Kura Clover Forage Yield Contribution Increases Over Time When Seeded in Mixture with Grasses in southwestern Québec

Kura Clover Forage Yield Contribution Increases Over Time When Seeded in Mixture with Grasses in Southwestern Québec

Philippe Seguin, Department of Plant Science, McGill University, Macdonald Campus, 21111 Lakeshore Road, Sainte-Anne-de-Bellevue, QC H9X 3V9, Canada

Abstract

An experiment was established to study Kura clover (KC, Trifolium ambiguum M.Bieb.) contribution to total forage yield in post-seeding years when mixed with different grass species and determine if it could be used to establish desirable legume:grass swards in extensively managed permanent pastures of southwestern Québec. Plots were established in 2001 in Sainte-Anne-de-Bellevue, Québec, Canada; treatments included solo-seeded KC, Kentucky bluegrass (KBG, Poa pratensis L.), smooth bromegrass (SB, Bromus inermis Leyss.), and timothy (TIM, Phleum pratense L.), and mixtures of KC with each grass species. Total forage yield and clover, grass, and weed yield contributions were determined from 2003 to 2006. Kura clover established slowly, its contribution to yield increasing over time, from 15% in the spring of 2003 when mixed with TIM or SB, to 72% in the spring of 2006. Such proportions could cause bloat in grazing animals. Kentucky bluegrass performed poorly when mixed with KC, its contribution to yield was always less than 20%. Grass yield and contribution to total forage yield decreased gradually from 2003 to 2006, grasses being replaced by weeds in solo-seeded grass plots and by KC in KC-grass mixtures. The presence of KC precipitated the decline of KBG and TIM, but not that of SB. Kura clover is a species that could contribute to extensively managed permanent pastures of southwestern Québec; however, KC-grass mixtures or management strategies that will maintain higher proportions of grass in the long-term must now be identified.

Introduction

There are 193,000 hectares of pastures in Québec (8). These fields are often characterized by a poor productivity and are usually dominated by low-producing grass species. Although legumes may be initially seeded, their contribution to yield is often minimal a few years after seeding, usually due to the combination of lack of persistence in pastures of species used and to poor management. For example, 68% of pastures do not receive mineral fertilizers, 71% do not receive manure from external sources, and management intensive grazing is used only by a fraction of producers (8). There is a need for persistent forage legumes, which would be adapted to the extensive management often practiced locally in permanent pastures.

Kura clover (KC) is a highly persistent rhizomatous forage legume whose potential has been demonstrated in several regions of North America (7). It produces a large network of roots and rhizomes that enable it to persist under frequent defoliation and climatic extremes (7,12). Exceptional persistence and high forage quality are characteristics making KC a good candidate for use in extensively managed permanent pastures (7). When introduced in pastures, compared to other legume species, KC can result in greater animal production by increasing forage yield and quality, and by improving seasonal yield distribution (10,15,16). Kura clover has the potential to cause bloat when contributing in large proportions to total forage yield (10,15). Kura clover has been reported to successfully establish with different grasses species, either when direct-seeded in mixtures or used to renovate grass-dominated pastures (1,5,6,16). Despite its great potential, KC use remains marginal mainly due to a characteristic slow development (3,5,6,13,14). Kura clover’s contribution to yield is initially minimal; it however gradually increases in post-seeding years (1,2,5,6). If KC’s development pattern is well known, there is however limited information on how KC yield contribution over time may differ when seeded with various grass species. Such information would be helpful in selecting appropriate KC-grass mixtures.

The specific objective of this project was thus to study KC’s contribution to total forage yield in post-seeding years when mixed with different grass species and determine if it could be used to establish desirable legume:grass swards in extensively managed permanent pastures of southwestern Québec. Kura clover was evaluated alone and in mixtures with grass species frequently found in permanent pastures in the region, namely Kentucky bluegrass (KBG), smooth bromegrass (SB), and timothy (TIM). Kura clover performance was determined by monitoring forage yield and species contribution to yield from the second to the fifth post-seeding year.

