Intercropping of oat or mustard with legumes under organic management in the semiarid Canadian Prairie

Abstract

Intercropping, the growing of more than one crop at the same time within the same land area, could be a sustainable method of crop production in semiarid regions, which could increase biodiversity, and productivity and quality of crops compared to monocultures. This may be of significance under limited N, such as in organic agriculture, and could be an alternative to green manure. An organic study was conducted in the semiarid Canadian Prairie in drier than average years (2017–2018) to determine if intercropping legumes with non‐legumes could reduce weeds and increase grain yield and quality of crops at different seeding rate ratios. Intercrops examined were lentil (Lens culinaris Medik.)–yellow mustard (Sinapis alba L.), and field pea (Pisum sativum L.)–oat (Avena sativa L.), at three seeding rate ratios, and their respective monocultures. Weed density was lower in the pea–oat intercrop than the pea monoculture, while weed biomass was lower in the lentil–mustard intercrop than the lentil monoculture. Legumes, when intercropped even at monoculture ratios, had lower aboveground biomass and grain yield than their monocultures, with pea showing higher tolerance than lentil to competition with its companion. Total biomass and grain yield were accounted for mostly by the non‐legumes, which performed better than expected based on their seeding ratios. Mustard grown with lentil appeared to be more competitive than oat grown with pea. Grain weight of oat was higher in all intercrops with pea than in its monoculture, while grain protein of pea was higher when intercropped with oat than in its monoculture.

Full text

Received: 28 February 2024 Accepted: 15 March 2025
DOI: 10.1002/agj2.70056
ORIGINAL ARTICLE
Organic Agriculture and Agroecology
Intercropping of oat or mustard with legumes under organic
management in the semiarid Canadian Prairie
Myriam R. Fernandez1Prabhath Lokuruge1Lobna Abdellatif1Noe Waelchli1
Julia Y. Leeson2Michael P. Schellenberg1Scott Chalmers3
1Swift Current Research and Development
Centre, Agriculture and Agri-Food Canada,
Swift Current, Saskatchewan, Canada
2Saskatoon Research and Development
Centre, Agriculture and Agri-Food Canada,
Saskatoon, Saskatchewan, Canada
3Westman Agricultural Diversification
Organization, Manitoba Agriculture and
Resource Development, Melita, Manitoba,
Canada
Correspondence
Myriam R. Fernandez, Swift Current
Research and Development Centre,
Agriculture and Agri-Food Canada, P.O.
Box 1030, Swift Current, SK, S9H 3×2,
Canada.
Email: myriam.fernandez@agr.gc.ca
Assigned to Associate Editor Drew Scott.
Funding information
Western Grains Research Foundation,
Saskatchewan Wheat Development
Commission, and Saskatchewan Pulse
Growers
Abstract
Intercropping, the growing of more than one crop at the same time within the same
land area, could be a sustainable method of crop production in semiarid regions,
which could increase biodiversity, and productivity and quality of crops compared to
monocultures. This may be of significance under limited N, such as in organic agri-
culture, and could be an alternative to green manure. An organic study was conducted
in the semiarid Canadian Prairie in drier than average years (2017–2018) to deter-
mine if intercropping legumes with non-legumes could reduce weeds and increase
grain yield and quality of crops at different seeding rate ratios. Intercrops exam-
ined were lentil (Lens culinaris Medik.)–yellow mustard (Sinapis alba L.), and field
pea (Pisum sativum L.)–oat (Avena sativa L.), at three seeding rate ratios, and their
respective monocultures. Weed density was lower in the pea–oat intercrop than the
pea monoculture, while weed biomass was lower in the lentil–mustard intercrop than
the lentil monoculture. Legumes, when intercropped even at monoculture ratios, had
lower aboveground biomass and grain yield than their monocultures, with pea show-
ing higher tolerance than lentil to competition with its companion. Total biomass and
grain yield were accounted for mostly by the non-legumes, which performed better
than expected based on their seeding ratios. Mustard grown with lentil appeared to
be more competitive than oat grown with pea. Grain weight of oat was higher in all
intercrops with pea than in its monoculture, while grain protein of pea was higher
when intercropped with oat than in its monoculture.
1INTRODUCTION
Legumes have been one of the few options for organic pro-
ducers to use in their crop rotations to increase soil N
(Lithourgidis et al., 2011). Currently, organic producers in
Abbreviations: CR, competitive ratio; MJJA, growing season (May, June,
July, August).
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided
the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
©2025 His Majesty the King in Right of Canada. AgronomyJour nal published byWiley Periodicals LLC on behalf of American Society of Agronomy. Reproduced with the permission
of the Minister of Agriculture and Agri-Food Canada.
the Canadian Prairies are meeting their fertility needs, and
much of their weed control, by using legume green manure
(Fernandez, Zentner, Schellenberg, Aladenola, et al., 2019;
Fernandez, Zentner, Schellenberg, Leeson, et al., 2019). How-
ever, most legume species are not very competitive against
weeds (Šar¯
unait˙
e et al., 2010) and are affected by water
stress, in addition to being susceptible to important dis-
eases that have been increasing in western Canada, such as
Agronomy Journal. 2025;117:e70056. wileyonlinelibrary.com/journal/agj2 1of17
https://doi.org/10.1002/agj2.70056

2of17 FERNANDEZ ET AL.
Fusarium root/crown rot (Fusarium spp.) and Aphanomyces
root rot (Aphanomyces euteiches) (Saskatchewan Pulse Grow-
ers, 2023a, 2023b,2023c).
It has been argued that satisfying the nutritional needs
of a rapidly growing human population while limiting envi-
ronmental impacts and trying to adapt to climate change
will require sustainable intensification of agriculture (Martin-
Guay et al., 2018). Growing at least two crops in the same
space at the same time could play a role in this endeavor.
Intercropping can be defined as the growing of two or more
crops together at the same time within the same land area
(Willey, 1979). Intercropping has the potential to optimize
land utilization and promote synergistic relationships among
crop species. In particular, growing legumes with more com-
petitive species may provide an alternative to the lack of
current year economic returns of green manure and their poor
weed suppression ability (Šar¯
unait˙
e et al., 2010). Intercrop-
ping often has weed suppression benefits, especially relative
to the least competitive crop when grown alone. In addition
to increasing the productivity of crops by enhancing resource
use efficiency through complementary and facilitative rela-
tionships, intercropping could provide many other valuable
agroecological services (Duchene et al., 2017).
Intercropping has been shown to be of benefit to low N
systems (Bedoussac et al., 2015, 2018; Finckh et al., 2000;
Ofori & Stern, 1987). The use of legumes in intercrops would
be expected to improve soil fertility in organically managed
fields through nitrogen fixation (Lithourgidis et al., 2011) and
would thus allow organic producers not to forego a year of
cash cropping compared to a sequence with summer fallow
or green manure. Given their weed suppressive ability, inter-
crops are particularly suitable under reduced tillage in organic
farming (Gronle et al., 2015).
The most anticipated advantage of organic intercropping is
a higher yield per unit area when using a mixture of crops of
different rooting ability, canopy architecture, plant height, and
nutrient requirements based on the complementary utilization
of growth resources by the component crops (Lithourgidis
et al., 2011). Disease reductions have also been observed
in intercrops (Boudreau, 2013). In addition, intercropping
could result in improved grain quality because of the poten-
tial higher protein concentration in the non-legume crops
(Lithourgidis et al., 2011). In a review of wheat (Triticum
aestivum L.)–faba bean (Vicia faba L.) intercrops in five
regions in Europe, Gooding et al. (2007) concluded that,
despite a 25%–30% reduction in wheat yield compared to
sole wheat, intercropping could still have an economic benefit
resulting from the higher protein concentration of the inter-
cropped wheat, combined with the added value of the legume
crop.
The N2fixed by the legume in an intercrop may be available
to the non-legume companion in the same growing season
in addition to the N leached from legume leaves and other
plant parts (Brophy & Heichel, 1989; Eaglesham et al., 1981),
Core Ideas
∙Productivity of the non-legumes in the intercrops
mostly exceeded projections based on their seeding
ratios.
∙Mustard intercropped with lentil had a higher inter-
crop competitiveness than oat intercropped with
pea.
∙The grain weight of oat was higher when inter-
cropped with field pea than when grown in
monoculture.
∙Pea intercropped with oat had higher grain protein
than the pea monoculture.
∙Weed density and biomass were lower in intercrops
than in legume monocultures when differences
were significant.
or as residual N for a subsequent cereal crop (Searle et al.,
1981). Some studies have reported little or no current N trans-
fer in legume/cereal mixed cropping (Ofori & Stern, 1987;
Papastylianou & Danso, 1991; Rerkasem & Rerkasem, 1988;
Van Kessel & Roskoski, 1988), suggesting that N transfer may
occur only under certain conditions. Regardless, the distance
between the cereal and legume root systems is important when
N is transferred through the intermingling of root systems
(Fujita et al., 1992).
Cereal–grain legume intercrops showed higher grain yield
stability than their respective sole crops in a meta-analysis
of organic and nonorganic trials under different conditions in
various regions of the world (Raseduzzaman & Jensen, 2017).
Intercropping studies with cereal and legume crops conducted
under organic management in England have also shown that
intercrops can provide several advantages, including higher
grain yield, over their respective sole crops (Bulson et al.,
1997). In India, row intercropping of Brassica juncea (L.)
Czern mustard and annual legumes also increased yield sta-
bility (Devi et al., 2014). Lithourgidis et al. (2011)havealso
suggested that intercropping could provide insurance against
crop failure or against unstable market prices, especially in
areas subject to extreme weather conditions. Under those con-
ditions, intercropping would be less risky than monoculturing,
given that if one crop in a mixture fails, the companion crop(s)
may still be harvested.
There could also be other potential environmental ben-
efits of intercropping. An increase in soil conservation
through greater ground cover than sole cropping would be
expected with intercropping (Lithourgidis et al., 2011). Grow-
ing legumes with non-legumes would also be expected to
reduce N losses to the environment (Jensen et al., 2015). Loss
of nitrates through leaching has been reported to be lower in
intercropping systems than in sole crops (Mariotti et al., 2015;

