Barley Grass: Comparison
View Latest Version
Please note this is a comparison between Version 3 by Camila Xu and Version 4 by Camila Xu.

BA recent investigation into effective integrated weed management strategies for barley grass (Hordeum murinum L. spp. glaucum and Hordeum murinum L. subsp. leporinum) typically invades southern Australian cropland, pastures, and disturbed sites, especially on high-phosphorus and -nitrogen soils and competes successfully against common pasture legumes, such as lucerne,in southern Australia during 2016 and 2017 examined the effect of post-emergent herbicide applications and strategic defoliation by mowing on barley grass survival and seed production in a mixed legume pasture. Propaquizafop was found to be more than 98% effective in reducing barley grass survival and seed production in both years. In contrast, paraquat was not effective in controlling barley grass (58% efficacy), but led to a 36% and 63.5% decrease in clover and other weed biomass, respectively, after 12 months and increased lucerne biomass by over three-fold after 24 months. A single repeated mowing treatment resulted in a 46% decline in barley grass seedling emergence after 12 months and, when integrated with herbicide applications, reduced other weed biomass after 24 months by 95%. Resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides observed in local barley grass populations led to an additional and more focused investigation comparing the efficacy of other pre- and post-emergent herbicides for barley grass management in legume pastures. Haloxyfop-R + simazine or paraquat, applied at early tillering stage, were most efficacious in reducing barley grass survival and fecundity. The impact of defoliation timing and frequency on barley grass seedlings was also evaluated at various population densities, highlighting the efficacy of repeated post-inflorescence defoliations in reducing theplant survival and seed productive life of these pastures and of subsequent grain cropson. Results highlight the importance of optimal environmental conditions and application timing in achieving efficacious control of barley grass and improving pasture growth and biomass accumulation.

 

  • barley grass
  • herbicide
  • defoliation
  • IWM
  • lucerne

1. Introduction

Historically, lucerne (Medicago sativa) is the most widely grown perennial pasture legume in southern Australia Historically, lucerne (Medicago sativa) is the most widely grown perennial pasture legume in southern Australia [1], supplying a livestock feed source [2][3], facilitating the high growth rates and carcass weights desired by prime lamb markets [4], and often the only quality forage available in dry seasons.

Reduced fertiliser use [5][6][7], the prevalence of soil acidity [8], continuous grazing, and drought conditions over time led to a decline in legume productivity across southern Australia [1][9]. Thus, a cascading effect on pasture and soil fertility ensued, creating canopy gaps within pasture stands [10] that are exploited by annual grass weed species [11], which are often introduced from other sites via attachment of seeds to the fleece of grazing sheep. The propagules and seeds produced by some grasses are also problematic to livestock producers,  due to their lodgement within animal tissue. Lodged seeds cause significant carcass damage and further welfare, production, and economic impacts at the farm and processing level [12]. Given the recent upward trend in Australian sheep meat prices [13], carcass damage due to grass seed penetration continues to pose significant challenges to the profitability of the Australian sheep industry.

Volunteer barley grass (Hordeum murinum L. spp. glaucum and Hordeum murinum L. subsp. leporinum) typically invades southern Australian cropland, pastures, and disturbed sites, especially on high-phosphorus [14][15] and -nitrogen [16] soils and competes successfully against common pasture legumes, such as lucerne [17], reducing the productive life of these pastures and of subsequent grain crops. Currently, barley grass is an important weed in Australian cropping regions, invading over 244,000 ha and incurring an annual Australian dollars (AUD) $1.7 million loss in grain crop revenue [18]. Its increased prevalence across southern Australia is attributed to climate variability [19][20], herbicide resistance [21][22], and variable seed dormancy patterns, which facilitate the escape of individual plants following herbicide treatment, allowing establishment in crop [23]. The recent appearance of biotypes exhibiting sporadic and/or later emergence results in greater reliance on post-emergent herbicide applications for management [24].

In legume crops and pastures, selective pre-emergent herbicides such as propyzamide (inhibitor of microtubule formation) [25], photosystem II (PS II) inhibitors [26], and post-emergent ACCase inhibitors (“fops” and “dims”) are commonly effective against grass weeds [1][27], as are the non-selective bypiridyl photosystem I inhibitors (paraquat and diquat) and the acetolactate sythase (ALS)-inhibiting imidazolinones [24][27][28]. Recently, the development of bypiridyl photosystem I and ACCase inhibitor resistance in South Australian barley grass populations led to increased use of imidazolinones for barley grass management [21][24][29]. However, imidazolinone resistance is also emerging in some southern Australian Hordeum murinum L. subsp. Leporinum populations [22][30][31], highlighting the need for additional integrated approaches to weed management to further reduce Hordeum spp. infestations in pastures and seed contamination in sheep.

