grain legumes in no-till cropping systems. The Saskatchewan Pulse Growers Association is also contributing to this project.

“When we started this study 11 years ago, I asked: 'Is starter nitrogen required with a grain legume like field pea?'" he says. "Secondly, what is an optimal frequency of field pea in the rotation? What I did is I set up the study so I could compare growing peas every year—which is the extreme practice—to growing peas every second year; and every three years. As time went on, this whole question of carbon sequestration and nitrous oxide emissions came into play.” This has now become an integrated component of Dr. Lafond’s research focus with this study.

Dr. Lafond was then in a position to investigate the effect of accelerated carbon sequestration on nitrous oxide emissions.

“Because this study has been developed and conducted over so many years, it has allowed us to answer two other important questions," he says. "One was: if you put legumes in the rotation, do you accelerate carbon sequestration? The thinking here is that legume residues have a higher nitrogen content than cereal. Any residue that has more nitrogen tends to decompose a little bit quicker and a little bit better, but there is also a feeling that more of it remains in a stable organic matter fraction than otherwise. So that was the second question we investigated.

“Because we have peas grown with and without nitrogen, we can compare against cereals grown with fertilizer, and we can compare to cereals grown with cereals and then to cereals grown with peas," he says.

Dr. Lafond conducted some in-depth soil sampling last spring, which showed some carbon sequestration, but because of the variability, he was unable to show conclusively that grain legumes accelerate carbon sequestration. Part of his current project involves sampling again in 2007.

“We wish to re-estimate it to see if there were sampling errors. But so far, in terms of nitrous oxide, there is no question that, if you are growing peas with just a little bit of phosphorus fertilizer, the nitrous oxide emissions are much less than for wheat grown with fertilizer."

Dr. Lafond is also finding that the spring wheat that is grown on a short rotation with peas every second year tends to emit a little more nitrous oxide than the spring wheat grown every three years. It may be that the presence of legume residue is priming the system and there could be a potential for a little more nitrous oxide emission during the spring wheat phase, but he stresses that this idea is very tentative. Dr. Lafond wishes to confirm the tendency by taking measurements to quantify it. This is why the funds were approved for 2005, 2006, 2007, he says.

The study also allows Dr. Lafond and his colleagues to address other agronomic issues, like the risks associated with the short rotations, and the impact of short rotations on diseases and populations.

Dr. Guy Lafond
Senior Research Scientist
Agriculture and Agri-Food Canada
Indian Head Agricultural Research Foundation