FERNANDEZ ET AL.3of17
Ofori & Stern, 1987), while Neumann et al. (2007) reported
that even at high pea (Pisum sativum L.) densities, intercrops
reduced the risk of N losses through leaching compared to
sole-cropped pea. Increased diversity would also be expected
to lower the contribution of crop production to greenhouse
gases (Jensen et al., 2015).
It is therefore expected that a successful intercropping sys-
tem would make more efficient use of resources on a land
area basis, have higher biomass and/or grain yield and quality,
stabilize yields, prevent lodging, improve soil quality, reduce
N leaching, suppress weeds and other pests, and thus might
contribute toward adaptation of cropping systems to climate
change. Intercropping systems could also be considered multi-
functional given that they could provide benefits for both grain
and forage production (Padel et al., 2010).
If successful, intercrops could be integrated into and extend
crop rotations in organic systems (Jensen et al., 2015). How-
ever, intercropping also has some disadvantages. This practice
requires more planning and it adds extra work in preparing and
planting the seed mixture(s), and separating the grain species
after harvest. For intercropping to be successful, the appro-
priate crop species combination and sowing densities would
need to be identified for the specific environmental condi-
tions, particularly soil type and most typical weather in the
region.
Although intercropping of legumes with cereal crops has
been studied in western Canada and the United States (Carr
et al., 1995; Fernandez et al., 2015; Malhi, 2012;Nelson
et al., 2012; Pridham & Entz, 2008; Szumigalski & Van Acker,
2005), reports on impacts of intercrops, especially under
organic management, have been more common from other
regions in the world (Bulson et al., 1997; Dordas et al., 2012;
Jensen et al., 2015; Lithourgidis et al., 2011; Neugschwandt-
ner & Kaul, 2015; Pelzer et al., 2012; Šar¯
unait˙
e et al., 2013).
Thus, most published studies on intercrops under organic
management have been conducted in different environments
than in the Canadian Prairies, especially in the semiarid
region.
Given the variety of different environments and approaches
used in studies on intercrops, there is variability in the agro-
nomic and economic advantages reported in the adoption of
this practice. Based on the dearth of information on the poten-
tial agronomic and economic merits of organic intercropping
systems in the semiarid region of the Canadian Prairies, where
climatic conditions could also be very variable (Fernandez
et al., 2016), the present study aims to examine such cropping
system in this region, which would also apply to any other
semiarid regions around the globe.
The objectives of this study conducted under organic man-
agement in the semiarid region (Brown soil zone) of the
western Canadian Prairies were to determine the ability
of intercrops to suppress weed populations, determine the
biomass and grain yield and quality of crops in intercrop
combinations at various ratios compared to their respective
monocultures, and determine the optimal seeding ratio of the
intercrops for achieving the greatest benefits. Their impact
on the soil health and growth of the following sole crop is
being reported elsewhere (Fernandez et al., 2025). It is hoped
that a better understanding of intercropping under organic
management in this region would also help in other semiarid
regions of Canada and beyond, especially in regions faced
with drought conditions that are becoming more common
due to climate change and weather variability. Drought is
forecasted to increase in severity and frequency due to cli-
mate change (Zhou et al., 2019). This research would also
be of value for production under low-input nonorganic meth-
ods where intercropping could potentially reduce synthetic
fertilizer and pesticide requirements.
2MATERIALS AND METHODS
2.1 Study area and experimental design
Field experiments were conducted south of Swift Current,
SK, at the Agriculture and Agri-Food Canada, Swift Current
Research and Development Centre (lat: 50˚17′N, long:
107˚48′W, elevation 825 m) from 2017 to 2018 on adjacent
fields that had been organically managed (CAN/CGSB, 2021)
for the previous 2 years. The soil type in this Brown soil
zone is an Aridic Haploboroll (Orthic Brown Chernozem),
with a soil organic matter of approximately 3.5%, where the
average annual and growing season precipitation is lower,
while evapotranspiration and mean annual temperature are
higher than in the other soil zones in the Canadian Prairies
(Fernandez et al., 2016).
The sites where these trials were going to be conducted
were seeded in the previous 2 years to a mixture of a legume,
an oilseed, and a cereal, which were then incorporated at
flowering using a tandem disk harrow. For each trial, in
order to remove weeds and give the crops an advantage, the
soil was cultivated with a cultivator with mounted harrows,
and the surface leveled with a harrow packer, just before
seeding.
In 2017 and 2018, the treatments examined consisted of
two intercrop combinations, each having a legume and a
non-legume crop at three different seeding ratios, in addi-
tion to their respective monocultures. These were small red
lentil (Lens culinaris Medik. ‘CDC Maxim’), yellow field
pea (CDC Meadow), yellow mustard (Sinapis alba L. ‘AC
Andante’), and oat (Avena sativa L. ‘AAC Oravena’). For
all crops, as recommended for organic production, seeding
rates were about 25% higher than what is normally rec-
ommended for conventional systems (Beavers et al., 2008).
For our region, these were for oat 140, field pea 269, lentil
192, and yellow mustard 15.3 kg ha−1. See Table 1for the
seeding ratios and expected number of seeds per unit area
in both years. The granular inoculant Novozymes TagTeam