Defoliation by grazing or mowing is a weed control strategy historically used to control barley grass. The impacts of grazing on its survival are conflicting in the literature with control seemingly dependent on stocking rates [32], time of year [33], and the provision of adequate fencing. In pasture legumes, mowing for hay production as an alternative to grazing was shown to be highly effective [34], particularly when defoliation coincides with the onset of the reproductive phase of the target species, thereby reducing seed rain and altering botanical composition [35]. Defoliating plants at boot stage [36] resulted in decreased barley grass fecundity [37] and seed size [34] and subsequently reduced viability post-flowering [38]. The growth and survival of plants under defoliation is also dependent on the frequency and intensity of defoliation, plant size, and stress due to intra- and inter-species competition. This suggests that the impacts of defoliation may be exacerbated at high density given reduced resource allocation for reproduction [39] and limited carbohydrate reserves for regrowth [40][41]. Although previous modelling suggested that weed density influenced efficacy of control in other annual grasses [42], the impact of these interactions in barley grass is unknown.

The integration of defoliation by grazing with additional herbicide application, termed “spray-grazing”, is a common method used for the control of broadleaf weeds in Australia [43], but is yet to be investigated for barley grass. Furthermore, the efficacy of integrating defoliation by mowing with herbicide application for effective barley grass management is currently unknown.

This research therefore investigated the interaction between herbicide application and defoliation by mowing, performed at specific barley grass phenological stages, on barley grass survival and reproduction and examined the impact of these treatments on dryland legume pasture production in southern New South Wales (NSW). Further investigative field studies were performed to compare the efficacy of a range of pre- and post-emergent herbicides for barley grass control within the same pasture, while greenhouse studies assessed the effects of defoliation frequency and timing on barley grass survival and seed production when placed under various levels of intraspecific competition.

2. Conclusion:

This enstrudy demonstrated that herbicide application and repeated defoliations are effective in legume pastures for reducing barley grass fecundity and seedbank deposition over time, resulting in improved control. However, under southern Australian conditions and an increasingly dry climate, integrated approaches for barley grass management will likely become increasingly important. The results from this study indicate that the combination of herbicide application and defoliations shows significant promise as an integrated weed management (IWM  ) strategy against barley grass, provided applications are timed accurately. Currently, modelling is underway to examine the long-term effect of defoliation and herbicides on both barley grass survival and fecundity, in order to better predict the utility of a systems-based approach for management under variable Australian conditions.