Field Management and Treatments Description

The experiment was established in 2001 in Sainte-Anne-de-Bellevue, Québec, Canada, (45°25'N, 73°56'W) on a Macdonald clay loam soil with pH, P, and K levels of 7.1, 393 kg/ha, and 526 kg/ha, respectively. Treatments included seven forage species combinations including solo-seeded KC (cv. ‘Endura’), KBG (common), SB (cv. ‘Radisson’), and TIM (cv. ‘Champ’) and KC combinations with each of the three grass species (i.e., KC+KBG, KC+SBG, and KC+TIM). Seeding was done on 7 June 2001 in 1.35- by 5-m plots using a disc-drill (Fabro, Swift Current, SK, Canada) in a prepared seedbed. Seeding rates were 12, 14, 13, and 10 kg PLS (pure live seeds)/ha in solo-seeded plots for KC, KBG, SBG, and TIM, respectively, and 10, 12, 10, and 7 kg PLS/ha in mixtures. Seeds of KC were inoculated using an appropriate rhizobial peat-based inoculant (Urbana-Labs, St-Joseph, MI). Plots were mowed twice in the seeding and first post-seeding years to control weeds. No herbicides or fertilizers were used during the course of the experiment; this was done to mimic conditions and management typically found in permanent pastures locally. Limited inputs and extensive management indeed often characterize permanent pastures in the region (8). Temperature and precipitation data for each experiment were retrieved from a nearby weather-recording station (Table 1).

Table 1. Monthly precipitations (mm) and average air temperature (°C) during experimentation and the 30-year average (1971-2000).

Month	2001	2002	2003	2004	2005	2006	Avg.
Month	Monthly precipitation (mm)						Avg.
January	—	34	23	34	64	148	70
February	—	41	62	40	44	65	60
March	—	84	88	59	44	29	72
April	14	73	77	69	159	114	76
May	71	97	111	82	43	173	76
June	59	68	72	64	129	—	84
July	37	31	55	139	126	—	90
August	57	9	80	94	134	—	94
September	78	64	104	72	113	—	91
October	79	70	156	36	198	—	78
November	84	106	134	87	96	—	93
December	54	34	164	128	83	—	82
Month	Average air temperature (°C)						Avg.
January	—	-4	-13	-15	-11	-5	-10
February	—	-5	-11	-8	-7	-7	-9
March	—	-2	-4	0	-3	-1	-2
April	7	7	4	6	8	8	6
May	15	11	13	13	12	15	13
June	19	17	19	18	22	—	18
July	19	21	22	22	22	—	21
August	21	21	22	19	22	—	20
September	16	17	18	16	17	—	14
October	10	7	8	9	10	—	8
November	5	1	3	2	3	—	2
December	0	-5	-5	-7	-6	—	-6

Harvest and Data Collection

Plots were harvested according to forage accumulation, dictated largely by precipitation patterns (Table 1). Number of harvests differed in each year with two harvests in 2003 (2 June and 14 July), three in 2004 (27 May, 23 July, and 19 August), and four in 2005 (4 June, 7 July, 4 August, and 6 September). A final harvest was also taken on 8 June 2006. The contribution of seeded clovers, seeded grasses and weeds were determined visually as a percentage of the total biomass at each harvest. Determinations were done by the same trained technician using benchmark visual references as suggested by Parsons et al. (11). A 0.6- by 4.4-m area was cut in the center of plots at each harvest to a 5-cm stubble height using a flail forage harvester (Swift Machine & Welding, Swift Current, SK, Canada). Representative 500-g samples of harvested forage were obtained from each plot, dried in a forced-air oven at 60°C for 48 h, and weighted to determine DM content, and express yield on a DM basis.

Statistical Design and Analyses

Plots were arranged in a randomized complete block design with four replications. Data were subjected to analysis of variance (ANOVA) using PROC GLM of the SAS software to identify significant (P < 0.05) treatment effects. Due to the presence of multiple harvest period × treatment interactions, data were analyzed separately for each harvest period. Least significant difference (LSD) values (P < 0.05) were used for mean comparisons, when F-tests were significant at P < 0.05.

Climate Data

Temperatures in the six years of experimentation were usually above the 30-year average between April and October, precipitation for the same period however varied substantially among years (Table 1). The seeding and first post-seeding years (i.e., 2001 and 2002) were both characterized by much lower precipitation than the 30-year average (i.e., 195 and 169 mm less, respectively). Precipitation in the second and third post-seeding years (i.e., 2003 and 2004) were near the 30-year average, with a noticeable deviation between June and August 2003 (i.e., 61 mm less than the 30-year average for the same period). Finally, the fourth and fifth post-seeding years were characterized by much more precipitation than the 30-year average, precipitations being 193 mm greater between April and October in 2005 and 135 mm greater in April and May 2006 alone. These differences in precipitations impacted forage growth and thus the number of harvest that could be made in each year of experimentation (i.e., two in 2003, three in 2004, and four in 2005).