4of17 FERNANDEZ ET AL.
TABLE 1 Monocultures and intercrop combinations at different seeding ratios, in a study conducted in southwest Saskatchewan, Canada, 2017
and 2018.
Seeding ratiobSeeding ratiocSeeds per meter square
Crop/intercropaLegume Non-legume Legume Non-legume Legume Non-legume
Lentil–mustard
Lentil100 1 0 1.00 0.00 204 0
Lentil100 +Mustard50 1 0.5 0.59 0.41 204 144
Lentil75 +Mustard75 0.75 0.75 0.41 0.59 153 217
Lentil50 +Mustard100 0.5 1 0.26 0.74 102 289
Mustard100 0 1 0.00 1.00 0289
Pea–oat
Pea100 1 0 1.00 0.00 150 0
Pea100 +Oat25 1 0.25 0.66 0.34 150 78
Pea100 +Oat50 10.5 0.49 0.51 150 157
Pea75 +Oat75 0.75 0.75 0.32 0.68 113 235
Oat100 1 0 0.00 1.00 0313
aCrop varieties: lentil CDC Maxim, yellow mustard AC Andante, field pea CDC Meadow, oat AAC Oravena.
bSeeding ratios based on monoculture rates (lentil 76, mustard 15.3, pea 269, and oat 140 kg ha−1). Lentil100 +Mustard50: 100% lentil +50% mustard; Lentil75 +
Mustard75: 75% lentil +75% mustard; Lentil50 +Mustard100: 50% lentil +100% mustard; Pea100 +Oat25: 100% pea +25% oat; Pea100 +Oat50: 100% pea +50%
oat; and Pea75 +Oat75: 75% pea +75% oat.
cSeeding ratios based on the number of seeds per m2.
(Novozymes North America Inc.) was applied to the legumes
at a rate of 1 g per seeded row.
Treatments were arranged as randomized complete blocks
with four replicates. Each plot (6 m long ×4 m wide) had 12
rows 30.5 cm apart, with the plots being 0.5 m apart from each
other, and a pathway of 15 m between replicates. All seed-
ing was done with a plot seeder equipped with double disk
openers, as mixed rows to maximize their interaction (Mari-
otti et al., 2009). Seeding was on May 23, 2017, and May 18,
2018.
Precipitation and air temperature were recorded daily
throughout the year at a meteorological station located 1 km
from the test sites (Table 2).
2.2 Sample collection and data calculations
Five random soil samples were collected with a hydraulic
soil corer at three depths (0–15, 15–30, 30–60 cm) from
each replicate before seeding, air-dried, ground, and analyzed
for sodium bicarbonate-extractable NO3–N, PO4-P, and K
(Hamm et al., 1970) using a SEAL AutoAnalyzer 3 Continu-
ous Segmented Flow Analyzer (Thermo Fisher Scientific) for
NO3-N and PO4-P, while the K analysis was performed on
an iCE 3300 AAS Atomic Absorption Spectrometer (Thermo
Fisher Scientific). The amount of each parameter in soil per
hectare was calculated by multiplying the amount of soil in a
given layer (using soil bulk density) by the concentration of
each soil variable. Table 3shows the levels of the major soil
nutrients in the spring of 2017 and 2018 prior to the seeding
of each trial.
After crop establishment, all destructive crop sampling was
done on both sides (“sampling area”) of the middle four rows
(“harvest area”) of each plot. Seedling counts were taken at the
two-leaf stage, approximately 2 weeks after seeding, by count-
ing the number of seedlings of each crop along a randomly
placed 1-m long stick in each of three rows in the harvest
areas. A mean seedling density per unit area was calculated for
each crop and plot based on the three measurements. At phys-
iological maturity, average plant height (cm) for each crop
was based on measurements from the ground to the top of the
plants at three random spots in each plot.
For crop and weed biomass determination, approximately
2 weeks after the start of flowering of the non-legume crop
(mid- to late July), small areas were hand harvested. A 50 cm
×50 cm metal grid was randomly placed twice along each of
the “sampling areas” of each plot, and all plants within the
grid were cut at the ground surface. Weeds and crop plants
were then separated and forced-air oven-dried (60˚C) for 48 h.
The dry weights of each crop and combined weeds in each
plot were used to calculate crop and weed biomass per unit
area (kg ha−1). Dried crop samples from each plot were finely
ground (2 mm) and analyzed for total N concentration (Noel &
Hambleton, 1976) following the digestion method established
by Varley (1966) and using a SEAL AutoAnalyzer 3 Contin-
uous Segmented Flow Analyzer (Thermo Fisher Scientific).
For weed densities, all weeds were identified and counted in
20 quarter m2quadrats in each plot in July–August.

FERNANDEZ ET AL.5of17
TABLE 2 Precipitation and temperature (2017 and 2018) at the site of an intercropping study conducted in southwest Saskatchewan, Canada,
and the long-term means (1981–2015).
Precipitation (mm) Mean temperature (˚C)
Month 2017 2018 Long term 2017 2018 Long term
January 8.3 5.5 13.8 −10.1 −8.5 −10.4
February 19.8 18.7 9.2 −6.9 −16.0 −8.6
March 12.6 90.3 17.4 −2.1 −5.7 −2.7
April 22.4 17.9 22.7 5.1 1.1 4.9
May 21.0 25.6 49.5 12.3 14.6 10.8
June 35.3 16.9 80.3 15.7 17.1 15.3
July 11.0 51.2 54.3 18.7 18.8 18.4
August 28.0 31.0 45.4 18.3 18.7 18.2
September 4.4 44.4 35.1 13.3 9.3 12.5
October 58.2 19.9 19.0 5.5 3.9 5.4
November 15.3 44.6 15.1 −4.8 −4.3 −3.3
December 10.7 26.8 15.1 −9.7 −5.9 −9.5
Total/mean 247.0 392.8 376.9 4.6 3.6 3.6
May–June–July–August 95.3 124.7 229.5 16.3 17.3 17.3
TABLE 3 Major soil nutrients levels at the trial sites in southwest Saskatchewan, Canada, in the spring of 2017 and 2018, before seeding the
respective cover crop trials.
Spring 2017 (kg ha−1) Spring 2018 (kg ha−1)
Nutrient 0–15 cm 15–30 cm 30–60 cm 0–15 cm 15–30 cm 30–60 cm
NO3−217.6 10.8 16.6 25.8 22.7 18.2
PO4+235.8 8.7 8.6 39.7 7.8 7.4
K+422.7 240.5 470.1 408.7 196.1 398.5
The middle four rows of each plot were harvested at the full-
ripe stage of the non-legume crop on September 6, 2017, and
from August 14 to 20, 2018, using a plot combine (Winter-
steiger Inc.). The harvested grain samples were dried at 35˚C
for 4 days to under 12% moisture. The lentil–mustard grain
was cleaned and separated using a small two-level screen
separator (Office tester and cleaner 400, Seedburo Equip-
ment Co.), while the pea–oat grain was cleaned using the
same two-level screen separator and then separated using a
gravity spiral separator (Double spiral separator, Seedburo
Equipment Co.). After cleaning and separation, the samples
were weighed and converted to grain yield per unit area. The
1000-grain weight was determined on a sample taken ran-
domly from the harvested grain of each crop in each plot.
Seedling counts, grain yield, and 1000-grain weight were used
to estimate the number of seeds per plant. Harvest index was
estimated using grain yield and crop biomass per unit area.
Noel and Hambleton’s (1976) protocol was used to determine
grain protein content. The total N values were converted to
crude protein using the conversion factors in Mariotti et al.
(2009).
The competitive ratio (CR) was used to quantify intercrop
competition (Willey & Rao, 1980). This ratio is an integration
of the land equivalency ratios (LERs) and sowing proportions
of the two crops, and measures the competitiveness of one
crop over the other in number of times, and thus provides
a quantification of the competitiveness of the crops grown
together: CR (cropA) = ( LERcropA
LERcropB
)(
𝑍ba
𝑍ab ) and CR (cropB) =
(LERcropB
LERcropA
)(
𝑍ab
𝑍ba )where Zab and Zba are the proportions of
intercropped area initially allocated to crop a and crop b,
respectively.
The total LER index, used to measure the individual and
collective performances of component crops in intercrop-
ping systems (Dhima et al., 2007; Willey & Rao, 1980),
was calculated as total LER =LER(cropA) +LER(cropB);
LER (cropA) = 𝑌ab
𝑌aand LER (cropB) = 𝑌ba
𝑌b,Yab and Yba
are the grain yields of crop A and crop B in the inter-
crops, while Ya and Yb are the monoculture grain yields
of crops A and B, respectively. When LER is >1, the
combined grain yield of the mixture is higher than the mono-
culture yield of either crop A or B. If LER is <1, the

