Crop Science 40:159-164 (2000)
© 2000 Crop Science Society of America
CROP ECOLOGY, PRODUCTION, & MANAGEMENT
Competitive Ability in Mixtures of Small Grain Cereals
P.E. Juskiwa,
J.H. Helma and
D.F. Salmona
a Field Crop Development Centre, Alberta Agriculture, Food and Rural Development, 5030 50 Street, Lacombe, AB, T4L 1W8, Canada
patricia.juskiw{at}agric.gov.ab.ca
 |
ABSTRACT
|
|---|
Morphological and physiological differences in competitive ability among species and genotypes can affect the growth, development, and subsequent composition and value of feedstuffs produced from small grain cereal mixtures. Our objective was determine the final grain yields of the components of mixtures and compare these yields with those expected based on the yields of the monocrops. Three field studies were conducted to evaluate the productivity of barley (Hordeum vulgare L.), oat (Avena sativa L.), triticale (x Triticosecale rimpaui Wittm.), and rye (Secale cereale L.) grown as monocrops and mixtures. Seeding rates ranging from 250 seeds m-2 to 750 seeds m-2 were evaluated to determine their effect on competitive ability of genotypes and species of small grains. Differences in competitive ability were found. The semi-dwarf barley `Kasota' was less competitive than the standard-height `AC Lacombe' and `Seebe'. `Noble' barley was more competitive than `AC Mustang' oat or `Wapiti' triticale. `Prima' winter rye was more competitive than `Pika' winter triticale. Relative grain yields were generally not different than 1.0 g g-1, but when significantly different they were usually higher than one, indicating that the yields of those mixtures were better than expected based on yields when the cultivars were grown as pure stands. Seeding rates had little effect on competitive ability. The specific factors that lead to better than expected grain yields of mixtures and to good competitive ability of cultivars and species are difficult to predict and must be evaluated on a case-by-case basis.
Abbreviations: M, cultivar yield as a monocrop • O, cultivar yield in mixture • RY, relative yield
|
INTRODUCTION
|
|---|
MIXTURES may be composed of different species (interspecific) or of different genotypes of the same species (intraspecific). Interspecific mixtures are used throughout the world for grain and forage production, often because of an assumed advantage over monocrops. In Ontario, Fejer et al. (1982) reported that although grain yield of barley–oat mixtures did not exceed the higher-yielding monocrop, 50% of the barley and oat production occurred as mixtures. Intraspecific mixtures may be composed of cultivars of the same species, multilines, or bulk hybrids. Intraspecific mixtures have been proposed as a means to use newly developed lines to increase crop heterogeneity and thereby give the crop a greater capacity to adjust to the many and varied stresses that can occur, and ultimately lead to better yield stability and potentially higher yields than pure-line monocrops (Jokinen, 1991a). However, in most cases reported in the literature, the yields of intraspecific mixtures are about the same as or only slightly higher than the weighted mean yield of the components (Jokinen, 1991a).
Competition between the components of mixtures has been found to change their relative composition in barley mixtures (Blijenberg and Sneep, 1975; Wolfe, 1990; Jedel et al., 1998), wheat (Triticum aestivum L.) mixtures (Khalifa and Qualset, 1974; Tapaswi et al., 1991), and barley–oat mixtures (Taylor, 1978; Fejer et al., 1982). Change in the composition of mixtures means that for specific uses they may need to be reconstituted on a regular basis. The change is attributed to differences in competitive ability between genotypes.