References

  1. Lodge, G. Management practices and other factors contributing to the decline in persistence of grazed lucerne in temperate Australia: A review. Aust. J. Exp. Agric. 1991, 31, 713–724.
  2. Puckridge, D.W.; French, R.J. The annual legume pasture in cereal—Ley farming systems of southern Australia: A review. Agric. Ecosyst. Environ. 1983, 9, 229–267.
  3. Reeves, T.; Ewing, M. Is Ley Farming in Mediterranean Zones Just A Passing Phase. In Proceedings of the XVII International Grassland Congress, Rockhampton, Australia, 26 September–1 October 2004; Fisher, T., Turner, N., Angus, J., McIntyre, L., Robertson, M., Borrell, A., Lloyd, D., Eds.; The Regional Institute Ltd.: Gosford, Australia, 2004; pp. 2169–2177.
  4. Kenny, P.; Reed, K. Effects of pasture type on the growth and wool production of weaner sheep during summer and autumn. Aust. J. Exp. Agric. 1984, 24, 322–331.
  5. Gramshaw, D.; Reed, J.; Collins, W.; Carter, E. Sown Pastures and Legume Persistence: An Australian Overview. In Persistence of Forage Legumes; Marten, G.C., Matches, A.G., Barnes, R.F., Brougham, R.W., Clements, R.J., Sheath, G.W., Eds.; American Society of Agonomy: Madison, WI, USA, 1989.
  6. Pulsford, J. Trends in fertilizer costs and usage on pastures in tropical and subtropical Australia. Trop. Grassl. 1980, 14, 188–193.
  7. Vere, D.T.; Muir, A. Pasture improvement adoption in south-eastern New South Wales. Review of marketing and Agricultural Economics. J. Agric. Resour. Econ. 1986, 54, 19–31.
  8. Ridley, A.; Helyar, K.; Slattery, W. Soil acidification under subterranean clover (Trifolium subterraneum L.) pastures in north-eastern Victoria. Aust. J. Exp. Agric. 1990, 30, 195–201.
  9. Kemp, D.; Dowling, P. Towards sustainable temperate perennial pastures. Anim. Prod. Sci. 2000, 40, 125–132.
  10. Kemp, D.; King, W.; Michalk, D.; Alemseged, Y. Weed-proofing pastures: How can we go about it. In Proceedings of the 12th Australian Weeds Conference, Hobart, Australia, 12–16 September 1999; Bishop, A.C., Boersma, M., Barnes, C.D., Eds.; Tasmanian Weed Society: Hobart, Australia, 1999; pp. 138–143.
  11. Leigh, J.; Halsall, D.; Holgate, M. The role of allelopathy in legume decline in pastures. I. Effects of pasture and crop residues on germination and survival of subterranean clover in the field and nursery. Crop. Pasture Sci. 1995, 46, 179–188.
  12. Kelly, J.E.; Quinn, J.C.; Loukopoulos, P.; Broster, J.C.; Behrendt, K.; Weston, L.A. Seed contamination in sheep: New investigations into an old problem. Anim. Prod. Sci. 2018, 58, 1538–1544.
  13. Meat and Livestock Australia. Industry Projections 2019: Australian Sheep. Available online: https://www.mla.com.au/globalassets/mla-corporate/prices--markets/documents/trends--analysis/sheep-projections/mla_australian-sheep-industry-projections-2019.pdf (accessed on 26 February 2018).
  14. Rossiter, R. The effect of phosphate supply on the growth and botanical composition of annual type pasture. Crop. Pasture Sci. 1964, 15, 61–76.
  15. Groves, R.; Austin, M.; Kaye, P. Competition between Australian native and introduced grasses along a nutrient gradient. Austral. Ecol. 2003, 28, 491–498.
  16. Cocks, P. Response to nitrogen of three annual grasses. Anim. Prod. Sci. 1974, 14, 167–172.
  17. Southwood, O.R. The chemical control of barley grass in dryland Lucerne. Weed Res. 1971, 11, 231–239.
  18. Llewellyn, R.; Ronning, M.; Ouzman, J.; Walker, S.; Mayfield, A.; Clarke, M. Impact of Weeds on Australian Grain Production—The Cost of Weeds to Australian Grain Growers and the Adoption of Weed Management and Tillage Practices; CSIRO: Canberra, Australia, 2016.
  19. Smith, D. The growth of barley grass (Hordeum leporinum) in annual pasture. 1. Germination and establishment in comparison with other annual pasture species. Aust. J. Exp. Agric. 1968, 8, 478–483.
  20. Kelly, J.E.; Quinn, J.C.; Loukopoulos, P.; Nielsen, S.G.; Weston, P.; Broster, J.C.; Weston, L.A. Current Perspectives on the Impact of Weed Seed Contamination in Sheep. In Science, Community and Food Security: The Weed Challenge, Proceedings of the 20th Australasian Weeds Conference, Perth, Australia, 11–15 September 2016; Randall, R., Lloyd, S., Borger, C., Eds.; Weeds Society of Western Australia: South Perth, Australia, 2017; pp. 122–126.