6of17 FERNANDEZ ET AL.
effect of intercropping is negative compared to the respec-
tive monocultures, while LER =1 indicates a breakeven, that
is, the effect of intercropping is neither advantageous nor
disadvantageous on a production per land area basis (Willey
& Rao, 1980).
2.3 Statistical analysis
Although the species, morphological characteristics, and
seeding ratios of the crops differed between the pea–oat and
lentil–mustard intercrop combinations, they were randomized
and managed as a single trial given that they shared the same
cultural practices and measured parameters; however, the
data from both combinations were analyzed separately. The
GLIMMIX procedure of SAS software was used for statisti-
cal analysis of the data (Littell et al., 2006; SAS Institute, Inc.,
2008). An exploratory analysis revealed that the main effect of
the year significantly affected productivity-related variables
such as grain yield and biomass. The differences in available
soil moisture between the 2 years likely accounted for this
effect. Apart from this quantitative difference, there were no
significant interactions between year and treatments. There-
fore, we analyzed the data from both years together, treating
the effects of treatments as fixed, and years and replicates as
random. This approach focused on the main objectives of this
study and simplified the presentation of the results. Resid-
uals of the models were evaluated for Gaussian distribution
using PROC UNIVARIATE. In some instances, such as weed
biomass and grain yield, the residual variance was heteroge-
neous between the 2 years. In such cases, the group option was
used in random statement to proceed with a unique residual
variance for each year. Mean differences were compared using
Fisher’s protected least significant difference test. In addition,
the relationships among crop and weed biomass, and grain
yield were evaluated using the PROC CORR procedure of
SAS (SAS Institute, Inc., 2008). For all tests, differences were
declared significant at p≤0.10, as used by Fernandez, Zent-
ner, Schellenberg, Leeson et al. (2019) for organic research
trials.
3 RESULTS AND DISCUSSION
3.1 Climatic conditions in 2017 and 2018
The weather data at the study site from 2017 to 2018 are
summarized in Table 2. The growing season (MJJA, where
MJJA is growing season [May, June, July, August]) precipi-
tation totals varied considerably from the long-term average
(1981–2015). Total precipitation in MJJA represents 45.7%
and 59.8% of the long-term average for 2017 and 2018,
respectively, and should thus be considered to represent mod-
erate drought conditions, especially in 2017. Precipitation in
July of 2018 helped to somehow ameliorate the drought in
that year. These conditions contrast with those in the preced-
ing year, 2016, where total precipitation was 397.2 mm for
MJAA and 588.3 mm for the whole year.
In regards to mean temperatures, MJJA was warmer than
the long-term average, especially in 2018, when the higher-
than-average temperatures in May and June resulted in
stressful growing conditions for the first half of the growing
season. Overall, crop growth stress was considered to be high
during the duration of this study.
3.2 Soil nutrients
Table 3shows the soil nutrient levels in the 2017 and 2018
sites prior to seeding. Soil NO3−2tended to be higher in 2018
than 2017, especially at 0–15 cm and 15–30 cm, while K
tended to be higher in 2017 than 2018. Differences in PO4+2
between the two sites appeared to be small. The lower NO3−2
levels in the 2017 site could be attributed to the high amount of
precipitation in 2016, which would have caused this nutrient
to move down the soil profile resulting in its low levels in the
upper soil layers the following spring (Geisseler & Horwath,
2016).
3.3 Weed identification, density, and
biomass
Across the plots, 19 weed species were identified in each
year. The two trials had 14 weed species in common, with
the additional species being relatively uncommon. Trials
were dominated by annual broadleaved species in both years
(98.5% of weeds in 2017 and 97.6% of weeds in 2018). The
most abundant species included lambsquarters (Chenopodium
album L.) and pigweeds: redroot (Amaranthus retroflexus
L.), tumble (A. albus L.), and prostrate (A. blitoides S. Wat-
son). Most of the other weeds were annual grasses, with few
perennial weeds in both trials.
Mean weed densities in 2017–2018 ranged from 3.3 to 11.2
plants m−2in the lentil–mustard and pea–oat intercrops, and
their respective monocultures (Table 4). The weed densities
reported in the monocultures in this study were lower than
those reported in the area in a 2015 provincial weed survey
in Saskatchewan, Canada (Leeson, 2016). Even though the
majority of the fields included in the provincial survey were
under nonorganic management, the average weed density
in each of those monocrops was higher than the average
density in the current study. In the provincial survey (Leeson,
2016), mustard had the lowest mean weed density at 6.9 m−2,
followed by lentil and pea at 18.2 m−2, and oat at 43.1 m−2.
Weather likely played a role in the lower weed densities in our
current study (Table 4) as it was drier than normal (Table 2),
but wetter than normal in the provincial survey year (Leeson,

FERNANDEZ ET AL.7of17
TABLE 4 Mean weed density and weed biomass in monocultures
and intercrop combinations at different seeding ratios, grown in
southwest Saskatchewan, Canada, 2017 and 2018.
Crop/intercrop
Weed density
(plants m−2)
Weed biomass
(kg ha−1)
Lentil–mustard
Lentil100a10.6ab1403a
Lentil100 +Mustard50 8.2a 283b
Lentil75+Mustard75 9.7a 339b
Lentil50 +Mustard100 9.1a 181b
Mustard100 5.7a 221b
Pea–oat
Pea100 11.2a 503a
Pea100 +Oat25 4.2b 267a
Pea100 +Oat50 3.3b 156a
Pea75 +Oat75 7.1ab 266a
Oat100 4.7b 392a
Note: Values are the LS means of 2 years and four replicates.
aSeeding ratios based on monoculture rates (lentil 76, mustard 15.3, pea 269, and
oat 140 kg ha−1): Lentil100 +Mustard50: 100% lentil +50% mustard; Lentil75
+Mustard75: 75% lentil +75% mustard; Lentil50 +Mustard100: 50% lentil +
100% mustard; Pea100 +Oat25: 100% pea +25% oat; Pea100 +Oat50: 100%
pea +50% oat; and Pea75 +Oat75: 75% pea +75% oat.
bLS means with the same letters within each column and lentil–mustard or pea–oat
intercrop combination are not significantly different (p≤0.10).
2016). Another study in Saskatchewan indicated that the
weed densities in organic fields were 4x to 7x greater under
organic management than under high or reduced conventional
management (Benaragama et al., 2016).
Similar to previously conducted organic trials in the same
region (Fernandez, Zentner, Schellenberg, Leeson, et al.,
2019), there was high variability in weed density in the current
study (Table 4). Thus, some of the lack of significant differ-
ences among treatments could be attributed to the variation in
weed growth among replicates and within plots.
Overall, the pea–oat intercrops had the lowest, or among
the lowest, mean weed densities, and even the smallest ratio
of oat resulted in a significant reduction in weed density com-
pared to the pea monoculture (Table 4). Weed biomass also
had a moderate negative correlation with the total grain yield
of the pea–oat intercrop (r=−0.45, p≤0.01), a reflec-
tion of the ability of this intercrop to control weeds. These
observations agree with previous studies conducted elsewhere
where nonorganic intercropping was associated with reduc-
tions in weed density in intercrops of cereals with legumes
(Banik et al., 2006; Hamzei & Seyedi, 2015). Under more
favorable weather for crop growth in Manitoba, Canada, than
in our study (Table 2), weed density was similar between
wheat monocultures and their intercrops with various crops
in organic and nonorganic studies (Pridham & Entz, 2008;
Szumigalski & Van Acker, 2005).
In turn, mean weed biomass was significantly lower in the
lentil–mustard intercrops and mustard monoculture than in
the lentil monoculture (Table 4). The large weed biomass
in the lentil monoculture, which did not have a significantly
higher weed density than its intercrops or the mustard mono-
culture (Table 4), is likely an indication that the weeds present
in those plots were large. The greater ability of pea than lentil
to suppress weed growth observed in these trials agrees with
findings by Fernandez et al. (2015) under organic conditions
in Minnesota. Furthermore, simple correlations on the 2017–
2018 intercrop data showed that weed biomass had a moderate
positive correlation with crop biomass (r=+0.44, p≤0.01)
and grain yield (r=+0.39, p≤0.05) of lentil, indicating that
the greater the presence of the latter crop, the higher the weed
biomass.
The observation that all the lentil–mustard ratios resulted
in a reduction in weed biomass compared to the lentil mono-
culture but were similar to that in the mustard monoculture
(Table 4) points to the weed-suppressive ability of the mus-
tard crop. The moderate negative correlation of weed biomass
with the grain yield of mustard (r=−0.35,p≤0.10) is also
a reflection of the competitiveness of this crop. There are
few studies previously conducted on intercrops with mustard
using a similar design to ours. When used as a cover crop,
weed biomass in organic mustard (Sinapis alba and B. juncea)
was reduced by more than 50% in 9 out of 10 fall-planted mus-
tard and in 15 out of 31 spring-planted mustard in the Great
Lakes Region (Björkman et al., 2015).
Other studies report a positive impact of intercropping on
weed biomass in cereal and legume intercrops. Trials with pea
and barley in organic replacement or additive intercropping
designs in several European sites showed that weed biomass
was 3x higher and more variable under the pea sole crops than
under both the intercrops and the barley sole crops at maturity
(Corre-Hellou et al., 2011). Other previous studies, conducted
under organic or nonorganic management in various regions,
have also shown that intercrops reduced weed biomass com-
pared to one or both of their respective sole crops, with cereals
being usually more competitive than legumes (Arlauskien˙
e
et al., 2011; Bedoussac et al., 2018; Bulson et al., 1997;
Carr et al., 1995; Hauggaard-Nielsen et al., 2001; Liebman &
Dyck, 1993; Neugschwandtner & Kaul, 2014, 2015; Šar ¯
unait˙
e
et al., 2013).
Overall, in this study, when statistically significant dif-
ferences among treatments were detected, weed density and
biomass were lower in the intercrops than in the legume
monocultures. This indicates that weed levels could be mit-
igated by the companion non-legumes, resulting in a lower
seed bank than in the legume monocultures, and thus a reduc-
tion in weed pressure in intercropping systems. However,
reductions in weed biomass in organic systems have not
always been associated with increases in crop biomass or
grain yield (Björkman et al., 2015; Fernandez et al., 2015;

