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Summer dormancy increases persistence of perennial grasses in a wheatbelt environment

Richard Hayes1,2, Brian Dear1,2, Guangdi Li1,2, J.M. Virgona1,2, Mark Conyers1 and Belinda Hackney1,2

1E H Graham Centre for Agricultural Innovation (NSW Department of Primary Industries and Charles Sturt University), Wagga Wagga Agricultural Institute, PMB, Wagga Wagga, NSW 2650. Email: richard.hayes@dpi.nsw.gov.au
2
Cooperative Research Centre for Plant-based Management of Dryland Salinity, 35 Stirling Highway, Crawley, WA 6009.

Abstract

Persistence and production of summer dormant cultivars, Kasbah cocksfoot (Dactylis glomerata L.) and Fraydo tall fescue (Festuca arundinacea Schreb.) was compared to that of Currie cocksfoot and Demeter tall fescue, both of which have higher levels of summer activity, at Wagga Wagga in southern NSW. Demeter tall fescue contributed the most (86% by dry weight) to total sward production in spring of the establishment year surpassing Currie cocksfoot (40%), and the summer dormant varieties, Fraydo tall fescue (15%) and Kasbah cocksfoot (7%). However, plant survival of Demeter tall fescue beyond the first summer (4 plants/m2) was low compared with Fraydo tall fescue (19), Currie cocksfoot (21), and Kasbah cocksfoot (33). The Demeter tall fescue sward had the lowest production (1250 kg/ha) in the subsequent winter compared with all other swards (average 2300 kg/ha). Both summer dormant cultivars were more persistent than their more summer active counterparts.

Introduction

Perennial grasses such as cocksfoot and tall fescue have long been used by graziers for animal production in Australia. However, their incorporation into cropping systems has not been widespread, largely due to their inability to withstand long periods of summer drought. Lucerne (Medicago sativa L.) on the other hand, is the most common perennial pasture species used in crop rotations in south-eastern Australia, largely due to its ability to produce high quality feed for livestock during the summer months and fix nitrogen for use by subsequent crops. However, lucerne is relatively inactive during the cooler months and there is a need to include alternative forage species in local farming systems to fill feed deficits during autumn and winter.

Summer dormancy is a term commonly used to describe the ability of perennial grasses to resist or avoid extended dry periods over summer (Norton et al. 2006). With an increased number of ‘summer dormant’ cultivars commercially available to Australian growers, there is a renewed interest in perennial grass species in the cropping zone. This study evaluates the effect of seasonal activity on the production and persistence of cocksfoot and tall fescue in a wheatbelt environment.

Methods

The summer dormant cultivars, Kasbah cocksfoot and Fraydo tall fescue were compared with more summer active perennial grass cultivars, Currie cocksfoot and Demeter tall fescue, at Wagga Wagga (3502′57S, 14721′18E) from May 2004-April 2006. The cocksfoot cultivars were sown at 4kg/ha, and the tall fescue cultivars were sown at 15kg/ha. Plot size was 6 х 4m, and the experiment was a randomised block design with 4 replications. Plant density was measured using 2 fixed 1m2 quadrats per plot in July 2004 after emergence, and again in July 2005. After this time plant density was measured in terms of basal frequency (%) as it was no longer possible to distinguish between individual perennial plants. Herbage yield was estimated at the end of each season through visual assessment at 6 locations within each plot, calibrated against 10 quadrats which were cut, dried and weighed. Botanical composition was assessed at the same time using the botanal technique (t’Mannetje and Haydock 1963). The experiment was grazed after each herbage yield and botanical composition assessment. Due to drought conditions there was no herbage measurement taken in summer 2004/05, and the production in autumn and winter in 2005 have been combined.

Results

All cultivars established successfully at densities exceeding 200 plants/m2, but declined significantly (P<0.001) within 1 year of sowing (Table 1). Demeter tall fescue had the lowest plant density (4 plants/m2) in July 2005, while Kasbah cocksfoot had the highest plant density (33 plants/m2). This trend was again reflected by the basal frequency counts taken 1 year later in April 2006.

Table 1. Plant density and basal frequency of 4 perennial grass cultivars grown at Wagga in 2004-06. Values within columns followed by the same superscript letter are not significantly different (P<0.001).

Cultivar/species

Plant density (plants/m2)

 

Frequency (%)

July 04

July 05

 

April 06

Currie cocksfoot

227a

21b

 

34c

Kasbah cocksfoot

205a

33c

 

45d

Demeter fescue

300b

4a

 

1a

Fraydo fescue

370c

19b

 

22b

Herbage production differed according to cultivar during the experimental period (Fig. 1a). The Kasbah cocksfoot sward had the highest yield in spring 2004 (Fig. 1a), but only 7% of the total herbage produced was from Kasbah cocksfoot (Fig. 1b). The bulk of the production in this sward in spring 2004 was from volunteer annual grass weeds. Conversely, Demeter tall fescue contributed 86% of the total herbage yield of its sward in the first spring, but as plant density declined significantly after this harvest (Table 1), Demeter failed to make any further significant contribution to the production of the sward. None of the grass cultivars made a significant contribution to sward herbage production during summer 2005/06.

Figure 1 a) Seasonal herbage yield (kg/ha) and b) contribution (%) of sown species to 4 perennial grass based swards grown at Wagga from 2004-06. Bars within each date with the same letter are not significantly different (P<0.01).

Conclusion

Autumn and winter pasture production in this experiment was largely driven by the sown perennial grass species. Demeter tall fescue was the least persistent of the grasses tested, and consequently the Demeter sward had the lowest cumulative autumn production in both years. Both summer dormant perennial grass cultivars were more persistent than their summer active counterparts suggesting that increased summer dormancy increases the persistence of perennial grasses in summer-dry environments. However, the more summer active Currie cocksfoot was shown to have greater persistence in this environment than the summer dormant Fraydo tall fescue. Our findings suggest that a higher level of summer dormancy and drought tolerance is required in tall fescue cultivars than is currently available, if this species is to be used more widely in the cropping zone of southern NSW.

References

Norton MR, Lelievre F, Volaire F (2006). Summer dormancy in Dactylis glomerata L.: the influence of season of sowing and simulated mid-summer storm on two contrasting cultivars. Australian Journal of Agricultural Research 57, 565-75.

t’Mannetje L, Haydock JNG (1963) The dry-weight-rank method for the botanical analysis of pasture. Journal of British Grassland Society 18, 268 – 275.

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