  21. Shergill, L.S.; Malone, J.; Boutsalis, P.; Preston, C.; Gill, G. Target-Site Point Mutations Conferring Resistance to ACCase-Inhibiting Herbicides in Smooth Barley (Hordeum glaucum) and Hare Barley (Hordeum leporinum). Weed Sci. 2015, 63, 408–415.
  22. Shergill, L.S.; Malone, J.; Boutsalis, P.; Preston, C.; Gill, G. Basis of ACCase and ALS inhibitor resistance in Hordeum glaucum Steud. Pest. Manag. Sci. 2017, 73, 1638–1647.
  23. Fleet, B.; Gill, G. Seed Dormancy and Seedling Recruitment in Smooth Barley (Hordeum murinum ssp. glaucum) Populations in Southern Australia. Weed Sci. 2012, 60, 394–400.
  24. Shergill, L.S.; Fleet, B.; Preston, C.; Gill, G. Management of ACCase-Inhibiting Herbicide-Resistant Smooth Barley (Hordeum glaucum) in Field Pea with Alternative Herbicides. Weed Technol. 2016, 30, 441–447.
  25. Thorn, C.; Perry, M. Effect of chemical removal of grasses from pasture leys on pasture and sheep production. Anim. Prod. Sci. 1987, 27, 349–357.
  26. Peoples, M.B.; Gault, R.R.; Scammell, G.J.; Dear, B.S.; Virgona, J.; Sandral, G.A.; Pau, J.; Wolfe, E.C.; Angus, J.F. Effect of pasture management on the contributions of fixed N to the N economy of ley-farming systems. Aust. J. Agric. Res. 1997, 49, 459–474.
  27. Leys, A.; Plater, B. Simazine mixtures for control of annual grasses in pastures. Aust. J. Exp. Agric. 1993, 33, 319–326.
  28. McGowan, A. The effect of four herbicides on pasture yield and composition. Aust. J. Exp. Agric. 1970, 10, 42–47.
  29. Preston, C.; Holtum, J.A.M.; Powles, S.B. On the Mechanism of Resistance to Paraquat in Hordeum glaucum and H. leporinum. Plant. Physiol. 1992, 100, 630.
  30. Owen, M.; Goggin, D.; Powles, S. Identification of resistance to either paraquat or ALS-inhibiting herbicides in two Western Australian Hordeum leporinum biotypes. Pest. Manag. Sci. 2012, 68, 757–763.
  31. Shergill, L.S.; Fleet, B.; Preston, C.; Gill, G. Incidence of Herbicide Resistance, Seedling Emergence, and Seed Persistence of Smooth Barley (Hordeum glaucum) in South Australia. Weed Technol. 2015, 29, 782–792.
  32. George, J. Effects of Grazing by Sheep on Barley Grass (Hordeum leporinum Link) Infestation of Pastures. Proc. Aust. Soc. Anim. Prod. 1972, 9, 221–224.
  33. Hartley, M.; Atkinson, G.; Bimler, K.; James, T.; Popay, A. Control of Barley Grass by Grazing Management. Proc. N. Z. Weed Pest Control Soc. 1974, 31, 198–202.
  34. Smith, D. The growth of barley grass (Hordeum leporinum) in annual pasture. 4. The effect of some management practices on barley grass content. Aust. J. Exp. Agric. 1968, 8, 706–711.
  35. Bowcher, A.J. Competition between Temperate Perennial Pasture Species and Annual Weeds: The Effect of Pasture Management on Population Dynamics and Resource Use. Ph.D. Thesis, Charles Sturt University, Wagga Wagga, Australia, 2002.
  36. Zadok, J.; Chang, T.; Konzak, C. A decimal code for the growth stages of cereals. Weed Res. 1974, 14, 415–421.
  37. El-Shatnawi, M.D.K.J.; Ghosheh, H.Z.; Shannag, H.K.; Ereifej, K.I. Defoliation time and intensity of wall barley in the Mediterranean rangeland. J. Range Manag. 1999, 52, 258–262.
  38. Halloran, G.M.; Pennell, A.L. Regenerative Potential of Barley Grass (Hordeum leporinum). J. Appl. Ecol. 1981, 18, 805–813.
  39. Weiner, J. Allocation, plasticity and allometry in plants. Perspect. Plant. Ecol. Evol. Syst. 2004, 6, 207–215.
  40. White, L. Carbohydrate Reserves of Grasses: A Review. J. Range Manag. 1973, 26, 13–18.
  41. Bradley, K.W.; Hagood, E.S. Influence of sequential herbicide treatment, herbicide application timing, and mowing on mugwort (Artemisia vulgaris) control. Weed Technol. 2002, 16, 346–352.
  42. Beltran, J.C.; Pannell, D.J.; Doole, G.J.; White, B. A bioeconomic model for analysis of integrated weed management strategies for annual barnyardgrass (Echinochloa crus-galli complex) in Philippine rice farming systems. Agric. Syst. 2012, 112, 1–10.
  43. Moore, J.; Douglas, A. Spray Grazing—For Broadleaf Weed Control in Pastures. Available online: https://www.agric.wa.gov.au/feeding-nutrition/spray-grazing-broadleaf-weed-control-pastures (accessed on 30 January 2020).
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
Feedback