The Benefits of Crop Rotation - PulseResearch
April 25, 2017
Researchers investigate effects of cropping sequence on nitrogen fixation and carbon and nitrogen inputs of pulse crops
Including pulse crops in crop rotations improves the economic and environmental sustainability of agricultural production in Saskatchewan. With this practice, producers are able to use less nitrogen fertilizer when they grow pulse crops and in the crops grown subsequently. Environmentally, they improve soil carbon storage, decrease greenhouse gas emissions, and improve the overall energy efficiency of the farm.
Those environmental benefits provide unique marketing opportunities for pulse crop producers as consumers become more conscious of the effects agriculture has on global climate change. It makes sense, then, that producers would want to know the best time to include a pulse crop in a rotation.
This led researchers at the University of Saskatchewan (U of S) to look at the placement of different pulse crops, namely pea, lentil, and chickpea, in rotations with wheat and mustard, or canola.
“We wanted to determine if where the pulse crop was placed affected biological nitrogen fixation in the pulse crop, and yield and microbial populations in the subsequent rotation crops,” says Dr. Diane Knight, a professor at the U of S and the project’s lead researcher.
“How can farmers get the most advantage from the nitrogen that is fixed by these pulse crops, not only in the pulse crop itself but also the benefit achieved by the cereals and oilseed crops that are grown in rotation with them?”
The project, funded by Saskatchewan Pulse Growers, arose from a study at the Scott Research Farm in Saskatchewan, where the placement of pea in rotation with canola and wheat had a significant effect on biological nitrogen fixation, but not on yields. “Depending on where it was in the rotation, the pea yielded the same, but got its nitrogen from different sources,” Knight says.
The information from Knight’s project should help producers develop the best rotations for their region.
“By optimizing both nitrogen fixation and the residual effect on the next crop in rotation, farmers should be able to grow more productive crops,” she says. “Chickpeas, for example, grew and yielded really well in the greenhouse, but did not in the field,” she says. “We suspect that the amount of water received under the two growing conditions is the big driver.”
The research also revealed that chickpea and lentil did not grow well after canola or mustard. The researchers did not see this with pea in the study at the Scott Research Farm, so soil zone, and perhaps the organic matter in the soil, affects the rotations differently.
“Growing any of the pulse crops continuously was not good, producing low yields, low biological nitrogen fixation, and lower microbial populations,” Knight says. “Often we think that the detrimental effect of growing a crop continuously has to do with weeds and especially pests decreasing yields, but in this study in the greenhouse, weeds and pests were non-existent.”
A similar project is now underway in the field, with researchers using stable isotopes to track the carbon and nitrogen from aboveground, below-ground, and fertilizer from chickpea, pea, lentil, and faba bean crops into a subsequent wheat crop.
“This project has additional emphasis on finding out sources for greenhouse gas emissions,” Knight says. “We are also looking to investigate why oilseeds have a detrimental effect on pulses.”
SPG Investment: $254,956
Project Length: 4 years
Co-Funder: Agriculture Development Fund - $160,927
Project Lead: Dr. Diane Knight - Professor and Ministry of Agriculture Strategic Research Chair, University of Saskatchewan