Blijenberg and Sneep (1975) found that competitive ability of seven of eight cultivars of barley was related to their yielding ability in monocultures. For triticale mixtures, Mergoum et al. (1998) found that the component with the best "mixing ability" or contribution to grain yield of the mixture was the highest-yielding triticale advanced line in their test. However, Jokinen (1991a, 1991b) and Jedel et al. (1998) found that competitive ability in barley was not related to yield potential of the monocrops. Valentine (1982) found that a barley genotype with erect growth habit had the competitive edge over a prostrate, short genotype. Jedel et al. (1998) found that for barley, the tallest cultivar in mixtures was dominant in four of six location–years. However, height alone did not explain competitive ability, as the semi-dwarf cultivar was also highly competitive. Competitive ability was also not related to tillering or row-type, as the two-rowed cultivar was the best competitor in some environments. For wheat, Khalifa and Qualset (1994) had found that the yields of short-statured components of mixtures were less than expected and attributed the loss of the short-statured component from their mixtures in 4 yr to its lower competitive ability. These authors speculated that the tall lines intercepted more light than the shorter lines, leading to better yields for the tall component and poorer yields for the short component.
Syme and Bremner (1968) found that when grown in the field as a mixture, barley yielded 17% higher and oat 6% lower than when each were grown in monoculture. The oat had greater dry matter production and was taller, but the barley had more grain yield. Barley had greater early growth as measured by dry matter production than the oat. Seeding densities of 172 and 344 plants m-2 did not affect the yielding ability of the mixture nor the competitive ability of the cultivars within the mixtures. Taylor (1978) also found in barley–oat mixtures that barley was a stronger competitor than oat and attributed its competitive ability to more leaf area, dry matter, and tillers. By final harvest, the oat was taller than the barley. Both species produced more grain in mixtures than in pure stands. Fejer et al. (1982) found that in one of two years of study of 1:1 barley–oat mixtures, the barley was highly competitive, resulting in 72% of the final grain yield, while in the other year of study it contributed only 56% to final grain yield.
The purpose of our study was to document postheading biomass distribution for several cereals and the effects of mixtures and seeding rate on that yield distribution. We wished to determine the competitive ability of different genotypes and species when grown in mixtures. In companion papers, we reported on the patterns of increases and decreases in biomass of morphological structures and how changes in biomass distribution could be related to the value of feedstuffs (Juskiw et al., 2000a) and the biomass yields and quality potential for silage of these tests (Juskiw et al., 2000b).
|
Materials and methods
|
|---|
Test Treatments and Design
This study consisted of three tests: Test 1, spring barley cultivar mixtures; Test 2, spring cereal mixtures of barley, oat, and triticale; and Test 3, winter cereal mixtures of winter rye and winter triticale. Seeding rates used for Tests 1 and 2 were 250 (standard), 375 (1.5 x), and 500 (2 x) seed m-2. Seeding rates used for Test 3 were 250 (standard), 500 (2 x) and 750 (3 x) seeds m-2. Germination tests were conducted on all seed lots prior to seed setup, and seeding rates were adjusted so rates were based on a live-seed basis. Within Tests 1 and 2, three subtests were run based on the principal cultivar or species of the test, while within Test 3, two subtests were run. The subtests were run to facilitate harvesting of the crop when the principal cultivar or species was at the heading, milk, or soft-dough stages, (the major objective of these tests was to assess biomass production and distribution reported in Juskiw et al. [2000a, 2000b]). For this study, all samples were removed after physiological maturity.
For Test 1, the three subtests were based on Kasota, an early, semi-dwarf, six-rowed spring barley; AC Lacombe, a mid-maturing, six-rowed spring barley; and Seebe, a late, two-rowed spring barley. Within each subtest of Test 1, the treatments were each cultivar as a monocrop and the mixtures of the principal component with the two other cultivars in the ratios 1:1, 3:1, 1:1:1, and 3:1:1, for a total of nine treatments.
For Test 2, the three subtests were based on Noble, a mid-maturing, six-rowed spring barley; AC Mustang, a late, spring oat; and Wapiti, a late, spring triticale. Within each subtest of Test 2, the treatments were each species as a monocrop and mixtures of the principal component with the two other species in the ratios 1:1 and 3:1, for a total of seven treatments.