8of17 FERNANDEZ ET AL.
TABLE 5 Seedling density and plant height of two intercrop combinations at different seeding ratios, grown in southwest Saskatchewan,
Canada, 2017 and 2018.
Crop/intercrop
No. of seedlings per meter square Plant height (cm)
Legume Non-legume Legume Non-legume
Lentil–mustard
Lentil100a106.4ab33.2a
Lentil100 +Mustard50 91.2b 58.5b 32.0ab 83.4ab
Lentil75 +Mustard75 70.0c 68.0b 32.2ab 85.7a
Lentil50 +Mustard100 61.1c 104.5a 30.9b 80.9b
Mustard100 104.6a 84.0ab
Pea–oat
Pea100 73.4a 60.9a
Pea100 +Oat25 66.8a 40.8d 48.3b 79.9a
Pea100 +Oat50 59.0ab 70.3c 42.8c 78.3ab
Pea75 +Oat75 49.1b 101.1b 39.7c 77.1b
Oat100 128.3a 79.2ab
Note: Values are the LS means of 2 years and four replicates.
aSeeding ratios based on monoculture rates (lentil 76, mustard 15.3, pea 269, and oat 140 kg ha−1): Lentil100 +Mustard50: 100% lentil +50% mustard; Lentil75 +
Mustard75: 75% lentil +75% mustard; Lentil50 +Mustard100: 50% lentil +100% mustard; Pea100 +Oat25: 100% pea +25% oat; Pea100 +Oat50: 100% pea +50%
oat; and Pea75 +Oat75: 75% pea +75% oat.
bLS means with the same letters within each column and lentil–mustard or pea–oat intercrop combination are not significantly different (p≤0.10).
Fernandez, Zentner, Schellenberg, Leeson, et al., 2019). The
relationship between crops and weeds has also been reported
to be dependent on environmental conditions, with weeds
appearing to be less detrimental to crop yields in harsh
environments. Stefan et al. (2021) reported that nonorganic
intercrop yields were related to weed biomass where water
and nutrients were abundant (Switzerland), but not where they
were limited (Spain).
3.4 Crop growth, biomass and grain yield,
and its components
In 2017–2018, the seedling density of most crops in the inter-
crops (Table 5) agrees with their seeding ratios (Table 1).
The exception was lentil, which had a lower number of
seedlings when grown at full rate with a half rate of
mustard (lentil100 +mustard50) than in its monoculture.
This is likely a reflection of some seedling death of the
lentil. Similarly, occasional death of pea seedlings was also
observed.
For all intercrops, the non-legume crops were overall taller
than the legume crops (Table 5). The mustard and oat plants
in their monocultures were approximately 2.5x and 1.3x taller
than the lentil and pea monocultures, respectively. Differences
in the height of mustard or oat plants between the monocul-
tures and their respective intercrops with legumes were not
statistically significant. In contrast, intercropping negatively
affected the height of the legumes in the intercrops (Table 5).
The lower the ratio of the legumes and the higher the ratio of
their companion crops, the greater the negative effect on the
height of the former, although this was not always statistically
significant. For lentil–mustard, lentil was shorter (by 6.9%)
in the intercrop with the highest ratio of mustard (lentil50 +
mustard100) than in the lentil monoculture (Table 5). In con-
trast, the growth of pea was stunted in all the intercrops with
oat, with the increasing ratios of oat consistently reducing the
height of pea to a greater extent than for lentil. This reduction
in the pea–oat intercrop ranged from 21% to 35% compared
to the height of the pea monoculture (Table 5). Nonetheless,
most maturing pea plants were observed climbing on their oat
companion plants.
For crop biomass, that of lentil was significantly higher in
its monoculture than in the intercrops, and there was no dif-
ference among the latter, while for mustard, crop biomass was
similar in its monoculture than in all its respective intercrops
(Table 6). For total crop biomass, there was no difference
among any of the lentil–mustard intercrop ratios, which were
not different from the respective monocultures. Pea also had a
higher crop biomass in its monoculture than in any of its inter-
crops. A close to two- to threefold increase in pea biomass was
observed in pea100 +oat25 compared to the other two inter-
crop mixtures, which had a higher ratio of oat with similar or
lower ratios of pea (Table 6). In contrast, the crop biomass of
oat was similar in its monoculture and the intercrop with its
highest ratio (pea75 +oat75). This resulted in a higher total
crop biomass in the latter intercrop ratio, comparable to that
of the oat monoculture.

FERNANDEZ ET AL.9of17
TABLE 6 Crop biomass, grain yield and harvest index of crops grown as monocultures and in intercrop combinations at different seeding
ratios, in southwest Saskatchewan, Canada, 2017 and 2018.
Crop biomass (kg ha−1)Grainyield(kgha
−1) Harvest index
Crop/intercrop Legume
Non-
legume Total Legume
Non-
legume Total Legume
Non-
legume
Lentil–mustard
Lentil100a3066ab3066a 1298a 1298a 0.50a
Lentil100 +Mustard50 740b 3811a 4554a 144b 714b 858b 0.25b 0.20a
Lentil75 +Mustard75 454b 3509a 3966a 105bc 804a 910b 0.23b 0.27a
Lentil50 +Mustard100 315b 3707a 4024a 55c 821a 877b 0.18b 0.24a
Mustard100 3938a 3938a 851a 851b 0.22a
Pea–oat
Pea100 4673a 4673b 1565a 1565c 0.37a
Pea100 +Oat25 1868b 3033b 4892b 575b 1657c 2232b 0.35a 0.56a
Pea100 +Oat50 979c 4213b 5182b 284c 2063b 2347b 0.36a 0.53a
Pea75 +Oat75 638c 6478a 7107a 145c 2224b 2369b 0.29a 0.36b
Oat100 7068a 7068a 2683a 2686a 0.36b
Note: Values are the LS means of 2 years and four replicates.
aSeeding ratios are based on monoculture rates (lentil 76, mustard 15.3, pea 269, and oat 140 kg ha−1): Lentil100 +Mustard50: 100% lentil +50% mustard; Lentil75 +
Mustard75: 75% lentil +75% mustard; Lentil50 +Mustard100: 50% lentil +100% mustard; Pea100 +Oat25: 100% pea +25% oat; Pea100 +Oat50: 100% pea +50%
oat; and Pea75 +Oat75: 75% pea +75% oat.
bLS means with the same letters within each column and lentil–mustard or pea–oat intercrop combination are not significantly different (p≤0.10).
Differences among the intercrop ratios were higher for
grain yield than for crop biomass, especially for lentil–
mustard (Table 6). In all cases, the grain yield of the legume
crops was negatively affected when grown with their respec-
tive non-legume companions. For lentil–mustard, the 89%
reduction in the lentil grain yield observed in the mixture
with the highest lentil and lowest mustard ratio (lentil100 +
mustard50) indicates that lentil was not productive in its inter-
crops. This effect was further intensified when the ratio of
lentil was reduced in the mixture; at its lowest ratio (lentil50
+mustard100) its yield was reduced by 95% compared to
its monoculture (Table 6). In contrast, except for lentil100 +
mustard50 with the lowest mustard ratio, which reduced its
yield by 16%, the other two ratios did not reduce the mus-
tard yield compared to its monoculture. In contrast to lentil,
the grain yield of the pea monoculture was lower than the
total yield in any of the pea–oat intercrops or oat monocul-
ture. Compared to its monoculture, the lowest reduction in pea
yield, observed when grown at full rate with the lowest ratio
of oat (pea100 +oat25), was 63% (Table 6). Decreasing the
oat ratio in its intercrops also consistently reduced its grain
yield, which in all cases was significantly lower than in the
oat monoculture. The greatest reduction in the intercropped
oat yield compared to its monoculture was 38%, observed in
pea100 +oat25.
The observation that total crop biomass and grain yield
appeared to be accounted for mostly by the non-legumes in
each of the intercrop combinations (Table 6) agrees with find-
ings from pea–oat intercrops by Arlauskien˙
eetal.(2011)
in organic trials under various soils in Lithuania, and from
organic pea–barley studies in Denmark showing higher com-
bined grain yields of the intercrops than of either of their
respective sole crops, which was accounted for by the bar-
ley crop (Hauggaard-Nielsen et al., 2001). In Newfoundland,
Canada, growing nonorganic pea with barley or oat reduced
the forage yield of each crop relative to their sole stands but
their total yield was often higher than in either of the sole
crops, which in most cases was attributed to the cereal crops
(Kwabiah, 2005).
Our observations of a higher productivity of oat than pea in
their intercrops (Table 6) also agree with a review of organic
studies in France and Denmark showing that in general inter-
cropped cereals were more productive than their companion
legumes, regardless of the cropping design (Bedoussac et al.,
2015), with the total average grain yield of intercrops being
greater than for the sole cereal in 64%, and for the sole legume
in 83%, of the experiments. Similar observations were made
by others in nonorganic studies. A survey by Ofori and Stern
(1987) in different regions of the world showed that the yield
of the legume intercrop component declined on average by
about 52% of the sole crop yield, whereas the cereal yield was
reduced by only 11%, while in an irrigated trial in Victoria,
Australia, Mason and Pritchard (1987) observed that regard-
less of their seeding ratios, pea did not contribute more than
10%, and oat 90%, of the total dry matter in all intercrops. Fur-
thermore, in an environment similar to ours in North Dakota,

