SUMMARYA total economic merit index (Pasture Profit Index, PPI) for perennial ryegrass variety selection was developed to rank perennial ryegrass varieties (Lolium perenne L.) based on their economic potential for grass-based ruminant production systems. The key traits of importance identified were: spring, mid-season (April 11–August 10) and autumn dry matter (DM) yield, first and second cut silage DM yield, grass quality April to July (inclusive) and sward persistency. Variety persistency was quantified by determining the ground score (GS) change across years, which was associated with a yield threshold which triggered sward replacement. Each one-unit decline in GS was associated with a 1683 kg loss in DM yield. Data generated in the Irish recommended list trials for value for cultivation and use were analysed to quantify the relative performance of each variety for each of the aforementioned traits. A previously developed methodology to generate economic values was used with updated price assumptions to develop economic values, which were applied to the analysed performance data of individual varieties. These data were used to estimate the total economic merit of each variety. Thirty-nine varieties were ranked on total economic merit with the highest performing variety (Cv111) generating €213 per ha/year compared with Cv201, which was the lowest ranking variety generating −€31 per ha/year. Use of the PPI provides information to end users in relation to the economic merit of one variety over another, facilitating a more informed decision-making process at farm level.

SUMMARYPerennial ryegrass evaluation schemes categorize varieties into three maturity (early, intermediate and late) and two ploidy (diploid and tetraploid) groups, and compare the relative yield, persistence and nutritive quality of varieties within these groups. The present study compared these groups for herbage yield, dry matter (DM) concentration and, using near infrared reflectance spectroscopy (NIRS), four quality characteristics (in vitro content of digestible dry matter (CDDM), water-soluble carbohydrate (WSC) and crude protein (CP) concentrations, and buffering capacity). A total of 1208 plots were sown across 5 years in Irish Recommended List trials and then harvested 6–7 times in each of 2 harvest years. This also allowed an assessment of the effect of sward age. Maturity group had no significant effect on annual herbage yield, quality or DM concentration except for in vitro CDDM (P<0·01) but differed significantly for in vitro CDDM (P<0·01), WSC concentration (P<0·01) and buffering capacity (P<0·05) at the first silage harvest. Tetraploid swards had greater annual herbage yields (P<0·001), in vitro CDDM values (P<0·001) and WSC concentrations (P<0·01), but lower CP and DM concentrations (P<0·001) than diploids. Swards in their first full year produced an additional 5·17 t/ha DM (P<0·001) and had a higher (P<0·01) WSC concentration at the second silage harvest than in their second year, but did not differ significantly for in vitro CDDM and WSC, CP or DM concentrations. The present study showed that differences exist in yield, nutritive quality and ensilability indices between maturity and ploidy groups. These observations justify their assessment in variety comparative trials and facilitates particular groups being selected for individual farming systems to increase efficiency.

Spatial analyses of yield trials allow adjustment of cultivar means for spatial variation, improving the statistical precision of yield estimation. While the relative efficiency of spatial analysis has been frequently reported in several yield trials, its application to long‐term Lolium spp. forage yield trials has not been characterized. The objective of this study was to evaluate the trend analysis, nearest‐neighbor analysis (NNA), and correlated error (CE) models for their ability to account for spatial variability in 138 Lolium spp. forage yield trials. This case study was performed on data from five locations and 11 yr (2001–2011) using randomized complete block design (RCBD) trials conducted by the Department of Agriculture, Food and Marine (DAFM) in Ireland. The relative efficiencies of trend, NNA, and CE models compared with RCBD models were 129, 143, and 193% for analysis by trial × year, and 121, 125, and 171% for analysis by trial, respectively. When the top one, two, three, four, or five cultivar(s) were compared between CE and RCBD models, the agreement between two models to find common cultivars varied from 66% for the top cultivar to 28% for the top five cultivars. Using CE models, four replicates were sufficient to detect mean yield differences between cultivars of 7% of the mean and 80% power. Spatial analysis should be added to the routine DAFM testing programs, not only to improve the precision of yield estimates, but also to reduce the risk of missing potential candidate cultivars, given the existence of spatial variation.

