DairyNZ Forage Value Index (FVI)
The main source of data for the initial formulation of a Forage Value Index (FVI) for ryegrass cultivars has been 70 small plot trials conducted throughout New Zealand over the past 20 years, under the auspices of the New Zealand Plant Breeders Research Association. The standard protocol for these trials stipulates that pure ryegrass swards are grown under high levels of soil fertility and with defoliation by mowing or grazing.
Commercial farms, however, usually have ryegrass/white clover pastures. The new trials now include ryegrass cultivars grown with and without white clover as a companion species, and in high and low soil fertility levels (determined by the levels of nitrogen fertiliser applied). The cultivars* are also being grown under the National Forage Variety Trial (NFVT) protocol, alongside the species interaction trial at each site, to determine if rankings (e.g. on seasonal dry matter yield) change depending on the method of assessment. If cultivar rankings do change, adjustments will be made to the FVI that is currently based on NFVT trial data. Data describing the persistence and nutritive value of cultivars will eventually be included in the FVI, assisting farmers to select the best cultivar for their region and requirements.
*Cultivars are Abermagic AR1, Alto AR37, Prospect AR37, Commando AR37, Bealey NEA2, Kamo AR37, Base AR37 and One50 AR37.
Improved pasture performance
DairyNZ has established pasture persistence trials in Waikato (Scott Farm), Northland and Canterbury in autumn 2011 to assess dairy pasture performance. This work was initiated because many farmers have experienced problems maintaining high yields using modern perennial ryegrass cultivars.
The aim is to monitor performance of modern and old perennial ryegrass cultivars drilled at 6, 12, 18, 24 or 30 kg/ha, as high seeding rates could be contributing to reduced persistence through increased between-plant competition for resources. This would result in smaller less-vigorous plants affecting survival when stressed (e.g. summer conditions). Decreased white clover content is also expected when high ryegrass seeding rates are used.
The ryegrasses being tested are Alto, Commando and Halo (each infected with AR37 endophyte) and Nui ryegrass infected with standard (wild-type) endophyte. Herbicide weed control was carried out within 6 weeks of drilling, and all plots have been over-sown with Tribute white clover. Plots are rotationally grazed by dairy cows, and pasture measurements include dry matter yield, botanical composition, tiller density, plant morphology and size (Year 1 only), and annual identification of traits or distinguishing characteristics (e.g. tiller number, flowering date, root distribution, endophyte status) of the surviving ryegrass plants as the trial progresses.
The characteristics of persistent ryegrass plants will be utilised in future breeding programmes to improve longevity of pasture yield and outcomes from pasture renewal on-farm.