Selecting the right ryegrass for short to medium term pastures
Understanding the species
There is now a wide range of short to medium term ryegrass germplasm for farmers to choose from. In itself, this can be very confusing without a good understanding of their background and place in farming systems.
Ryegrass that is limited to one year’s production is also referred to as annual ryegrass or Westerwold ryegrass and is a sub species of Lolium multiflorum. Westerwold annual ryegrass is well known for its quick establishment and early vigour. It should be sown from the beginning of autumn until early winter and under favourable conditions can produce up to 5 to 6 grazings/cuts. These annual ryegrass varieties can be diploid or tetraploid and can vary in maturity from early to late season. Mid-late maturity varieties are better suited to New Zealand where late grazing or a second cut can be achieved. Annual ryegrass has no associated animal health issues caused by toxic endophyte.
The true italian ryegrass is capable of producing feed over one to three years depending on climate and management. Italian ryegrass varieties can be diploid or tetraploid and can vary in maturity from mid to late season. They are quick to establish and provide growth over the full season. In addition, production starts early in the spring and goes through late into the autumn thus providing quality dry matter at these critical times. Italian ryegrass has no associated animal health issues caused by toxic endophyte.
Hybrid ryegrass offers similar production capabilities as italian ryegrass with the additional benefit of greater persistence. Hybrids offer flexibility in pasture systems, providing productivity over a longer period with quick establishment and good cool season production.
Perennial ryegrass is the primary species in New Zealand’s permanent pastures. It tolerates a range of conditions and management practices. It establishes quickly, has a high feed value and yields well. Diploid varieties are more suited to rotational-set stocking and can tolerate drier climates whereas tetraploid varieties require rotational grazing management and need adequate moisture to persist.
Diploids or tetraploids
Ryegrass exists naturally as a diploid (2n) plant. Using plant breeding techniques developed in Europe, some plants were found to have twice the number of chromosomes in relation to diploids.
These tetraploid (4n) varieties have broader leaves with a dark green colour and are often more palatable due to a higher ratio of soluble carbohydrates (sugars) in the cell in relation to structural carbohydrate in the cell wall (fibre).
Tetraploids have larger plant cells which lead to larger leaves and larger seed. This large seed usually establishes faster due to greater energy reserves per seed, but with less seed per kg. As such, tetraploids should be sown at a higher sowing rate than diploids. They have a more open growing habit which makes them more suited to planting with slower growing legumes. Diploids usually have better tiller density and can be sown at lower seeding rates. If sown alone this will help overcome weed problems but can shade legumes in pasture mixes.
Seed Force has developed a rigorous quality mark for its top diploid grass varieties. Dip Q stands for Diploid Quality and it is only assigned to the best diploid cultivators. Long term tests show they consistently produce ME levels akin to tetraploid grasses and NDF levels that are low enough for stock to extract as much energy as possible during digestion.
Seed Force’s plant breeders seek to boost resistance and maximise chloroplasts (and therefore sugar production) in the plant by selecting for increased leaf growth.
The Dip Q technology mark is applied to Seed Force diploid grass varieties which have been bred for reduced levels of Neutral Detergent Fibre and enhanced levels of Metabolisable Energy as key drivers of animal production.
These varieties have shown quality characteristics significantly different to other varieties in their class in one or more seasons during the year and can improve profitability.