Total Forage Yield

Total forage yield was consistently greater with solo-seeded KC or KC-grass mixtures than solo-seeded grasses (Fig. 1). The only exception was at the first harvest in the second post-seeding year when yield was similar for all treatments except solo-seeded KBG, for which yield was lower. Averaged over 10 harvests, total forage yield of KC and KC-grass mixtures was 80% greater than solo-seeded grasses (i.e., 2627 vs 1463 kg/ha per harvest), differences increasing over time (i.e., yield were 49, 110, and 133% greater in 2003, 2004, and 2005, respectively). Such results illustrate the potential of KC for permanent pastures of southwestern Québec, confirming previous shorter-length studies (5,6). Differences between solo-seeded grass treatments were consistent. Total forage yield was lower with KBG than SB and TIM at the first harvest in every year, no differences being observed between species in subsequent harvests. Total forage yield observed for the KC-grass mixtures are in the range of yield reported in other studies for KC-grass mixtures (16).

Fig. 1. Total forage dry matter (DM) yield (2003 to 2006) of plots of Kura clover (KC), Kentucky bluegrass (KBG), smooth bromegrass (SBG), and timothy (TIM) seeded alone and in mixtures of KC with each of the three grass species. Seeding was done in Sainte-Anne-de-Bellevue, QC in the spring 2001. Vertical bars indicate LSD_0.05 values; NS indicating a lack of differences between treatments (P > 0.05).

Kura Clover

Overall, clover yield and contribution to total forage yield gradually increased each year in all treatments (Fig. 2). Between 2003 and 2005, total annual clover yield increased 1, 1.4, 6, and 12-fold in KC, KC-KBG, KC-TIM, and KC-SB plots, respectively. In the spring of 2006, five years after seeding, KC yield was 4106, 3842, 3265, and 2932 kg/ha in KC, KC-KBG, KC-TIM, and KC-SB plots, respectively. Such yield illustrates the excellent long-term vigour of KC; it has been reported in the Midwest to remain productive 10 to 15 years after seeding (7). Kura clover contribution to total forage yield increased from an average of 15% in 2003 to 72% in the spring of 2006 in mixtures with SB and TIM, and from 66 to 92% in the KC-KBG mixture (Figs. 3 and 4). Clover yield was generally lower when mixed with SB and TIM than when either solo-seeded or mixed with KBG, the difference however diminished over the years being of 460, 80, and 30% in 2003, 2004, and 2006, respectively (Fig. 2). In 2005, an unusually wet year, differences in clover yield between treatments in the last three of four harvests was not significant, clover yield was however 50% lower in the KC-SB mixture than other treatments at the first harvest.

Fig. 2. Clover dry matter (DM) yield (2003 to 2006) of plots of Kura clover (KC) seeded alone, and of mixtures of KC with Kentucky bluegrass (KBG), smooth bromegrass (SBG), and timothy (TIM). Seeding was done in Sainte-Anne-de-Bellevue, QC in the spring 2001. Vertical bars indicate LSD_0.05 values; NS indicating a lack of differences between treatments (P > 0.05).

Fig. 3. Clover contribution to total forage dry matter yield of plots of Kura clover (KC) and Kura clover-grass mixtures (KBG, Kentucky bluegrass; SBG, smooth bromegrass; TIM, timothy) established in Sainte-Anne-de-Bellevue, QC in 2001. Vertical bars represent the LSD_0.05 values for each cut. NS, Not significant (P > 0.05).

The high clover:grass ratios observed in the spring of the fifth post-seeding year for all KC-grass mixtures could potentially be problematic for grazing animals, KC having the potential to cause bloat (10,15). Such results are in accordance with previous studies, which also reported a gradual increase in KC contribution to total forage yield, and a propensity for KC to dominate swards several years after seeding (1,2,6,16). The present study suggests that KBG should not be seeded with KC in southwestern Québec, since it does not have the ability to sufficiently contribute to yield in proportions (i.e., at least 50%) that would limit bloat potential (4). Results also suggest that more grass species should be evaluated for their capacity to maintain a greater grass proportion in the long term when mixed with KC. Finally, the feasibility of using grasses to renovate KC-dominated swards 5 to 7 years after seeding KC should also be investigated.

Grasses

Overall, grass yield and contribution to total forage yield steadily decreased from 2003 to 2006 in all treatments (Fig. 5). Compared to solo-seeded grass plots, the presence of KC only reduced grass yield, in some mixtures, in four out of ten harvests. The presence of KC never resulted in a SB yield reduction when compared to solo-seeded plots, but in contrast increased yield at three harvests by an average of 494 kg/ha. In contrast, TIM yield was reduced by KC at three harvests. This reduction was substantial in the spring of 2006, when yield was reduced by 1300 kg/ha compared to solo-seeded TIM. At the other two harvests (harvest 2 and 3 in 2005), the reduction was proportionally larger but averaged only 420 kg/ha. Kentucky bluegrass yield was reduced by the presence of KC only at the first harvests in 2003 and 2006, but in each case the reduction was substantial averaging 1232 kg/ha or 81% of the solo-seeded KBG yield. Kentucky bluegrass yield was minimal throughout experimentation, yield averaging less than 500 kg/ha per harvest over 10 harvests. It is a species that is frequently found in extensively managed permanent pastures of southwestern Québec; however, it is not recommended for use locally due to its low productivity (9).