For Test 3, the two subtests were based on Prima, a winter rye, and Pika, a winter triticale. Within each subtest of Test 3, the treatments were each species as a monocrop and 1:1 mixture for a total of three treatments in 1994-1995 and mixtures of the principal component with the other species in the ratios 1:1, 2:1, and 3:1, for a total of five treatments in 1995-1996.
The experimental design for each subtest was a split-plot design with three replicates for Tests 1 and 2, and four replicates for Test 3. Main plots were the rate of seeding and subplot treatments were the mixture and monocrop treatments. Seeding rate and cultivar and mixture treatments were treated as fixed effects. Errors appropriate to this model were used to test effects (Steel and Torrie, 1980). Each subtest was analyzed across years using the GLM procedure (SAS Institute, 1988).
Field Techniques and Trait Measurements
Plots were established from 1994 to 1996 at Lacombe, AB, on a Penfold loam [orthic Black Chernozem (coarse loamy, frigid Typic Haplustoll)] and for Test 3 only, in 1994 and 1995 at Botha, AB, on a Daysland loam [60% orthic Black Solod (coarse loamy, Typic Argiustoll with a natric horizon) and 40% thin orthic Black Chernozem (coarse loamy, frigid Typic Haplustoll)]. Due to hail in June 1996 at Botha, data were not collected from that location–year. For more detailed information on field techniques, refer to our companion paper (Juskiw et al., 2000b).
Spring cereal tests were sampled in 1994 and 1995 only. Winter cereal tests were sampled in 1995 and 1996 only. Plots were sampled by pulling one 0.5-m row (0.07 m-1) by hand. Plots were sorted into their component cultivars and species. Subsamples were threshed for grain yield determinations. Relative yield ratios (RY) of the components were determined as described by Jokinen (1991b). They were based on yield of the cultivar or species in the mixture (O) relative to the yield of the cultivar or species as a monocrop (M), or O/M. Relative yield totals were obtained by adding together the RY ratios for all the cultivars or species in a mixture. Due to sampling problems in 1995 at Lacombe, RYs and RY totals were not determined for the rye-based treatments. Because RY totals were calculated on a plot basis and then means were taken, there is some discrepancy between the RYs and totals due to missing observations from some plots and to rounding errors.
|
Results
|
|---|
Test 1—Spring Barley Mixtures
At maturity, samples were collected, sorted, and threshed to determine relative grain yields. In a 1:1 mixture, if the yields in the mixture of the components were the same as in the monocrop, each would be 0.50; in a 3:1 mixture, the relative yields would be 0.75 and 0.25; in a 1:1:1 mixture, the relative yields would each be 0.33; and in a 3:1:1 mixture, they would be 0.60, 0.20, and 0.20, respectively. Where relative grain yields differ from these, the component in the mixture was doing better or worse than it did in a monocrop. By looking at the relative yields of component cultivars in mixtures, competitive ability could be determined.
The treatment x cultivar interaction was significant for all three barley subtests (Table 1)
. Thirteen out of eighteen barley mixtures had relative grain yield totals that were not significantly different than 1.0, and five mixtures were significantly higher than expected based on the monocrop yields (Table 2)
. Kasota tended to yield more poorly in mixtures than expected (significantly so in three of 14 mixtures), while AC Lacombe and Seebe did better (significantly so in four of 14 mixtures for AC Lacombe and six of 14 for Seebe). In some cases, these two cultivars did so much better, the total relative yield was much greater than 1.00, indicating that these mixtures may have been better than growing the cultivars as monocrops. However there was a lot of variability for this trait, as the 1:1 Kasota–Seebe mixture had a total relative yield of only 0.98 in the Kasota-based test, while in the Seebe-based test the total was 1.08. AC Lacombe was not as competitive as Seebe. Seebe tended to have lower grain yields than either Kasota or AC Lacombe in all three subtests (Table 2).