The selection and feeding of perennial ryegrass (Lolium perenne L.) varieties (PRV) or perennial grass species (PGS) may affect enteric methane (CH 4 ) output because of changes in the fermentation dynamics in the rumen as a result of differences in herbage chemical composition. The objective of this study was to determine the effects of PRV and PGS harvested throughout the growing season on herbage chemical composition, and in vitro rumen fermentation variables and CH 4 output per unit of feed using a batch culture technique. Seven PRV (Experiment 1: Alto, Arrow, Bealey, Dunluce, Greengold, Malone, Tyrella) and six perennial grasses [Experiment 2: perennial ryegrass (Navan), perennial ryegrass (Portstewart), cocksfoot, meadow fescue, tall fescue, timothy; defined as PGS], managed under a simulated grazing regime, were incubated for 24 h with buffered rumen fluid in two separate experiments. The CH 4 output per unit of feed dry-matter (DM) incubated was not affected (P > 0AE05) by PRV (range of mean values across PRV of 23AE9-25AE3 (SEM 0AE41) mL g )1 DM) or by PGS (25AE6-26AE6 (SEM 0AE37) mL g )1 DM). The CH 4 output per unit feed DM disappearing during the in vitro rumen incubation was not affected by PRV (33AE9-35AE1 (SEM 0AE70) mL g )1 DM), and although there was an overall PGS effect (P < 0AE05; 37AE2-40AE3 (SEM 0AE71) mL g )1 DM), none of the paired contrasts between PGS were significant when analysed using Tukey adjusted comparisons. This outcome reflected either small-scale or a lack of treatment effects on individual herbage chemical composition (e.g. 454-483 g NDF kg )1 DM, 215-224 g CP kg )1 DM and 94-122 g water-soluble carbohydrate (WSC) kg )1 DM across PRV; 452-506 g NDF kg )1 DM, 208-243 g CP kg )1 DM and 73-131 g WSC kg )1 DM across PGS) and in vitro rumen fermentation variables. Hence, these results provide no encouragement that choices among the grasses examined, produced within the management regimes operated, would reduce enteric CH 4 output per unit of feed in vivo. However, the technique utilized did not take account of animal · PRV or PGS interactions, such as potential differences in intake between animals, that may occur under farm conditions.

Core Ideas The row‐column designs were 36% more efficient than the randomized complete block designs. The impact of block size and number of replicates on trial precision was dependent on block shape. Increasing number of replicates decreased LSD only in wider blocks compared to narrow blocks. Field‐based agronomic and genetic research relies heavily on data generated from field trials. Therefore, it is imperative to optimize the precision of yield estimates in cultivar evaluation trials. Experimental error in yield trials is sensitive to several factors, some of which are classified as experimental design factors (i.e., plot size, block size, and number of replicates). The objective of this study was to conduct a retrospective case‐study analysis of long‐term perennial ryegrass (Lolium perenne L.), Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot], and hybrid ryegrass (Lolium boucheanum) forage yield trials to quantify the effects of block size, block shape, plot size, and number of replicates on trial precision. A total of 142 forage yield trials sown 2001 to 2011 across five locations by the Department of Agriculture, Food and the Marine (DAFM), Ireland, were considered. The contribution of row and column sum of squares (SS) to total SS decreased with increasing block size from 6 (71% of total SS) to 33 cultivars per block (51% of total SS). Empirical estimates of LSD decreased with increasing number of replicates only for square blocks, but not for rectangular blocks. Across different block sizes from 6 to 42 plots per block, row‐column designs were 36% more efficient than complete blocks. Increasing plot size was consistently ineffective. Use of incomplete block designs would significantly improve precision for the DAFM trials. This case study provides a template by which any research with long‐term data can be used to design more efficient field trials.