Biomass production in multispecies and grass monoculture swards under cutting and rotational grazing

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Biomass production in multispecies and grass monoculture swards under cutting and rotational

grazing

R.P. Collins, Remy Delagarde, S. Hussey

To cite this version:

R.P. Collins, Remy Delagarde, S. Hussey. Biomass production in multispecies and grass monoculture

swards under cutting and rotational grazing. 25. General Meeting of the European Grassland Fed-

eration, Sep 2014, Aberyswyth, United Kingdom. Institute of Biological, Environmental and Rural

Sciences (IBERS), Grassland Science in Europe, 19, 2014, Grassland Science in Europe. �hal-01210819�

Biomass production in multispecies and grass monoculture swards under cutting and rotational grazing

Collins R.P. ¹ , Delagarde R. ² and Husse S. ³

1

/nstitute of Biological, Environmental and Rural Sciences, Aberystwyth University, UK

2

/nstitut National de la Recherche Agronomique, UMR1348 PEGASE, Saint-Gilles, France

3

Agroscope, /nstitute for Sustainability Sciences, CH-8046 Zürich, Switzerland Corresponding author: rpc@aber.ac.uk

Abstract

A Common Experiment (CE) was set up within the EU-FP7 project 'Multisward' across a subset of partner sites to analyse responses of multispecies swards (MSS) to grazing and cutting managements. Across sites and managements there was no detriment to yield in moderately fertilized legume-based MSS compared with perennial ryegrass monocultures receiving high inputs of externat nitrogen fertilizer. The response of sward types to grazing depended on sward composition and the identity of the grazing animal species.

Keywords: grazing, legumes, multispecies mixtures, perennial ryegrass, yield Introduction

Strategically designed multispecies swards (MSS) could be a key element in improving the delivery of provisioning services from grassland-based production systems (Finn et al., 20 13).

A Common Experiment (CE) was set up within the EU-FP7 project 'Multisward' across a subset of three partner sites to analyse responses of MSS compared with highly fertilized perennial ryegrass (PRG) monocultures to grazing and cutting managements under temperate maritime (Aberystwyth (UK) and Rennes (FR)) and continental (Tanikon (CH)) environmental conditions. The CE imposed contrasting defoliation managements (grazing and cutting) typical of intensive production systems for 2-3 years on sward types differing in species number and composition. Differences in biomass production between sward types within each management were analysed. Within each sward type, grazed and eut plots received the sa me externat applications of nitrogen fertilizer (N) and were defoliated at the same frequency to the same residual height, so that differences in sward responses to cutting and grazing managements could be attributed directly to the influence of the grazing animal. The effect of defoliation management on sward type was also analysed.

Materials and methods

Four forage species in common agronomie use in Europe were included in the CE: two grasses (perennial rye grass - PRG; tall fescue - FA) and two legumes (white clover-WC; red clover- RC). The second grass was replaced with chicory (Ci) in Rennes and Tanikon. Over ali s ites the CE included MSS treatments (two legumes + PRG; two legumes+ two grasses; two grasses;

two legumes+ two grasses+ Ci) and monoculture swards ofPRG, a subset ofwhich received a ' high ' application ofN. Ali MSS received a ' moderate' application ofN (150 kg N ha·• yr·•

in Aberystwyth and Tanikon, and 70 kg N ha·• yr·• in Rennes). High-N PRG monocultures received 300 kg N ha·• yr·• in Aberystwyth, 350 kg N ha·• yr"

in Tanikon and 165 kg N ha·• yr·

1

in Rennes. Biomass production was measured during 2011-2013 in Tanikon (18 harvests), and during 2012-2013 in Aberystwyth (12 harvests) and Rennes (13 grazing and 10 cutting harvests).

Grazing management: Management was based on the concept of biomass accumulation and removal, as in rotational grazing systems. Diff erent animais were used in the three si tes: non- lactating ewes in Aberystwyth; dairy cows in Rennes; beefheifers in Tanikon. In each grazing interval, plots were grazed to a target sward height appropriate for the animal (5 cm in

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Aberystwyth; 4 cm in Rennes; 6 cm in Tanikon), and the animais were then removed. The length of the regrowth period between grazing intervals was defined for each site and adjusted ifnecessary to take account ofvariation in forage production in response to climatic conditions.

Biomass productivity in grazed plots was measured immediately prior to grazing by cutting the herbage in known areas within the plot to the target sward height. These samples were oven- dried and weighed.

Cutting management: Cut plots had the same species composition as grazed plots, with the same leve! of replication. In Tiinikon these were fixed subplots within the grazed plots; in Aberystwyth they were randomized in a separate block beside the grazed plots; in Rennes cutting was only carried out on fixed subplots (high and moderate N) within PRG monocultures.

Cut plots were mechanically defoliated, and biomass productivity was measured by subsampling the eut herbage, drying and weighing.

Ali sward type treatments were randomized and replicated three times, except for high-N PRG- monoculture plots, which were replicated four times. Results for biomass production were analysed by appropriate ANOV A structures (Rennes and Tanikon) and by REML (Aberystwyth). Preliminary results from these analyses are presented here.