View this table:
[in this window]
[in a new window]
|
Table 1 Mean squares from the analysis of variance for relative yields (RY) and RY totals for barley mixtures grown at Lacombe, AB in 1994 and 1995
|
|
View this table:
[in this window]
[in a new window]
|
Table 2 Monocrop yields and relative grain yields (RY) of mixture components, by cultivar, of barley grown at Lacombe, AB in 1994 and 1995
|
|
Seeding rate was without significant effect on relative yields for the Kasota- and AC Lacombe-based tests (Table 1). For the Seebe-based tests, Kasota in mixtures had higher relative yields at the higher seeding rates (Table 3)
. Seebe in mixtures had its highest relative yield at the rate of 375 seeds m-2, while AC Lacombe in mixtures had its lowest relative yield at this seeding rate.
View this table:
[in this window]
[in a new window]
|
Table 3 Effects of seeding rate on relative grain yields (RY) of barley cultivars grown as mixtures in the Seebe barley-based test averaged across treatments. (Where the expected relative yields average across mixtures treatments for Kasota and AC Lacombe were 0.32 and that for Seebe was 0.57.)
|
|
Test 2—Spring Cereal Mixtures (Barley, Oat, and Triticale)
As for the barley tests, the treatment x cultivar interaction was significant for all three spring subtests (Table 4)
. For these spring cereal mixtures, the relative yield totals of nine mixtures were not significantly different than 1.0, indicating that yields were as expected based on the yields of the monocrops, while three mixtures had relative yield totals significantly higher than expected (Table 5)
. Yields of the Noble component in mixtures with oat and triticale were higher than expected (significantly so in five of eight mixtures), indicating that Noble was a good competitor and benefitted from growing in mixtures with either of these two species. In the oat–triticale mixtures, AC Mustang was more competitive than Wapiti, but significantly so in only one of four mixtures. Despite the 1:1 Noble–Wapiti mixture having the best total relative grain yield of all treatments in the Wapiti triticale-based Test at 1.30, in the Noble barley-based tests this treatment had a total relative yield of only 0.98 (Table 5). The 1:1 AC Mustang–Wapiti mixture had total relative yields of 1.08 and 1.17, indicating a more consistent or stable type of yield advantage. Wapiti had significantly higher grain yields than Noble (Table 5).
View this table:
[in this window]
[in a new window]
|
Table 4 Mean squares from the analysis of variance for relative yields (RY) and RY totals for barley oat, and triticale mixtures grown at Lacombe, AB in 1994 and 1995
|
|
View this table:
[in this window]
[in a new window]
|
Table 5 Monocrop yields and relative grain yields (RY) of mixture components, by species, of barley, oat, and triticale grown at Lacombe, AB in 1994 and 1995
|
|
Seeding rate was without significant effect on relative yields for these three spring cereal subtests (Table 4).
Test 3—Winter Cereal Mixtures (Rye and Triticale)
For the Prima rye-based test, the cultivar effect and rate x cultivar interaction were signifcant, while for the Pika triticale-based test the cultivar effect and the treatment x cultivar interaction were significant (Table 6)
. Of the nine location–years where relative yield totals could be calculated for these winter mixtures, none were significantly different than one (Table 7) . Prima was much more competitive than Pika in these studies, having RYs significantly higher than expected in eight of nine mixtures (Table 7). There was little difference in grain yield of the monocrops of Pika and Prima in any location–year (Table 7).
View this table:
[in this window]
[in a new window]
|
Table 6 Mean squares from the analysis of variance for relative yields (RY) and RY totals for winter rye and triticale mixtures grown at Botha in 1995 and Lacombe, AB in 1995 (triticale data only) and 1996
|
|
View this table:
[in this window]
[in a new window]
|
Table 7 Monocrop yields and relative grain yields (RY) of mixture components, by species, of winter cereal mixtures grown on Botha in 1994-1995 (B95) and Lacombe in 1994-1995 (L95) and 1995-1996 (L96). (Due to missing plots, relative yields were not calculated for the Prima winter rye based test in L95)
|
|
When in mixtures, the RYs of Pika were significantly lower than expected at all seeding rates but were highest at the highest seeding rate (Table 8)
. For Prima, RYs were significantly higher than expected at all seeding rates (Table 8).
