Managing Annual & Italian ryegrass in a tight spring

Aaron Kemp, AusWest Seeds, New England & Mid North Coast NSW

It is proving to be a tough year for New South Wales farmers on the coast and in the Tablelands area with little rain falling since June, putting stress on many dairy, beef and sheep operations that use annual and or Italian ryegrasses as a winter feed. There are many cases where later sown pastures haven’t received rainfall since sowing and may have only had one grazing. Recent observations indicate that warm weather and moisture stress has, in some cases, pushed annual ryegrasses to flower earlier than usual causing flow on effects for farmers.

Good grazing, fertiliser and irrigation management is key to getting the best out of these grasses and inputs during spring. As ryegrass approaches flowering the feed quality declines, (Launders et. al., 2010) and in some instances drymatter production also declines. Grazing management is key during the period leading up to and during flowering to manage the quality and quantity of the pasture produced. Later flowering varieties such as Italian ryegrasses, will maintain quality pasture longer than shorter season varieties (Jennings & Fulkerson, n.d.).To limit flowering and extend the production of quality pasture, stocking rates need to be increased and/or rotations shortened to keep the grass short as well as limit and delay flowering. Flowering is, however inevitable and for best results it does need to be managed.
Bonville Trial Site | AusWest & Stephen Pasture Seeds
Figure 2: We know because we grow. AusWest Seeds Bonville trial 2017, where many observations regarding current season performance have been made before being collaborated with observations from other sites.
Fertiliser & Irrigation:
During a tight spring, it is important to maximise the efficiency of pasture inputs such as fertiliser and irrigation. It is always tempting to put a large amount of fertiliser and/or irrigation water on an annual ryegrass as while it is elongating towards flowering it appears tall, with big leaves and on first glance looks to be trying to grow. In reality, applying fertiliser and water to annual ryegrass as it is flowering will generally have only a small impact on the amount and quality of feed produced and may not produce a positive return. Italian ryegrasses however are generally later in flowering, and will not senesce immediately post flowering and will respond to both fertiliser and irrigation inputs. When available fertilising and irrigating Italian ryegrass is a much better proposition as the plant will continue to produce quality feed both before and after the flowering period.

Summary:
Know what you have planted and how it is likely to respond to the current dry and warm conditions.

If you have annual ryegrass that is starting to elongate, graze closely to maximise yield and quality – but be aware that irrigating and fertilising the pasture is likely to have limited effect and the pasture will be beginning to die off. As annual ryegrasses have been observed elongating due to the conditions already, it can be assumed that Italian ryegrasses will be doing so in the next 3 – 4 weeks. Start to increase grazing pressure on Italian ryegrasses to delay flowering and continue pressure through the flowering period. Use fertiliser and irrigation wisely. There is not much benefit to fertilising or watering flowering annual ryegrasses. However Italian ryegrasses that are as yet still vegetative, and will return to vegetative growth post flowering, will benefit from additional inputs.

References:
Launders, T. Beale, P. Griffiths, N. Lattimore, M. 2010; “Annual, Italian and Short Rotation Ryegrass Varieties 2010” Primefacts, Primefact 1002; www.dpi.nsw.gov.au
Jennings, N. Fulkerson, B. n.d; “Managing Short Term Ryegrass in the Subtropical Dairy Region” Local Land Services Fact Sheet. www.northcoastlls.nsw.gov.au

There are number of fundamental differences between annual and Italian ryegrasses that should be addressed. Below are a few generalisations.

  • Annual ryegrasses typically flower earlier than Italians (usually in the magnitude of 3 – 4 weeks)
  • After flowering, annual ryegrasses, senesce (or die)
  • After flowering, good Italian ryegrasses return to vegetative growth, even if they don’t make it to their second year potential as is the case on the Mid North and North coast of New South Wales

Grazing:
As annual ryegrasses approach flowering, increase stocking rates to delay flowering, and maintain stocking rates through the flowering period. This will help to improve pasture quality and get the best out of the grass. Leaving the ryegrass to go to head will potentially increase drymatter slightly over a more tightly managed pasture, but will result in a significant drop in pasture quality. This drop in quality will negatively affect live weight gains and milk yields. In a tight spring, it is also important to consider where the stock will go once the annual ryegrass starts to senesce and if feed needs to be brought in.

Italian ryegrasses also need to be managed through this period. While they will still flower, close grazing management can help to delay this slightly, prolonging the quality of the pasture. Similar to annual ryegrasses, once the pasture starts to elongate and set itself up for flowering, maintain or increase grazing pressure to keep the stems short. This will help to minimise the drop in pasture quality. Unlike annual ryegrass, Italian ryegrasses won’t immediately senesce after flowering. Good quality Italian ryegrasses, with low aftermath heading, will return to vegetative growth and quality will return. Ryegrass varieties with a significant amount of aftermath heading will continue to flower through the spring, always having lower quality feed compared to low aftermath heading varieties which continue to produce more leaf.

Tetila Thumpa comparison | AusWest & Stephen Pasture Seeds
Figure 1: Early flowering Tetila Annual ryegrass on the left and later flowering Thumpa Italian ryegrass on the right. The stems on the Tetila are thicker and starting to elongate towards flowering, while the Thumpa is still vegetative. Photo taken 13 Sept 17

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