Chickpea-flax intercrop shows greater efficiencies
Intercropping chickpea and flax resulted in eight to 22 per cent of biologically fixed nitrogen being transferred from chickpea to flax during the growing season. This resulted in reduced soil nitrogen depletion compared to monocrop flax. The land equivalent ratio was at or above 1 for the intercrop at the four site-years.
Interest in intercropping is growing on the Canadian Prairies. Farmers are interested in whether intercropping can maintain or increase yield while improving yield stability and helping crops resist biotic and abiotic stresses.
A research study was conducted over two years to investigate yield response, nitrogen and phosphorus uptake, and biological nitrogen (N) fixation in a chickpea-flax intercrop system. The research was conducted in 2019 and 2020 near Central Butte on a Brown Chernozem farm field soil in southwestern Saskatchewan, and a Black Chernozem soil near Redvers on the SERF farm in southeastern Saskatchewan.
The research compared monocrop chickpea, monocrop flax, chickpea-flax intercrop in alternate rows, and chickpea-flax intercrop in mixed rows. Seeding rates varied depending on treatment. CDC Orion kabuli chickpea was seeded at 205 lbs/ac (231 kg/ha) as monocrop, with reduced rates of 102 lbs/ac (115 kg/ha) in alternate row intercrop, and 182 lbs/ac (205 kg/ha) in mixed row intercrops. CDC Glas brown flax was seeded at 50 lbs/ac (56 kg/ha) as a monocrop, and alternate row intercrop seeding rate was 24 lbs/ac (27 kg/ha), and 11 lbs/ac (12 kg/ha) for the mixed row intercrop.
The treatments were seeded into wheat stubble except Central Butte 2020, which was seeded into fallow due to low stubble soil moisture reserves. Row spacing was 10 inches (25 cm) and seeding depth was 0.6 inches (1.5 cm). No fertilizer was applied to any treatment. However, 15N double-labelled ammonium nitrate was applied to microplots within the main plots to calculate the biological nitrogen fixation (BNF) of the chickpea crop, and how it was influenced by intercropping.
Chickpea yield trends were similar between site and year. As expected, monocrop chickpea yield was significantly higher than in intercrops. For example, in 2020, monocrop chickpea yielded 2172 lbs/ac (2441 kg/ha) compared to alternate row at 687 lbs/ac (772 kg/ha) and mixed row at 266 lbs/ac (299 kg/ha). No clear yield trend between alternate and mixed row chickpea yields was observed.
Flax yields did not show any clear trends between monocrop and intercrop trends. Yields were highest in monocrop flax at some site-years, but higher in intercrops at other site years.
The land equivalent ratio (LER), a measure of productivity of intercropping was calculated. A value of 1 indicates that intercropping is as productive as monocropping. A value of greater than 1 indicates that the land use in intercropping was more productive than monocropping.
In 2019, the grain yield LER was greater at both sites for intercropping. At Redvers, the LER was 1.4 for the alternate row, which was similar to the mixed row at 1.3. At Central Butte, the grain yield LER was 2.6 for the alternate row, which was statistically higher than the 1.3 for the mixed row LER.
In 2020, the grain yield LER at both sites and both intercrop types were statistically similar at 1.0 to 1.1 LER.
N and P uptake
Nitrogen and phosphorus (P) uptake was highest in monocrop chickpea. Monocrop N uptake was 44 lbs/ac (49 kg/ha) in 2019 and 65 lbs/ac (73 kg/ha) in 2020. In 2019, there was no significant difference between the two intercrop seeding treatments ranging from 16 to 21 lbs/ac (18 to 24 kg N/ha) uptake, but in 2020, N uptake was significantly higher in the alternate row at 21 lbs/ac (23 kg N/ha) compared to the mixed row treatment at 7 lbs/ac (8 kg N/ha).
Phosphorus uptake by chickpea followed the same trend in both years. For example, monocrop P uptake was highest in 2020 at 6.8 lbs/ac (7.6 kg/ha) in 2020. This compared to 1.7 lbs/ac (1.9 kg/ha) for the alternate row in 2020 and 0.7 lbs/ac (0.8 kg/ha) for the mixed row.
Nitrogen and P uptake by flax varied across site years with no clear trend between treatments.
Nutrient use efficiency (NUE) for N and P varied by site-year and mono/intercrop treatments, also with no clear trends.
The total amount of N derived from BNF found in above ground biomass was highest in monocropped chickpea with no difference between the intercrop treatments. For example, Redvers 2020 had 60 lbs/ac (67 kg N/ha) fixed in the monocrop chickpea treatment, while the chickpea intercrops ranged from 17 to 27 lbs/ac (19 to 30 kg N/ha).
The percent of N fixed from the atmosphere (%Ndfa) found in the grain of chickpea was not significantly different for the monocrop and intercrop treatments. The amount of this fixed N that was transferred from the chickpea to flax ranged from eight per cent to 22 per cent.
Significantly less N was removed in the intercropped flax than monocrop flax. For example at Redvers 2020, chickpea in a mixed-row intercrop removed 4.8 lbs/ac (5.4 kg N/ha) while the flax monocrop removed 39 lbs/ac (44 kg N/ha) from the system.
Overall, the results showed that a chickpea-flax intercrop had greater yield and LER than flax or chickpea monocrops. Improved nutrient use efficiency, and a reduction in net N removal in the intercrop systems were also observed. The in-season transfer of N from chickpea to the flax intercrop also contributed to better NUE than the monocrops.
Funding was provided by the Saskatchewan Agriculture Development Fund, the Western Grains Research Foundation and Saskatchewan Flax Development Commission. Scholarship funding was also provided by the Saskatchewan Flax Development Commission to the graduate student who conducted the research.
M. Reid, J. Schoenau, J.D. Knight, and R. Hangs. 2024. Yield, nitrogen, and phosphorus uptake, and biological nitrogen fixation in chickpea–flax intercropping systems in southern Saskatchewan. Canadian Journal of Plant Science. 104(1): 41-55. https://doi.org/10.1139/cjps-2023-0054
M. Reid, J. Schoenau, J.D. Knight and L. Shaw, 2021. Mixed Row and Alternate Row Intercropping of Chickpea-Flax and Pea-Mustard to Enhance Yield and Nutrient Availability. Abstracts of 2021 Canadian Society of Soil Science Virtual Annual Meetings, June 7 – 10, 2021.
Photo of mixed row intercrop by Jeff Schoenau