View this table:
[in this window]
[in a new window]
|
Table 8 Effect of seeding rate on relative grain yields of rye and triticale grown as mixtures in the Prima rye-based test. (Where expected relative yield averaged over mixture treatments for Pika was 0.43 and for Prima was 0.57.)
|
|
|
Discussion
|
|---|
Relative yields and yield totals were calculated to determine the competitive ability of cultivars in mixtures and the overall yield ability of the mixtures. Because a producer may not take all of a crop for forage, but may decide to leave some for seed as a source for replanting in a subsequent year, it is important to understand what may be happening in a mixture. Generally, the mixtures were as productive as the monocrops with relative yield totals not significantly different than unity. There was a lot of variability in their total relative yields, which may have been due to the small sampling size.
Differences between cultivars in competitive ability were found. Kasota was less competitive than Seebe or AC Lacombe; this may have been due to its semi-dwarf stature and/or its earliness. AC Lacombe was less competitive than Seebe, perhaps due to its earlier maturity. Seebe and Noble, although having lower grain yields as monocrops than the other components of the barley and spring cereal mixtures, respectively, were highly competitive. Noble was more competitive than Wapiti triticale or AC Mustang oat, despite its earlier maturity. Better competitive ability of barley than oat agrees with the findings of Syme and Bremner (1969) and Taylor (1978). Prima rye was more competitive than Pika triticale, and this may have been due to better winterhardiness and earlier reinitiation of spring growth. Jedel and Salmon (1995) reported that rye reinitiated spring regrowth 
2 wk earlier than triticale. Cousens (1996) found for barley, wheat, and ryegrass (Lolium rigidum Gaud.) mixtures that rate of loss of a component from the mixture was not related to relative phenological development or height but was related to rate of early leaf production. The competitive ability of rye may also be related to its alleopathic properties (Rice, 1984).
Competitive ability did not always relate to high monocrop yield potential. Also, it did not always relate to final plant height, as Noble was shorter at maturity than either Wapiti triticale or AC Mustang oat. It did not always relate to biomass production as reported in the companion studies (Juskiw et al., 2000a, 2000b), where it was observed that both Seebe and Wapiti had high total biomass production, but while Seebe was highly competitive, Wapiti was not. Competitiveness may be related to early-season growth as found by Taylor (1978). Juskiw et al. (2000b) reported that Seebe and Wapiti had high biomass yields on a per plant basis by anthesis. Therefore, the prediction of cultivar competitive ability in mixtures cannot be based on any formula of traits. Inclusion of a highly competitive cultivar or species in a mixture may not lead to any overall yield advantage. Selection of cultivars for inclusion in a mixture may be based on specific traits such as disease resistance, straw-strength, or drought tolerance (Jedel et al., 1998).
The intraspecific mixture of barley cultivars used in this study had a neutral or positive yield response, as did the interspecific mixtures of triticale with barley and oat. The interspecific cultivar mixture of Noble barley and AC Mustang oat did not show any grain yield advantage, although the barley–oat mixture harvested early for biomass did have a yield advantage (Juskiw et al., 2000b). The advantage of intra- and interspecific mixtures is difficult to predict and can only be evaluated on a case-by-case basis over locations and years.Blijenburg Sneep 1975
|
ACKNOWLEDGMENTS
|
|---|
The technical assistance of Donna Westling, Dave Dyson, Susan Lajeunese, Deanna Runge, and Tom Zatorski is gratefully acknowledged. A portion of this research was funded by Alberta Agricultural Research Institute.
Received for publication December 22, 1998.
|
REFERENCES
|
|---|
- Blijenburg J.G., Sneep J. Natural selection in a mixture of eight barley varieties, grown in six successive years. 1. Competition between the varieties. Euphytica 1975;24:305-315.
