http://hdl.handle.net/11019/27 Irish Journal of Agriculture & Food Research, Volume 50, no. 1, 2011 Mon, 06 Nov 2017 23:29:22 GMT 2017-11-06T23:29:22Z http://hdl.handle.net/11019/55 Title: The economics of reseeding on a dairy farm Authors: Shalloo, Laurence; Creighton, P.; O'Donovan, Michael Abstract: Herbage production and utilization on Irish dairy farms is well below its potential. A number of factors influence herbage production and utilization, not least the level of annual reseeding (introduction of a new grass ley) on the farm. The potential farm performance is reduced by old permanent pasture due to the combined effects of reduced out-of-season herbage production and lower overall herbage yield when compared to perennial ryegrass. Based on the sales of grass seed, it is estimated that approximately 2% of the land area on dairy farms in Ireland is reseeded annually. This has created a situation where the overall percentage of perennial ryegrass in sward is low. The objective of the present study was to investigate the economic benefits of reseeding through simulating the consequences of reseeding different proportions of the farm on an annual basis. Four levels of an annual reseeding programme were evaluated: 1%, 5%, 10% and 15% of the farm reseeded annually; evaluated at three milk prices (20 c/L, 27c/L and 33 c/L). Increasing the level of reseeding resulted in an increase in total and seasonal herbage production and, when accompanied by an increased stocking rate, increased herbage utilization. At a milk price of 27 c/L, farm profitability was €20 764, €24 794, €30 073 and €33 515 on a 40 ha farm when 1%, 5%, 10% and 15%, respectively, of the farm was reseeded annually. Irrespective of milk price, increasing the level of reseeding had a positive effect on profitability and the highest gain was achieved at the highest milk price. Sensitivity analysis showed that sward persistency and, to a lesser extent, herbage utilization had significant effects on the benefit from reseeding. Description: peer-reviewed Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/11019/55 2011-01-01T00:00:00Z http://hdl.handle.net/11019/54 Title: Studies into the dynamics of perennial ryegrass (Lolium perenne L.) seed mixtures Authors: Gilliland, T.J.; Hennessy, D.; Griffith, V. Abstract: The dynamic interactions of four perennial ryegrass seed mixtures sold in Northern Ireland were studied under simulated grazing and conservation managements. Mixture composition was determined as changes in phosphoglucoisomerase isozyme frequencies by calculation from known isozyme frequencies of the component varieties. Mixture productivity was measured over 4 growing seasons and compared with yields predicted from those of the components in monoculture, weighted for their actual proportion in the mixture. No significant differences were found between actual yields for mixtures and their predicted yields, but when these differences were regressed against the heading date range among the varieties in each mixture, a significant relationship was observed. A wide range in heading date among the components of the mixtures was associated with increased yield stability over years and with a declining yield advantage for the mixture compared to its components grown as monocultures. In this aspect, the mixtures showed a more rapid decline under conservation management than under simulated grazing. Mixtures also had a flatter seasonal yield-production profile than their component varieties. Tetraploid components were more aggressive than diploids, though a more open-growing diploid maintained its proportion in the sward better than a dense-growing type and manipulating the sowing ratios could be used to influence final sward composition after 2 years. It was concluded that the differences in heading date range within mixtures had a significant impact on mixture dynamics, with the tetraploid component being the most aggressive. Description: peer-reviewed Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/11019/54 2011-01-01T00:00:00Z http://hdl.handle.net/11019/53 Title: Capturing the economic benefit of Lolium perenne cultivar performance Authors: McEvoy, M.; O'Donovan, Michael; Shalloo, Laurence Abstract: Economic values were calculated for grass traits of economic importance in Irish grass-based ruminant production systems. Traits considered were those that had the greatest potential to influence the profitability of a grazing system. These were: grass dry matter (DM) yield in spring, mid-season and autumn, grass quality (dry matter digestibility; DMD), 1st and 2nd cut silage DM yield and sward persistency. The Moorepark Dairy Systems Model was used to simulate a dairy farm. Economic values were calculated by simulating the effect of a unit change in the trait of interest while holding all other traits constant. The base scenario involved a fixed herd size and land area (40 ha), and an annual DM yield of 13 t/ha. The economic values generated under the base scenario were: € 0.152/kg for DM yield in spring, € 0.030/kg for DM yield in mid-season and € 0.103/kg for DM yield in autumn; € 0.001, € 0.008, € 0.010, € 0.009, € 0.008 and € 0.006 per 1 g/kg change in DMD for the months of April to September, respectively; € 0.03/kg for 1st cut silage DM yield, € 0.02/kg for 2nd cut silage DM yield; and − € 4.961 for a 1 percent reduction in persistency. Alternative scenarios were examined to determine the sensitivity of the economic values to changes in annual DM yield, sward utilisation and a scenario where silage production was the focus of the system. The economic values were used to calculate a total merit index for each of 20 perennial ryegrass cultivars based on production data from a 3 year plot study. The rank correlation between the merit index values for the cultivars under the base scenario and the scenario involving a reduction in herbage utilisation was 1.0, while that with the scenario involving reduced annual DM yield was 0.94. It is concluded that the total merit index can be used to identify cultivars that can generate the greatest economic contribution to a grass-based production system, regardless of system or intensity of grass production. Description: peer-reviewed Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/11019/53 2011-01-01T00:00:00Z http://hdl.handle.net/11019/52 Title: A review of perennial ryegrass variety evaluation in Ireland Authors: Grogan, D.; Gilliland, T.J. Abstract: Official National List (NL) testing of perennial ryegrasses commenced in Ireland at the start of the 1970s with Northern Ireland (NI) having one site as part of the UK NL testing network, and the Republic of Ireland (ROI) using 5 sites. The different testing strategies adopted to achieve sufficient precision for regional Recommended Listing in ROI from a multi-site system and from a single-site system in NI were considered, including the test protocols, use of sequential sowings, timeframes and ‘merit scores’. The precision with which varieties can be discriminated for yield potential was shown to decline at lower trial plot yields. Furthermore, reducing the number of data sets used for decision making was shown to increase the ‘breeder’s risk’ of having an improved variety incorrectly rejected but not the ‘tester’s risk’ of erroneously recommending a variety that was not a clear improvement, because statistical analysis expanded confidence limits. These variety lists initially assessed only yield and persistency, giving a progressive improvement in recommended varieties and despite high genotype-x-environment interaction effects was most clearly evident in spring productivity improvements. The lists have been highly influential in both jurisdictions as almost all agricultural grass seed sales were recommended in ROI or NI, but the overuse of late maturing varieties in the ROI market and declining reseeding levels across Ireland indicated the current limits of this influence. This, and increasing requirements from Irish farmers for improvement in the nutritive value of varieties to support greater dependence on grass for animal production, has led to increased testing for digestibility and other quality parameters. While there is valid scientific evidence that shows that improvements in perennial ryegrass varieties has increased milk and meat production, more detailed information is required to satisfy the specific needs of local farmers. Consequently, a research initiative has been instigated to develop an index that will incorporate all the yield, persistence and quality performances of each recommended variety into a ranking score for a specific herd management system. This guidance should simplify recommendations and better quantify variety improvements in financial terms. It is envisaged that this will encourage an increase in the renewal of Irish pastures, promote selection of varieties based on enterprise-specific value and will continue to enhance the profitability and sustainability of grass-dependent Irish farming as has been achieved since recommended lists were first introduced in Ireland. Description: peer-reviewed Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/11019/52 2011-01-01T00:00:00Z