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The experiment was to study the allelopathic effect of alfalfa extract on seed germination of perennial ryegrass. The effect of five extracts (0, 2.5, 5.0, 10.0 and 20.0 g/L) from roots, stems and leaves of alfalfa wl-963-HQ on seed germination and seedling growth of perennial ryegrass were determined by Petri dish filter paper method. The results showed that the germination rate, germination potential, germination index and vigor index of the seeds decreased obviously with the increase of the concentration of the extracts from the roots, stems and leaves of alfalfa. The root and leaf extracts of alfalfa had a stronger inhibitory effect on the germination of perennial ryegrass seeds. When the concentration was 20.0 g/L, perennial ryegrass seeds could not germinate normally. Alfalfa extract had no inhibitory effect on root length and seedling height of perennial ryegrass seedlings, but had significant effect on seedling weight. The extracts from the roots, stems and leaves of alfalfa significantly decreased the chlorophyll content of perennial ryegrass seedlings (P<0.05), and the POD activity was significantly increased (P<0.05). Compared with the control group, CAT activity of perennial ryegrass seedlings was significantly increased when the stem extract of alfalfa was 10.0 and 20.0 g/L (P<0.05). The study indicates that alfalfa extract has obvious allelopathy on perennial ryegrass, and reasonable row spacing was needed to reduce allelopathy when the two herbage are mixed. [ABSTRACT FROM AUTHOR]

Autumn closing date (CD) in intensive pasture‐based systems influences spring herbage availability. Little is known about the impact of earlier closing of swards in autumn on sward structure. A two‐year experiment was undertaken to investigate the impact of five CD on herbage production, leaf extension rate (LER), leaf senescence rates (LSR), sward free leaf lamina (FLL) content and the production and survival of tillers over winter and into spring. The five CD ranges were October 1–15 (CD1), October 16–30 (CD2), October 31––November 14 (CD3), November 15–29 (CD4), November 30–December 14 (CD5) and sward measurements were made on four measurement dates (MD): December 11 (MD1), January 6 (MD2), January 27 (MD3) and prior to spring defoliation (MD4). Thirty perennial ryegrass tillers were measured until the first defoliation in spring (average 1 March). Herbage mass was greatest in early CD and tillers had greater LER and LSR (4.6 and 4.5 mm tiller−1 day−1 respectively) compared to swards with a later CD (3.2 and 2.3 mm tiller−1 day−1 respectively). Early CD had greater parent and daughter tiller mortality than later CD (parent tiller mortality 1.1 and 0.3 ± 0.19 tillers; daughter tiller mortality 1.1 and 0.3 ± 0.27 tillers respectively). Early CD also had greater LER and LSR in daughter tillers (2.6 and 1.5 mm tiller−1 day−1, respectively) compared to late (1.5 and 0.5 mm tiller−1 day−1, respectively). Earlier closing of sward increased herbage mass in spring, however, there were negative implications, such as increased LSR and tiller mortality. [ABSTRACT FROM AUTHOR]

Grazing efficiency has been shown to differ between perennial ryegrass varieties. Such differences affect the utilization of grass within grazing systems, influencing the profitability of grass-based ruminant production systems. The Pasture Profit Index (PPI) is an economic merit grass variety selection tool developed to identify varieties with the greatest economic potential for grass-based dairy production systems. A new grass utilization subindex was developed and incorporated into the PPI to identify varieties with superior grazing efficiency. The subindex rewards varieties with superior grazing efficiency, measured as Residual grazed height, as these varieties allow increased amounts of herbage dry matter to be used by grazing animals. The economic values of all other traits within the PPI were reviewed and updated to ensure that the index was reflective of the current economic scenarios with appropriate assumptions included in the models, thus ensuring that varieties excelling in the agronomic traits with the greatest effect on profitability were recognized. The difference between the highest and lowest performing varieties for the grass utilization trait ranged from €23 to −€24. A range of €211 to €43 was recorded between the highest and lowest ranked varieties within the updated PPI. Spearman's rank correlation between the updated and original PPI lists was 0.96. The introduction of the utilization subindex will allow farmers to make informed variety selection decisions when reseeding pasture, particularly on their grazing platforms and it will allow a demand-based communication process between the farmer and the grass merchant or breeder, ultimately affecting trait selection for future breeding strategies. [ABSTRACT FROM AUTHOR]