Organic Durum Wheat Productivity and Quality Following Intercrops
A diversified organic cropping system including legume intercrops resulted in some of the highest grain yield and biomass of the subsequent sole durum wheat crop in the semiarid region of the Canadian Prairies. Legume intercropping can be part of a diversified organic cropping system, providing higher and more stable returns than the more traditional legume green manure or summerfallow.
Growing various intercropping combinations that include legumes may provide agronomic and economic benefits to growing durum wheat in the subsequent year in the semiarid region of the Canadian Prairies. The durum crop could benefit from increased N from the preceding intercropped legume, and lower weed growth due to the more competitive companion crop. Legume intercropping combinations with competitive crops may also reduce weed competition and disease development compared to the legume monocultures.
A recent study compared growing legume monocultures and organic legumes intercropped with a cereal or oilseed, followed by a sole durum wheat crop. The objectives of the study were to determine if intercropping would affect soil N (NO3-N) the following spring, weed levels, as well as the growth, productivity, and quality of the following sole durum wheat crop. In preparation for the study, the fields had been organically managed for two years prior to the intercrops with a mixture of a legume, an oilseed and a cereal grown and incorporated at flowering using a tandem disk harrow.
In 2017 and in 2018, selected intercropping treatments including two combinations of a legume and a nonlegume crop at three different seeding ratios and their respective monocultures were compared. The crops included small red lentil, yellow field pea, yellow mustard and oat, along with summerfallow and forage pea manure as checks. The forage pea was terminated at flowering by mowing and the residue left at the surface until the following spring. In 2018 and 2019, durum wheat was seeded on each plot that had been cultivated once with a cultivator with mounted harrows down to 8–12 cm, and the surface leveled with a harrow packer right before seeding.
The growing conditions in 2018 and 2019 in this semiarid region were drier than average, with precipitation varying from below 60% of average in 2018 to slightly below average in 2019. Although study results were significant for most factors, under more suitable growing conditions, the legumes in such intercrops would have greater growth and a higher contribution to soil N than in the dry years of this study.
Durum wheat productivity and quality
Durum wheat grain yields grown after oat, pea-oat intercrop, grain legume monocultures and forage pea manure were similar and among the highest, although the highest yields were after summerfallow. The pea-oat intercrop resulted in significantly higher biomass and grain yield of the following durum wheat than lentil–mustard intercrops, which reduced the growth and productivity of the durum crop. The 1000-kernel weight and test weight of durum wheat were not significantly different among the treatments.
The weed density in the durum wheat tended to be lower after the intercrops than the grain or legume monocultures. However, volunteer crops contributed to the higher weed density in the durum wheat, particularly after the lentil–mustard intercrops. Overall, the weeds tended to be smaller in the durum wheat, suppressed by competition with the durum wheat plants and other weeds.
Soil N
Overall, the study showed that NO3-N was similar after forage pea manure and the lentil and oat monocultures, however NO3-N was significantly higher after summerfallow than all other treatments. The average NO3-N was higher after the pea-oat than the lentil-mustard intercrops. The intercrops with mustard also reduced the growth and productivity of the durum wheat crop. Intercropping had a negligible impact on available soil P and K the following spring.
The study results showed that legume intercropping can be part of a diversified, more sustainable organic cropping system, providing higher and more stable returns than the more traditional legume green manure or summerfallow in this region. A diversified cropping system including legume intercrops would also provide greater financial stability than monocultures. The results can also apply to nonorganic management, with effective intercropping systems reducing the dependence on synthetic chemical inputs, reducing production costs and soil and environment concerns, in addition to herbicide-resistant weeds.
A new organic intercropping project has been underway at the Swift Current Research and Development Centre since 2021. For more information on any research being conducted by the Organic Research Program, please contact myriam.fernandez@agr.gc.ca
This project was funded by the Western Grains Research Foundation, Saskatchewan Wheat Development Commission, and Saskatchewan Pulse Growers.
Fernandez, M. R., Lokuruge, P., Abdellatif, L., Waelchli, N., Leeson, J. Y., Zvomuya, F., & St. Luce, M. (2025). Cereal crop following organic intercrops and their respective monocultures in the semiarid Canadian Prairie. Agronomy Journal, 117, e70032. OPEN ACCESS https://doi.org/10.1002/agj2.70032
Photo by Myriam Fernandez