Fig. 4. Plots of Kura clover and Kura clover-grass mixtures in the spring of the fifth post-seeding year in Sainte-de-Bellevue, QC, Canada: (A) solo-seeded Kura clover; (B) Kura clover seeded with Kentucky bluegrass; (C) Kura clover seeded with smooth bromegrass; (D) Kura clover seeded with timothy.

Fig. 5. Grass dry matter (DM) yield (2003 to 2006) of plots of Kentucky bluegrass (KBG), smooth bromegrass (SBG), and timothy (TIM) seeded alone, and of mixtures of Kura clover (KC) with each of the three grass species. Seeding was done in Sainte-Anne-de-Bellevue, QC in the spring 2001. Vertical bars indicate LSD_0.05 values; NS indicating a lack of differences between treatments (P > 0.05).

When mixed with KC, KBG contribution to total forage yield was minimal in all years averaging 14% over 10 harvests (data not shown). In the case of SB and TIM it declined from 90 and 76% respectively in the spring of 2003, to 27% for both species in the spring of 2006. When solo-seeded, grass contribution to total forage yield declined from 78, 97, and 92% for KBG, SB, and TIM, respectively to 48, 45, and 66%, for the same period, illustrating the inevitable decline of grasses locally under extensive management.

Weeds

In most treatments weed biomass harvested was minimal and there were generally few differences between treatments (Fig. 6). Weed contribution to total forage yield remained below 10% for most harvests in solo-seeded KC or KC-grass mixtures (data not shown). Weed biomass was greatest in KBG and KC-KBG plots and lowest in SB and KC-SB plots at the first harvest in 2003. At the first harvest in 2004 weed biomass was greater in KBG than any other treatments. Finally, at the third harvest in 2005, and in the spring of 2006, weed biomass was greater in solo-seeded grass plots than KC or KC-grass plots. In 2006, weed biomass averaged 1700 and 110 kg/ha in solo-seeded grass plots, and KC and KC-grass mixtures, respectively. Weed biomass increased 4-fold between 2003 and 2005 in solo-seeded grass plots (i.e., from 376 to 1860 kg/ha per year), but was stable, averaging 340 kg/ha per year, in KC and KC-grass mixtures for the same period. Results suggest that the introduction of KC in extensively managed permanent pastures of southwestern Québec would be desirable, as it reduces weed encroachment and contribution to total forage yield, compared to grass-only pastures.

Fig. 6. Weed dry matter (DM) yield (2003 to 2006) of plots of Kura clover (KC), Kentucky bluegrass (KBG), smooth bromegrass (SBG), and timothy (TIM) seeded alone, and of mixtures of KC with each of the three grass species. Seeding was done in Sainte-Anne-de-Bellevue, QC in the spring 2001. Vertical bars indicate LSD_0.05 values; NS indicates a lack of differences between treatments (P > 0.05).

Summary, Implications, and Conclusions

Minimal differences in total forage yield were observed between KC-grass mixtures in the present study. Mixtures, however, differed in their clover and grass yield, and hence the resulting clover:grass ratio. Of the three species evaluated, SB and TIM maintained the best clover:grass ratio during the 6 years of experimentation. Smooth bromegrass had a slight advantage over TIM due to the fact that in face of gradually increasing clover yield, SB yield were never reduced by the presence of KC and were actually occasionally increased when compared to solo-seeded SB. Grass decline was inevitable under the extensive management used, but with SB it was not accelerated by the presence of KC; this was not the case for KBG and TIM. Kentucky bluegrass, a species not recommended locally, generally performed poorly. It should not be seeded with KC in southwestern Québec, since it does not have the ability to sufficiently contribute to yield in proportions (i.e., at least 50%) that would limit bloat potential. Although KC is presently not a species recommended in Québec (9), the present study confirms its adaptation and potential in southwestern Québec. The introduction locally of KC in extensively managed permanent pastures seems desirable, as it not only maintains but actually increases total forage yield over time, while reducing weed contribution to total forage yield in later years. As the defoliation of plots in present study was done mechanically, results should be confirmed by a grazing experiment. The feasibility of reintroducing grasses into KC dominated pastures 5 to 7 years after establishment, to ensure an optimal clover:grass ratio that would limit bloat potential, should also be investigated.

Acknowledgments

This research was partially supported by a research grant from the Natural Sciences and Engineering Research Council of Canada (NSERC). The author thanks James Straughton and Amélie Désîlets-Roy for help in the field.

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