Results and discussion

To integrate the effects of ti me, biomass productivity was expressed as cumulative dry matter (DM) yield. Results for total yield (sown + unsown species) are shown in Table 1.

Table 1. Cumulative total DM yields (sown + unsown species; kg ha'

over 2/3 years in three sites of the Multisward CE. Sward types: 1 M = PRG mono; 2 = 2 non-legumes; 3 = 2 legumes+ PRG; 4 = 2 legumes + 2 non- legumes; 5 = 2 legumes + 3 non-legumes; lH = PRG mono receiving high N .

(a) Aberystwyth (12 harvests)

Sward type lM 2 3 4 5 lH Mean

Management

CUT 15510 15683 27089 25073 - ^{17459 20163}

GRAZED 12852 11944 19229 20865 - ^{1753 1 16484}

Mean 1418 1 13814 23 159 22969 17495 (b) Tanikon (18 harvests)

Sward type lM 2 3 4 5 lH Mean

Management

CUT 17382 21769 24491 26678 - ^{22905 22645}

GRAZED 20423 243 63 28989 31 651 - ^{2971 8 27029}

Mean 18903 23066 2 6740 29164 26312 (c) Rennes (13 grazmg harv ests; 10 cuttmg harvests)

Sward type lM lM 2 3 4 5 IH Mean

Management

CUT 23865 - - ^- - ^{263 52 25109}

GRAZED 22901 * ²⁶⁵²⁰ - ^{28590 2 9481 290 11} - ²⁸⁴⁰¹

Mean 23393

Note: Two non-legume spec1 es m Aberystwy th = PRG and FA; m Zünch and Rennes = PRG and C1.

Sward type 5 = 2 legumes + PRG + Ci + FA.* Yield calcul ated from 10 harvests to allow direct comparison with eut treatment

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Aberystwyth: There were significant effects of management and sward type (P< O.OO 1 ), toge th er with an interaction between them (P<0.047). Overall, cumulative yield was higher under cutting than grazing (20 163 vs. 16484 kg ha"

Sward types 3 and 4 were the highest-yielding swards, overall. The management x sward typ e interaction resulted from a large diff erence in response between legume-based and non-legume-based MSS to defoliation. Yields of the legume-based sward types 3 and 4 were significantly higher under cutting than under grazing, whereas yields of the grass-based treatments 1 M, 1 H and 2 were not affected by management.

Tanikon: There was a significant effect of management averaged over sward type (P<0.008), and cumulative yield under grazing was higher th an under cutting (27029 vs. 22645 kg ha-

A veraged over managements, the effect of sward type was significant (P<0.006). Sward types 3, 4 and lH were the highest yielding, and l M was the lowest. There was no management x

sward type interaction, so ali sward types responded to defoliation in a similar way.

Rennes: The experimental design at this site reduced the number of sward types under cutting.

Within this management there was a significant diff erence between high and moderate N PRG monocultures (P<0.007), the former being more productive. There was no effect of defoliatio n management on cumulative yields of the lM treatment. Under grazing there was no difference in the yields of the variou s sward type s.

The agronomie utility of MSS was tested here by comparing the yields of sward types under realistic defoliation managements. We observed different sward responses to defoliation management in different s ites. However, the re was a confounding effect of the use of different grazing animais at each site (although this aspect of the CE also added to its agronomie relevance). In Aberystwyth, grazing either had no effect on sward yield (grass-based swards), or reduced it (legume-based swards) compared with the cutting management. Sheep grazing appeared to have a direct and detrimental effect on the legu me component of MSS. In Tanikon, cattle grazing had a pos itive effect on yield in ali sward types and there was no interaction of defoliation management with sward type. Thus, the most productive swards under grazing would be also the most productive under cutting in this site. Rennes carried out only one eut vs.

grazed sward-type comparison, in which there was no effect of defoliation management on yield. Taken together, these results support the hypothesis that selective grazing can have a large effect on the yield of MSS, and that the identity of the grazing animal is the key determinant. It is weil known that species of grazing animal differ in th e ir ability to select sward components. Yarrow and Penning (1994) found that the proportion ofwhite clover in mixtures was lower when they were grazed by sheep than by cattle, both ofwhich were lower than if the swards were harvested by cutting. Our results show that there was no detriment to yield in legume-based MSS compared with high-N PRG monocultures, and in sorne instances MSS were more productive. Increased use of MSS therefore potentially represents a subst antial economie and environmental saving when the various costs associated with the use ofnitrogen fertilizer are considered.

Acknowledgements

The research leading to these results received funding from the European Community's FP7 Programme under grant a greement no. 244983 (Multisward).

References

Finn J.A. Kirwan L., Connoll y J ., Scbastià M. T., Hclgadottir A., Baadshaug O. H., Bél anger G., et al. (2013) Ecosystem fun ction enhanced by combining four functional types of plant species in intensively managed grass land mixtures: a 3-year continental-scale field experiment. Journal of Applied Eco/ogy 50, 365-375.

Yarrow N.H. and Penning P.O. (1994) Managing grass-clover swards to produce different clover proportions.

Grass and Forage Science 49, 496-50 1.

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