10 of 17 FERNANDEZ ET AL.
Carr et al. (1995) reported that while the grain yield of wheat
was maintained at a sole crop level when intercropped with
lentil, the yield of the latter was reduced by 70 to >90%,
depending on the design and crop ratio.
Compared to intercrops with cereals, there are fewer reports
from mustard grown with legumes. For Brassica campestris
L. mustard, Banik et al. (2000) reported that this crop was
dominant in its nonorganic intercrops with legumes, agree-
ing with our findings that mustard was dominant when
intercropped with lentil.
In addition to the dry conditions under which these
intercropping trials were conducted, the lower growth and
productivity of both lentil and pea, especially the former,
when intercropped with mustard and oat, respectively, should
also be attributed, at least partly, to the shading by their com-
panion crops (Arlauskien˙
e et al., 2014; Carr et al., 1995;Dusa
& Stan, 2013; Neugschwandtner & Kaul, 2014;Ofori&Stern,
1987).
Compared to their respective monocultures, lentil and pea
had biomass and grain yield decreases that were higher than
expected based on their seeding ratios (Table 6). In contrast,
comparison of the biomass and grain yield of the non-legumes
with their expected values showed that in most cases, their
productivity was favored. Both non-legumes, especially mus-
tard, were able to compensate for lower seeding ratios when
grown with the respective legumes (Table 6). The observa-
tion that the grain yield of oat in its intercrops with pea
exceeded expectations agrees with observations from nonor-
ganic intercropping trials in Melita, MB, Canada, where
out of various combinations of pea with flax, wheat, mus-
tard, canola (Brassica spp.), or oat in 2019 and 2020, oat
provided the best combination with pea resulting in no sig-
nificant change in oat yields despite the seeding ratio being
cut in half compared to its monoculture (Chalmers & Zhanda,
2020).
In regards to the harvest index, there was a significant
reduction for lentil (ranging from 50% to 64%) when grown
in the intercrops with mustard compared to the lentil mono-
culture (Table 6). As suggested by the plant height differences
(Table 5), lentil might have invested more energy than pea for
stem elongation to compete with mustard for solar radiation
(Murphy & Dudley, 2007). The stress on the lentil caused by
the more competitive mustard in their intercrops would have
resulted in a lower grain formation, and thus a lower harvest
index. These observations agree with results by Carr et al.
(1995), where in a similar environment, the harvest index in
nonorganic lentil intercropped with wheat showed that repro-
ductive growth was more adversely affected by intercropping
than vegetative growth. In contrast, the harvest index of pea
did not appear to be affected by intercropping (Table 6), being
able to maintain the partition ratio between vegetative growth
and reproduction as in its monoculture. This does not agree
with Neugschwandtner and Kaul’s (2014) observation that
pea grown with oat had a lower harvest index than the sole
stand.
For the non-legumes, while the harvest index of mustard
was not affected by intercropping, that of oat was highest
in the intercrops at its lowest ratios and highest pea ratios
(pea100 +oat25 and pea100 +oat50) (Table 6). The obser-
vation that the reproductive growth and seed formation of oat
appeared to be positively affected by intercropping at lower
seeding ratios does not agree with results from a study in a
different environment by Neugschwandtner and Kaul (2014),
who reported a lower harvest index of nonorganic oat at lower
seeding ratios when intercropped with pea in a fertile soil in
Austria.
Furthermore, in nonorganic European sites, Chen et al.
(2021) reported that compared to monocultures, mixtures of
two to four species, including legumes and non-legumes,
increased productivity resulting in higher biomass and, to
a lesser extent, higher seed yield, which led them to con-
clude that the observed reduced harvest index of crops in
mixtures might be attributed to their breeding for maximum
performance in monocultures.
Regardless of the combination of legumes with non-
legumes in previous studies, there is considerable variation
in their reported productivity, which is most likely related to
growing conditions, among other factors. Under organic man-
agement, in more favorable environments for crop growth,
Pridham and Entz (2008) reported that in Manitoba, Canada,
intercrops of wheat with other cereals or non-cereals provided
no yield benefit over the wheat monoculture, while intercrop-
ping of legumes with various non-legume crops in Minnesota,
did not consistently increase, and often decreased, yield and
profitability compared to the field pea and lentil sole crops
(Fernandez et al., 2015).
The CR, which further quantifies the competitiveness of
each crop when grown together (Willey & Rao, 1980),
also suggests that for both intercrop combinations, the non-
legumes outperformed the legumes in grain yield, with
mustard grown with lentil appearing to be more competitive
than oat with pea, and pea appearing to be more competitive
than lentil (Table 7). For pea–oat, there was a significant vari-
ation in the CR of both crops, with the competitiveness of oat
appearing to be progressively reduced when intercropped at
lower ratios with higher ratios of pea, while that of pea was
reduced as the oat ratio increased. In contrast, mustard and
lentil appeared to be able to adjust to the intercrop competi-
tion, with the competitiveness of mustard not appearing to be
affected by its seeding ratios in its intercrops.
The higher partial LER of the non-legumes than the
legumes agrees with their higher CR (Table 7). In general,
the partial LERs of the legumes for crop biomass and yield
were numerically lower than for the non-legumes, with those
for pea being numerically higher than for lentil. In addition,
for both intercrop combinations, the partial LER for the crop

