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Improved production from undersown medics

M.R. Moerkerk and R.S. Eldridge

Department of Agriculture, Victorian Institute for Dryland Agriculture Private Bag 260, Hors/tam VIC 3401

Establishing pastures under cereals or other crops is a well established practice aimed at compensating for poor pasture production in the first year, by obtaining a cash return from the crop. In adverse seasons, satisfactory establishment of undersown pastures is not always achieved. Although the practice is not recommended by the Victorian Department of Agriculture, 50-70% of pastures in north-west Victoria are established in this way. This indicates that farmers consider it to be an economical proposition.

In order to increase the reliability of pastures established under crops, a new technique is being evaluated in North-west Victoria. This involves sowing pasture and crop in alternate rows thus accurately controlling seeding depth and spatial isolation of crop and pasture which are considered to be crucial to establishing more productive undersown pastures (1).

Methods

Replicated plot trials were established in 1989, 1990 and 1991 to assess the benefits of alternate row sowing of pastures (Medicago truncatula) under cereal crops. Plot were 2.5x20 m sown in 4 randomised blocks. Wheat or barley was sown with a modified combine using, 100 mm points, at 50 mm depth with 60 kg/ha double super (17.5% P, 4% S) on 34 cm row spacing. A smudge bar was dragged behind the cereal sowing tynes to create a flat seed bed into which pasture was sown. Floating pasture boots were used which place the pasture seed at 1-5 mm depth with fertiliser. Alternate row sowing was compared to a conventional undersowing technique of cereal on 17 cm row spacing and the pasture distributed out of a small seeds box onto the ground before covering harrows.

Emergence of crop and pasture were assessed (10 quadrats, 0.1 m2), yields of cereals (1.2x20 m) and burr production (3 quadrats, 0.25 m2) were measured in the first year of each trial. Regeneration of the pasture in the following season was assessed with emergence counts (5 quadrats, 0.1 m2).

Results and discussion

Significant increases in the emergence of medics from alternate row sown treatments in the year of sowing of these trials have been observed (P<0.05). Burr production of the medics was higher in alternate row treatments in 1989. In 1990, which had a quick dry finish there was no difference in burr production. Cereal yields were not significantly affected by sowing in alternate rows. Regeneration of the pasture following establishment with alternate rows reflected the burr production of the preceding year.

Alternate row establishment of undersown pastures increases the reliability of pasture establishment, and production in the following year with minimal yield reduction in cereal crops compared to traditional undersowing techniques.

References

Santhirasegaram, K. and Black, J.N. 1965. Herbage Abstracts 4, 221-225.

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