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Using Legume Species Mixtures to increase and stabilise Legume Content in Pastures

A. Liu and C. K. Revell

Pasture Science, Centre for Cropping Systems, Agriculture Western Australia, Northam, WA.

Abstract

Pasture degradation is characterised by a declining and unstable legume content and is widespread in the wheatbelt of southern Australia. A mixture of pasture legume species with varying characteristics could be a solution to this problem and therefore increase a pasture’s contribution to subsequent crops. A project primarily funded by GRDC has been started to examine the potential benefits that may arise from this approach. This poster will outline the project undertaken and highlight the potential benefits from using legume species mixtures.

key words

Pasture, species mixture, degradation, legume content.

Introduction

Ley farming has long been a common practice in the wheatbelt of southern Australia, in which crop rotates with pastures regularly and the pasture will self-regenerate after each crop phase. Despite the benefits that pasture can bring to a farming system, there are often difficulties in maintaining a high and stable legume content in pastures (1, 2), especially in the face of increased cropping frequency, reduced input to pastures due to a low animal return, heavy dependency on single species, and the occurrence of false breaks of season. The negative consequence to pasture is generally known as pasture degradation.

The use of pasture species mixtures has various advantages (3). Compared to a single legume species based pastures, pastures based on mixtures of recently developed alternative legume species may offer the following potential benefits to the system:

  • Through differences in growth patterns and adaptabilities, legume species mixtures will better tolerate environmental variations (seasonal or spatial) and use the environmental resources more efficiently, and hence will be more productive;
  • High seed production with variable hardseededness will increase the size of the seed bank, survive false breaks of season better, and hence lead to a higher and more stable legume content in regenerating pastures and thereby better pasture quality for animal production;
  • With varying susceptibilities, legume pasture species mixtures will have a greater tolerance of pests and diseases, which will help maintain a high and stable legume content in the pasture;
  • A higher legume content will compete better with weeds, fix more nitrogen, build up organic matter in the soil and thus improve performance of subsequent crops.

The approach

A project has been started to test: 1) whether pasture species mixtures will result in better pasture production with a higher legume content; 2) whether the increased pasture production (if any) will result in better animal performance and better crops; and 3) whether pasture species mixtures will regenerate better after cropping, particularly in the face of false breaks. The main approach of this project will be the use of a key site for in-depth studies with collaborations from scientists of different organisations. A ‘participatory research’ will also be used to test the mixtures under different environmental conditions and management, to demonstrate findings from the key site trial, and to enable more farmers to have their input into the new system under test.

The key site is a subclover-based pasture on a sand-over-loam duplex soil within the medium rainfall zone of the WA wheatbelt. Two treatments are used: species mixtures vs subclover (Table 1). The species in the mixtures differed in various characteristics. Yellow serradella (O. compressus) is adapted better to acidic, deep sandy soils than subclover (4,5). Biserrula (Biserrula pelecinus) can tolerate summer grazing, is tolerant to lucerne flea and is very hard seeded. Gland clover (Trifolium glanduliferum) has small seeds, tolerates redlegged earth mite, and has a broad soil type adaptation. Arrowleaf clover (T. vesiculosum) is deep rooted, easy to harvest and has an extended growing period when finishing rain is good (6). French serradella (Ornithopus sativus) grows well on acid sandy soils and will have high second year densities. All species used in the mixture, except French serradella, are hard-seeded with different softening patterns (6, 7, 8). Seeds of these species can also resist sheep ingestion differently (9). At this stage we have tried to include more species than are probably required in developing the mixture to see how they will perform under various practical conditions. The rotation to be used will be: sown pasture - wheat – regenerating pasture – regenerating pasture – wheat. During the establishment year of the pasture phase, grazing will be minimal to increase seed production. The following regenerating pastures will be grazed to optimise animal production and seed set. Pasture performance, occurrence of insect pests, and animal performance (weight gain and wool) will be monitored. During the wheat phase, biomass production, grain yield and protein content will be measured. Similar treatments will be used in the participatory research trials with the major management left to the farmer’s decision based on the guidelines supplied. Based on information collected, a management package will be developed, tested and recommended to the farming community.

Table 1 The legume species used in the two pasture treatments.

Pasture mixture (with equal weight of the following)

Subclover

Subclover (Trifolium subterraneum) cv Dalkeith



Subclover
(T. subterraneum) cv Dalkeith

Arrow leaf clover (T. vesiculosum) cv Cefalu

Gland clover (T. glanduliferum)

French serradella (Ornithopus sativus) cv CadizA

Yellow serradella (O. compressus) cv Santorini

Biserrula (Biserrula pelecinus) cv Casbah

A Cadiz was only included in the key site experiment in the establishment year.

Acknowledgments

We thank Dr Bill Bowden, Dr Caixian Tang and Mr Donald Nicholas for their comments and Mr D.G. Ferris for his initial input. The project is funded by GRDC.

References

1. Rossiter, R.C. 1966. Advances in Agronomy. 18, 1-56.

2. Carter, E.D. 1982. Proceedings of the 2nd Australian Agronomy Conference. Wagga Wagga, p. 180.

3. Oram, R.N. 1993. Alternative Pasture Legumes 1993 -- Proceedings 2nd National Alternative Pasture legumes Workshop. York, pp. 199-202.

4. Revell, C.K., and Ewing, M.A. 1994. Alternative Pasture Legumes 1993 -- Proceedings 2nd National Alternative Pasture legumes Workshop. York, pp. 47-9.

5. Nutt, B. 1994. Alternative Pasture Legumes 1993 -- Proceedings 2nd National Alternative Pasture legumes Workshop. York, pp. 50-52.

6. Wiley, T.J., Snowball, R., and Craig, A.D. 1994. Alternative Pasture Legumes 1993 -- Proceedings 2nd National Alternative Pasture legumes Workshop. York, pp. 139-142.

7. Loi, A., Cocks, P.S., Howieson, J.G., and Carr, S.J. 1999. Aust. J. Agric. Res. 50, 1073-81.

8. Norman, H.C., Cocks, P.S., Smith, F.P., and Nutt, B.J. 1998. Aust. J. Agric. Res. 49, 973-82.

9. Edward, A.Y., Ewing, M.A., and Revell, C.K. 1998. Proceedings 9th Australian Agronomy Conference, Wagga Wagga, pp. 199-202.

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