FERNANDEZ ET AL.11 of 17
TABLE 7 Competitive ratio of land equivalency ratio (LER) for crop biomass and grain yield in two intercrop combinations at different
seeding ratios, grown in southwest Saskatchewan, Canada, 2017 and 2018.
Competitive ratio LER crop biomass LER grain yield
Crop/intercrop Legume
Non-
legume Legume
Non-
legume Total Legume
Non-
legume Total
Lentil–mustard
Lentil100a1.00ab1.00b 1.00a 1.00a
Lentil100 +Mustard50 0.10a 11.8a 0.37b 0.97a 1.34a 0.11b 0.84b 0.95a
Lentil75 +Mustard75 0.13a 11.0a 0.16b 0.88a 1.05b 0.08c 0.96a 1.04a
Lentil50 +Mustard100 0.13a 12.5a 0.15b 0.94a 1.09ab 0.04d 0.97a 1.01a
Mustard100 1.00a 1.00b 1.00a 1.00a
Pea–oat
Pea100 1.00a 1.00ab 1.00a 1.00a
Pea100 +Oat25 0.34a 3.2b 0.46b 0.49b 0.94ab 0.38b 0.61c 1.00a
Pea100 +Oat50 0.26b 4.1ab 0.23c 0.61b 0.84b 0.19c 0.77b 0.95a
Pea75 +Oat75 0.24b 4.8a 0.14c 1.00a 1.14a 0.09d 0.83b 0.92a
Oat100 1.00a 1.00ab 1.00a 1.00a
Note: Values are the LS means of 2 years and four replicates.
aSeeding ratios are based on monoculture rates (lentil 76, mustard 15.3, pea 269, and oat 140 kg ha−1): Lentil100 +Mustard50: 100% lentil +50% mustard; Lentil75 +
Mustard75: 75% lentil +75% mustard; Lentil50 +Mustard100: 50% lentil +100% mustard; Pea100 +Oat25: 100% pea +25% oat; Pea100 +Oat50: 100% pea +50%
oat; and Pea75 +Oat75: 75% pea +75% oat.
bLS means with the same letters within each column and lentil–mustard or pea–oat intercrop combination are not significantly different (p≤0.10).
biomass and grain yield of the legumes decreased as the com-
panion seeding ratio increased. This was also the case for
oat (Table 7). In contrast, in most cases the partial LER for
mustard was similar between its monoculture and most of its
intercrops with lentil, and was numerically higher than for
oat. The numerically higher partial LERs for mustard than oat
resulted in mostly higher total LERs for lentil–mustard than
for pea–oat. The total LER for crop biomass was ≥1 for all
the lentil–mustard ratios, with lentil100 +mustard50 being
significantly higher than for either monocrop (Table 7). For
the pea–oat intercrops, only pea75 +oat75 had a total LER
for biomass ≥1 but was not significantly different than for
either monocrop. For grain yield, the total LER was ≥1for
lentil–mustard at the lowest ratios of lentil and highest ratios
of mustard, and for pea–oat at the lowest oat ratio, although
none of these differences were significant (Table 7).
According to a meta-analysis of N-fertilized and unfertil-
ized intercropping studies in 15 countries around the world,
the partial LERs of the cereals were also higher than that
of the legumes in 71% of cases (Pelzer et al., 2014). How-
ever, in our trials, the total LERs were lower than expected
(Table 7), which could be attributed to the drier than average
weather conditions prevalent in 2017–2018 (Table 2) affect-
ing legumes to a greater extent than non-legumes, especially
in the intercrops (Table 7). Large variability in precipitation is
not uncommon in this semiarid region where drought occurs
often, as it was the case in this study in 2017–2018 (Table 2),
but where higher precipitation than normal could also occur
(Fernandez et al., 2016).
Furthermore, the consistently higher partial LERs for crop
biomass than grain yield in the legumes, especially lentil
(Table 7), strongly suggest that under more favorable growing
conditions, the grain productivity of these intercrops might be
likely higher than in the present trials and would thus increase
their harvest index. In a nonorganic intercrop of oat and pea
in a fertile soil in Austria (Neugschwandtner & Kaul, 2014),
the LER of >1 for aboveground dry matter and straw yields,
and of <1 for grain yields indicated that intercrops enhanced
vegetative growth, which might not fully transfer to increased
grain yield due to dry conditions.
Examination of the number of seeds per plant, estimated
for each of the crops, indicated that seed production in the
legumes was significantly reduced when intercropped at the
same or lower ratio as their respective monocultures (Table 8).
However, compared to lentil, the number of seeds per pea
plant was not reduced as much in the intercrops relative to the
monoculture (68% for pea and 88% for lentil), which suggests
a higher tolerance of pea to competition from oat than of lentil
to competition from mustard. In contrast, the number of seeds
per non-legume plant tended to increase when their seeding
ratio in lentil–mustard or pea–oat decreased. This trend was
more apparent for pea100 +oat25 where oat had a 53% higher
number of seeds than the oat monoculture (Table 8).
Compared to its monoculture, the grain weight of oat
increased in all the pea–oat intercrop ratios by an average
of 25% (Table 8). Thus, in addition to the intercropping
with pea being of benefit to the crop biomass and especially
the grain yield of oat, the grain weight of the latter was

12 of 17 FERNANDEZ ET AL.
TABLE 8 Seeds per plant, 1000-grain weight, and grain protein concentration, of monocultures and intercrop combinations at different seeding
ratios, grown in southwest Saskatchewan, Canada, 2017 and 2018.
Seeds per plant 1000-grain weight (g) Grain protein (g kg−1)
Crop/intercrop Legume
Non-
legume Legume
Non-
legume Legume
Non-
legume
Lentil–mustard
Lentil100a33.6ab38.4a 191b
Lentil100 +Mustard50 5.0b 243.6ab 36.5bc 5.7a 192ab 256a
Lentil75 +Mustard75 4.5b 255.2a 37.4ab 5.6a 198a 258a
Lentil50 +Mustard100 2.6b 176.1c 35.9c 5.6a 196ab 256a
Mustard100 204.1bc 5.5a 261a
Pea–oat
Pea100 13.6a 208.5a 185b
Pea100 +Oat25 6.3b 105.5a 186.2b 42.9a 206a 99a
Pea100 +Oat50 4.3bc 80.0b 175.7c 42.9a 204a 101a
Pea75 +Oat75 2.3c 54.9c 176.5c 42.2a 214a 105a
Oat100 68.9bc 34.0b 111a
Note: Values are the LS means of 2 years and four replicates.
aSeeding ratios based on monoculture rates (lentil 76, mustard 15.3, pea 269, and oat 140 kg ha−1): Lentil100 +Mustard50: 100% lentil +50% mustard; Lentil75 +
Mustard75: 75% lentil +75% mustard; Lentil50 +Mustard100: 50% lentil +100% mustard; Pea100 +Oat25: 100% pea +25% oat; Pea100 +Oat50: 100% pea +50%
oat; and Pea75 +Oat75: 75% pea +75% oat.
bLS means with the same letters within each column and lentil–mustard or pea–oat intercrop combination are not significantly different (p≤0.10).
significantly higher in the intercrops than in its monoculture.
This was particularly so at the lowest ratios of oat with the
highest ratio of pea, although this was not significantly differ-
ent among the three pea–oat ratios (Table 8). This observation
suggests that differences in the oat grain yield among the pea–
oat ratios cannot be accounted for by its lower grain weight.
These results partly agree with Neugschwandtner and Kaul
(2014), who reported that the grain weight of nonorganic oat
increased with decreasing percentages of oat in intercrops
with pea in one of 2 years. This appears to be also true for
other cereals. In an organic study in Italy, De Stefanis et al.
(2017) reported that durum wheat [Triticum turgidum L. ssp.
durum (Desf.) Husn.] had a higher seed weight in intercrops
with faba bean in two of 3 years, with its grain yield in the
intercrops being lower than in its sole crop in two of the
years, while Pelzer et al. (2016) reported that the grain weight
of nonorganic wheat in France was either similar or higher
when intercropped with winter pea than in its sole stand. How-
ever, our results do not agree with a report of a mostly lower
grain weight of organic oat, barley, and wheat when grown
at fixed rates with increasing rates of pea, which explained
the cereal grain yield decreases (Lauk & Lauk, 2008). Differ-
ences with the trials in our study (Table 8) might be attributed
to our lower oat seeding ratios in these intercrops than in its
monoculture and/or to the poor growth of the pea due to dry
conditions (Table 2). The higher grain weight of oat in the
intercrops is likely attributed to the lower competition among
oat plants due to its lower seeding ratios than to a positive
effect of the pea (Table 8).
Mustard intercropped with lentil responded differently than
oat grown with pea (Table 8). The observation that similar to
its crop biomass and most of its grain yield (Table 6), the grain
weight of mustard was similar among the intercrop ratios with
lentil (Table 8) partly agrees with Singh et al. (2014) in India,
who reported that when row intercropped with wheat or lentil
at different ratios, B. juncea mustard had a similar or lower
grain weight than its sole stand.
In contrast to the non-legumes, the grain weight of lentil
and pea responded in a similar manner to intercropping
(Table 8). In general, intercrops significantly reduced the
1000-grain weight of the legume crops. The lower their ratio
and/or the higher the ratio of the non-legumes in the inter-
crops, the lower their grain weight. In addition, while the
maximum reduction of grain weight in the intercropped lentil
was 6.5%, with a mean of 5%, the grain weight reduction
in pea when intercropped with oat ranged from 11% to 16%
(Table 8). The decrease in legume grain weight with lower
seeding ratios, and higher non-legume seeding ratios, would
account, at least partly, for the decrease in their grain yield
when intercropped. These observations also agree with those
by Neugschwandtner and Kaul (2014) that nonorganic pea had
a lower grain weight in intercrops with oat than in its sole
stand, and they also partly agree with Pelzer et al. (2016) that
the grain weight of winter pea was similar or lower in the
intercrops with wheat than in its sole stand. For lentil, Singh
et al. (2014) also reported that when intercropped with mus-
tard, lentil had a lower grain weight than in its respective sole
stand.