- Cousens R.D. Comparative growth of wheat, barley and annual ryegrass (Lolium rigidum) in monoculture and mixture. Aust. J. Agric. Res. 1996;47:449-464.
- Fejer S.O., Fedak G., Clark R.V. Experiments with a barley–oat mixture and its components. Can. J. Plant Sci. 1982;62:497-500.
- Jedel P.E., Helm J.H., Burnett P.A. Yield, quality and stress tolerance of barley mixtures in central Alberta. Can. J. Plant Sci. 1998;78:429-436.
- Jedel P.E., Salmon D.F. Forage potential of spring and winter cereal mixtures in a short-season growing area. Agron. J. 1995;87:731-736.[Abstract/Free Full Text]
- Jokinen K. Competition and yield advantage in barley–barley and barley–oats mixtures. J. Agric. Sci. Finl. 1991;63:255-285 a.
- Jokinen K. Yield and competition in barley variety mixtures. J. Agric. Sci. Finl. 1991;63:287-305 b.
- Juskiw P.E., Helm J.H., Salmon D.F. Forage yield and quality for monocrops and mixtures of small grain cereals. Crop Sci. 2000;40:138-147 a (this issue).[Abstract/Free Full Text]
- Juskiw P.E., Helm J.H., Salmon D.F. Postheading biomass distribution for monocrops and mixtures of small grain cereals. Crop Sci. 2000;40:148-158 b (this issue).[Abstract/Free Full Text]
- Khalifa M.A., Qualset C.O. Intergenotypic competition between tall and dwarf wheats. I. In mechanical mixtures. Crop Sci. 1974;14:795-799.[Abstract/Free Full Text]
- Mergoum, M., W.H. Pfeiffer, and J.L. Crossa. 1998. Triticale mixtures: A way to improve and/or stabilize yield under adverse environments. p. 245–251. In P.E. Juskiw (ed.) Proc. of the 4th International Triticale Symposium. Vol. 1. Oral presentations. Red Deer, AB, Canada. 26–31 July 1998. International Triticale Assoc., Sidney, Australia.
- Rice E.L. Allelopathy, 2nd ed Orlando, FL: Academic Press, 1984.
- SAS Institute. SAS user's guide: Statistics. Version 6.03 ed. Cary, NC: SAS Inst, 1988.
- Steel R.G.D., Torrie J.H. Principles and procedures of statistics, 2nd ed New York: McGraw-Hill, 1980.
- Syme J.R., Bremner P.M. Growth and yield of pure and mixed crops of oats and barley. J. Appl. Ecol. 1968;5:659-674.
- Tapaswi P.K., Mitra N., Banerjee R.N., Bagchi D.K. Intraspecific interaction in two varieties of wheat. Indian Agric. 1991;35:135-142.
- Taylor B.R. Studies on a barley–oats mixture. J. Agric. Sci. (Cambridge) 1978;91:587-591.
- Valentine J. Variation in monoculture and in mixture for grain yield and other characters in spring barley. Ann. Appl. Biol. 1982;101:127-141.
- Wolfe M.S. Intra-crop diversification: Disease, yield and quality. BCPC Monogr. 1990;45:105-114.
This article has been cited by other articles:
|
|
|
|
 
S. M. Ross, J. R. King, J. T. O'Donovan, and D. Spaner
Intercropping Berseem Clover with Barley and Oat Cultivars for Forage
Agron. J.,
November 1, 2004;
96(6):
1719 - 1729.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. M. Ross, J. R. King, J. T. O'Donovan, and D. Spaner
Forage Potential of Intercropping Berseem Clover with Barley, Oat, or Triticale
Agron. J.,
July 1, 2004;
96(4):
1013 - 1020.
[Abstract]
[Full Text]
[PDF]
|
|
|
TOP
ABSTRACT
INTRODUCTION
