Pasture legume production severely reduced when co-sown with winter forage cereals

Lindsay Bell, John Lawrence, Simon Jasper and Chris Guppy - Caputring Opportunities and Overcoming Obstacles in Australian Agronomy

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

The useful research article on pasture legume production and the effect when co-sown with winter forage cereals. Interesting to note that impacts of forage cereal competition on legume regeneration and/or survival in subsequent years remain to be measured.

What is the problem?

First-year productivity of pasture legumes is lower than subsequent years due to low soil seed bank (in annual species such as medics) or because of slow early vigor (in perennial legumes such as lucerne and sulla). Establishing legumes into existing summer-growing grass pastures in autumn is difficult because of low soil moisture and competition with emerging seedlings. This study examined the effects on the establishment, early productivity, and persistence of a range of sown pasture legumes when co-sown with winter-growing cereal forage crops.

What did the research involve?

Five different winter-sown legume species (Snail medic, Barrel medic, Strand medic, Sulla, and Lucerne) and one blank treatment were sown alone and in combination with forage barley (Clifton, southern Qld) or oats (Warialda, northern NSW) at full (50 kg/ha) and half seeding rate (25 kg/ha). Competition from the forage cereals at both sowing rates reduced the growth of the pasture legumes by 80-98% in all species, but forage cereal production was not reduced by the legumes.

What were the key findings?

Of the legumes sown alone, Sulla was the most productive (>4.5 t DM/ha), but this was still about 50% of the forage cereal yield. While co-sowing pasture legumes with reduced densities of grain wheat or barley crops may be successful, doing so with forage varieties sown at higher rates (>25 kg/ha) is liable to reduce seed set of annual species and establishment density of perennial species resulting in unviable pasture populations in subsequent years.

Final Comment

It appears that early competition imposed by the vigorous forage cereals swamped the less vigorous legumes reducing seedling numbers and their productivity. While various studies have shown that co-sowing pasture legumes with reduced densities of grain wheat or barley crops (Brownlee and Scott 1974; Lloyd et al. 1998), doing so with forage varieties sown at higher rates (>25 kg/ha) is not recommended as it is likely to reduce seed set of annual species and establishment density of perennial species resulting in unviable pasture populations in subsequent years.

2012 - Australia - Lindsay Bell, John Lawrence, Simon Jasper and Chris Guppy - Caputring Opportunities and Overcoming Obstacles in Australian Agronomy
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