Grazed pastures based on ryegrass species provide most of the feed for dairy cattle in New Zealand. There are many cultivars of perennial (Lolium perenne), annual and Italian (L. multiflorum), and hybrid (L. boucheanum) ryegrasses available for dairy farmers to use in pasture renewal. This study describes an index which ranks ryegrass cultivars relative to a genetic base according to the estimated economic value (EV) of seasonal dry matter (DM) traits. A farm system model was used to derive EVs ($ ha−1 calculated as change in operating profit divided by unit change of the trait) for additional DM produced in different seasons of the year in four regions. The EV of early spring DM was consistently high across all regions, whereas EV for late spring DM was moderate to low. Genotype × environment analysis revealed significant reranking of DM yield among ryegrass cultivars across regions. Hence, separate performance values (PVs) were calculated for two mega‐environments and then combined with the corresponding season and region EV to calculate the overall EV for twenty‐three perennial ryegrass and fifteen short‐term ryegrass cultivars. The difference in operating profit between the highest ranked and lowest ranked perennial ryegrass cultivar ranged from $556 ha−1 to $863 ha−1 year−1 depending on region. For short‐term ryegrasses used for winter feed, the corresponding range was $394 to $478 ha−1 year−1. Using PV for DM yield, it was estimated that plant improvement in perennial ryegrass has added $12–$18 ha−1 year−1 (depending on region) operating profit on dairy farms since the mid‐1960s.

Perennial ryegrass (Lolium perenne) cultivars adapted to New Zealand conditions are bred by several scientifically equipped New Zealand interests. New cultivars are evaluated in a network of trials organised by the New Zealand Plant Breeding and Research Association. This paper presents data from 17 trials completed throughout New Zealand since 1991. Data were analysed for each trial and then in a multi-site analysis enabling comparison of estimated cultivar means, over all New Zealand trials, North Island trials and Canterbury trials. New cultivars released to the market yielded on average 6% more herbage annually, and 9% in summer, than cultivars available before 1991. Other cultivars were evaluated but showed no yield advantage and have not been commercially released. Point analysis of plots in the final season of trials indicated that recently released cultivars maintain ground cover at least as well as the older ones. Limited data for rust infection indicated that the oldest cultivars are the most severely affected. Keywords: cultivar evaluation, endophyte, NZPBRA, pasture plant breeding, perennial ryegrass

This paper reviews the requirement for inoculation of white clover (Trifolium repens) seed with rhizobia bacteria in New Zealand. The pastoral industry relies on the nitrogen fixed by clover's rhizobia bacteria. These rhizobia were not present in soils prior to European settlement, but were introduced as contaminants, and naturally spread with pastoral development. The advent of large scale land development in the 1950s identified areas where clovers failed to nodulate and establish due to the absence of rhizobia, which led to the development of inoculated lime coated seed. Rhizobia have spread widely throughout New Zealand, and in the great majority of situations where pasture is being sown, soils now contain high levels of resident rhizobia capable of nodulating white, red and alsike clover, and inoculation of clover seed is not required. However, it is suggested the use of inoculated clover seed should be considered in the following three situations as an insurance against nodulation failure: undeveloped grasslands with no evidence of resident clover; virgin pastoral land cleared directly from scrub; and paddocks cropped with maize continually for over 10 years. It has been hypothesised that inoculating clover seed may improve clover growth through introducing more effective rhizobia with better nitrogen fixation ability, but the research in this area suggests there is little likelihood of any significant response from doing this. Keywords: rhizobia, inoculation, coated seed, white clover, red clover, alsike clover

Ecologically sustainable pastures remain the base of New Zealand's competitive advantage in livestock production, but while modest but steady productivity gains from pasture plant breeding have been documented, these appear to be difficult to convert to livestock production, and pasture production is perceived as up against a ceiling. This paper discusses the contribution of pasture plant breeding, focusing on the ryegrasses, and to a lesser extent on white clover. Heritable variation is evident in the basic components of herbage growth and herbage quality. However, changes to individual traits are not reflected in improved integrated field performance. More precise information is required on how factors interact. New breeding technologies will allow integrated improvement of interacting factors. Evaluation trials and modelling should be managed to provide feed-back identifying the specific requirements of future high-performing systems. Keywords: New Zealand, plant breeding, ryegrass, white clover

The agronomic performance of a range of perennial ryegrass cultivar-endophyte combinations was compared in 16 trials conducted at sites throughout New Zealand. Each trial was run for 3 years according to seed industry evaluation protocols, measuring variables including: dry matter (DM) yield (total annual and seasonal DM yield), ryegrass ground cover at the end of 3 years, susceptibility to plant pulling, and rust incidence. The change in DM yield over the 3-year term of each trial was also analysed. There were significant differences among cultivars in total annual DM yield, and in seasonal DM yield for each of the five periods of the year among which yield was split (winter, early spring, late spring, summer, and autumn). Mean annual yield declined between Year 1 and Year 3 in all regions except Taranaki, by between 0.8 t DM/ha (Canterbury) and 5.3 t DM/ha (Waikato). There were significant region, year, region × year, and cultivar × year interactions in yield change. Significant differences in ground cover score for perennial ryegrass at the end of 3 years were recorded among cultivars. However, these differences did not mirror on-farm observations of ryegrass persistence in the Waikato during the drought of 2007/08, suggesting that the standard trial protocols currently used do not adequately test persistence. It is recommended that industry cultivar testing needs to more accurately assess perennial ryegrass persistence, using new protocols including running trials on commercial farms, for more than 3 years, and using mixed swards. Genetic differences in persistence could be generated more quickly by choosing sites known to challenge perennial ryegrass growth and survival. Keywords: perennial ryegrass, cultivar evaluation, DM yield, persistence testing, plant pulling, rust