FERNANDEZ ET AL.13 of 17
For grain protein concentration, lentil intercropped with
mustard tended to have a higher protein content than its
monoculture, although this was significant only for lentil75
+mustard75 (Table 8). In contrast, the grain protein of pea
was higher in all its intercrops than in its monoculture. These
findings agree with Neumann et al. (2007) in Germany, who
reported that the grain N content of pea increased in inter-
crops with oat, but appear to disagree with Bedoussac et al.
(2015), who found that for a range of intercrops in France
and Denmark, there was no difference in the average legume
grain protein concentration between sole crops and intercrops.
Differing results among studies may be attributed to factors
such as grain yield in the intercrops versus monocultures and
environmental stresses, among others. For the non-legumes
in both the lentil–mustard and pea–oat combinations in our
study, there was no difference in grain protein among the
intercrop seeding ratios and their respective monocultures
(Table 8). In contrast to our results, other organic and nonor-
ganic studies have shown that intercropping with legumes
could increase the protein content of the cereal crops. For a
range of legume and cereal intercrops, Bedoussac et al. (2015)
reported that the grain protein concentration of intercropped
cereals under organic management was mostly greater than
in their respective sole crops, while similar results of higher
protein in the companion cereals were found in other organic
and nonorganic trials (Af Geijersstam & Mårtensson, 2006;
De Stefanis et al., 2017; Gooding et al., 2007; Lauk & Lauk,
2008; Szumigalski & Van Acker, 2005). Among other studies,
Bulson et al. (1997) revealed that the protein content of wheat
grain increased when the density of faba beans in the inter-
crops increased, while according to Neumann et al. (2007),
although the grain N content of oat increased when inter-
cropped with pea, it was not influenced by the density of the
pea whose N content increased in the intercrops.
In our study, a higher grain protein concentration of oat in
the intercrops (Table 8) was expected given the lower grain
yield per unit area in the latter compared to its monoculture
(Table 6). In a nonorganic study in Finland, grain yield was
generally negatively associated with grain protein concen-
tration in sole spring cereals, including oat (Peltonen-Sainio
et al., 2012), while in an organic trial in the same location
as the current study, Fernandez, Zentner, Schellenberg, Lee-
son et al. (2019) indicated no negative association between
the two parameters in spring wheat, which was attributed to N
mineralization throughout the growing season from a previous
legume green manure or legume grain crop. For intercrop-
ping, an increase in the grain N concentration of wheat grown
with legumes was associated with a yield reduction of wheat
(Gooding et al., 2007). De Stefanis et al. (2017) also reported
that the higher protein concentration of durum wheat in inter-
crops with faba bean than in its sole crops was also associated
with a lower grain yield, while Bedoussac and Justes (2010)
attributed a higher grain protein concentration of wheat in
intercrops than in its sole stands to fewer plants and grains
per unit area in the former. However, a negative correlation
between grain yield and grain N content was observed by Neu-
mann et al. (2007) only when oat was intercropped, leading
them to conclude that the increased N content with reduced
yields was induced by interspecific competition rather than
lower crop densities.
Available N from legumes in intercrops might contribute
to greater growth and/or protein concentration in the com-
panion non-legumes. Although in our study, the higher grain
weight of oat when intercropped might have been partly the
result of an N transfer effect from the companion pea, the
lack of a positive effect on the protein concentration of the
non-legumes (Table 8) might be attributed, at least partly, to
the poor legume growth (Table 6) due to unfavorable growing
conditions during our study (Table 2). It has been reported that
symbiotically fixed N could be transferred from a legume to a
companion non-legume, especially when soil mineral N is low
(Bedoussac et al., 2018), while Xiao et al. (2004) also reported
that the amount of N exchanged between faba bean and wheat
was higher when soil mineral N was low and roots were inter-
mingled, which is what would have occurred in the mixed
rows in the current study. Intermingling of roots in crop mix-
tures is deemed important for optimizing resource utilization
(Thorsted et al., 2006). However, an N transfer has also been
reported to be either limited or non-existent in nonorganic
pea–oat intercrops elsewhere (Af Geijersstam & Mårtensson,
2006), and in other intercrops with legumes (Cowell et al.,
1989; Jensen, 1996).
Although crop growth in our trials was noticeably affected
by the dry weather (Tables 2and 6), several advantages of
intercropping were still identified. In addition, there are other
potential benefits of pea–oat intercrops. Even though in this
study there was no lodging of the pea plants in the monocul-
tures, our observation that pea climbed on the oat plants in
their intercrops agrees with Bedoussac et al.’s (2015) obser-
vations that intercropping cereals with legumes provided a
physical support that reduced lodging of the latter. Thus, due
to their climbing growth habit, legumes such as pea could ben-
efit by intercropping with oat, while the latter could not only
provide legumes with physical support but could also facil-
itate mechanical harvesting (Caballero et al., 1995;Cowell
et al., 1989; Kontturi et al., 2011). All this would be expected
to contribute to a greater stability of pea–oat intercrops than
of the sole pea (Kontturi et al., 2011).
Last, in regards to seeding densities in the intercrops, our
results showed that for most of the parameters measured, there
were more differences among seeding ratios in each inter-
crop combination for the legumes than for the non-legumes
(Tables 4–8). This would be attributed to the greater impact
of intercropping on the legumes, which also resulted in most
of the differences in the latter crops being between their
monocultures and their respective intercrop ratios rather than

14 of 17 FERNANDEZ ET AL.
among the latter. Although the intercrops with the highest
ratios of legumes and lowest ratios of non-legumes had the
greatest growth of the former, this was not always signifi-
cant. Based on the agronomic data collected in this study, it
appears that the best ratios of the lentil–mustard and pea–
oat intercrops in this soil and environment are those with
the highest ratios of legumes and lowest ratios of the non-
legumes. However, due to the unfavorable conditions in this
semiarid environment in 2017–2018 (Table 2), which resulted
in moisture being the most limiting factor for crop growth, it
was not possible to reach more definite conclusions regarding
intercrop seeding ratios.
4CONCLUSIONS
To the best of our knowledge, there is not much information on
organic grain intercropping in semiarid regions. The field tri-
als in this study provided new knowledge on the performance
under organic management of legumes and non-legumes com-
monly grown in the semiarid region of the Canadian Prairies
when intercropped under drier-than-average environmental
conditions for this region.
Agreeing with other studies, legumes were the most
negatively affected by intercropping and the dry condi-
tions under which this study was conducted. Based on
their seeding ratios, growth reductions in the legumes were
higher than expected, while in most cases the produc-
tivity of the non-legumes increased, although these crops
did not react to inter- and intra-crop competition in the
same manner. Our results also suggest that it would be
rather difficult to propose a generic approach with intercrop
combinations and ratios of the component crops. Identifica-
tion of a most successful intercropping system is expected
to depend not only on the interaction between the com-
ponent species, crop management, production objectives,
and prevalent environmental conditions but also on the
expected increased fluctuation of the latter due to climate
change.
Even under unfavorable dry environments, the current
study showed that a role for the non-legume crops to reduce
weed pressure and, in the case of oat, to provide mechanical
support, was realized. It is not known if similar results would
be obtained under more favorable conditions for crop growth
in this region. Thus, similar intercropping studies over a range
of soil and growing conditions, especially under more favor-
able weather for crop growth, would continue to be needed in
order to identify the best composition(s) for a given region and
objective, in view of the expected environmental variability.
More long-term studies would also help determine if peren-
nial weed populations, which might likely develop in these
sites over time, can be managed effectively using such a crop-
ping system under organic methods. Furthermore, the effects
of these intercrops of legumes with non-legumes on soil N
and growth of the following sole crop need to be considered
(Fernandez et al., 2025).
AUTHOR CONTRIBUTIONS
Myriam R. Fernandez: Conceptualization; formal analy-
sis; funding acquisition; investigation; methodology; project
administration; resources; supervision; validation; writing—
original draft; writing—review and editing. Prabhath Loku-
ruge: Data curation; formal analysis; investigation; method-
ology; software; supervision; validation; writing—review
and editing. Lobna Abdellatif: Investigation; methodol-
ogy; supervision; validation. Noe Waelchli: Data curation;
methodology; resources. Julia Y. Leeson: Data curation;
investigation; methodology; resources; supervision; valida-
tion; writing—original draft; writing—review and editing.
Michael P. Schellenberg: Writing—review and editing.
Scott Chalmers: Writing—review and editing.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interest.
ACKNOWLEDGMENTS
We gratefully acknowledge funding by the Western Grains
Research Foundation, Saskatchewan Wheat Development
Commission, and Saskatchewan Pulse Growers, and in-kind
contributions by Grain Millers, and the Advisory Committee
on Organic Research for the Organic Research Program at the
Swift Current Research and Development Centre. We thank
Greg Ford, Kati Braaten, Ray Leshures and his field crew, and
summer students for technical assistance.
Open Access funding provided by the Gouvernement du
Canada Agriculture et Agroalimentaire Canada library.
ORCID
Myriam R. Fernandez https://orcid.org/0000-0002-2420-
0571
Julia Y. Leeson https://orcid.org/0000-0002-0074-8700
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How to cite this article: Fernandez, M. R.,
Lokuruge, P., Abdellatif, L., Waelchli, N., Leeson, J.
Y., Schellenberg, M. P., & Chalmers, S. (2025).
Intercropping of oat or mustard with legumes under
organic management in the semiarid Canadian Prairie.
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