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HERBAGE YIELDS OF ANNUAL RYEGRASS VARIETIES AT OUTENIQUA AND CEDARA.

Pasture based dairy production on the eastern seaboard is often based on perennial pasture species such as kikuyu, perennial ryegrass or lucerne. One of the main challenges when these species make up the primary pasture base within a pasture system, are the mutually low growth rates during winter or poor persistence over years. As a result, producers establish annual Italian and Westerwolds ryegrass (Lolium multiflorum), either as pure swards, mixtures or over-sown into existing perennial pastures. The large number of annual ryegrass varieties commercially available necessitates continuous evaluation to assist producers in selecting the most suitable variety based on dry matter (DM) production and the specific requirements within a fodder flow program. Thus, the aim of a study at Outeniqua was to determine the monthly growth rate and total annual DM production of commercially available ryegrass varieties.                                                          

The study was carried out as an irrigated small plot cutting trial where one hybrid ryegrass, 15 Italian ryegrass, and 10 Westerwolds ryegrass varieties were evaluated. The trial was harvested to a residual height of 50 mm at an approximate interval of 28 days or at canopy closure when the growing points are over-shadowed, to determine DM yield. The plots received 50 kg N per ha after each harvest.

Sukari, which is a long-duration Italian ryegrass variety, and the hybrid ryegrass variety Shogun had a similar total DM yield to the varieties Barmultra II, Yolande, Agriboost and Inducer, but a significantly higher DM yield than the rest of the Italian ryegrass varieties. All mentioned varieties had superior winter production and an extended growth period compared to the rest.  The total annual yield of the Westerwolds ryegrass variety Hogan was similar to Performer, Zoom and Bullet, but significantly higher than the other varieties. In terms of total annual DM yield the best performing varieties have a long growth duration and good winter growth activity. This combination made the cultivars Sukari and Shogun the best performing varieties producing above 10 ton DM per ha, with Barmultra II and Yolande somewhat less than 10 ton DM per ha over the growing season. Both characteristics, namely growth duration and winter activity, are a recent combination in Italian ryegrass breeding, since they were mostly inversely related. The inverse relationship is commonly seen in older varieties and varieties originating from climatic zones with cold winters where winter dormancy is desirable. However, for southern hemisphere conditions and especially in purely pasture based systems, winter growth activity is an important attribute. 

At Cedara, the ARC-API’s role over the years has been to breed new locally-adapted varieties and to evaluate and compare these varieties in yield trials with various other imported varieties marketed locally.  In this study the DM herbage yields of 34 Italian ryegrass and two perennial ryegrass varieties were determined in an irrigated lattice-designed yield trial with three replications.  The varieties were planted at Cedara on 13 April 2015 and cut at the three-leaf stage from late autumn through to late summer with a mower, its blade set at 5 cm above ground level.  Data from 16 varieties in this trial are highlighted, including nine ARC-API Cedara-bred Italian ryegrass varieties, five imported Italian ryegrass varieties which are marketed locally, and two perennial ryegrass varieties.  Significant differences were recorded in seasonal DM yield between these 16 selected varieties from autumn through to late spring (November) when all varieties were in early flower, and into the summer months December through to the end of February. Notably the two perennial ryegrass varieties Alto (diploid) and Base (tetraploid) had relatively lower autumn and winter DM herbage yields than most of the Italian ryegrass varieties.  In spring however, Alto and Base had similar DM yields to most of the Italian ryegrass varieties.   After flowering, on the other hand, only a few varieties yielded exceptionally well. These included the two perennial ryegrass varieties, the locally-bred Italian ryegrass variety Sukari (diploid) and the imported varieties Icon (tetraploid), Thumpa (tetraploid), Tabu (diploid) and Feast ll (tetraploid).  Also relatively high in summer DM yield were the most recently-bred ARC-API Italian ryegrass lines ARC 148 (diploid) and ARC 214 (tetraploid), which will shortly be considered for release as new varieties.

It was concluded that the varieties Sukari, Icon, Thumpa, Tabu, Feast ll and the two new ARC-API lines ARC 148 and ARC 214 might have a significant role to play in future as an alternative to perennial ryegrass varieties.  In this regard, apart from some of these Italian ryegrasses significantly out-yielding the two perennial ryegrass varieties in autumn and winter, their performance in summer in some cases matches the summer yield of the perennial ryegrass varieties.  It is noteworthy that the variety Sukari was superior at both Outeniqua and Cedara and should be prioritized for milk yield trials.

References:

J. van der Colf, S. B. Ammann, L. B. Zulu & M. M. Lombard, 2016. The growth rate and total dry matter production of annual ryegrass in the southern Cape. Proc. 51st Annual Congress of the GSSA, Wilderness, 4 -8 July 2016. 

N. K. Mohubedu, M. S. Nzeru & D. C. W. Goodenough, 2016. Seasonal herbage yield of Lolium multiflorum varieties with emphasis on those with extended summer growth after flowering. Proc. 51st Annual Congress of the GSSA, Wilderness, 4 -8 July 2016.